Lithium ion battery, preparation method thereof and power utilization device

Abstract

The invention discloses a lithium ion battery, a preparation method thereof and an electric device. The lithium ion battery comprises a shell, a battery cell assembly and electrolyte, the battery cell assembly and the electrolyte are arranged in the shell, the battery cell assembly is located in the electrolyte, the battery cell assembly comprises a positive pole piece, a negative pole piece and a diaphragm, the diaphragm is located between the positive pole piece and the negative pole piece, the negative pole piece comprises a negative current collector and a negative membrane layer arranged on at least one side of the negative current collector, and the negative membrane layer is located between the positive pole piece and the negative pole piece. The negative electrode film layer comprises a graphite material, 70% or more of secondary particles of the graphite material are formed by compounding three or more primary particles, and the primary particles are at least one of spherical and rod-shaped particles. Through the arrangement of the graphite material, the surface of the graphite material is loose and porous, lithium embedding channels are rich, rich lithium ion transmission paths can be provided, rapid diffusion and embedding of lithium ions are facilitated, the charging process is accelerated, and the rapid charging performance is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to lithium-ion batteries, their preparation methods, and electrical devices. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, energy storage, and power applications due to their advantages such as high output voltage, high energy density, high power density, long cycle life, and good environmental friendliness.

[0003] With the continuous development of technology in the field of battery applications, there are increasing demands on the rapid energy replenishment capability of lithium-ion batteries. Summary of the Invention

[0004] This application provides a lithium-ion battery and its preparation method and power device, which improves the rapid energy replenishment capability of lithium-ion batteries.

[0005] To address the aforementioned technical problems, the first aspect of this application provides a lithium-ion battery, comprising: a casing, a cell assembly disposed within the casing, and an electrolyte. The cell assembly is located in the electrolyte and includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The negative electrode includes a negative current collector and a negative electrode film disposed on at least one side of the negative current collector. The negative electrode film includes graphite material, wherein 70% or more of the secondary particles of the graphite material are composed of three or more primary particles, and the primary particles are at least spherical or rod-shaped.

[0006] In this embodiment, 70% or more of the secondary particles of the graphite material are composed of three or more primary particles. The primary particles are at least one of spherical or rod-shaped, which makes the surface of the graphite material loose and porous with abundant lithium intercalation channels. This provides abundant lithium-ion transport paths, which helps the rapid diffusion and intercalation of lithium ions, thereby accelerating the charging process and improving fast charging performance.

[0007] In one embodiment, the average particle size of the primary particles is 1 μm-6 μm.

[0008] By setting the average particle size of the primary particles to 1μm-6μm, the smaller particle size of the primary particles can increase the specific surface area of ​​the material, which can greatly increase the number of reaction sites. In addition, the smaller particle size is beneficial to reducing the solid-phase diffusion path of lithium ions, which is beneficial to improving fast charging performance.

[0009] In one embodiment, the median volumetric particle size of the secondary particles is 10 μm-20 μm.

[0010] By setting the volume median particle size Dv50 of the secondary particles in the graphite material as described above, the particle size of the secondary particles is smaller, which can provide a shorter lithium-ion diffusion path, thereby accelerating the migration speed of lithium ions during charging and discharging, and is beneficial to improving the fast charging capability of the battery.

[0011] In one embodiment, the OI value of the graphite material is less than or equal to 15.

[0012] The OI value of the ink material is less than or equal to 15, and the crystal orientation is different and relatively random. Lithium can be inserted from various faces of the crystal, which is conducive to increasing the number of lithium insertion channels and enriching the lithium insertion channels. This helps the rapid diffusion and insertion of lithium ions and improves fast charging performance.

[0013] In one embodiment, the OI value of the graphite material is less than or equal to 10, and the OI value of the graphite material is greater than or equal to 2.

[0014] By setting the OI value of graphite material to be less than or equal to 10 and greater than or equal to 2, and the random crystal orientation, a richer lithium transport path can be provided, which helps the rapid diffusion and embedding of lithium ions and improves fast charging performance.

[0015] In one embodiment, the oil absorption value of the graphite material is greater than or equal to 55 ml / 100g, and the oil absorption value of the graphite material is less than or equal to 85 ml / 100g.

[0016] By setting the oil absorption value of the graphite material as described above, the graphite material can effectively absorb and retain the electrolyte, which helps to increase the permeability of the electrolyte inside the graphite material, which is beneficial to accelerating the transport of lithium ions and thus improving fast charging performance.

[0017] In one embodiment, the specific surface area of ​​the graphite material is 1.0 m². 2 / g-2.0m 2 / g.

[0018] By setting the specific surface area of ​​the graphite material as described above, it is beneficial to increase the contact area between the graphite material and the electrolyte, improve the wettability of the electrolyte on the graphite material, and accelerate the transport of lithium ions. In addition, it can provide more active sites for lithium ion insertion and extraction, which is beneficial to accelerate the diffusion rate of lithium ions in the graphite material, shorten the migration time of lithium ions during fast charging, and improve the fast charging capability.

[0019] In one embodiment, the initial delithiation capacity of the graphite material is 325 mAh / g to 355 mAh / g.

[0020] By setting the specific capacity of the graphite material as described above, the interlayer spacing of the graphite material is larger, which is conducive to the solid-phase diffusion of lithium ions, thereby promoting the improvement of fast charging capability.

[0021] In one embodiment, the powder compaction density of the graphite material at 20000N is 1.45g / cc-1.65g / cc.

[0022] By setting the compaction density of the graphite material as described above, it is beneficial to the electrical contact between graphite particles, forming a denser conductive network, accelerating the migration speed of lithium ions, and thus improving the fast charging capability.

[0023] To address the aforementioned technical problems, a second aspect of this application provides a method for preparing a lithium-ion battery, comprising: sequentially stacking a negative electrode sheet, a separator, and a positive electrode sheet to form a cell assembly; placing the cell assembly in a casing; and injecting an electrolyte into the casing and sealing it to form a lithium-ion battery; wherein the negative electrode sheet includes a current collector and a negative electrode film layer disposed on at least one side of the current collector, the negative electrode film layer including graphite material, and the method for preparing the graphite material comprising: providing coke fine powder, the median particle size of the coke fine powder being 1μm-6μm; compacting the coke fine powder to form a compact; crushing the compact to form a first precursor; granulating the first precursor using a binder to form a second precursor; graphitizing the second precursor to form a graphitized product; and coating the graphitized product using a coating agent to form a graphite material; wherein 70% or more of the secondary particles of the graphite material are composed of three or more primary particles, the primary particles being at least one of spherical or rod-shaped.

