Preparation method of negative electrode active material, negative electrode active material, battery cell and electrical equipment

Abstract

The present application discloses a method for preparing a negative electrode active material, a negative electrode active material, a battery cell, and an electrical device. The method comprises: subjecting a graphitized powder to an oxidation treatment to oxidize the surface of the graphitized powder. Oxidation of the surface of the graphitized powder effectively increases the adhesion, specific surface area, and compaction density of the negative electrode active material, thereby increasing the cohesion and compaction density of the negative electrode sheet.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for preparing a negative electrode active material, a negative electrode active material, a battery cell, and an electrical device. Background Art

[0002] At present, the research on negative electrode sheets mainly focuses on how to improve the capacity, charge rate, cycle performance, etc. of negative electrode active materials to improve the corresponding performance of negative electrode sheets. However, there is less research on how to improve the cohesion and compaction density of negative electrode sheets. The cohesion and compaction density of negative electrode sheets need to be improved. Summary of the Invention

[0003] In view of the above problems, the present application provides a method for preparing a negative electrode active material, a negative electrode active material, a battery cell and an electrical device, which can improve the adhesion, specific surface area and compaction density of the negative electrode active material, thereby improving the cohesion and compaction density of the negative electrode sheet.

[0004] The embodiment of the present application is implemented as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a negative electrode active material, comprising: subjecting a graphitized powder to an oxidation treatment so that the surface of the graphitized powder is oxidized.

[0006] In the technical solution of the embodiment of the present application, the graphitized powder is oxidized to improve the adhesion, specific surface area and compaction density of the negative electrode active material, thereby improving the cohesion and compaction density of the negative electrode sheet, which is beneficial to improving the energy density of the electrode assembly.

[0007] In some embodiments, the oxidation treatment includes heating by introducing a gas at a temperature of 600° C. to 900° C. In this embodiment, a suitable treatment temperature and a suitable degree of oxidation can effectively improve the adhesion, specific surface area, and compaction density of the negative electrode active material, thereby effectively improving the cohesion and compaction density of the negative electrode sheet.

[0008] In some embodiments, the heating temperature is 700° C. to 900° C. In this embodiment, the appropriate treatment temperature ensures a more appropriate degree of oxidation, which can significantly improve the adhesion, specific surface area, and compaction density of the negative electrode active material, thereby significantly and effectively improving the cohesion and compaction density of the negative electrode sheet.

[0009] In some embodiments, the graphitized powder is oxidized for a period of 20 to 200 minutes. In this embodiment, a suitable treatment time ensures a suitable degree of oxidation, effectively improving the adhesion, specific surface area, and compaction density of the negative electrode active material, thereby effectively improving the cohesion and compaction density of the negative electrode sheet.

[0010] In some embodiments, the graphitized powder is oxidized for 20 to 100 minutes. In this embodiment, with an appropriate treatment time, the bonding strength, specific surface area, and compaction density of the active material are significantly improved over time, thereby significantly improving the cohesion and compaction density of the negative electrode sheet.

[0011] In some embodiments, the graphitized powder is oxidized for 100 to 200 minutes. In this embodiment, a suitable treatment time and a suitable degree of oxidation can significantly improve the adhesion, specific surface area, and compaction density of the negative electrode active material, thereby significantly and effectively improving the cohesion and compaction density of the negative electrode sheet.

[0012] In some embodiments, the graphitized powder is oxidized in a ventilated heating device that is fed in a rotary manner. In this embodiment, the reaction device facilitates feeding, ventilation, and heating, and can achieve better oxidation.

[0013] In some embodiments, the oxidation treatment of the graphitized powder is performed in a rotary kiln. In this embodiment, the oxidation treatment in a rotary kiln is convenient to operate and easy to industrialize.

[0014] In some embodiments, the following conditions (a1) and / or (a2) are met: (a1) the rotary kiln has an inclination angle of 1° to 4°; (a2) the rotary kiln has a furnace tube speed of 2 rpm to 6 rpm. In this embodiment, the rotary kiln is operated at a suitable inclination angle and furnace tube speed to ensure a suitable material transport speed within the rotary kiln, thereby conveniently and effectively controlling the oxidation treatment time.

[0015] In some embodiments, the oxidation treatment of the graphitized powder is performed under an oxidizing gas atmosphere. In this embodiment, the oxidation treatment is performed under an oxidizing gas atmosphere to ensure that the graphitized powder can be well oxidized.

[0016] In some embodiments, the ventilation rate of the oxidizing gas is 1m 3 / h~9m 3 In this embodiment, during the oxidation treatment, an oxidizing gas is introduced at a suitable ventilation rate to ensure that the graphitized powder can be better oxidized.

