Negative electrode active material, negative electrode sheet, battery, and power consumption device

Abstract

This application relates to a negative electrode active material, a negative electrode sheet, a battery, and a power consumption device, wherein the negative electrode active material comprises artificial graphite particles and a carbon layer placed on the surface of at least a portion of the artificial graphite particles, and the volume average particle diameter D of the negative electrode active material v 50 is 3μm≦D v The volume distribution of the negative electrode active material satisfies 50 ≤ 7 μm, and particle size D v 1 is D v The value 1 ≤ 1.5 μm is satisfied.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to Chinese Patent Application No. 202311641387.4, filed on 30 November 2023, titled "Negative Electrode Active Material, Negative Electrode Sheet, Battery and Power Consumption Device," the entirety of which is incorporated herein by reference.

[0002] This application relates to a negative electrode active material, a negative electrode sheet, a battery, and a power consumption device. [Background technology]

[0003] Batteries have a wide range of applications due to their advantages, such as reliable performance, no pollution, and no memory effect. For example, as environmental protection issues become increasingly important, new energy vehicles are becoming more widespread, and the demand for power battery cells is exploding.

[0004] As the range of battery applications expands, the demands on battery performance have also become more stringent. In environments with low relative temperatures, batteries have poor rapid charging capabilities and typically require long charging times. [Overview of the project] [Problems that the invention aims to solve]

[0005] This application provides a negative electrode active material, a negative electrode sheet, a battery, and a power consumption device, and when the negative electrode active material is applied to a battery, it can improve the low-temperature rapid charging capability of the battery. [Means for solving the problem]

[0006] According to the first aspect, the present application proposes a negative electrode active material comprising artificial graphite particles and a carbon layer placed on the surface of at least a portion of the artificial graphite particles, wherein the volume average particle diameter D of the negative electrode active material v 50 satisfies 3μm ≤ Dv50 ≤ 7μm, and the volume distribution particle size D of the negative electrode active material. v 1 is D vIt satisfies 1≦1.5μm.

[0007] Thus, in the embodiments of the present application, D of the negative electrode active material v 50 and D v By adjusting 1, it is possible to simultaneously improve the diffusion ability of lithium ions in the negative electrode active material and the negative electrode film layer, reduce the side reaction between the negative electrode active material and the electrolyte, and is advantageous for significantly improving the charging ability under low temperature conditions.

[0008] In some embodiments, 0.8μm≦D v 1≦1.5μm, and optionally, 0.9μm≦D v 1≦1.3μm, and more optionally, 0.9μm≦D v 1≦1.0μm. The negative electrode active material can further adjust the proportion of fine powder by further adjusting the volume particle size distribution D v 1, and it is advantageous for the active material to contain an appropriate amount of fine powder and further improve the charging power under low temperature conditions.

[0009] In some embodiments, D v 99≦18μm, and optionally, 12μm≦D v 99≦18μm. By further selecting the volume particle size distribution D v 99, the low temperature charging performance of the battery cell can be further improved.

[0010] In some embodiments, the negative electrode active material contains primary particles, and the quantitative ratio of the primary particles in the negative electrode active material is ≧90%, and optionally, ≧95%. The particle size of the primary particles is small, which is advantageous for further shortening the movement path of lithium ions and improving the low temperature rapid charging ability of the battery cell.

[0011] In some embodiments, the gram capacity of the negative electrode active material is 330mAh / g~340mAh / g. The gram capacity of the negative electrode active material is relatively high, the energy density of the battery cell is high, and on the basis of high energy density, the negative electrode active material can also improve the rapid charging ability of the battery cell at the same time.

[0012] In some embodiments, the tap density of the negative electrode active material is 0.78 g / cm³. 3 ~1.2g / cm 3 Therefore, selectively, 0.9 g / cm³ 3 ~1.1g / cm 3 Therefore, by having the tap density of the negative electrode active material within the above range, good contact can be formed between particles in the negative electrode film layer, which is advantageous for improving the rapid charging capability of the battery cell, and the close deposition between particles can also improve the energy density of the battery cell.

[0013] In some embodiments, the degree of graphitization of the artificial graphite particles is 90% to 93%, and selectively, 91% to 93%. When the degree of graphitization of the artificial graphite particles is within the above range, it is possible to give the particle structure a large interlayer distance and low powder resistance, which can further improve the rapid charging capability of the battery cell.

[0014] In some embodiments, the average thickness of the carbon layer is ≥2 nm, and selectively between 2 nm and 20 nm. By coating the surface of the artificial graphite particles with a carbon layer, the low-temperature rapid charging performance of the battery cell can be further improved.

[0015] According to a second aspect, the present application proposes a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer installed on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material comprises the negative electrode active material described in any embodiment according to the first aspect of the present application.

[0016] According to a third aspect, the present application proposes a battery including a positive electrode sheet as described in any embodiment according to a second aspect of the present application.

[0017] According to a fourth aspect, the present application proposes a power consumption device including a battery as described in any embodiment according to a third aspect of the present application, the battery being used to provide electrical energy.

[0018] To more clearly illustrate the technical concept in the embodiments of this application, the drawings necessary for the embodiments of this application are briefly described below. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain further drawings based on these drawings without requiring any creative effort. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of one embodiment of the battery cell of this application. [Figure 2] Figure 1 is a schematic exploded view of an embodiment of the battery cell shown. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment of a power consumption device that includes the battery cell of this application as a power source. [Figure 7] This is a scanning electron microscope (SEM) image 1 of the negative electrode active material in Example 1 of this application. [Figure 8] This is a scanning electron microscope (SEM) image 2 of the negative electrode active material in Example 1 of this application. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments of the negative electrode active material, negative electrode sheet, battery cell, battery, and power consumption device of this application will be described and specifically disclosed with reference to the attached drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of substantially identical structures may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. The attached drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0021] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, the selected lower and upper limits define the boundary of a particular range. The range thus limited may or may not include the endpoints and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Furthermore, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all expected. In this application, unless otherwise stated, the numerical range “a-b” is an abbreviation representing any combination of real numbers from a to b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated representation of combinations of these numbers. Also, when a parameter is described as being an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0023] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0024] Unless otherwise specified, all steps S of this application may be performed sequentially or randomly, preferably in order. For example, if a method includes steps S(a) and (b), it means that the method may include steps S(a) and (b) performed sequentially, or steps S(b) and (a) performed sequentially. For example, if a method mentioned may further include step S(c), it means that step S(c) may be added to the method in any order, for example, the method may include steps S(a), (b), and (c), or steps S(a), (c), and (b), or steps S(c), (a), and (b), and so on.