[0024] In this embodiment of the application, during the preparation of graphite materials, fine coke powder is compacted to form a compact, and the compact is then crushed to form a first precursor. Since fine coke powder with a small median particle size is used as raw material, it is advantageous to form a first precursor with a smaller particle size. The compact is easier to crush than the larger-particle-size coke, resulting in lower energy consumption and higher yield for forming the smaller-particle-size first precursor, thus reducing costs. The fine coke powder contains a significant amount of light components, such as cycloalkanes and oxygen-containing compounds. These light components have strong binding properties, allowing the fine coke powder to bond together during compaction to form a compact, i.e., the particles bond together to form a multi-oriented block material. Crushing the compact yields the multi-oriented first precursor. By using a first precursor with a small particle size for granulation and graphitization to form graphite materials, graphite materials with small particle size can be obtained. Maintaining the loose and porous surface of the graphite material with abundant lithium intercalation channels can provide more lithium ion transport paths, which helps the rapid diffusion and intercalation of lithium ions, thereby accelerating the charging process and improving fast charging performance.

[0025] In one embodiment, the step of providing coke fine powder specifically includes: pulverizing the coke to obtain coke powder and coke fine powder; the median particle size of the coke powder is 7μm-17μm.

[0026] According to Jacob Bohr's Law (the broken vase theory), the material crushing process is uncontrollable, naturally resulting in both large and small particles. During the crushing of raw coke, both large-particle raw coke powder and small-particle raw coke fine powder are naturally obtained. The larger-particle raw coke powder can be used as a raw material for preparing other substances, resulting in higher utilization of raw coke and reducing costs. Alternatively, it can be understood that the raw material for preparing other substances is raw coke powder with a Dv50 of 7μm-17μm. Raw coke powder is obtained by crushing raw coke, while the fine raw coke powder is a byproduct. Using this byproduct to prepare graphite materials achieves the reuse of waste materials.

[0027] In one embodiment, the median particle size of the first precursor is 6 μm-10 μm.

[0028] By setting the median particle size Dv50 of the first precursor as described above, and using a smaller particle size for granulation, graphitization, and coating, the specific surface area of ​​the graphite material can be increased, thereby providing more active sites for lithium ion insertion. It can also shorten the diffusion path of lithium ions, which is conducive to achieving rapid lithium ion transport. At the same time, a narrower and more uniform particle size distribution helps to maintain effective contact between the electrolyte and the graphite material, promotes uniform insertion and extraction of lithium ions, and is beneficial to improving battery performance.

[0029] In one embodiment, the median particle size of the second precursor is 12 μm-16 μm.

[0030] By setting the volume median particle size Dv50 of the second precursor formed by granulation as described above, the specific surface area of ​​the graphite material can be increased, thereby providing more active sites for lithium ion insertion. It can also shorten the diffusion path of lithium ions, which is conducive to achieving rapid lithium ion transport. At the same time, the narrower and more uniform particle size distribution helps to maintain effective contact between the electrolyte and the graphite material, promotes uniform insertion and extraction of lithium ions, and is beneficial to improving battery performance.

[0031] In one embodiment, the mass ratio of the binder to the first precursor is (1-2):10.

[0032] By setting the mass ratio of the binder to the first precursor as described above, the first precursors are fully bonded together to form a second precursor with a stable structure. The particle size distribution of the second precursor formed by granulation is relatively uniform, and the particle structure is stable.

[0033] In one embodiment, the adhesive includes at least one of asphalt and resin.

[0034] Asphalt and / or resins are viscous and maintain good adhesion at different temperatures, which helps the first precursor aggregate into particles and maintains structural stability during subsequent processing. Furthermore, asphalt is relatively inexpensive, contributing to lower overall manufacturing costs.

[0035] In one embodiment, the mass ratio of graphitized product to coating agent is 100:(2-15).

[0036] With the above-mentioned mass ratio of graphitized product to coating agent, the additives in the coating agent are more suitable. While maintaining the porosity between graphite particles, the coating agent can form a coating layer on the particle surface, maintain the structural stability of the graphite material, and improve the transport dynamics of lithium ions on the graphite particle surface.

[0037] In one embodiment, the coating agent includes at least one of asphalt, liquid residue oil, and resin.

[0038] By selecting the above materials as coating agents, amorphous carbon is formed after carbonization, which can effectively improve the surface conductive network of graphitized products, promote the rapid migration of lithium ions, and thus improve the fast charging performance of the battery.

[0039] To solve the above-mentioned technical problems, a third aspect of this application provides an electrical device, including a lithium-ion battery as described in any of the above claims or a lithium-ion battery prepared by any of the above-mentioned lithium-ion battery preparation methods.

[0040] The electrical device has at least the same advantages as the lithium-ion battery described above or the lithium-ion battery prepared by the aforementioned method.

[0041] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the structure of a lithium-ion battery provided in an embodiment of this application;

[0044] Figure 2 This is an exploded structural diagram of a battery cell provided in an embodiment of this application;

[0045] Figure 3 This is a scanning electron microscope (SEM) image of the graphite material provided in the embodiments of this application at 1000X magnification;

[0046] Figure 4 This is a schematic flowchart of the method for preparing a lithium-ion battery provided in the embodiments of this application;

[0047] Figure 5 yes Figure 4 A schematic flowchart of the preparation method of graphite material in the method shown;

[0048] Figure 6 This is a schematic diagram of the vehicle structure provided in an embodiment of this application. Detailed Implementation

[0049] To make the objectives, technical solutions, and effects of this application clearer and more explicit, the embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0051] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0052] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0053] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0054] Quantities, ratios, and other numerical values ​​are presented in range format in this document. It should be understood that this range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0055] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) may be performed simultaneously in parallel. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0056] With the continuous development of technology in battery applications, there are increasing demands on the rapid energy replenishment capability of lithium-ion batteries. Graphite, as a commonly used negative electrode material in lithium-ion batteries, significantly impacts the rapid energy replenishment capability of these batteries.

[0057] Therefore, embodiments of this application provide a lithium-ion battery and its preparation method, as well as an electrical device, to improve the rapid energy replenishment capability of lithium-ion batteries.

[0058] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a lithium-ion battery provided in an embodiment of this application.

[0059] The lithium-ion battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10.

[0060] The housing 10 provides a space for accommodating the battery cell 20, and can adopt various structures. In some embodiments, the housing 10 may include a first part 11 and a second part 12, which overlap each other, and together define a space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one open end, and the first part 11 may be a plate-like structure, covering the open side of the second part 12 so that the first part 11 and the second part 12 together define the space; alternatively, the first part 11 and the second part 12 may both be hollow structures with one open side, with the open side of the first part 11 covering the open side of the second part 12. Of course, the housing 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0061] In the lithium-ion battery 100, there can be multiple battery cells 20. These multiple battery cells 20 can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 20 is housed in the housing 10. Alternatively, the lithium-ion battery 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed in the housing 10.