[0017] In some embodiments, the dew point temperature of the oxidizing gas at a pressure of 0.55 MPa is -20° C. to -15° C. In this embodiment, the oxidizing gas has a suitable dew point temperature to ensure that the graphitized powder can be oxidized well.

[0018] In some embodiments, the oxidizing gas is one of air, oxygen, carbon dioxide, and water vapor. In this embodiment, different oxidizing gases can provide a suitable oxidizing atmosphere, which can effectively oxidize the graphitized powder.

[0019] In some embodiments, the graphitized powder is obtained by graphitizing specified raw materials, which include one or more of calcined needle coke, green needle coke, and petroleum coke. In this embodiment, the specified raw materials can better meet the performance requirements of the negative electrode active material, and the calcined needle coke also contributes to the negative electrode active material having a higher compaction density and capacity.

[0020] In some embodiments, the preparation process of the graphitized powder includes: crushing and shaping a specified raw material, followed by grading and screening to remove fine powder to obtain a precursor; granulating the precursor to obtain an intermediate; and graphitizing the intermediate. In this embodiment, the graphitized powder is prepared by crushing, screening, granulating, and then graphitizing, resulting in the graphitized powder having good mechanical and electrochemical properties.

[0021] In some embodiments, the following conditions (b1) and / or (b2) are met: (b1) the Dv50 of the precursor is 9 μm to 13 μm; (b2) the Dv50 of the intermediate is 15 μm to 20 μm. In this embodiment, the precursor has an appropriate particle size to ensure that subsequent graphitization and oxidation can proceed well.

[0022] In a second aspect, the present invention provides a negative electrode active material, which is prepared by the preparation method of the negative electrode active material of the above embodiment, and the negative electrode active material satisfies the following conditions (c1) and / or (c2); (c1) the specific surface area of ​​the negative electrode active material is ≥1.35m 3 / g; (c2) the compaction density of the negative electrode active material under a pressure of 50000N is ≥1.9g / cc.

[0023] In some embodiments, the negative electrode active material satisfies the following conditions (d1) and / or (d2): (d1) the specific surface area of ​​the negative electrode active material is ≥ 1.50 m 3 / g; (d2) the compaction density of the negative electrode active material under a pressure of 50000N is ≥1.95g / cc.

[0024] In a third aspect, an embodiment of the present application provides a battery cell comprising the negative electrode active material according to the above embodiment.

[0025] In a fourth aspect, an embodiment of the present application provides an electrical device comprising a battery cell as described in the above embodiment.

[0026] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0029] Figure 2 An exploded view of a battery provided in accordance with some embodiments of the present application;

[0030] Figure 3 An exploded view of a battery cell provided in some embodiments of the present application;

[0031] Figure 4 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0032] Figure 5 This is a process flow chart of a method for preparing negative electrode active materials provided in some embodiments of the present application.

[0033] icon:

[0034] 1000-vehicles;

[0035] 100-battery; 200-controller; 300-motor;

[0036] 10-box; 11-first part; 12-second part; 13-accommodation space;

[0037] 20 - battery cell; 21 - housing; 22 - electrode assembly; 23 - electrode terminal; 24 - pressure relief structure;

[0038] 211-housing; 212-cover; 213-sealed space;

[0039] 221 - positive electrode plate; 222 - negative electrode plate; 223 - separator. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0041] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0043] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0044] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0045] In the description of the embodiments of the present application, the technical term "and / or", such as "Feature 1 and / or Feature 2", refers to three situations: it can be "Feature 1" alone, "Feature 2" alone, or "Feature 1" plus "Feature 2".

[0046] In the description of the embodiments of the present application, unless otherwise specified, the “multiple” in “one or more” means two or more than two.

[0047] In the description of the embodiments of this application, unless otherwise specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on specific circumstances.

[0048] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0049] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the heights, lengths, widths, and other dimensions of the various components in the embodiments of this application, as well as the overall heights, lengths, widths, and other dimensions of the integrated device shown in the drawings are merely illustrative and do not constitute any limitation on this application.

[0050] Currently, in some studies, the performance of negative electrode sheets, electrode assemblies and battery cells is improved by modifying the graphite negative electrode active materials.

[0051] In some technical solutions, the capacity is increased by oxidizing and calcining the raw materials before carbonization; the material is hard-carbon coated to enable it to have high-rate charging capability; and defects are repaired through impregnation treatment to improve the material's cycle performance.

[0052] The current improvement process mainly studies how to improve the capacity, charge rate, cycle performance, etc. of the negative electrode active material to improve the corresponding performance of the negative electrode sheet, but there is less research on how to improve the cohesion and compaction density of the negative electrode sheet.