[0025] A battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator. During charging and discharging of the battery cell, active ions are intercepted and released between the positive electrode sheet and the negative electrode sheet via the electrolyte. The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer installed on at least one side of the negative electrode current collector. The negative electrode active material contained in the negative electrode film layer is an important component of the battery cell, and active ions can be intercepted and released by the negative electrode active material.

[0026] Under low-temperature conditions, the conductivity of the electrolyte decreases, and the solid electrolyte interface (SEI) membrane impedance, charge transfer impedance, and diffusion impedance of active ions in the negative electrode sheet all increase, leading to enhanced polarization and consequently, poor low-temperature performance of the battery cell. The negative electrode sheet is a crucial element that constrains the low-temperature dynamic performance of the battery cell. To improve the low-temperature dynamic performance of the battery cell, methods such as improving the performance of the negative electrode film layer, for example, adjusting the thickness of the negative electrode film layer or reducing the compaction density of the negative electrode film layer, are usually considered. However, there are limitations to improving the dynamic performance of the battery cell during charging using these methods.

[0027] In view of the above problems, the embodiments of this application provide a negative electrode active material and adjust the particle size distribution of the negative electrode active material, specifically the volume average particle size D of the negative electrode active material. v 50 and D vBy adjusting 1, the kinetic performance can be significantly improved in both the initial and late stages of battery cell charging, enabling rapid charging of the battery cell. Then, the embodiments of this application will be described in detail.

[0028] Negative electrode active material

[0029] According to the first aspect, the embodiments of this application propose a negative electrode active material.

[0030] The negative electrode active material includes artificial graphite particles and a carbon layer disposed on at least a part of the surface of the artificial graphite particles. The volume average particle diameter D v 50 of the negative electrode active material satisfies 3 μm ≤ D v 50 ≤ 7 μm, and the volume particle size distribution D v 1 of the negative electrode active material satisfies D v 1 ≤ 1.5 μm.

[0031] When the negative electrode active material satisfies the above particle size distribution conditions, it is possible to achieve both improvement in rapid charging performance under low temperature conditions and improvement in high temperature cycle performance. The possible reasons are as follows: The charging of a battery cell is a process in which active ions, such as lithium ions and sodium ions, are released from the positive electrode active material and occluded in the negative electrode active material. In the battery industry, in order to reflect the capacity of the battery after charging, the "state of charge (abbreviated as SOC)" is often used. Its value is defined as the percentage of the current capacity in the capacity after the battery is fully charged, and the value range is 0 - 100%. When "SOC = 0", it means the battery is not charged. When "SOC = 100%", it means the battery is in a fully charged state. When "0 < SOC < 100%", it means the battery is charged and has a certain capacity but is not in a fully charged state. In the embodiments of this application, the initial stage of charging is defined as a low SOC state (≤ 30% SOC), and the late stage of charging is defined as a high SOC state (≥ 60% SOC).

[0032] At low temperatures, the diffusion rate of active ions, such as lithium ions, between graphite layers is slow, and the kinetic process of lithium ion intercalation in the negative electrode sheet is also slow. This slow kinetic process causes overpotentialing, which brings the actual potential of lithium intercalation in graphite closer to the lithium metal deposition potential. As a result, lithium deposition is more likely to occur during low-temperature charging, degrading the low-temperature charging performance of the battery cell.

[0033] Volume-average particle size D of the negative electrode active material v 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%, and is the volume-average particle size D of the negative electrode active material. v When 50 is 3 μm to 7 μm, the negative electrode active material has a small particle size, a large active area, and many active lithium storage sites, resulting in a large number of lithium ions diffusing to the surface of the negative electrode active material. This accelerates the reaction rate at the interface of the negative electrode active material, which is advantageous for improving the dynamic performance of the battery cell in the low SOC state, thereby improving its rapid charging capability. When the battery cell is in the high SOC state, the diffusion rate of lithium ions becomes a charging rate limiting step. A negative electrode active material with a small particle size can shorten the lithium storage pathway, increase the diffusion rate of lithium ions within the negative electrode active material, and reduce polarization, which is advantageous for the low-temperature performance of the battery cell. Therefore, in the embodiments of this application, the volume-average particle size D v By adjusting 50, the diffusion channels and diffusion rates on the surface and within the lithium ion negative electrode active material can be adjusted.

[0034] However, simply adjusting the diffusion capacity of lithium ions in the negative electrode active material is not sufficient to effectively improve the low-temperature charging performance of the battery; it is necessary to simultaneously adjust the diffusion capacity of lithium ions in the negative electrode film layer. Therefore, in the embodiments of this application, the D of the negative electrode active material v In addition to adjusting 50, further D v Simultaneously adjust 1 and the volume particle size distribution D of the negative electrode active material. v 1 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 1%, and D vBy adjusting 1, the proportion of fine powder in the negative electrode active material can be affected, D v By adjusting the particle size to 1 ≤ 1.5 μm, the negative electrode active material contains an appropriate amount of fine powder, which is advantageous for improving charging power under low-temperature conditions. Furthermore, the active surface of the negative electrode active material is not excessively exposed, reducing side reactions between the negative electrode active material and the electrolyte. In addition, the risk of aggregation of the negative electrode active material in the negative electrode film layer is low, which improves the porosity of the negative electrode film layer and is advantageous for the diffusion of lithium ions in the negative electrode film layer. In the embodiments of this application, fine powder refers to particles with a relatively small particle size.

[0035] Therefore, in the embodiments of this application, the negative electrode active material D v 50 and D v By adjusting parameter 1, the diffusion capacity of lithium ions in the negative electrode active material and the negative electrode film layer can be simultaneously improved, and side reactions between the negative electrode active material and the electrolyte can be reduced, which is advantageous for significantly improving charging capacity under low-temperature conditions.