[0062] The lithium-ion battery 100 may also include other structures, for example, the lithium-ion battery 100 may also include a busbar for realizing electrical connection between multiple battery cells 20.

[0063] Each battery cell 20 can be a secondary battery. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0064] Please see Figure 2 , Figure 2 This is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0065] The battery cell 20 refers to the smallest unit that makes up a lithium-ion battery 100. For example... Figure 2 As shown, the battery cell 20 includes an end cap 21, a housing 22, a cell assembly 23, and other functional components.

[0066] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. In any case, the shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that end cap 21 is less prone to deformation under pressure and impact, enabling battery cell 20 to have higher structural strength and improved stability.

[0067] The end cap 21 may be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect with the cell assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 may also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold.

[0068] The end cap 21 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special restrictions on this.

[0069] In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0070] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the cell assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the cell assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0071] The cell assembly 23 is the component in the battery cell 20 where the electrochemical reaction occurs. The casing 22 may contain one or more cell assemblies 23. The cell assembly 23 includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode. The positive and negative electrode are wound or stacked to form the cell assembly 23. The portions of the positive and negative electrode with active material constitute the main body of the cell assembly 23, while the portions without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or at opposite ends. During the charging and discharging of the lithium-ion battery 100, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals 21a to form a current loop.

[0072] In one embodiment, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0073] The positive electrode current collector can be a metal foil or a composite positive electrode current collector. Optionally, aluminum foil can be used as the metal foil. Optionally, the composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite positive electrode current collector can be formed by forming a metal material on the polymer material substrate; the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy; the polymer material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0074] Positive electrode active materials include, but are not limited to, one or more of lithium transition metal oxides, lithium phosphates with olivine structures, and their respective modified compounds.

[0075] Optionally, the positive electrode active material may include materials with the general formula Li a Ni b Co c M d O e A f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

[0076] Optionally, the lithium transition metal oxide may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0077] Optionally, the lithium phosphate with an olivine structure may include one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0078] Optionally, the positive electrode active material may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4 and LiMnPO4.

[0079] In one embodiment, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector.

[0080] The negative electrode current collector can be a metal foil or a composite negative electrode current collector. Optionally, copper foil can be used as the metal foil. Optionally, the composite negative electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite negative electrode current collector can be formed by forming a metal material on the polymer material substrate; the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy; the polymer material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0081] Please see Figure 3 , Figure 3 This is a scanning electron microscope (SEM) image of the graphite material provided in the embodiments of this application at 1000X magnification.

[0082] The negative electrode film layer includes graphite material, and 70% or more of the secondary particles of the graphite material are composed of three or more primary particles. The primary particles are at least one of spherical or rod-shaped.

[0083] Primary particles refer to particles formed directly in the initial stage of graphite material formation, without subsequent aggregation or reorganization. Secondary particles refer to particles reconstructed through the interactions of primary particles. When primary particles are spherical, their shape is close to spherical, though not necessarily a perfect sphere. The size of the particle is similar in all directions, with no obvious long or short axis, exhibiting isotropic morphology. When primary particles are rod-shaped, their shape is non-spherical, with one or both ends being relatively pointed, exhibiting obvious long and short axes, and displaying anisotropy. Primary particles are formed by chemical bonding between them.

[0084] The method for testing the proportion of secondary particles in graphite materials composed of three or more primary particles is as follows: Take 1g of graphite powder and disperse it uniformly using an airflow dispersion device. Take a picture of the uniformly dispersed particles using a scanning electron microscope to observe their morphology. Use image intelligent recognition software to identify the secondary particles using AI or manual identification to obtain the number A of secondary particles (≥3 primary particles combined) and the total number of particles B. A / B is the proportion of secondary particles.

[0085] In this embodiment, by configuring the graphite material as described above, the graphite material surface is loose and porous with abundant lithium intercalation channels, which can provide rich lithium ion transport paths, facilitate the rapid diffusion and intercalation of lithium ions, thereby accelerating the charging process and improving fast charging performance.

[0086] In one embodiment, the average particle size of the primary particles is 1 μm-6 μm.

[0087] The method for testing the average particle size of primary particles is as follows: the negative electrode active material is tested using a scanning electron microscope, and then tested according to standard JY / T010-1996, observing the sample morphology. AI-based image recognition software is used to identify primary particles, which can draw particle outlines, particle quantity, number, area, maximum caliper diameter, average, and provide manual intervention. The average particle size of primary particles = the sum of the particle sizes of all measured primary particles / the sum of the number of measured primary particles.

[0088] By setting the average particle size of the primary particles to 1μm-6μm, the smaller particle size of the primary particles can increase the specific surface area of ​​the material, which can greatly increase the number of reaction sites. In addition, the smaller particle size is beneficial to reduce the solid-phase diffusion path of lithium ions and accelerate the charging and discharging reaction rate.

[0089] The average particle size of a primary particle can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc., or it can be a range of any two of the above values, such as 2μm-6μm, 1μm-5μm, etc.

[0090] In one embodiment, the volume median particle size Dv50 of the secondary particles is 10 μm-20 μm.

[0091] The volumetric median particle size (Dv50) represents the particle diameter at which the cumulative volume distribution reaches 50%. By setting the Dv50 of the secondary particles in the graphite material as described above, the smaller particle size provides a shorter lithium-ion diffusion path, thereby accelerating the migration speed of lithium ions during charging and discharging, which is beneficial for improving the fast-charging capability of the battery. The Dv50 of the secondary particles in the graphite material can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc., or it can be any two of the above values ​​within the range of 10μm-15μm, 14μm-19μm, etc.

[0092] In one embodiment, the OI value of the graphite material is less than or equal to 15.

[0093] The OI value refers to the ratio of the peak areas of the characteristic diffraction peaks on the 004 / 110 crystal plane of graphite materials detected by X-ray diffraction (XRD), used to represent the orientation degree of the crystal. It should be noted that the OI value test can refer to JIS K 0131-1996. Graphite materials with an OI value less than or equal to 15 have diverse and relatively random crystal orientations, allowing for lithium intercalation from various facets. This increases the number of lithium intercalation channels, facilitating rapid diffusion and insertion of lithium ions, and improving fast-charging performance. The OI value of graphite materials can be 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, etc., or a range of any two of these values, such as 8-15, 5-13, etc.

