Negative electrode active material and method for producing the same, negative electrode sheet, lithium ion battery, and power consumption device

Abstract

This application discloses a negative electrode active material and a method for manufacturing the same, a negative electrode sheet, a lithium-ion battery, and a power consumption device. The lithium-ion battery includes one or more battery cells including a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector and including a negative electrode active material. The negative electrode active material includes a core including graphite and a coating layer located on at least a portion of the surface of the core and including a hard carbon. The negative electrode active material has an R50 of 0.15 to 0.40, which is the R value at which 50% of the cumulative distribution from the lower limit is obtained using a laser confocal Raman microscope in area scanning mode. The negative electrode active material provided herein enables batteries to combine high energy density with good dynamic and cycle characteristics.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese Patent Application No. 202410129306.0, filed on January 30, 2024, for "Negative electrode active material and manufacturing method thereof, as well as negative electrode sheet, battery, and power consumption device containing the same," the entire contents of which are incorporated herein by reference. [Technical Field]

[0002] The present application relates to a negative electrode active material and a method for producing the same, a negative electrode sheet, a lithium ion battery, and a power consuming device. [Background technology]

[0003] As the application fields of batteries continue to expand, the requirements for fast charging of batteries are becoming increasingly higher. The anode is a key component of a battery, and its performance affects the overall performance of the battery. Currently, graphite is the commonly used anode active material, but its fast charging performance is not excellent. For this reason, fast charging anode active materials such as fast charging hard carbon have been developed. Batteries constructed from fast charging hard carbon have low energy density and insufficient cycle life, limiting their practical use. Therefore, while batteries have high energy density, how to improve fast charging performance and cycle characteristics remains a challenge in battery development. The above description is intended only to provide background information related to the present application and does not necessarily constitute prior art. Summary of the Invention

[0004] The present application provides a negative electrode active material that can provide a battery with high energy density, good dynamic characteristics, and good cycle characteristics, a method for manufacturing the same, a negative electrode sheet, a lithium ion battery, and a power consumption device.

[0005] In a first aspect, the present application provides a lithium-ion battery including one or more battery cells including a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector and including a negative electrode active material, the negative electrode active material including a core including graphite and a coating layer located on at least a portion of the surface of the core and including hard carbon, wherein the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit reaches 50%, in a cumulative distribution curve of R values ​​obtained using a laser microscopic confocal Raman spectroscopy in an area scanning mode.

[0006] The R value of a negative electrode active material can characterize the degree of defects and disorder in the negative electrode active material. When the R value R50, at which the cumulative distribution of the negative electrode active material is 50%, is 0.15 to 0.40, not only can the charge exchange ability of ions on the surface of the negative electrode active material be improved, but also side reactions on the surface of the negative electrode active material particles can be reduced. Therefore, the negative electrode active material provided by the embodiments of the present application can enable batteries to have both high energy density and good dynamic and cycle characteristics.

[0007] In some embodiments, the R value R50 at which the cumulative distribution of the negative electrode active material is 50% is 0.20 to 0.30, which allows the battery to have a high energy density, good dynamic characteristics, and good cycle characteristics.

[0008] In some embodiments, the proportion of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the cores is 50% is 10% or less.Optionally, the proportion of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the cores is 50% is 6% or less.

[0009] The smaller this value, the smaller the degree of uncoated area of ​​the negative electrode active material, the more isotropic the negative electrode active material is, and the more active sites there are in the negative electrode active material, which increases the ionic charge exchange capacity on the surface of the negative electrode active material, thereby further improving the dynamic properties of the negative electrode active material and the battery. In addition, the smaller the degree of uncoated area of ​​the negative electrode active material, the more the co-intercalation phenomenon of the electrolyte solvent during cycling can be reduced, and the battery can have better cycling properties.

[0010] In some embodiments, the R value R50 of the core at which the cumulative distribution reaches 50% is smaller than the R value R50 of the coating layer at which the cumulative distribution reaches 50%.

[0011] When the coating layer of the negative electrode active material has a large R50 (50% cumulative distribution) and high disorder, the negative electrode active material and the battery can have good dynamic properties. When the core of the negative electrode active material has a small R50 (50% cumulative distribution) and low disorder, the negative electrode active material as a whole can have a high specific capacity, and the battery can have a high energy density.

[0012] In some embodiments, the coating layer has an R value R50 of 0.9 to 1.4, where the cumulative distribution of the coating layer is 50%. When the R value R50 of the coating layer is within the above range, the coating layer itself has good dynamic properties, which can improve the dynamic properties of the negative electrode active material and the battery. Furthermore, the negative electrode active material can have a small specific surface area, which can reduce side reactions in the battery and provide the battery with good cycle characteristics.