[0053] The applicant's research found that after the material is graphitized, the graphitized powder is subjected to a certain degree of oxidation treatment so that the surface of the graphitized powder is oxidized, which can effectively improve the adhesion, specific surface area and compaction density of the negative electrode active material, thereby improving the cohesion and compaction density of the negative electrode sheet.

[0054] Based on this, an embodiment of the present application proposes a method for preparing a negative electrode active material, in which the graphitized powder is oxidized so that the surface of the graphitized powder is oxidized, thereby effectively improving the adhesion, specific surface area and compaction density of the negative electrode active material.

[0055] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device in the embodiments of the present application.

[0056] See also Figure 1 , Figure 1A schematic structural diagram of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000. The battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000. For example, the battery 100 may serve as an operating power source for the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements for starting, navigating and driving the vehicle 1000.

[0057] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0058] In this application, a battery 100 refers to a single physical module that includes multiple battery cells 20 to provide higher voltage and capacity. It can be in the form of a battery pack, a battery module, etc. The battery 100 can include a housing 10 for enclosing the multiple battery cells 20. The housing 10 can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells 20.

[0059] See also Figure 2 , Figure 2 This is an exploded view of a battery 100 provided in some embodiments of the present application. The battery includes a housing 10 and a plurality of battery cells 20, which are housed within the housing 10. The housing 10 is used to house the battery cells 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space 13 for accommodating the battery cells 20. The second portion 12 can be a hollow structure with one end open, and the first portion 11 can be a plate-like structure. The first portion 11 overlaps the open side of the second portion 12 to form the housing 10 with the storage space 13. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12 to form the housing 10 with the storage space 13. Of course, the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0060] In the battery 100, multiple battery cells 20 can be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections among the multiple battery cells 20. Multiple battery cells 20 can be directly connected in series, in parallel, or in a hybrid configuration, and then the entire structure of the multiple battery cells 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can be first connected in series, in parallel, or in a hybrid configuration to form a module, which is then connected in series, in parallel, or in a hybrid configuration to form a complete structure housed within the housing 10. The battery 100 may also include other structures. For example, multiple battery cells 20 can be electrically connected via a busbar to enable parallel, series, or hybrid connection of the multiple battery cells 20.

[0061] The battery cell 20 is the smallest unit that makes up the battery pack. The battery cell 20 can be a secondary battery 100 or a primary battery 100; it can also be a lithium-sulfur battery 100, a sodium-ion battery 100, or a magnesium-ion battery 100, but is not limited thereto.

[0062] See also Figure 3 The battery cell 20 may include a housing 21 , an electrode assembly 22 and an electrolyte, and both the electrode assembly 22 and the electrolyte are contained in the housing 21 .

[0063] The outer shell 21 may include a shell 211 and a cover 212. The shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space 213 of the battery cell 20, wherein the formed sealed space 213 can be used to accommodate the electrode assembly 22, electrolyte and other components. The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211. Functional components such as electrode terminals 23 and pressure relief structures 24 can also be provided on the cover 212. A sealing ring can be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.

[0064] The shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell 211 and the cover 212 can be various, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance. A coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0065] See also Figure 4The electrode assembly 22 can be composed of a positive electrode sheet 221, a negative electrode sheet 222 and a separator 223. The battery cell 20 mainly relies on the movement of metal ions between the positive electrode sheet 221 and the negative electrode sheet 222 to work. The positive electrode sheet 221 includes a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector. The material of the positive electrode current collector can be aluminum, and the positive electrode active material in the positive electrode active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganese oxide, lithium-rich manganese-based materials, lithium sulfur and other materials. The negative electrode sheet 222 includes a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. The material of the negative electrode current collector can be copper, and the negative electrode active material in the negative electrode active material layer is prepared by the preparation method of the negative electrode active material provided in the embodiment of the present application. In addition, the electrode assembly 22 can be a winding structure or a laminated structure, and the embodiment of the present application is not limited to this.

[0066] Next, the preparation method of the negative electrode active material proposed in the examples of this application is described in detail.

[0067] See also Figure 5 In a first aspect, an embodiment of the present application provides a method for preparing a negative electrode active material, comprising: subjecting a graphitized powder to an oxidation treatment so that the surface of the graphitized powder is oxidized.

[0068] The graphitized powder refers to a powder obtained by graphitizing a negative electrode active material raw material, wherein the negative electrode active material raw material can be a natural graphite raw material or an artificial graphite raw material.