[0094] In one embodiment, the OI value of the graphite material is less than or equal to 10, and the OI value of the graphite material is greater than or equal to 2.

[0095] By setting the OI value of graphite materials to be less than or equal to 10 and greater than or equal to 2, and by creating a disordered crystal orientation, more and shorter lithium transport paths can be provided, which helps the rapid diffusion and insertion of lithium ions and improves fast charging performance. The OI value of graphite materials can be 10, 9, 8, 7, 6, 5, 4, 3, 2, etc., or it can be a range of any two of the above values, such as 4-10, 3-8, etc.

[0096] In one embodiment, the oil absorption value of the graphite material is greater than or equal to 55 ml / 100g, and the oil absorption value of the graphite material is less than or equal to 85 ml / 100g.

[0097] Oil absorption value refers to the volume of liquid that a unit mass of graphite material can absorb and retain. It is a comprehensive indicator reflecting particle size distribution, surface morphology, and specific surface area. By setting the oil absorption value of graphite material as described above, the graphite material can effectively absorb and retain electrolyte, which helps to improve the electrolyte permeability inside the graphite material, accelerates lithium-ion transport, and thus improves fast-charging performance. The oil absorption value of graphite material can be 55ml / 100g, 60ml / 100g, 65ml / 100g, 70ml / 100g, 75ml / 100g, 80ml / 100g, 85ml / 100g, etc., or it can be a range of any two of the above values, such as 55ml / 100g-75ml / 100g, 60ml / 100g-58ml / 100g, etc.

[0098] The test method for oil absorption value can refer to GB / T 3780.2-2017. Optionally, the test method for oil absorption value is as follows: a certain mass of graphite material is placed in a mixing chamber, and paraffin oil is dripped into the material using a titrator. During the titration process, the rotor torque is tested simultaneously to obtain the torque-oil absorption value curve. The oil absorption value corresponding to 70% of the maximum torque value is taken as the test value.

[0099] In one embodiment, the specific surface area of ​​the graphite material is 1.0 m². 2 / g-2.0m 2 / g.

[0100] Specific surface area refers to the total surface area per unit mass of graphite material. By adjusting the specific surface area of ​​the graphite material as described above, it is beneficial to increase the contact area between the graphite material and the electrolyte, improve the wettability of the electrolyte on the graphite material, and accelerate lithium-ion transport. Furthermore, it provides more active sites for lithium-ion insertion and extraction, which helps to accelerate the diffusion rate of lithium ions in the graphite material, shorten the lithium-ion migration time during fast charging, and improve fast charging capability. The specific surface area of ​​the graphite material can be 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, 2.0m2 / g, etc., can also be a range consisting of any two of the above values, for example, 1.0m. 2 / g-1.5m 2 / g, 1.2m 2 / g-1.9m 2 / g etc.

[0101] In one embodiment, the initial delithiation capacity of the graphite material is 325 mAh / g to 355 mAh / g.

[0102] Specific capacity refers to the number of lithium ions that can be intercalated or deintercalated from a unit mass of graphite material. By setting the specific capacity of graphite material as described above, the interlayer spacing of graphite material is larger, which is conducive to the solid-phase diffusion of lithium ions, thereby promoting the improvement of fast charging capability. The specific capacity of graphite material can be 325mAh / g, 330mAh / g, 335mAh / g, 340mAh / g, 345mAh / g, 350mAh / g, 355mAh / g, etc., or it can be a range of any two of the above values, such as 325mAh / g-345mAh / g, 330mAh / g-350mAh / g, etc.

[0103] In one embodiment, the powder compaction density of the graphite material at 20000N is 1.45g / cc-1.65g / cc.

[0104] By setting the compaction density of the graphite material as described above, it is beneficial to the electrical contact between graphite particles, forming a dense conductive network and accelerating the migration speed of lithium ions, thereby improving fast charging capability. The compaction density of the graphite material can be 1.45 g / cc, 1.50 g / cc, 1.55 g / cc, 1.60 g / cc, 1.65 g / cc, etc., or it can be a range of any two of the above values, such as 1.45 g / cc-1.60 g / cc, 1.50 g / cc-1.65 g / cc, etc.

[0105] Please see Figure 4 and Figure 5 , Figure 4 This is a schematic flowchart of the method for preparing a lithium-ion battery according to an embodiment of this application. Figure 5 yes Figure 4 The flowchart shown is a schematic diagram of the preparation method of graphite material in the method shown.

[0106] This application also provides a method for preparing a lithium-ion battery, which can be used to prepare the lithium-ion battery provided in the above embodiments. The method for preparing the lithium-ion battery provided in this application specifically includes:

[0107] Step S01: Stack the negative electrode, the separator, and the positive electrode in sequence to form a cell assembly.

[0108] Specifically, the steps for forming a battery cell assembly include: sequentially preparing a positive electrode sheet and a negative electrode sheet, alternately stacking the positive and negative electrode sheets, and setting a separator between the positive and negative electrode sheets to serve as an isolation, thereby obtaining a battery cell assembly. Alternatively, the battery cell assembly can be obtained by winding.

[0109] In this embodiment, the negative electrode sheet includes a current collector and a negative electrode film layer disposed on at least one side of the current collector. The negative electrode film layer includes a graphite material, and the method for preparing the graphite material includes:

[0110] Step S011: Provide coke fine powder, the volume median particle size Dv50 of the coke fine powder is 1μm-6μm.

[0111] Step S012: Compact the raw coke powder to form a compacted embryo.

[0112] Step S013: Crush the compact to form the first precursor.

[0113] Step S014: The first precursor is granulated using a binder to form the second precursor.

[0114] Step S015: Graphitize the second precursor to form a graphitized product.

[0115] Step S016: The graphitized product is coated with a coating agent to form a graphite material; 70% or more of the secondary particles of the graphite material are composed of three or more primary particles, and the primary particles are at least one of spherical or rod-shaped.

[0116] Step S02: Place the battery cell assembly in the housing.

[0117] Specifically, the housing is a component used to form an internal environment that can accommodate the battery cell assembly. The shape of the housing can be determined according to the specific shape and size of the battery cell assembly. The housing can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this.

[0118] Step S03: Inject electrolyte into the casing and seal it to form a lithium-ion battery.

[0119] Specifically, the internal environment formed by the casing also serves to contain the electrolyte, which affects the performance of the lithium-ion battery. The electrolyte provides a path for lithium ions to move between the positive and negative electrodes, promoting the charging and discharging process of the battery. The specific composition of the electrolyte is designed according to needs.