[0013] In some embodiments, the R value R50 at which the cumulative distribution of the core is 50% is 0.06 to 0.13. When the R value R50 at which the cumulative distribution of the core is 50% is within the above range, the battery can have both high energy density and good dynamic characteristics.

[0014] In some embodiments, the mass of the coating layer is 0.3% to 4.5% of the mass of the core, and optionally 1% to 3.2%, which is advantageous for the battery to have high energy density, good dynamic properties, and long cycle life.

[0015] In some embodiments, the difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core is 1 μm to 5.5 μm, and optionally 1.5 μm to 4.2 μm. When the difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core is within this range, not only can the charge exchange ability of ions on the surface of the negative electrode active material be improved, but side reactions on the surface of the negative electrode active material particles can be reduced, and the negative electrode active material can have a high specific capacity, which is advantageous for batteries to have high energy density, good dynamic characteristics, and long cycle life.

[0016] In some embodiments, the negative electrode active material has a volumetric particle size distribution Dv50 of 8 μm to 25 μm, and optionally 12 μm to 17 μm. When the volumetric particle size distribution Dv50 of the negative electrode active material is within this range, lithium ions can have good solid-state conductivity within the negative electrode active material particles, and the negative electrode active material can have a small specific surface area, which is advantageous for batteries to have both good cycle characteristics and dynamic characteristics. When the volumetric particle size distribution Dv50 of the negative electrode active material is within this range, the negative electrode paste can also have good dispersibility.

[0017] In some embodiments, the graphite is synthetic graphite. The core comprises synthetic graphite, which allows the battery to have high energy density and good cycling characteristics.

[0018] In some embodiments, the graphite is in the form of secondary particles. When the graphite is in the form of secondary particles, the degree of isotropy of the graphite is increased, which is favorable for rapid intercalation of lithium ions, thereby helping the battery to have good dynamic properties and further improving the specific capacity of the negative electrode active material and the energy density of the battery.

[0019] In some embodiments, the graphite has an intensity ratio C(004) / C(110) of the 004 plane diffraction peak to the 110 plane diffraction peak, measured by X-ray diffraction, of 5.5 to 6.5.

[0020] In some embodiments, the specific capacity of the negative electrode active material is 354 mAh / g to 361 mAh / g.

[0021] In some embodiments, the negative electrode active material has a green density of 1.68 g / cm at a pressure of 20,000 N. 3 ~1.78g / cm 3 is.

[0022] In some embodiments, the specific surface area of ​​the negative electrode active material is 1.5 m 2 / g~4.5m 2 / g.

[0023] In some embodiments, the negative electrode layer includes a first negative electrode layer and a second negative electrode layer located between the first negative electrode layer and the negative electrode current collector, the thickness of the first negative electrode layer is 30% to 60% of the thickness of the negative electrode layer, the first negative electrode layer includes a first negative electrode active material, and the second negative electrode layer includes a second negative electrode active material, and the first negative electrode active material includes the negative electrode active material described in any one of the preceding claims.

[0024] In some embodiments, the second negative electrode active material comprises the negative electrode active material described above, and the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, thereby reducing the problem of the negative electrode binder floating up during the paste drying process and reducing the content of the negative electrode binder on the outer surface of the negative electrode film layer, which is favorable for the liquid phase conduction of ions inside the negative electrode porous electrode and the charge exchange of ions on the surface of the negative electrode active material, thereby further improving the dynamic properties of the battery.

[0025] Optionally, the mass content w1 of the first negative active material in the first negative film layer is 96.9% or more, and the mass content w2 of the second negative active material in the second negative film layer is less than 96.9%.

[0026] In some embodiments, the second negative electrode active material includes graphite, the graphite being in the form of secondary particles, and the R value R50 at which the cumulative distribution of the graphite is 50% is 0.06 to 0.13.

[0027] Optionally, the mass content w1 of the first negative active material in the first negative film layer is greater than the mass content w2 of the second negative active material in the second negative film layer.

[0028] Optionally, the mass content w1 of the first negative active material in the first negative film layer is 96.9% or more, and the mass content w2 of the second negative active material in the second negative film layer is less than 96.9%.

[0029] This can reduce the problem of the negative electrode binder floating up during the drying process of the paste, and reduce the content of the negative electrode binder on the outer surface of the negative electrode film layer, which is favorable for the liquid phase conduction of ions inside the negative electrode porous electrode and the charge exchange of ions on the surface of the negative electrode active material, and can further improve the dynamic properties of the battery.