[0036] In some embodiments, the volume particle size distribution D of the negative electrode active material v 99 is D v The condition 99 ≤ 18 μm is satisfied.

[0037] In the embodiments of this application, the negative electrode active material is D v 50 and D v In addition to adjusting 1, D v 99 can be further adjusted, and the volume particle size distribution D of the negative electrode active material v 99 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 99%, and D v By adjusting 99, the upper limit of the particle size of the negative electrode active material can be substantially adjusted, and the volume particle size distribution D of the negative electrode active material can be controlled. v 99 is D vBy satisfying the condition 99 ≤ 18 μm, the upper limit of the particle size of the negative electrode active material is small, and the difference in particle size between negative electrode active materials of different particle sizes is small, which improves the consistency of the degree of lithium absorption, further lowers the degree of polarization of the negative electrode sheet, and by adjusting the overall particle size of the negative electrode active material, a better pore distribution can be provided in the negative electrode film layer, and the diffusion rate of lithium ions in the negative electrode film layer can be accelerated, thereby improving the low-temperature charging performance of the battery cell. In the embodiment of this application, D v When the thickness is 99 ≤ 18 μm, the coating performance of the negative electrode slurry can be further improved, resulting in consistent performance of the negative electrode film layer formed by coating the negative electrode slurry. Furthermore, scratches are less likely to occur even when applied thinly, thus avoiding subsequent problems such as interface abnormalities and performance degradation caused by scratches.

[0038] In summary, in the embodiments of this application, the volume-average particle diameter D of the negative electrode active material is further specified. v 50, D v 1 and D v By simultaneously adjusting 99, the number of active sites on the surface of the negative electrode active material is increased, increasing the number of lithium ion diffusion channels. As the diffusion pathway for lithium ions becomes shorter, the diffusion rate is improved, the consistency of lithium storage between particles is improved, the degree of polarization of the negative electrode sheet is reduced, and the lithium ion diffusion capacity in the negative electrode film layer is improved. This significantly improves the dynamic performance of the battery cell both in the early and late stages of charging, and improves the low-temperature rapid charging capability of the battery cell.

[0039] Volume-average particle size D of the negative electrode active material v 50 is 3μm≦D v Satisfying 50 ≤ 7 μm, D v Specifically, 50 may be a range consisting of 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, or any two of the above values. Volume average particle diameter D v By further selecting 50, the low-temperature charging performance of the battery cells can be improved.

[0040] Volume particle size distribution D of negative electrode active material v 1 is D v Satisfying 1 ≤ 1.5 μm, D v Specifically, 1 may be a range consisting of 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any two of the above values. Selectively, 0.8 μm ≤ D v 1 ≤ 1.5 μm, and more selectively, 0.9 μm ≤ D v 1 ≤ 1.3 μm, and more selectively, 0.9 μm ≤ D v The particle size is 1 ≤ 1.0 μm. The negative electrode active material has a volume particle size distribution D v By further adjusting step 1, the proportion of fine powder can be further adjusted, which is advantageous for the active material to contain an appropriate amount of fine powder and for further improving charging power under low-temperature conditions.

[0041] Volume particle size distribution D of negative electrode active material v 99 is D v Satisfying 99 ≤ 18 μm, D v Specifically, 99 may be a range consisting of 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, or any two of the above values. Selectively, 12 μm ≤ D v The particle size is 99 ≤ 18 μm. Volume particle size distribution D v By further selecting 99, the low-temperature charging performance of the battery cells can be improved.

[0042] In some embodiments, the negative electrode active material includes primary particles.

[0043] Selectively, the quantity ratio of primary particles in the negative electrode active material is ≥90%, selectively ≥95%, selectively ≥98%, and selectively ≥99%. When the quantity ratio of primary particles in the negative electrode active material is 100%, it indicates that the negative electrode active material consists of primary particles. The small particle size of the primary particles is advantageous in further shortening the lithium ion migration path and improving the low-temperature rapid charging capability of the battery cell.

[0044] In some embodiments, the gram capacity of the negative electrode active material is 330 mAh / g to 340 mAh / g. A relatively high gram capacity of the negative electrode active material results in a high energy density of the battery cell, and on top of that high energy density, the negative electrode active material can also simultaneously improve the rapid charging capability of the battery cell.

[0045] For example, the gram capacity of the negative electrode active material may be in the range of 330 mAh / g, 331 mAh / g, 332 mAh / g, 333 mAh / g, 334 mAh / g, 335 mAh / g, 336 mAh / g, 337 mAh / g, 338 mAh / g, 339 mAh / g, 340 mAh / g, or any two of the above values.

[0046] In some embodiments, the tap density of the negative electrode active material is 0.78 g / cm³. 3 ~1.2g / cm 3 Therefore, selectively, 0.9 g / cm³ 3 ~1.1g / cm 3 Therefore, by having the tap density of the negative electrode active material within the above range, good contact can be formed between particles in the negative electrode film layer, which is advantageous for improving the rapid charging capability of the battery cell, and the close deposition between particles can also improve the energy density of the battery cell.

[0047] For example, the tap density of the negative electrode active material is 0.78 g / cm³. 3 , 0.8 g / cm³ 3 , 0.82 g / cm³ 3 , 0.85 g / cm³ 3 0.88 g / cm³ 3 , 0.9 g / cm³ 3 , 0.92 g / cm³3 0.95 g / cm³ 3 , 0.98 g / cm³ 3 , 1 g / cm³ 3 1.05 g / cm³ 3 , 1.10 g / cm³ 3 , 1.15 g / cm³ 3 , 1.2 g / cm³ 3 Alternatively, it may be a range consisting of any two of the above values.

[0048] In some embodiments, the degree of graphitization of the artificial graphite particles is 90% to 93%, and selectively, 91% to 93%. For example, the degree of graphitization of the artificial graphite particles is in the range of 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, or any two of the above values. When the degree of graphitization of the artificial graphite particles is within the above range, it is possible to give the particle structure a large interlayer distance and low powder resistance, which can further improve the rapid charging capability of the battery cell.