[0069] The oxidation treatment is carried out in a treatment device, treatment temperature, and treatment atmosphere that can achieve oxidation. The treatment temperature can be, for example, higher than room temperature and lower than the temperature at which graphite is oxidized to carbon monoxide or carbon dioxide; the treatment atmosphere can be, for example, air, oxygen, or other oxidizing gas atmospheres; the treatment device can be fed by, for example, at least one of rotation, rolling, spiral descent, vertical drop, and horizontal movement; the treatment device can be heated by, for example, at least one of arc heating, plasma heating, and resistance heating; and the specific form of the treatment device can be, for example, a roller kiln, a pusher kiln, a mesh belt kiln, a high sand kiln, and a rotary kiln.

[0070] In the technical solution of the embodiment of the present application, the graphitized powder is oxidized to improve the adhesion, specific surface area and compaction density of the negative electrode active material, thereby improving the cohesion and compaction density of the negative electrode plate 222, which is beneficial to improving the energy density of the electrode assembly 22.

[0071] In some embodiments, the oxidation treatment includes heating by introducing gas, and the heating temperature is 600°C to 900°C.

[0072] In this embodiment, with a suitable treatment temperature and ensuring a suitable oxidation degree, the adhesion, specific surface area and compaction density of the negative electrode active material can be effectively improved, thereby effectively improving the cohesion and compaction density of the negative electrode sheet 222.

[0073] In some embodiments, the heating temperature is 700°C to 900°C.

[0074] In this embodiment, a suitable treatment temperature is provided to ensure a more suitable oxidation degree, which can significantly improve the adhesion, specific surface area and compaction density of the negative electrode active material, thereby significantly and effectively improving the cohesion and compaction density of the negative electrode sheet 222 .

[0075] Based on the above embodiments, in the present application, the heating temperature of the oxidation treatment refers to the ambient temperature in the reaction chamber during the oxidation treatment, which is, for example but not limited to, any one of 600°C, 650°C, 700°C, 750°C, 800°C, 850°C and 900°C, or a range between any two of them.

[0076] In some embodiments, during the oxidation treatment of the graphitized powder, the treatment time is 20 minutes to 200 minutes.

[0077] In this embodiment, with a suitable treatment time and ensuring a suitable oxidation degree, the adhesion, specific surface area and compaction density of the negative electrode active material can be effectively improved, thereby effectively improving the cohesion and compaction density of the negative electrode sheet 222.

[0078] In some embodiments, during the oxidation treatment of the graphitized powder, the treatment time is 20 minutes to 100 minutes.

[0079] In this embodiment, with a suitable treatment time, as time increases, the adhesion, specific surface area and compaction density of the negative electrode active material are significantly improved, so that the cohesion and compaction density of the negative electrode sheet 222 are significantly improved.

[0080] In some embodiments, during the oxidation treatment of the graphitized powder, the treatment time is 100 min to 200 min.

[0081] In this embodiment, with a suitable treatment time and ensuring a suitable oxidation degree, the adhesion, specific surface area and compaction density of the negative electrode active material can be significantly improved, thereby significantly and effectively improving the cohesion and compaction density of the negative electrode sheet 222.

[0082] Based on the above embodiments, in the present application, the processing time of the oxidation treatment refers to the time that the graphitized powder stays in the highest temperature zone in the cavity, that is, if there is only one temperature zone in the cavity, then the time is the total time that the powder stays in the cavity; if the cavity is divided into multiple temperature zones, then the time is the time that the powder stays in the highest temperature zone, which may be, for example but not limited to, any one of 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, 190min and 200min, or a range value between any two of them.

[0083] In some embodiments, the process of oxidizing the graphitized powder is performed in a ventilated heating device that feeds the powder in a rotary manner.

[0084] In this embodiment, the reaction equipment is convenient for feeding, ventilation and heating, and can achieve oxidation well.

[0085] In some embodiments, the process of oxidizing the graphitized powder is performed in a rotary kiln.

[0086] In this embodiment, the oxidation treatment in the rotary kiln is easy to operate and can be easily industrialized.

[0087] In some embodiments, the following conditions (a1) and / or (a2) are satisfied: (a1) the inclination angle of the rotary kiln is 1° to 4°; (a2) the furnace tube speed of the rotary kiln is 2 r / min to 6 r / min.

[0088] In condition (a1), the inclination angle of the rotary kiln refers to the angle between the transverse central axis of the rotary kiln and the horizontal direction. The value of the inclination angle is, for example but not limited to, any one of 1°, 1.5°, 2°, 2.5°, 3°, 3.5° and 4°, or a range between any two of them.

[0089] In condition (a2), the furnace tube speed of the rotary kiln is, for example but not limited to, any one of 2 r / min, 2.5 r / min, 3 r / min, 3.5 r / min, 4 r / min, 4.5 r / min, 5 r / min, 5.5 r / min and 6 r / min, or a range between any two of them.