[0030] In some embodiments, the negative electrode film layer has a green density of 1.62 g / cm 3 ~1.80g / cm 3 and selectively 1.65 g / cm 3 ~1.80g / cm 3 is.

[0031] In some embodiments, the thickness of the negative electrode film layer is 45 μm to 100 μm, and preferably 70 μm to 100 μm. Adjusting the thickness of the negative electrode film layer within this range helps the battery have good dynamic properties while maintaining high energy density.

[0032] In a second aspect, the present application provides a power consuming device including a lithium ion battery of the first aspect of the present application used to supply electrical energy.

[0033] The power consuming device of the present application includes a lithium ion battery as provided by the present application, and therefore has at least the same advantages as said lithium ion battery.

[0034] In a third aspect, the present application provides a negative electrode active material including a core containing graphite and a coating layer containing hard carbon located on at least a portion of the surface of the core, wherein the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit becomes 50%, in a cumulative distribution curve of R values ​​obtained using a laser microscopic confocal Raman spectroscopy in an area scanning mode.

[0035] In a fourth aspect, the present application provides a method for producing a negative electrode active material, the method including the steps of: preparing a coke raw material; crushing, shaping, and classifying the coke raw material to obtain aggregate; mixing the obtained aggregate with a binder and sequentially granulating and graphitizing the mixture to obtain graphite; solid-liquid mixing the obtained graphite with a liquid-phase hard-carbon coating agent; and carbonizing the solid-liquid mixed product in a protective gas atmosphere to carbonize the liquid-phase hard-carbon coating agent into hard carbon and coat at least a portion of the surface of the graphite, thereby obtaining a negative electrode active material, the negative electrode active material including a core containing graphite and a coating layer containing hard carbon located on at least a portion of the surface of the core, and the negative electrode active material has an R50 of 0.15 to 0.40, at which a cumulative distribution curve of R values ​​obtained using a laser confocal Raman microscope in an area scanning mode is 50%.

[0036] The manufacturing method provided by the present embodiment employs a solid-liquid mixing step of a liquid hard carbon coating agent and graphite. The liquid hard carbon coating agent has good fluidity, allowing it to be uniformly distributed on the surface of the graphite particles, improving the coating effect and reducing the degree of uncoated particles. Furthermore, the carbonization of the liquid hard carbon coating agent reduces the R50 of the anode active material, thereby improving the ionic charge exchange capacity on the surface of the anode active material and improving the dynamic properties of the anode active material and the battery. Reducing the degree of uncoated particles in the anode active material further reduces side reactions on the surface of the anode active material particles, further contributing to the battery's excellent cycling performance. Therefore, the anode active material manufactured by the manufacturing method provided by the present embodiment can enable batteries to combine high energy density with excellent dynamic and cycling performance.

[0037] In some embodiments, the coke raw material comprises one or more of petroleum-based needle coke and coal-based needle coke, which are anisotropic materials and are advantageous for reducing the disorder of the core material and improving the specific capacity of the core material and the overall specific capacity of the negative electrode active material.

[0038] In some embodiments, the graphitization temperature is 2800° C. to 3800° C., and optionally 2850° C. to 3300° C. By selecting an appropriate graphitization temperature, the battery can have both high energy density and good dynamic properties.

[0039] In some embodiments, the mass of the liquid hard carbon coating agent is 0.7% to 10% of the mass of the graphite, and preferably 3% to 7%. By using the liquid hard carbon coating agent in this range, the degree of non-coating of the negative active material can be narrowed, which not only improves the ionic charge exchange capacity on the surface of the negative active material, but also reduces side reactions on the particle surface of the negative active material. Furthermore, the negative active material can have a high specific capacity, which is advantageous for batteries having high energy density, good dynamic characteristics, and long cycle life.

[0040] In some embodiments, the liquid hard carbon coating agent includes a liquid resin, and the viscosity of the liquid resin at 25° C. is 150 mPa·s to 2000 mPa·s, and the solid content of the liquid resin is 50% to 85%.

[0041] Optionally, the viscosity of the liquid resin at 25° C. is 300 mPa·s to 900 mPa·s, and the solid content of the liquid resin is 60% to 82%.

[0042] When the viscosity of the liquid resin is within the above range, the liquid resin not only has good fluidity and diffusibility, but also has good curing and coating effects, which allows the liquid resin to be uniformly dispersed on the surface of the graphite particles, which is advantageous for improving the coating effect and reducing the degree of non-coating, and further improving the coating uniformity on the surface of the graphite particles, which is advantageous for the battery to have both good dynamic properties and a long cycle life.