[0049] Artificial graphite particles are formed by heat-treating a carbon source at high temperatures. The arrangement of carbon atoms in the carbon source may be disordered, mainly consisting of an ordered arrangement in two-dimensional space, i.e., a chaotic layer structure. After high-temperature heat treatment, the arrangement changes from disordered or two-dimensional ordered to three-dimensional ordered, i.e., from amorphous carbon to graphite. The process of ordering the atomic arrangement is called the graphitization process, and the degree of ordering is called the degree of graphitization, which can be measured by X-ray diffraction.

[0050] At least a portion of the surface of the artificial graphite particles is coated with a carbon layer, which mainly contains amorphous carbon. Amorphous carbon refers to carbon material that is in an amorphous region that has not completely crystallized or is in an amorphous solid form. The crystal lattice structure of amorphous carbon tends to be disordered, while the crystal lattice structure of artificial graphite particles tends to be ordered, and can be observed and distinguished by transmission electron microscopy (TEM). By coating the surface of artificial graphite particles with a carbon layer, the low-temperature rapid charging performance of battery cells can be further improved.

[0051] In some embodiments, the coverage of the carbon layer on the surface of the artificial graphite particles is ≥50%, and selectively between 60% and 100%. When the coverage of the carbon layer on the surface of the artificial graphite particles is 100%, it may be understood that the carbon layer covers the entire surface of the artificial particles, and when the coverage of the carbon layer on the surface of the artificial graphite particles is <100%, it may be understood that the carbon layer covers a portion of the surface of the artificial particles.

[0052] In some embodiments, the average thickness of the carbon layer is ≥2 nm, and selectively between 2 nm and 20 nm, for example, 2 nm to 15 nm, 2 nm to 10 nm, or 5 nm to 10 nm.

[0053] In the embodiments of this application, the negative electrode active material is D v 99, D v 50, D v 1 may be detected using instruments and methods known in this field, for example, by taking a certain amount of negative electrode active material as a sample and using a Mastersizer2000E laser particle size analyzer according to the test standard GB / T19077-2016 to determine the volume average particle size D v 50. Volume particle size distribution D v 99 and volume particle size distribution D v Test 1, and here, D v 99 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 99%, and D v 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%, and D v 1 represents the particle size corresponding to the point when the cumulative volume distribution percentage of the negative electrode active material reaches 1%.

[0054] In the embodiments of this application, the manufactured negative electrode active material may be taken directly as a sample for detection, or a negative electrode sheet may be manufactured from the negative electrode active material, and the type of graphite material in the negative electrode active material may be observed by performing an ion milling cross-sectional morphology (CP) test on the negative electrode sheet. As an example, the test method may be as follows: First, the manufactured negative electrode sheet is cut into a test sample of a certain size (e.g., 2 cm x 2 cm), and the negative electrode sheet is fixed to the sample stage via paraffin wax. Then the sample stage is attached to the sample holder and securely locked in place, the power to the argon ion cross-sectional milling apparatus (e.g., IB-19500CP) is turned on, and a vacuum is created (e.g., 10 -4 Set the pressure (Pa), argon gas flow rate (e.g., 0.15 MPa), voltage (e.g., 8 KV), and milling time (e.g., 2 hours), adjust the sample stage to the oscillating mode, and start milling. For sample testing, refer to JY / T010-1996. A random area may be selected from the sample under test and scanned to obtain an ion milling cross-sectional morphology (CP) image of the negative electrode sheet under a certain magnification (e.g., 5000x).

[0055] In embodiments of this application, the structure of the negative electrode active material (e.g., artificial graphite particles and carbon layer) may be tested using instruments and methods known in the art. For example, the procedure may be carried out according to step S below: a microgrid of a specific diameter (e.g., 3 mm in diameter) is selected; the edge of the microgrid is grasped with pointed tweezers; the film surface (the surface where gloss is observed under lamp light is the film surface) is placed lightly flat on white filter paper with the film surface facing upwards; an appropriate amount of negative electrode active material sample (e.g., 1 g) is added to a beaker containing an appropriate amount of ethanol; ultrasonic vibration is performed for 10 to 30 minutes; the sample is drawn up with a glass capillary tube; 2 to 3 drops of the test sample are dropped onto the microgrid; after drying in an oven for 5 minutes, the microgrid with the test sample is placed on a sample stage; and a transmission electron microscope (e.g., Hitachi HF-3300SCs-corrected STEM) is used to test at a certain magnification (e.g., 60,000x) to obtain a transmission electron microscope (TEM) image of the test sample.

[0056] In the embodiments of this application, primary particles and secondary particles are both known in the art. Primary particles refer to particles in a non-aggregated state, while secondary particles refer to particles in an aggregated state formed by the aggregation of two or more primary particles. Primary and secondary particles can be easily distinguished by taking SEM images using a scanning electron microscope.

[0057] The quantity ratio of primary particles in the negative electrode active material may be tested by adopting methods known in the art. An exemplary testing method is as follows: The negative electrode active material is laid and adhered on a conductive adhesive to produce a test sample with a length×width = 6 cm×1.1 cm, and the particle morphology is tested using a scanning electron microscope (for example, ZEISS Sigma300). The test may refer to JY / T 010-1996. To ensure the accuracy of the test results, a plurality (for example, 5) of different regions may be randomly selected from the test sample for a scanning test, and under a certain magnification (for example, 1000 times), the percentage of the quantity of primary particles in each region in the total particle quantity is calculated, which is the quantity ratio of primary particles in the corresponding region, and the average value of the test results of multiple test regions is taken as the quantity ratio of primary particles in the negative electrode active material. To ensure the accuracy of the test results, a plurality of test samples (for example, 10) may be taken and the above test may be repeated, and the average value of each test sample is taken as the final test result.

[0058] In the embodiments of the present application, the graphitization degree of artificial graphite particles in the negative electrode active material has the meaning known in the art and may be tested by adopting methods known in the art. For example, an X-ray diffractometer (for example, Bruker D8 Discover) may be used, and the test may refer to JIS K0131-1996, JB / T 4220-2011, and the 002 size of d is measured, and the graphitization degree is calculated based on the formula G=(0.344 - d 002 ) / (0.344 - 0.3354)×100%, where d 002 is the interlayer distance in the graphite crystal structure represented in nanometers (nm). In the X-ray diffraction analysis test, a copper target may be adopted as the anode target, CuK α radiation may be used as the radiation source, the radiation wavelength λ = 1.5418 Å, the scanning 2θ angle range is 20° to 80°, and the scanning speed may be 4° / min.