[0090] In this embodiment, the rotary kiln moves at a suitable inclination angle and furnace tube speed, so that the material has a suitable conveying speed in the rotary kiln, thereby conveniently and effectively controlling the processing time of the oxidation treatment.

[0091] In some embodiments, the process of subjecting the graphitized powder to oxidation treatment is performed under an oxidizing gas atmosphere.

[0092] In this embodiment, the oxidation treatment process is carried out in an oxidizing gas atmosphere to ensure that the graphitized powder can be well oxidized.

[0093] In some embodiments, the ventilation rate of the oxidizing gas is 1m 3 / h~9m 3 / h.

[0094] The ventilation rate of the oxidizing gas is, for example but not limited to, 1 m 3 / h、2m 3 / h、3m 3 / h、4m 3 / h、5m 3 / h、6m 3 / h、7m 3 / h、8m 3 / h and 9m 3 / h Any point value or any range between them.

[0095] In this embodiment, during the oxidation treatment process, an oxidizing gas is introduced at a suitable ventilation rate to ensure that the graphitized powder can be better oxidized.

[0096] In some embodiments, the dew point temperature of the oxidizing gas at a pressure of 0.55 MPa is -20°C to -15°C.

[0097] The dew point temperature may be, for example but not limited to, any one of -20°C, -19°C, -18°C, -17°C, -16°C and -15°C, or a range between any two of them.

[0098] In this embodiment, the oxidizing gas has a suitable dew point temperature, ensuring that the graphitized powder can be oxidized well.

[0099] In some embodiments, the oxidizing gas is one of air, oxygen, carbon dioxide, and water vapor.

[0100] In this embodiment, different oxidizing gases can provide a suitable oxidizing atmosphere, which can effectively oxidize the graphitized powder.

[0101] In some embodiments, the graphitized powder is obtained by graphitizing specified raw materials, and the specified raw materials include one or more of calcined needle coke, green needle coke, and petroleum coke.

[0102] Optionally, the designated raw material satisfies at least one of the following conditions: sulfur content ≤ 0.2%, further sulfur content ≤ 0.1%; ash content ≤ 0.2%, further ash content ≤ 0.1%; volatile matter content is 5% to 9%, further volatile matter content is 6% to 8%.

[0103] In this embodiment, the specified raw materials can better meet the performance requirements of the negative electrode active material, and the needle coke also has a higher energy density.

[0104] In some embodiments, the preparation process of graphitized powder includes: crushing and shaping the specified raw materials, and then classifying and screening out fine powder to obtain a precursor; then granulating the precursor to obtain an intermediate; and then graphitizing the intermediate.

[0105] In this embodiment, the graphitized powder is prepared by graphitizing after crushing, screening, and granulation, so that the graphitized powder has good mechanical and electrochemical properties.

[0106] In some embodiments, the following conditions (b1) and / or (b2) are satisfied: (b1) the Dv50 of the precursor is 9 μm to 13 μm; (b2) the Dv50 of the intermediate is 15 μm to 20 μm.

[0107] In the condition (b1), the Dv50 of the precursor is, for example but not limited to, any one of 9 μm, 10 μm, 11 μm, 12 μm and 13 μm, or a range between any two of them.

[0108] In the condition (b2), the Dv50 of the intermediate is, for example but not limited to, any one of 15 μm, 16 μm, 17 μm, 18 μm, 19 μm and 20 μm, or a range between any two of them.

[0109] In this embodiment, the precursor has a suitable particle size to ensure that subsequent graphitization and oxidation can be carried out well.

[0110] In a second aspect, the present invention provides a negative electrode active material, which is prepared by the preparation method of the negative electrode active material of the above embodiment, and the negative electrode active material satisfies the following conditions (c1) and / or (c2); (c1) the specific surface area of ​​the negative electrode active material is ≥1.35m 3 / g; (c2) the compaction density of the negative electrode active material under a pressure of 50000N is ≥1.9g / cc.

[0111] In some embodiments, the negative electrode active material satisfies the following conditions (d1) and / or (d2): (d1) the specific surface area of ​​the negative electrode active material is ≥ 1.50 m 3 / g; (d2) the compaction density of the negative electrode active material under a pressure of 50000N is ≥1.95g / cc.

[0112] In a third aspect, an embodiment of the present application provides a battery cell 20 comprising the negative electrode active material according to the above embodiment.

[0113] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising a battery cell 20 as described in the above embodiment.