[0043] When the solids content of the liquid resin is within the above range, the liquid resin not only has good fluidity and diffusibility, but also has good curing and coating effects. This allows the liquid resin to be uniformly dispersed on the surface of the graphite particles, which is beneficial for improving the coating effect and reducing the degree of uncoated particles. Furthermore, it allows the R value (R50) at which the cumulative distribution of the negative electrode active material is 50% to be adjusted, which increases the disorder on the surface of the negative electrode active material particles and improves the charge exchange ability of ions on the surface of the negative electrode active material, which is beneficial for the battery to have both good dynamic properties and a long cycle life.

[0044] In some embodiments, the liquid resin comprises at least one of a liquid phenolic resin, a liquid epoxy resin, a liquid vinyl ester resin, a liquid unsaturated polyester resin, a liquid furan resin, and derivatives of each.

[0045] In some embodiments, the liquid hard carbon coating agent includes a liquid phenolic resin, and the solid content of the liquid phenolic resin is 60%-82% and the weight average molecular weight is 300-800.

[0046] Optionally, the liquid phenolic resin has a solid content of 68%-78% and a weight average molecular weight of 450-700.

[0047] Compared to other liquid resins, the hard carbon formed by carbonizing and coking the liquid phenolic resin itself has better performance.

[0048] By further adjusting the solid content and weight average molecular weight of the liquid phenolic resin to fall within the above ranges, the hard carbon formed by carbonizing the liquid phenolic resin can have better dynamic properties, improve the coating effect, and reduce the degree of non-coating, thereby improving the charge exchange ability of ions on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material.

[0049] In some embodiments, the device for solid-liquid mixing the graphite and the liquid-phase hard carbon coating agent is a mixer, and the mixer's stirring rotation speed is 350 r / min to 1000 r / min, and the stirring time for solid-liquid mixing is 4 min to 10 min. Optionally, the mixer's stirring rotation speed is 450 r / min to 850 r / min, and the stirring time for solid-liquid mixing is 6 min to 8 min. Increasing the mixer's stirring rotation speed is beneficial for improving the coating effect and reducing the degree of uncoated area, thereby improving the ionic charge exchange capacity on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material. Increasing the stirring time for solid-liquid mixing is beneficial for improving the coating effect and reducing the degree of uncoated area, thereby improving the ionic charge exchange capacity on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material.

[0050] In some embodiments, the temperature for the carbonization treatment is 900°C to 1500°C.

[0051] In some embodiments, the heat retention time for the carbonization treatment is 2 hours to 10 hours.

[0052] In a fifth aspect, the present application provides a negative electrode sheet including: a negative electrode current collector; and a negative electrode film layer located on at least one surface of the negative electrode current collector and including a negative electrode active material, wherein the negative electrode active material includes a core including graphite; and a coating layer located on at least a portion of the surface of the core and including hard carbon, wherein the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit becomes 50%, in a cumulative distribution curve of R values ​​obtained in an area scanning mode of a laser microscopic confocal Raman spectroscopy instrument. [Brief explanation of the drawings]

[0053] In order to more clearly describe the technical solutions in the embodiments of the present application, the following briefly describes the drawings required in the embodiments of the present application. It should be understood that the drawings shown below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without any creative efforts. [Figure 1] FIG. 1 is a schematic diagram of a battery cell according to some embodiments of the present application. [Figure 2] 1 is a schematic diagram of a battery module according to some embodiments of the present application. [Figure 3] FIG. 1 is a schematic diagram of a battery pack according to some embodiments of the present application. [Figure 4] FIG. 4 is an exploded schematic view of the battery pack shown in FIG. 3. [Figure 5] FIG. 1 is an exploded schematic view of a battery cell according to some embodiments of the present application. [Figure 6] 1 is a schematic diagram of a power consuming device according to some embodiments of the present application;

[0054] In the drawings, the drawings are not drawn to scale. [Explanation of symbols]

[0055] 1 battery pack 2 Upper case 3 Lower housing 4 Battery Module 5 battery cells 51 Housing 52 Electrode Assembly 53 Cover plate DETAILED DESCRIPTION OF THE INVENTION

[0056] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of structures that are actually the same may be omitted. This is to avoid unnecessary lengthening of the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0057] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and are arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" represents a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that the present specification has already listed all real numbers between "0 and 5," and "0 to 5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] All embodiments and alternative embodiments of the present application, unless otherwise specified, can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0059] All technical features and optional technical features of the present application, unless otherwise specified, can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0060] All steps in this application can be performed in order or randomly, and are preferably performed in order, unless otherwise specified. For example, when the method includes steps (a) and (b), this means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when the method may further include step (c), this means that step (c) may be added to the method in any order, such as the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0061] As used herein, the terms "plurality" and "plurality" mean two or more than two.