[0059] In the embodiments of this application, the tap density of the negative electrode active material is as known in the art and may be tested using methods known in the art. For example, it may be measured using a powder tap density tester, referring to standard GB / T5162-2006. For example, a FZS4-4B tap density tester manufactured by Beijing Iron & Steel Research Institute was used, with test parameters of vibration frequency: 250 ± 15 times / min, amplitude: 3 ± 0.2 mm, number of vibrations: 5000 times, and graduated cylinder: 25 mL.

[0060] In the embodiments of this application, the gram capacity of the negative electrode active material is as known in the art and may be tested using methods known in the art. An exemplary test method is as follows: The manufactured negative electrode active material is uniformly mixed with the conductive agent carbon black (SuperP) and the binder polyvinylidene fluoride (PVDF) in the solvent N-methylpyrrolidone (NMP) in a mass ratio of 91.6:1.8:6.6 to produce a slurry. The produced slurry is applied to a copper foil current collector and dried in an oven before being prepared for use. A metallic lithium sheet is used as the counter electrode and a polyethylene (PE) film is used as the separator. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, where the concentration of LiPF6 is 1 mol / L. Assemble a CR2430 coin cell in a glove box protected by argon gas. After letting the resulting coin cell stand for 12 hours, discharge it at 25°C with a constant current of 0.05C down to 0.005V, let it stand for 10 minutes, discharge it again with a constant current of 50μA down to 0.005V, let it stand for 10 minutes, discharge it again with a constant current of 10μA down to 0.005V, and then charge it with a constant current of 0.1C down to 2V, and record the charge capacity. The ratio of the charge capacity to the mass of the negative electrode active material is the gram capacity of the manufactured negative electrode active material.

[0061] It should be explained that the various parameter tests for the negative electrode active material described above can be performed by taking a sample of the negative electrode active material directly, or by taking a sample from a battery cell.

[0062] When collecting the above test sample from a battery cell, as an example, the collection may be performed according to the following step S:

[0063] (1) Discharge the battery cell (usually, the battery is made to be in a fully discharged state for safety reasons), disassemble the battery to take out the negative electrode sheet, immerse the negative electrode sheet in dimethyl carbonate (DMC) for a certain period of time (for example, 2 to 10 hours), then take out the negative electrode sheet, and perform a drying treatment at a certain temperature and time (for example, 60 °C, 4 h), and take out the negative electrode sheet after drying.

[0064] (2) Bake the negative electrode sheet dried in step S(1) at a certain temperature and time (for example, 400 °C, 2 h), select an arbitrary area from the baked negative electrode sheet, and collect a sample from the negative electrode active material (the sample may be collected by scraping the powder with a blade).

[0065] (3) Sieve the negative electrode active material collected in step S(2) (for example, sieve it through a 200-mesh sieve) to finally obtain a negative electrode active material sample that can be used to test the above various material parameters of the present application.

[0066] Method for manufacturing negative electrode active material

[0067] According to a second aspect, an embodiment of the present application proposes a method for manufacturing a negative electrode active material.

[0068] The method includes step S100 of providing artificial graphite particles, and step S200 of coating the artificial graphite particles to form a carbon layer on at least a part of the surface of the artificial graphite particles to obtain a negative electrode active material, where the volume average particle diameter D v 50 of the negative electrode active material satisfies 3 μm ≤ D v 50 ≤ 7 μm, and the volume distribution particle diameter D v 1 of the negative electrode active material satisfies D v 1 ≤ 1.5 μm.

[0069] In some embodiments, step S100 specifically is: Step S110 provides coke raw materials, Step S120 involves shaping the coke raw material to obtain a precursor, The process may also include step S130, in which a precursor is graphitized to obtain artificial graphite particles.

[0070] In step S110, the coke raw material may be a commercially available product, or it may be obtained by crushing coke material.

[0071] In some embodiments, the coke material may be pulverized. The coke material may be pulverized using equipment and methods known in the art, such as a jet mill, a mechanical mill, or a roll mill. During the pulverization process, a large amount of particles that are too small are often produced, and in some cases, particles that are too large are also produced. Therefore, after pulverization, classification is performed as needed to remove the particles that are too small and too large from the pulverized powder. After classification, a coke raw material with a desired particle size distribution can be obtained. Classification may be performed using equipment and methods known in the art, such as a classifying sieve, a gravity classifier, or a centrifugal classifier.

[0072] The coke material grinding process may be carried out in a process unit including a grinder, a classifier, and an induced draft fan. During the grinding process, the feed frequency, grinding frequency, classification frequency, and induced draft fan frequency can be adjusted to obtain the D of the obtained coke material. v 50, D v 1 and D vThe frequency 99 can be adjusted to a desired range. Compared to conventional grinding processes where the classification frequency is low, the method of this application can improve the classification frequency, which is advantageous for removing particles that are too small. Compared to conventional grinding processes where the induced draft frequency is high, the method of this application can lower the induced draft frequency, which is advantageous for removing particles that are too large. Furthermore, compared to conventional grinding processes where the frequency is controlled over a wide range, the method of this application can also control the main motor frequency, classification frequency, and induced draft frequency over a narrow frequency range, thereby reducing the width of the particle size distribution of the coke raw material, for example, allowing the particle size of the coke raw material to be adjusted within a narrow range. In addition, the supply frequency can be adjusted simultaneously to control the supply amount, thereby further improving the grinding effect of the material.

[0073] In some embodiments, the coke raw material in step S110 may include one or more types of petroleum-based non-acinth coke and petroleum-based acinth coke. Selectively, the coke raw material includes raw petroleum coke.

[0074] In some embodiments, in step S120, the coke raw material may be shaped using equipment and methods known in the art, such as a shaping machine or other shaping equipment.