[0120] Electrolyte is injected into the casing and sealed to obtain a single battery cell. Multiple battery cells are integrated to form a battery module, which can provide higher voltage and capacity, and has specific output functions. The battery module is then installed in a battery housing, usually with the addition of a battery management system, to form a battery pack, which is typically provided to the user. Alternatively, multiple battery cells can be directly installed in a housing to form a battery pack.

[0121] Currently, graphite materials are mainly produced by crushing centimeter-sized coke into smaller aggregate particles to increase the end-to-base ratio and enriching lithium insertion / extraction channels through granulation to achieve rapid lithium insertion / extraction. However, existing crushing equipment requires high energy consumption and is costly to crush coke into smaller particles. This application's embodiment addresses this by compacting fine raw coke powder into compacts during graphite material preparation, and then crushing the compacts to form a first precursor. Using fine raw coke powder with a small median particle size as raw material facilitates the formation of a smaller-sized first precursor. Compacted compacts are easier to crush than larger-sized raw coke particles, resulting in lower energy consumption, higher yield, and reduced costs. The fine raw coke powder contains numerous light components, such as cycloalkanes and oxygen-containing compounds. These light components have strong binding properties, allowing the fine raw coke powder to bond together during compaction to form compacts, i.e., forming multi-oriented blocky materials. Crushing the compacts yields the multi-oriented first precursor. The volume median particle size Dv50 of the coke fine powder can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, etc., or it can be a range composed of any two of the above values, such as 2μm-6μm, 4μm-6μm, etc.

[0122] By using a first precursor with a small particle size for granulation and graphitization to form graphite materials, graphite materials with small particle size can be obtained. Maintaining the loose and porous surface of the graphite material with abundant lithium intercalation channels can provide more lithium ion transport paths, which helps the rapid diffusion and intercalation of lithium ions, thereby accelerating the charging process and improving fast charging performance.

[0123] In one embodiment, step S011, the step of providing coke fine powder specifically includes: pulverizing the coke to obtain coke powder and coke fine powder; the volume median particle size Dv50 of the coke powder is 7μm-17μm.

[0124] Raw coke can be either coal-based or oil-based. According to Jacob Bohr's Law (the broken vase theory), the material crushing process is uncontrollable, naturally resulting in both large and small particles. During the pulverization of raw coke, both large-particle-size raw coke powder and small-particle-size fine raw coke powder are naturally obtained. The larger-particle-size raw coke powder can be used as a raw material for preparing other substances, resulting in higher utilization of raw coke and reducing costs. Alternatively, it can be understood that the raw material for preparing other substances is raw coke powder with a Dv50 of 7μm-17μm. Raw coke powder is obtained by pulverizing raw coke, while fine raw coke powder is a byproduct. This byproduct is then used to prepare graphite materials, achieving the reuse of waste materials. The volume median particle size Dv50 of the raw coke powder can be 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, etc., or it can be a range composed of any two of the above values, such as 7μm-15μm, 7μm-10μm, etc.

[0125] Optionally, the mass percentage of fine coke powder obtained from coke pulverization is 20%-30%. The mass percentage of fine coke powder obtained from coke pulverization can be 20%, 22%, 24%, 26%, 28%, 30%, etc., or it can be a range of any two of the above values, such as 24%-30%, 22%-28%, etc.

[0126] In one embodiment, step S012, the step of compacting the coke powder, specifically includes: isostatic pressing the coke powder.

[0127] The isostatic pressing process applies high pressure uniformly from all directions, so that the coke powder is subjected to equal pressure in all directions. This is beneficial for obtaining a compact with uniform density, which in turn helps to maintain a narrow particle size distribution of the first precursor and helps to control the particle size distribution of the graphite material.

[0128] In one embodiment, the coke powder is compacted using a pressurizing device such as an isostatic press, a twin-screw extruder, or a powder molding machine to form a compact.

[0129] In one embodiment, the volume median particle size Dv50 of the first precursor is 6 μm-10 μm.

[0130] By setting the median volumetric particle size Dv50 of the first precursor as described above, and using smaller particle sizes through granulation, graphitization, and coating, the specific surface area of ​​the graphite material can be increased, thereby providing more active sites for lithium-ion intercalation. This also shortens the lithium-ion diffusion path, facilitating rapid lithium-ion transport. Simultaneously, a narrower and more uniform particle size distribution helps maintain effective contact between the electrolyte and the graphite material, promoting uniform lithium-ion intercalation and deintercalation, which is beneficial for improving battery performance. The median volumetric particle size Dv50 of the first precursor can be 6μm, 7μm, 8μm, 9μm, 10μm, or any range of two of these values, such as 6μm-8μm, 7μm-10μm, etc.

[0131] Existing crushing equipment crushes coke into aggregates with a particle size of 8μm-9μm and below, requiring high energy consumption and incurring high costs. Furthermore, the use of aggregates with a particle size of 8μm-9μm and below for subsequent granulation, graphitization, and coating processes is crucial. This application uses fine raw coke powder as raw material to obtain a first precursor with a Dv50 of 6μm-10μm. Using this smaller first precursor for subsequent granulation, graphitization, and coating processes results in relatively lower energy consumption and helps reduce costs.

[0132] In one embodiment, the volume median particle size Dv50 of the second precursor is 12 μm-16 μm.

[0133] By setting the above-mentioned volumetric median particle size Dv50 of the granulated second precursor, the specific surface area of ​​the graphite material can be increased, thereby providing more active sites for lithium-ion intercalation. It can also shorten the lithium-ion diffusion path, facilitating rapid lithium-ion transport. Simultaneously, a narrower and more uniform particle size distribution helps maintain effective contact between the electrolyte and the graphite material, promoting uniform lithium-ion intercalation and deintercalation, which is beneficial for improving battery performance. The volumetric median particle size Dv50 of the second precursor can be 12μm, 13μm, 14μm, 15μm, 16μm, or any range of two of the above values, such as 12μm-15μm, 14μm-16μm, etc.

[0134] In one embodiment, in step S014, the mass ratio of the adhesive to the first precursor is (1-2):10.

[0135] By setting the mass ratio of the binder to the first precursor as described above, the first precursors are fully bonded together to form a second precursor with a stable structure. The particle size distribution of the second precursor formed by granulation is relatively uniform, and the particle structure is stable.

[0136] By selecting the above-mentioned range for the mass ratio of binder to the first precursor, the amount of binder added is suitable, the bonding between the first precursors is relatively strong, and the bonding remains effective in subsequent cell manufacturing and cell application, which is beneficial to reducing lithium consumption. Furthermore, the particle size of the second precursor formed by the bonding of the first precursor is suitable, and the target particle size of 12μm-16μm can be controlled without depolymerization, reducing problems such as increased surface defects and surface side-reaction active sites caused by the depolymerization process. The mass ratio of binder to the first precursor can be 1:10, 1.1:10, 1.2:10, 1.3:10, 1.4:10, 1.5:10, 1.6:10, 1.7:10, 1.8:10, 1.9:10, 2:10, etc., or it can be a range of any two of the above values, such as 1:10-1.5:10, 1.3:10-2:10.