[0114] According to some embodiments of the present application, a method for preparing a negative electrode active material is provided, comprising:

[0115] One or more of calcined needle coke, green needle coke and petroleum coke are used as designated raw materials, the designated raw materials are crushed and shaped, and then graded and sieved to remove fine powder to obtain a precursor with a Dv50 of 9μm to 13μm; the precursor is then granulated to obtain an intermediate with a Dv50 of 15μm to 20μm; and the intermediate is graphitized to obtain a graphitized powder.

[0116] In the rotary kiln with an inclination of 1° to 4°, the furnace tube speed is controlled at 2r / min to 6r / min. 3 / h~9m 3 An oxidizing gas with a dew point temperature of -20°C to -15°C at a pressure of 0.55 MPa is introduced at a ventilation volume of / h, and oxidation treatment is performed at a treatment temperature of 600°C to 900°C and a treatment time of 20min to 200min, so that the surface of the graphitized powder is slightly oxidized.

[0117] Some specific embodiments are listed below to better illustrate the present application.

[0118] 1. Preparation of negative electrode sheet

[0119] Preparation of negative electrode active materials:

[0120] S1: The specified raw materials are fed to the jaw crusher through a vibrating feeder for coarse crushing. The qualified materials are then sent to the mechanical mill for fine crushing, and the particles are shaped to make them round and graded to obtain a precursor with a Dv50 of 11μm.

[0121] S2: Add the precursor obtained in step S1 to a reactor, and add 10% of a binder pitch (Dv50 of 5 μm to 8 μm) relative to the weight of the precursor for granulation for granulation. The stirring speed is 1200 r / min, and the temperature is increased to 560°C at a rate of 10°C / min at room temperature. The temperature is then maintained for 8 hours, and granulation is performed until the Dv50 is 18 μm to obtain an intermediate.

[0122] S3: adding the intermediate obtained in step S2 into a graphitization furnace, heating to 3000° C. for graphitization treatment, and sieving with a 200-mesh sieve to remove fine powder to obtain a graphitized powder;

[0123] S4: The rotary kiln is heated to the treatment temperature. The furnace tube speed is determined according to the treatment time. The gas flow rate of the oxidizing atmosphere is 4m 3 / h. The graphitized powder obtained in step S3 is fed into the feed port and fed into the cavity at a constant speed via a rotary feeder. After micro-oxidation treatment within the cavity, the material cools and falls into a discharge bag through the discharge port, yielding the negative electrode active material.

[0124] Preparation of negative electrode sheet:

[0125] The negative electrode active material, conductive agent (Super P), binder (SBR), and thickener (CMC-Na) prepared above were mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96.2:0.8:1.8:1.2 to form a uniform negative electrode slurry. The negative electrode slurry was coated on the surface of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The compacted density of the negative electrode sheet is 1.65 g / cm 3 , with a surface density of 11.4 mg / cm 2 .

[0126] 2. Test Method

[0127] BET analysis of negative electrode active materials: A certain mass of carbon material sample (e.g., 1.5 to 3.5 g) is placed in a sample tube, dried, and degassed at 200°C for 2 hours. The sample is then placed in a Tristar II 3020 instrument analysis station for testing to determine the specific surface area of ​​the carbon material. The adsorption gas used during the test can be nitrogen, and the adsorption temperature can be 77 K (K represents the Kelvin temperature).

[0128] The compaction density of the negative electrode active material at a pressure of 50,000 N is as follows: Weigh 1 g of carbon material powder and add it to a bottom area of ​​1.327 cm 2 The mold was pressurized to 5000 kg (equivalent to 50000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the carbon material under a pressure of 50000 N was recorded and calculated.

[0129] Negative electrode cohesion:

[0130] Apply double-sided tape to both sides of a 2cm wide stainless steel plate. Evenly attach the electrode to be tested to the double-sided tape, ensuring a consistent length and width. Apply copper foil tape evenly to the electrode surface (ensuring a smooth, wrinkle-free surface after application), leaving a small section of copper foil tape attached to a piece of paper (aligning the copper foil and paper). Set the parameters of the tensile testing machine and place the electrode vertically in the center of the machine's slot, ensuring it is vertically aligned. Click Start Test on the computer to obtain the cohesion data.

[0131] Limit compression of negative electrode:

[0132] 1) Confirm that the appearance of the electrode before cold pressing is normal and the edge thinning of the coating area is normal.

[0133] 2) Calculate the target thickness (±0.003mm) after cold pressing based on the actual coating weight and compaction gradient of the electrode before cold pressing.

[0134] 3) Cold Press Density Window Verification: Adjust and set the left and right gaps and roller tonnage of the cold press according to the designed density. After adjusting the roller gap using the designed density, only the cold press pressure is adjusted to achieve the desired density. After cold pressing, the electrode must ensure that the thickness of the active material layer on both sides of the electrode is consistent (lateral consistency). When adjusting the consistency of the two sides of the electrode, it is necessary to adjust under low density conditions.