[0075] In some embodiments, the coke raw material is subjected to a shaping process followed by a classification process. Here, the classification process may be carried out using equipment and methods known in the art, such as a classifying sieve, gravity classifier, centrifugal classifier, etc.

[0076] The shaping and classification processes may be carried out in a process unit including a shaping machine, a classifier, and an induced draft fan. During the shaping and classification process, the particle size of the resulting precursor can be adjusted to a desired range by adjusting the shaping frequency (e.g., the main and auxiliary frequencies of the shaping machine), the classification frequency, and the induced draft fan frequency. Compared to conventional shaping and classification processes, the method of this application improves the shaping frequency during the process, appropriately extends the shaping time, and further reduces the classification frequency and induced draft fan frequency during the process, thereby adjusting the particle size of the resulting precursor to a target range.

[0077] In some embodiments, in step S130, the precursor is graphitized at a temperature of 2800°C to 3200°C to obtain artificial graphite having an appropriate degree of graphitization. Selectively, the temperature of the graphitization treatment may be 2900°C to 3100°C.

[0078] In step S130, graphitization may be carried out using equipment known in the art, such as a graphitization furnace, or more precisely, an Acheson graphitization furnace. After the graphitization process is complete, sieving can be used to remove small amounts of oversized particles that have formed by aggregation during the high-temperature graphitization process, and the final negative electrode active material D v 50, D v 1 and D v This is advantageous for adjusting 99 to a desired range.

[0079] In some embodiments, an organic carbon source is used in step S200 to coat the artificial graphite particles, and after heat treatment, an amorphous carbon layer is formed on at least a portion of the surface of the artificial graphite particles to obtain a negative electrode active material.

[0080] As an example, the artificial graphite obtained in step S130 may be mixed with an organic carbon source, at least a portion of the surface of the artificial graphite may be coated with the organic carbon source, and then the mixture may be heat-treated at a temperature of 700°C to 1800°C to carbonize the organic carbon source and form an amorphous carbon layer on at least a portion of the surface of the artificial graphite. Selectively, the heat treatment temperature is 1100°C to 1400°C, and the heat treatment time is 1 to 5 hours. Selectively, the mass ratio of artificial graphite to organic carbon source is 98:2 to 75:25.

[0081] In some embodiments, the organic carbon source may be selected from one or more of the following: pitch (e.g., coal pitch, petroleum pitch), phenol aldehyde resin, coconut shell, etc., and more preferably, pitch.

[0082] In the manufacturing process described above, the coke raw materials typically contain several impurity elements (e.g., iron, nickel, chromium, zinc, sulfur, silicon, etc.), and some impurity elements (e.g., iron, copper, etc.) are also introduced from the equipment used in the crushing and shaping processes. In most cases, the content of impurity elements in the core is trace, generally less than 1 ppm.

[0083] During the manufacturing process described above, trace amounts of impurity elements may be introduced into the coating layer from the organic carbon source used in the coating process and the equipment used for coating.

[0084] Negative electrode sheet

[0085] According to a third aspect, embodiments of the present application further provide a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and comprising a negative electrode active material, wherein the negative electrode active material comprises a negative electrode active material described in any embodiment according to the first aspect of the present application, or a negative electrode active material manufactured by the method described in any embodiment according to the second aspect of the present application. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode active material may further include at least one of natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials may include at least one of mono-tin, tin oxide, and tin alloy materials.

[0087] In some embodiments, the negative electrode film layer further selectively comprises a negative electrode conductive agent. In embodiments of this application, the type of negative electrode conductive agent is not particularly limited, and as an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent relative to the total weight of the negative electrode film layer is ≤5%.

[0088] In some embodiments, the negative electrode film layer further selectively comprises a negative electrode binder. In embodiments of this application, the type of negative electrode binder is not particularly limited, and for example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resins (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder relative to the total weight of the negative electrode film layer is ≤5%.

[0089] In some embodiments, the negative electrode film layer selectively further comprises other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives relative to the total weight of the negative electrode film layer is ≤2%.

[0090] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used for the metal foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0091] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a selective conductive agent, a selective binder, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0092] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of this application further includes a conductive undercoat layer (e.g., consisting of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and placed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet of the embodiments of this application further includes a protective layer that covers the surface of the negative electrode film layer.

[0093] battery cell

[0094] According to a fourth aspect, embodiments of the present application further provide a battery cell.

[0095] A battery cell, also known as a rechargeable battery or storage battery, is a type of battery that can be used continuously by recharging after it has discharged, thereby activating its active material. Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes while also allowing active ions to pass through.

[0096] In some embodiments, the battery cell includes a negative electrode sheet according to any embodiment of the third aspect of the embodiments of this application. This allows the battery cell of the embodiments of this application to effectively improve the low-temperature rapid charging capability of the battery cell.

[0097] [Positive electrode sheet]

[0098] The battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer installed on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0099] The positive electrode active material may include, but is not limited to, at least one of lithium-containing transition metal oxides, lithium-containing phosphates, and their modified compounds. Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one 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 modified compounds. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate-carbon composites, lithium manganese phosphate, lithium manganese phosphate-carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate-carbon composites, and their modified compounds.

[0100] In some embodiments, in order to further improve the energy density of the battery cell, the cathode active material for the lithium-ion battery may include at least one of lithium-containing transition metal oxides and their modified compounds having the general formula Li a Ni b Co c M d O e A f where 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M includes at least one of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes at least one of N, F, S and Cl.

[0101] For example, the cathode active material for the lithium-ion battery may include at least one of 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 0.80 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0102] In the embodiments of the present application, the modified compounds of the above cathode active materials may be those obtained by doping modification and / or surface coating modification of the cathode active materials.

[0103] Battery cells undergo the release, absorption, and consumption of active ions, such as Li, during charging and discharging, resulting in different molar Li content when discharged to different states. In the description of the positive electrode active material in the embodiments of this application, the molar Li content is that of the material in its initial state, i.e., before the material is introduced. As the positive electrode active material is applied in a battery system and charge-discharge cycles progress, the molar Li content may change.

[0104] In the enumeration of positive electrode active materials in the embodiments of this application, the molar content of oxygen (O) is merely a theoretical value, and the molar content of oxygen (O) changes due to oxygen release from the crystal lattice, so in reality, the molar content of oxygen (O) fluctuates.