[0137] In one embodiment, in step S014, the adhesive includes at least one of asphalt and resin.

[0138] Asphalt and / or resins are viscous and maintain good adhesion at different temperatures, which helps the first precursor aggregate into particles and maintains structural stability during subsequent processing. Furthermore, asphalt is relatively inexpensive, contributing to lower overall manufacturing costs.

[0139] Optionally, in step S014, the softening point of the asphalt is 150℃-250℃, which is beneficial for forming particles with uniform particle size. The softening point temperature of the asphalt can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, etc., or it can be a range composed of any two of the above values, such as 150℃-210℃, 170℃-240℃, etc.

[0140] Optionally, in step S014, the granulation temperature is 500℃-700℃, which is beneficial for forming particles with uniform size. The granulation temperature can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, etc., or it can be a range composed of any two of the above values, such as 500℃-640℃, 540℃-680℃, etc.

[0141] In one embodiment, step S015, the step of graphitizing the second precursor specifically includes: graphitizing the second precursor at a temperature of 3000°C or higher, followed by sieving and demagnetization to form a graphitized product.

[0142] Optionally, sieving can be performed using 200 mesh + 325 mesh screens.

[0143] In one embodiment, in step S016, the mass ratio of graphitized product to coating agent is 100:(2-15).

[0144] With the above-mentioned mass ratio of graphitized product to coating agent, the additives in the coating agent are more suitable. While maintaining the porosity between graphite particles, the coating agent can form a coating layer on the particle surface, maintain the structural stability of the graphite material, and improve the transport dynamics of lithium ions on the graphite particle surface.

[0145] By selecting the above-mentioned range for the mass ratio of graphitized material to coating agent, the amount of coating agent added is appropriate, the amorphous carbon formed on the surface of graphitized material is appropriate, reducing the initial coulombic efficiency loss caused by excessive amorphous carbon, and the particle size of graphitized material is appropriate, allowing for disordered deagglomeration and reducing problems such as increased particle surface defects and increased surface side reaction active sites caused by deagglomeration introduced by graphitized material adhesion. In addition, the coating agent can form a uniform and continuous coating layer on the surface of graphite particles, which is beneficial to achieving high kinetics. The mass ratio of graphitized product to coating agent can be 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, 100:15, etc., or it can be a range between any two of the above values, such as 100:(3-10), 100:(5-15), etc.

[0146] In one embodiment, in step S016, the coating agent includes at least one of asphalt, liquid phase residue oil, and resin. The liquid phase residue oil has a residual carbon value of 15%.

[0147] By selecting the above materials as coating agents, amorphous carbon is formed after carbonization, which can effectively improve the surface conductive network of graphitized products, promote the rapid migration of lithium ions, and thus improve the fast charging performance of the battery.

[0148] Optionally, the resin includes phenolic resin.

[0149] Optionally, the residual carbon value of the liquid phase residue oil is 10%-20%. The residual carbon value of the liquid phase residue oil refers to the percentage of non-volatile solid carbon remaining after the residue oil is heated, evaporated, and cracked. The residual carbon value of the liquid phase residue oil can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., or it can be a range of any two of the above values, such as 13%-17%, 15%-20%, etc.

[0150] Optionally, the residual carbon value of the resin is 40%-50%. The residual carbon value of the resin refers to the percentage of non-volatile solid carbon remaining after the resin undergoes thermal decomposition. The residual carbon value of the resin can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, etc., or it can be a range of any two of the above values, such as 43%-48%, 42%-45%, etc.

[0151] Optionally, the asphalt includes at least one of solid-phase asphalt and liquid-phase asphalt. The residual carbon value of solid-phase asphalt is 30%-70%. The residual carbon value of solid-phase asphalt refers to the percentage of non-volatile solid carbon remaining after the solid-phase asphalt undergoes thermal decomposition. The residual carbon value of solid-phase asphalt can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., or it can be a range composed of any two of the above values, such as 30%-55%, 45%-65%, etc. The residual carbon value of liquid phase asphalt is 10%-20%. The residual carbon value of liquid phase asphalt refers to the percentage of non-volatile solid carbon remaining after the liquid phase asphalt undergoes thermal decomposition. The residual carbon value of liquid phase asphalt can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., or it can be a range of any two of the above values, such as 13%-17%, 15%-20%, etc.

[0152] In one embodiment, in step S016, the graphitized material is coated with a coating agent, and after carbonization, a high-kinetics graphite material is obtained. Optionally, the carbonization temperature is 1100℃-1200℃, and the carbonization time is 1h-4h. The carbonization temperature can be 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, etc., or it can be a range composed of any two of the above values, for example, 1120℃-1200℃, 1110℃-1180℃, etc. The carbonization time can be 1h, 2h, 3h, 4h, etc., or it can be a range composed of any two of the above values, for example, 1h-3h, 2h-4h, etc.

[0153] In one specific embodiment, the method for preparing graphite material includes:

[0154] 1) Raw coke is pulverized to obtain raw coke powder with Dv50 = 7μm-17μm and raw coke fine powder with Dv50 = 1μm-6μm.

[0155] 2) The coke powder is passed through a cold isostatic press to obtain a compact, which is then crushed to obtain the first precursor with Dv50 = 6μm-10μm.

[0156] 3) The first precursor is granulated using asphalt, wherein the ratio of asphalt to first precursor is 10-20:100, to obtain a second precursor with Dv50 = 12μm-16μm.

[0157] 4) The second precursor is graphitized at high temperature, and then screened and demagnetized to obtain the graphitized product.

[0158] 5) Mix the graphitized material with the coating agent, which can be asphalt, liquid residue oil, phenolic resin, etc. Here, liquid residue oil (with a residual carbon value of 15%) is selected. The ratio of graphitized material to coating agent is 100:2-15. After carbonization, a high-kinetic graphite material is obtained.

[0159] The lithium-ion batteries and their preparation methods disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices include the lithium-ion batteries provided in the above embodiments or the lithium-ion batteries prepared by the methods provided in the above embodiments. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0160] For ease of explanation, the following embodiments use a vehicle 1000 as an example of an electrical device according to an embodiment of this application. Please refer to... Figure 6 , Figure 6 This is a schematic diagram of the vehicle structure provided in an embodiment of this application.

[0161] Vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A lithium-ion battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The lithium-ion battery 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the lithium-ion battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during starting, navigation, and driving.