[0135] 4) You can first adjust the cold pressing pressure at a low speed. When it approaches the required cold pressing thickness value, increase the speed to a cold pressing speed of ≥35m / min, keep the machine running, and run at high speed for 1min~2min to confirm whether the appearance of the electrode is OK, whether there are edge overpressure, broken belts, sticking to the roller, wrinkles, etc., and take pictures to save; use a micrometer to measure the thickness of the electrode after cold pressing and record it; record the actual cold pressing parameters and fill in the form according to the attached document. The thickness of the electrode at low speed will be significantly different from that at high speed. The actual thickness of the electrode should be based on the thickness of the electrode after high cold pressing.

[0136] 5) Each time the cold pressing reaches a compaction, record the lateral thickness of the electrode within 2 minutes and take a photo with a camera; record the cold pressing pressure, electrode appearance, and cold pressing thickness corresponding to each compaction; pay attention to the appearance of the cold pressing roller and the electrode.

[0137] 6) Summarize the appearance photos of the electrode after cold pressing and the pressure vs. compaction data.

[0138] 3. Experimental conditions and test results

[0139] The main parameters of the preparation method of the negative electrode active material in each experimental group are shown in Table 1. The experimental method of the comparative example refers to the embodiment, and the differences are shown in Table 1.

[0140] Table 2 shows the performance test results of the negative electrode active materials prepared in each experimental group and the performance test results of the negative electrode sheets using the negative electrode active materials.

[0141] Table 1

[0142]

[0143]

[0144]

[0145] Table 2

[0146]

[0147]

[0148] According to Table 1 and Table 2, we can see that:

[0149] Compared with Comparative Examples 1 to 3, Examples 1 to 3 were subjected to micro-oxidation treatment after graphitization, so that the specific surface area and compaction density of the negative electrode active material were improved, and the cohesion and ultimate compaction of the negative electrode sheet were also improved.

[0150] Compared with Example 1 and Comparative Example 4, Example 1 performs micro-oxidation treatment after graphitization, and Comparative Example 4 performs micro-oxidation treatment before graphitization. The specific surface area and compaction density of the negative electrode active material of Example 1 are more significantly improved, and the cohesion and ultimate compaction of the negative electrode sheet prepared from the negative electrode active material of Example 1 are also more significantly improved.

[0151] Among Examples 1 and 4-8, Examples 1 and 5-7 have suitable treatment temperatures, and the specific surface area and compaction density of the negative electrode active material, as well as the cohesion and ultimate compaction of the negative electrode sheet, are all improved to a certain extent. Among them, when the treatment temperature is between 700°C and 900°C, the improvements in the specific surface area and compaction density of the negative electrode active material, as well as the cohesion and ultimate compaction of the negative electrode sheet, are more significant. In Example 4, the treatment temperature is relatively low, and the improvement in the specific surface area and compaction density of the negative electrode active material is not significant. In Example 8, the treatment temperature is relatively high, and while the temperature is increased compared to Example 7, the specific surface area and compaction density of the negative electrode active material are not effectively improved.

[0152] Among Examples 1 and 9-15, Examples 1 and 10-14 had appropriate treatment times, and the specific surface area and compaction density of the negative electrode active material, as well as the cohesion and ultimate compaction of the negative electrode sheet, were all improved to a certain extent. Specifically, when the treatment temperature was between 20 minutes and 100 minutes, the performance of these aspects improved significantly with increasing time; when the treatment temperature was between 100 minutes and 200 minutes, the performance of these aspects was improved even more significantly. In Example 10, the treatment time was relatively short, and the improvement in the specific surface area and compaction density of the negative electrode active material was not significant. In Example 15, the treatment time was relatively long, and compared with Example 14, the treatment time was increased, but the specific surface area and compaction density of the negative electrode active material actually decreased.

[0153] In Example 1 and Examples 16 to 18, oxidation treatment was performed under different oxidizing gas atmospheres, and the specific surface area and compaction density of the negative electrode active material as well as the cohesion and ultimate compaction of the negative electrode sheet were effectively improved.

[0154] Among Examples 1 and 19-20, Example 1 has an appropriate ventilation volume, and the specific surface area and compaction density of the negative electrode active material, as well as the cohesion and ultimate compaction of the negative electrode sheet are effectively improved; in Example 19, the ventilation volume is too small, and the improvement of the specific surface area and compaction density of the negative electrode active material is not obvious; in Example 20, the ventilation volume is too large, and compared with Example 1, the ventilation volume is increased, but the compaction density of the negative electrode active material is not effectively improved, and the specific surface area is reduced.