[0105] In some embodiments, the mass percentage of the positive electrode active material relative to the total mass of the positive electrode film layer may be 85 wt% to 95 wt%. A positive electrode active material within this content range can provide the positive electrode sheet with high capacity and good cycle performance.

[0106] In some embodiments, the cathode film layer further optionally comprises a cathode conductive agent. In embodiments of this application, the type of cathode conductive agent is not particularly limited, and for example, the cathode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the cathode conductive agent relative to the total mass of the cathode film layer is ≤5%.

[0107] In some embodiments, the positive electrode film layer further optionally comprises a positive electrode binder. In embodiments of this application, the type of positive electrode binder is not particularly limited, and for example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resins. In some embodiments, the mass percentage of the positive electrode binder relative to the total mass of the positive electrode film layer is ≤5%.

[0108] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0109] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing a positive electrode active material, a selective conductive agent, a selective binder, and any other components in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP).

[0110] [Electrolyte]

[0111] In some embodiments, the battery cell further includes an electrolyte.

[0112] During charging and discharging of the battery cell, active ions are intercepted and released by moving back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in transporting the active ions between the positive electrode sheet and the negative electrode sheet. In the embodiments of this application, the type of electrolyte is not particularly limited and can be selected according to actual needs.

[0113] The electrolyte solution comprises an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0114] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0115] As an example, the solvent may include, but is not limited to, at least one of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate, methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), methylsulfonylmethane (MSM), ethyl methanesulfonate (EMS), and diethylsulfone (ESE).

[0116] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve some of the battery's performance characteristics, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature power performance.

[0117] [Separator]

[0118] In some embodiments, the battery cell further includes a separator. In embodiments of this application, the type of separator is not particularly limited, and any well-known porous separator having excellent chemical and mechanical stability can be selected.

[0119] In some embodiments, the separator material may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0120] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be manufactured into an electrode assembly via a winding process and / or a lamination process.

[0121] In some embodiments, the battery cell may include an outer casing. This casing may be used to package the electrode assembly and the electrolyte.

[0122] In some embodiments, the battery cell casing may be a rigid case such as a hard plastic case, an aluminum case, or a steel case. The battery cell casing may also be a soft pack, for example, a bag-type soft pack. The material of the soft pack may be at least one of plastics, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0123] In the embodiments of this application, the shape of the battery cell is not particularly limited and may be cylindrical, rectangular, or any other shape. Figure 1 shows a rectangular battery cell 5 as an example.

[0124] In some embodiments, as shown in Figure 2, the exterior may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates surrounding each other to form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The positive electrode sheet, negative electrode sheet and separator may form an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is packaged in the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted according to demand.

[0125] The method for manufacturing a battery cell according to the embodiments of this application is known. In some embodiments, a battery cell may be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly may be formed by winding and / or laminating processes on the positive electrode sheet, separator, and negative electrode sheet, the electrode assembly may be placed in an outer casing, the electrolyte may be injected after drying, and a battery cell may be obtained through processes such as vacuum packaging, standing, chemical conversion, and shaping.

[0126] In some embodiments of the present invention, the battery cells according to the present invention may be assembled to form a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0127] Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, the multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed together with fasteners.

[0128] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of battery cells 5 are housed.

[0129] In some embodiments, the battery modules may be further assembled to form a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack. Battery cells, battery modules, and battery packs may all be examples of batteries.

[0130] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed inside the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 being used to cover the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged inside the battery box in any manner.

[0131] power consumption equipment

[0132] According to a fifth aspect, embodiments of the present application provide a power consumption device comprising at least one of a battery cell, battery module, or battery pack according to embodiments of the present application. The battery cell, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0133] The power consumption device can select battery cells, battery modules, or battery packs according to its usage needs.

[0134] Figure 6 is a schematic diagram of an example power consumption device 6. This power consumption device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or battery module may be used to meet the high power and high energy density requirements of the power consumption device 6.

[0135] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are typically required to be lightweight and thin, and can use battery cells as their power source.

[0136] Examples

[0137] The following examples illustrate more specifically the content disclosed by the examples of this application, and these examples are merely illustrative, as various modifications and changes made within the scope of the content disclosed by the examples of this application will be obvious to those skilled in the art. Unless otherwise specified, all parts, percentages and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and all equipment used in the examples is commercially available.

[0138] Example 1: Manufacturing of a lithium-ion battery

[0139] 1. Manufacturing of negative electrode sheets

[0140] Manufacturing of negative electrode active material

[0141] Raw petroleum coke was crushed to obtain coke raw materials. The coke raw materials were then shaped and classified to obtain precursors.

[0142] The precursor was graphitized at a temperature of 3000°C and sieved to obtain artificial graphite. The artificial graphite was then coated with organic carbon source pitch and subjected to carbonization to obtain a negative electrode active material containing artificial graphite particles and a carbon layer located on at least some of the surfaces of the artificial graphite particles. The negative electrode active material consists of primary particles.

[0143] Manufacturing of negative electrode sheets

[0144] The negative electrode active material, the conductive agent carbon black (SuperP), the thickener sodium carboxymethylcellulose (CMC-Na), and the binder styrene-butadiene rubber (SBR) were thoroughly stirred and mixed in an appropriate amount of deionized water as a solvent in a weight ratio of 96.4:1:1.2:1.4 to form a uniform negative electrode slurry. This slurry was then uniformly applied to the surface of the copper foil of the negative electrode current collector, and after drying and cold pressing, a negative electrode sheet was obtained.

[0145] 2. Manufacturing of positive electrode sheets

[0146] Aluminum foil was used as the positive electrode current collector.

[0147] LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) were thoroughly stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone NMP in a weight ratio of 90:5:5 to form a uniform positive electrode slurry. This slurry was then uniformly applied to the surface of the aluminum foil of the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained.

[0148] 3. Separator

[0149] A porous polyethylene (PE) film was used as a separator.