[0162] In some embodiments of this application, the lithium-ion battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0163] This application also investigates the performance of lithium-ion batteries prepared using the lithium-ion battery preparation method provided in the embodiments of this application.

[0164] The preparation process of Example 1 is as follows:

[0165] (1) Preparation of graphite materials:

[0166] (a) Raw coke was pulverized to obtain raw coke powder with Dv50 = 12 μm and raw coke fine powder with Dv50 = 3 μm.

[0167] (b) The coke powder from step (a) is passed through a cold isostatic press to obtain a compact, which is then crushed to obtain the first precursor with Dv50 = 8μm.

[0168] (c) The first precursor is granulated with asphalt, wherein the ratio of asphalt to first precursor is 1.5:10 (mass ratio), to obtain a second precursor with Dv50 = 15.2 μm.

[0169] (d) The second precursor was graphitized at 3000℃, sieved using a 200-mesh + 325-mesh sieve, and demagnetized to obtain the graphitized product.

[0170] (e) The graphitized material and the coating agent are mixed. The coating agent is liquid-phase pitch with a residual carbon rate of 15%. The ratio of graphitized material to coating agent is 100:6 (mass ratio). The mixture is carbonized at 1150°C for 2 hours to obtain a graphite material with high kinetics.

[0171] (2) Preparation of negative electrode sheet:

[0172] (a) Obtain a copper foil for the negative electrode current collector with a thickness of 8 μm.

[0173] (b) A negative electrode active material (graphite), a conductive agent (carbon black (Super P), a thickener (sodium carboxymethyl cellulose), and a binder (styrene-butadiene rubber) are mixed thoroughly in water at a weight percentage ratio of 96.4:1:1.2:1.4 to prepare a negative electrode active slurry. The negative electrode active slurry is then coated onto a copper foil current collector to form a negative electrode active material layer with a thickness of 75 μm.

[0174] (c) After drying and cold pressing, a negative electrode sheet is obtained.

[0175] (3) Preparation of positive electrode sheet:

[0176] (a) Obtain the positive current collector aluminum foil with a thickness of 13 μm.

[0177] (b) The positive electrode active material lithium iron phosphate, conductive agent carbon black, and binder polyvinylidene fluoride are dispersed in the dispersant N-methylpyrrolidone at a mass percentage ratio of 96:2:2 and stirred until homogeneous to prepare a positive electrode active slurry. The positive electrode active slurry is coated on both surfaces of the positive electrode current collector aluminum foil to form a positive electrode active material layer with a thickness of 90 μm.

[0178] (c) After drying and cold pressing, a negative electrode sheet is obtained.

[0179] (4) Preparation of electrolyte:

[0180] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0181] (5) Separating membrane:

[0182] A 12μm polyethylene film was used as the separator.

[0183] (6) Assembly:

[0184] The prepared negative electrode and positive electrode are stacked in sequence, with the separator placed between the positive and negative electrode to provide isolation. The cells are then wound to obtain a bare cell, which is then inserted into the battery casing. After drying, electrolyte is injected, and the lithium-ion battery (secondary battery) is obtained through vacuum sealing, settling, formation, and shaping processes.

[0185] It should be noted that the SEM image of the graphite material prepared in Example 1 is as follows: Figure 3 As shown.

[0186] The difference between Examples 2 to 5 and Example 1 is: the ratio of asphalt to the first precursor in the granulation step; and the ratio of graphitized product to coating agent in the coating step.

[0187] The differences between Examples 6 and 7 and Example 1 are: the particle size of the raw coke powder, the particle size of the fine raw coke powder, and the particle size of the first precursor are different. It should be noted that in the preparation process of graphite materials, step (b) may include classifying the fine raw coke powder from step (a) and using the classified fine raw coke powder to form a compact.

[0188] The difference between Example 8 and Example 1 is that step (3) of preparing the positive electrode sheet was not performed. Specifically, the negative electrode sheet was dried in a vacuum drying oven for later use; a lithium metal sheet was used as the counter electrode, and a 12μm polyethylene (PE) film was used as the separator. The electrolyte prepared above was assembled into a CR2430 coin cell in an argon-protected glove box.

[0189] The difference between Comparative Example 1 and Example 1 is that step (b) was not performed in the graphite material preparation process, and in step (c) the raw coke fine powder was granulated using pitch, that is, the first precursor in step (c) was replaced with raw coke fine powder.

[0190] The difference between Comparative Example 2 and Example 8 is that step (b) was not performed in the graphite material preparation process, and in step (c) the raw coke fine powder was granulated using pitch, that is, the first precursor in step (c) was replaced with raw coke fine powder.

[0191] The relevant parameter tests for each embodiment and comparative example are as follows:

[0192] 1. Specific surface area test.

[0193] Referring to GB / T 19587-2017, the nitrogen adsorption specific surface area was tested using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0194] 2. Dv50 test.

[0195] Particle size distribution can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0196] 3. Powder compaction density test at 20000N.

[0197] The test shall be performed in accordance with GB / T 24533-2009 using an electronic pressure testing machine (e.g., a UTM7305 electronic pressure testing machine). An exemplary test method is as follows: Weigh 1g of carbon material powder and add it to a mold with a bottom area of ​​1.327cm². Apply pressure to 2000kg (equivalent to 20000N), hold the pressure for 30s, then release the pressure and hold for 10s. Record and calculate the compacted density of the carbon material powder under 20000N pressure.

[0198] 4. First coulombic efficiency test of secondary battery.

[0199] The prepared secondary battery was formed at 45°C and charged at a constant current of 0.02C for 10 hours (the charging capacity C0 was recorded at this time). At 25°C, the secondary battery was discharged at a constant current of 0.2C to 2.0V, and the discharge capacity D0 was recorded. It was then charged at a constant current of 0.33C to 3.8V, followed by constant voltage charging to a current of 0.05C, and the charging capacity C1 was recorded. It was then discharged at a constant current of 0.33C to 2.5V, allowed to stand for 5 minutes, discharged at a constant current of 0.33C to 2.0V, and then discharged at a constant current of 0.1C to 2.0V, and the discharge capacity D1 was recorded. The initial coulombic efficiency (%) of the secondary battery = D1 / (C0-D0+C1).

[0200] 5. Fast charging performance test of secondary batteries (charging time).