[0155] In Examples 1 and 21-24, and in Examples 1 and 22-23, the oxidizing gas had an appropriate dew point temperature, effectively improving the specific surface area and compaction density of the negative electrode active material, as well as the cohesion and ultimate compaction of the negative electrode sheet. In Example 21, the dew point temperature of the oxidizing gas was lower, meaning the air was drier. Compared to Example 1, the dew point temperature was lower, making the conditions more difficult to achieve, but the specific surface area and compaction density of the negative electrode active material were not effectively improved. In Example 21, the dew point temperature of the oxidizing gas was higher, meaning the air was more humid. Compared to Example 1, the dew point temperature was higher, which deepened the degree of oxidation of the negative electrode active material. While its specific surface area and compaction density were somewhat improved, the study found that its controllability was poor.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a negative electrode active material, characterized in that: include: performing an oxidation treatment on the graphitized powder so that the surface of the graphitized powder is oxidized; The oxidation treatment includes heating by introducing gas, wherein the heating temperature is 600° C. to 900° C.; The process of oxidizing the graphitized powder is carried out in a ventilated heating device that feeds the material in a rotary manner.

2. The method for preparing the negative electrode active material according to claim 1, wherein: The heating temperature is 700°C to 900°C.

3. The method for preparing the negative electrode active material according to claim 1 or 2, characterized in that: During the oxidation treatment of the graphitized powder, the treatment time is 20 minutes to 200 minutes.

4. The method for preparing the negative electrode active material according to claim 3, wherein: During the oxidation treatment of the graphitized powder, the treatment time is 20 minutes to 100 minutes.

5. The method for preparing the negative electrode active material according to claim 3, wherein: During the oxidation treatment of the graphitized powder, the treatment time is 100 minutes to 200 minutes.

6. The method for preparing the negative electrode active material according to claim 1 or 2, characterized in that: The process of oxidizing the graphitized powder is carried out in a rotary kiln.

7. The method for preparing the negative electrode active material according to claim 6, characterized in that: The following conditions (a1) and / or (a2) are met; (a1) The inclination angle of the rotary kiln is 1° to 4°; (a2) The furnace tube rotation speed of the rotary kiln is 2 r / min~6 r / min.

8. The method for preparing the negative electrode active material according to claim 1 or 2, characterized in that: The process of oxidizing the graphitized powder is carried out under an oxidizing gas atmosphere.

9. The method for preparing the negative electrode active material according to claim 8, characterized in that: The ventilation rate of the oxidizing gas is 1m3 / h~9m3 / h.

10. The method for preparing the negative electrode active material according to claim 9, characterized in that: The dew point temperature of the oxidizing gas at a pressure of 0.55 MPa is -20°C to -15°C.

11. The method for preparing the negative electrode active material according to claim 9, wherein: The oxidizing gas is one of air, oxygen, carbon dioxide and water vapor.

12. The method for preparing a negative electrode active material according to claim 1 or 2, characterized in that: The graphitized powder is obtained by graphitizing specified raw materials, and the specified raw materials include one or more of calcined needle coke, green needle coke and petroleum coke.

13. The method for preparing the negative electrode active material according to claim 12, characterized in that: The preparation process of the graphitized powder includes: crushing and shaping the specified raw materials, and then classifying and screening to remove fine powder to obtain a precursor; then granulating the precursor to obtain an intermediate; and then performing the graphitization treatment on the intermediate.

14. The method for preparing the negative electrode active material according to claim 13, characterized in that: The following conditions (b1) and / or (b2) are met; (b1) The Dv50 of the precursor is 9 μm to 13 μm; (b2) The Dv50 of the intermediate is 15 μm to 20 μm.

15. A negative electrode active material, characterized in that: Prepared by the method for preparing a negative electrode active material according to any one of claims 1 to 14, the negative electrode active material satisfies the following conditions (c1) and / or (c2); (c1) The specific surface area of ​​the negative electrode active material is ≥1.35 m 3 / g; (c2) The compaction density of the negative electrode active material under a pressure of 50,000 N is ≥1.9 g / cc.

16. The negative electrode active material according to claim 15, characterized in that The negative electrode active material satisfies the following conditions (d1) and / or (d2); (d1) The specific surface area of ​​the negative electrode active material is ≥1.50 m 3 / g; (d2) The compaction density of the negative electrode active material under a pressure of 50,000 N is ≥1.95 g / cc.

17. A battery cell, characterized in that: The negative electrode active material according to claim 15 or 16 is included.

18. An electrical device, characterized in that: Comprising the battery cell according to claim 17.

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