[0150] 4. Preparation of the electrolyte

[0151] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent. Subsequently, lithium hexafluorophosphate, a lithium salt, was mixed with the electrolyte solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0152] 5. Manufacturing of battery cells

[0153] The positive electrode sheet, separator, and negative electrode sheet described above were sequentially stacked so that the separator was positioned between the positive and negative electrode sheets to act as an isolation layer, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer case, dried, and then injected with electrolyte. A lithium-ion battery was obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0154] Comparative Example 1 and Comparative Example 2

[0155] A lithium-ion battery was manufactured in the same manner as in Example 1, but the difference from Example 1 was that the particle size of the negative electrode active material, particularly D, was different in Comparative Example 1. v The difference was that the value 50 was adjusted.

[0156] Examples 2-1 to 2-8

[0157] A lithium-ion battery was manufactured using the same method as in Example 1, but it differed from Example 1 in that the particle size of the negative electrode active material was adjusted in Examples 2-1 to 2-3.

[0158] Examples 3-1 to 3-5

[0159] A lithium-ion battery was manufactured using the same method as in Example 1, but it differed from Example 1 in that the tap density of the negative electrode active material and other parameters were adjusted in Examples 3-1 to 3-5.

[0160] Examples 4-1 to 4-3

[0161] A lithium-ion battery was manufactured using the same method as in Example 1, but it differed from Example 1 in that the degree of graphitization of the artificial graphite particles in the negative electrode active material was adjusted in Examples 4-1 to 4-3.

[0162] Examples 5-1 to 5-2

[0163] A lithium-ion battery was manufactured using the same method as in Example 1, but it differed from Example 1 in that the average thickness of the carbon layer of the negative electrode active material was adjusted in Examples 5-1 to 5-2.

[0164] The relevant parameters for the examples and comparative examples are shown in Table 1 below.

[0165] Performance testing

[0166] 1. Performance testing of lithium-ion batteries

[0167] At -10°C, the lithium-ion batteries manufactured in the examples and comparative examples were adjusted to 80% SOC, charged at 20C for 5s, discharged at 20C for 5s, and repeated 500 cycles. After that, the lithium-ion batteries were fully charged at 0.33C at room temperature and then disassembled, and the lithium deposition state on the negative electrode sheet surface was observed. Here, if the lithium deposition area on the negative electrode sheet surface was less than 5%, it was described as mild lithium deposition; if the lithium deposition area was between 5% and 40%, it was considered moderate lithium deposition; and if the lithium deposition area was greater than 40%, it was considered severe lithium deposition.

[0168] Test results

[0169] The test results are shown in Table 1.

[0170] [Table 1]

[0171] As can be seen from Table 1, the D of the negative electrode active material in Comparative Example 1 v 50 and D vBoth values ​​were large, and under low-temperature conditions, the polarization of the battery increased, the active specific surface area of ​​the negative electrode interface reaction decreased, and lithium ions transported to the surface of the negative electrode sheet could not participate in the interface reaction in a timely manner, leading to lithium deposition at the interface. v Because the value of 50 is large, the transport distance of lithium ions increases in high SOC states, and the low-temperature charging capability deteriorates.

[0172] In Comparative Example 2, D v 1 is large, the fine powder content in the negative electrode active material is small, which is unfavorable for the rapid transport of lithium ions and electrons in the high SOC state, whereas D v If 99 is too large, the consistency of lithium absorption in the particles becomes relatively poor, which tends to intensify the polarization phenomenon and is unfavorable for rapid charging of the battery cell.

[0173] Compared with Comparative Examples 1 and 2, Figures 7 and 8 together show that in the embodiment of this application, the negative electrode active material D v 99, D v 50 and D v By adjusting 1 to an appropriate range, the diffusion rate of lithium ions can be improved, as can the consistency of lithium storage, thereby improving the low-temperature rapid charging performance of the battery cell.

[0174] While exemplary embodiments are shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on this application, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of this application. [Explanation of Symbols]

[0175] The explanation of the symbols is as follows: 1 Battery pack 2 Upper cabinet 3 Lower cabinet 4 Battery Modules 5 battery cells 51 cases 52 Electrode Assembly 53 Cover Plate 6. Electricity Consumption Devices

Claims

1. A negative electrode active material comprising artificial graphite particles and a carbon layer placed on the surface of at least a portion of the artificial graphite particles, Volume-average particle size D of the negative electrode active material ｖ 50 is 3 μm ≤ D ｖ Satisfying the condition 50 ≤ 7 μm, Volume distribution particle size D of the negative electrode active material ｖ 1 is D ｖ A negative electrode active material that satisfies the condition 1 ≤ 1.5 μm.

2. 0.8 μm ≤ D ｖ 1 ≤ 1.5 μm, and selectively, 0.9 μm ≤ D ｖ 1 ≤ 1.3 μm, and more selectively, 0.9 μm ≤ D ｖ The negative electrode active material according to claim 1, wherein the size is 1 ≤ 1.0 μm.

3. D ｖ 99 ≤ D ≤ 18 μm, and optionally, 12 μm ≤ D ｖ The negative electrode active material according to claim 1 or 2, wherein 99 ≤ D ≤ 18 μm.

4. The negative electrode active material according to any one of claims 1 to 3, wherein the negative electrode active material includes primary particles, and the quantitative ratio of the primary particles in the negative electrode active material is ≥90%, and selectively ≥95%.

5. The gram capacity of the negative electrode active material is 330 mAh / g to 340 mAh / g, and / or The tap density of the negative electrode active material is 0.78 g / cm³. ３ ~1.2 g / cm ３ The negative electrode active material according to any one of claims 1 to 4.

6. The negative electrode active material according to any one of claims 1 to 5, wherein the degree of graphitization of the artificial graphite particles is 90% to 93%, and selectively 91% to 93%.

7. The negative electrode active material according to any one of claims 1 to 6, wherein the average thickness of the carbon layer is ≥ 2 nm, and selectively between 2 nm and 20 nm.

8. A negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer installed on at least one surface of the negative electrode current collector and containing a negative electrode active material, wherein the negative electrode active material comprises the negative electrode active material described in any one of claims 1 to 7.

9. A battery comprising the negative electrode sheet described in claim 8.

10. A power consumption device including the battery described in claim 9.

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