[0201] At 25℃, the secondary battery was charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to a current of 0.05C. After resting for 5 minutes, the secondary battery was discharged at a constant current of 0.33C to 2.0V, and its actual capacity was recorded as C0. Then, the secondary battery was sequentially charged at constant currents of 0.5C0, 1.0C0, 1.5C0, 2.0C0, 3.0C0, 4.0C0, 5.0C0, 7.0C0, and 9.0C0 to 3.65V or 0V negative cutoff potential (whichever comes first). After each charge, it was discharged at 1C0 to 2.0V. The SOC (State of Charge) was recorded at different charging rates to 20%, 30%, ..., 80%. The negative electrode potential corresponding to the state of charge (SOC) is plotted, and the charging rate-negative electrode potential curves are drawn for different SOC states. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V under different SOC states is obtained. This charging rate is the charging window under that SOC state, denoted as C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC, respectively. The charging time T (assuming no lithium plating in the secondary battery) from 20%SOC to 80%SOC is calculated according to the formula (60 / C20%SOC+60 / C30%SOC+60 / C40%SOC+60 / C50%SOC+60 / C60%SOC+60 / C70%SOC+60 / C80%SOC)×10%, in minutes.

[0202] 6. Gram capacity test.

[0203] At 25°C, the prepared coin cell was first discharged to 0.005V with a constant current of 0.15mA, allowed to stand for 5 minutes, and then discharged to 0.005V with a constant current of 10μA. The first discharge capacity of the coin cell was recorded. After that, it was charged to 2.0V with a constant current of 0.3mA, and the first charge capacity of the coin cell was recorded. The ratio of the charge capacity to the sample mass is the material's specific capacity.

[0204] 7. Oil absorption value test

[0205] A certain mass of graphite material is placed in a mixing chamber, and paraffin oil is dripped into the material using a titrator. During the titration process, the rotor torque is tested simultaneously to obtain the torque-oil absorption curve. The oil absorption value corresponding to 70% of the maximum torque value is taken as the test value.

[0206] 8. OI value test

[0207] Graphite electrode sheets were prepared according to a formula in which graphite material (negative electrode active material), carbon black (Super P) (conductive agent), sodium carboxymethyl cellulose (thickener), and styrene-butadiene rubber (binder) were in a weight percentage ratio of 96.4:1:1.2:1.4, and pressed to a density of 1.45 g / cm³. 3 After compaction, X-ray diffraction analysis was performed with a 2Theta angle of 20° to 80° and a scanning rate of 4° / min to obtain the XRD curve of the material. The OI value was obtained by dividing the peak areas of the 004 crystal plane and the 110 crystal plane.

[0208]

[0209]

[0210] By comparing Examples 1 to 7 with Comparative Example 1, it can be seen that the graphite material prepared by the method provided in this application for preparing the graphite material to make the secondary battery is beneficial to improving fast charging performance, requiring a shorter charging time, and also beneficial to improving the battery's first efficiency.

[0211] By comparing Example 8 with Comparative Example 2, it can be seen that using the graphite material prepared by the method provided in this application to prepare coin cells is beneficial to improving the specific capacity and the performance of the battery.

[0212] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A lithium-ion battery, characterized in that, include: The battery includes a housing, a battery cell assembly disposed within the housing, and an electrolyte. The battery cell assembly is located in the electrolyte. The battery cell assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes graphite material, and 70% or more of the secondary particles of the graphite material are composed of three or more primary particles. The primary particles are at least spherical or rod-shaped.

2. The lithium-ion battery according to claim 1, characterized in that, The average particle size of the primary particles is 1μm-6μm.

3. The lithium-ion battery according to claim 1 or 2, characterized in that, The median volumetric particle size of the secondary particles is 10μm-20μm.

4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The OI value of the graphite material is less than or equal to 15.

5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The OI value of the graphite material is less than or equal to 10, and the OI value of the graphite material is greater than or equal to 2.

6. The lithium-ion battery according to any one of claims 1 to 5, characterized in that, The oil absorption value of the graphite material is greater than or equal to 55 ml / 100g, and the oil absorption value of the graphite material is less than or equal to 85 ml / 100g.

7. The lithium-ion battery according to any one of claims 1 to 6, characterized in that, The specific surface area of ​​the graphite material is 1.0 m². 2 / g-2.0m 2 / g.

8. The lithium-ion battery according to any one of claims 1 to 7, characterized in that, The initial delithiation capacity of the graphite material is 325 mAh / g-355 mAh / g.

9. The lithium-ion battery according to any one of claims 1 to 8, characterized in that, The powder compaction density of the graphite material at 20000N is 1.45g / cc-1.65g / cc.

10. A method for preparing a lithium-ion battery, characterized in that, include: A battery cell assembly is formed by sequentially stacking negative electrode plates, a separator, and positive electrode plates; The battery cell assembly is placed inside the housing; as well as An electrolyte is injected into the casing and sealed to form a lithium-ion battery; The negative electrode sheet includes a current collector and a negative electrode film layer disposed on at least one side of the current collector. The negative electrode film layer includes a graphite material, and the preparation method of the graphite material includes: Provide raw coke fine powder, wherein the volume median particle size of the raw coke fine powder is 1μm-6μm; The raw coke powder is compacted to form a compacted embryo; The compressed embryo is broken to form a first precursor; The first precursor is granulated using a binder to form the second precursor; The second precursor is graphitized to form a graphitized product; The graphitized product is coated with a coating agent to form the graphite material; 70% or more of the secondary particles of the graphite material are composed of three or more primary particles, and the primary particles are at least one of spherical or rod-shaped.

11. The method for preparing a lithium-ion battery according to claim 10, characterized in that, The step of providing raw coke powder specifically includes: The raw coke is pulverized to obtain raw coke powder and raw coke fine powder; the median particle size of the raw coke powder is 7μm-17μm.

12. The method for preparing a lithium-ion battery according to any one of claims 10 or 11, characterized in that, The median particle size of the first precursor is 6 μm-10 μm.

13. The method for preparing a lithium-ion battery according to any one of claims 10 to 12, characterized in that, The median particle size of the second precursor is 12 μm-16 μm.

14. The method for preparing a lithium-ion battery according to any one of claims 10 to 13, characterized in that, The mass ratio of the binder to the first precursor is (1-2):

10.

15. The method for preparing a lithium-ion battery according to any one of claims 10 to 14, characterized in that, The adhesive includes at least one of asphalt and resin.

16. The method for preparing a lithium-ion battery according to any one of claims 10 to 15, characterized in that, The mass ratio of the graphitized product to the coating agent is 100:(2-15).

17. The method for preparing a lithium-ion battery according to any one of claims 10 to 16, characterized in that, The coating agent includes at least one of asphalt, liquid phase residue oil, and resin.

18. An electrical appliance, characterized in that, The lithium-ion battery includes the lithium-ion battery as described in any one of claims 1 to 9 or the lithium-ion battery prepared by the method described in any one of claims 10 to 17.

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