[0062] Unless otherwise explained, terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0063] Unless otherwise specified, the values ​​of the parameters described herein can be measured by various test methods commonly used in the art, for example, by the test methods described in the examples of the present application. Unless otherwise specified, the test temperature for each parameter is 25°C.

[0064] The battery referred to in the embodiments of this application may include a single physical module containing one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in this application may include a battery cell, a battery module, or a battery pack.

[0065] A battery cell is the smallest unit that makes up a battery and can independently perform charging and discharging functions. Battery cells may be cylindrical, rectangular, or have other shapes, and the embodiments of the present application are not limited thereto. Figure 1 shows an example of a battery cell 5 with a rectangular parallelepiped structure.

[0066] When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or series-parallel via a bus member. In some embodiments, the battery may be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a single battery module. In some embodiments, the battery may be a battery pack, and the battery pack includes a housing and battery cells, and the battery cells or battery modules are housed in the housing. In some embodiments, the housing may be part of a chassis structure of a vehicle. For example, a portion of the housing may be at least a portion of a bottom plate of the vehicle, or a portion of the housing may be at least a portion of a cross member and a side member of the vehicle.

[0067] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, or the like.

[0068] In some embodiments, the battery cells can be assembled into a battery module. The battery module can include multiple battery cells, with the specific number being adjustable depending on the application and capacity of the battery module. FIG. 2 is a schematic diagram of an example battery module 4. As shown in FIG. 2, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, any other arrangement is also possible. The multiple battery cells 5 can also be fastened together using fasteners.

[0069] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating the plurality of battery cells 5.

[0070] In some embodiments, the battery modules can be further assembled into 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.

[0071] 3 and 4 are schematic diagrams of an example battery pack 1. As shown in FIGS. 3 and 4, the battery pack 1 may include a housing and a plurality of battery modules 4 installed in the housing. The housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the housing in any manner.

[0072] The battery according to the embodiment of the present application may include a lithium ion battery.

[0073] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly may have a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto.

[0074] The battery cell may further include an exterior material, which may be used to encapsulate the electrode assembly and the electrolyte. The exterior material may be a hard case, such as a hard plastic case, an aluminum case, or a steel case. The exterior material may also be a soft pack, such as a pouch-type soft pack. The material of the soft pack may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0075] In some embodiments, as shown in Fig. 5, the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, forming a storage cavity surrounded by the bottom plate and the side plate. The housing 51 has an opening communicating with the storage cavity, and the cover plate 53 is used to cover the opening and seal the storage cavity. The electrode assembly 52 is enclosed in the storage cavity. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0076] The electrode assembly generally includes a positive electrode sheet and a negative electrode sheet, the negative electrode being an electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging, and the positive electrode being an electrode that releases or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging. The positive electrode sheet includes a positive electrode active material, and the negative electrode sheet includes a negative electrode active material.

[0077] During battery charging, the electrical and chemical processes that occur at the negative electrode can be broadly divided into the following three steps: (1) The liquid-phase conduction process of ions inside the porous negative electrode, which includes the liquid-phase diffusion process and the electromigration process; (2) The charge exchange process of ions on the surface of the negative electrode active material; and (3) The solid-phase conduction process of ions inside the particles of the negative electrode active material.

[0078] The charge exchange capability of ions on the surface of the negative electrode active material is crucial for achieving rapid charging. Rapid charging refers to charging a battery to a fully charged or nearly fully charged state in a short period of time. The time taken to charge a battery from 0% SOC to 100% SOC is recorded, and the rapid charging performance of the battery can be characterized by this time. A shorter time indicates a better rapid charging capability. For example, if this time is approximately 20 minutes (within a 1-minute error), it is generally referred to as a 3C rapid charging battery. Furthermore, if this time is approximately 15 minutes (within a 1-minute error), it is generally referred to as a 4C rapid charging battery.

[0079] Currently, graphite is the most commonly used negative electrode active material, but its dynamic properties are not excellent. Although fast-charging hard carbon has good dynamic properties, the batteries obtained by assembling it have low energy density and insufficient cycle life.

[0080] Based on this, the examples of the present application provide a negative electrode active material.

[0081] The negative electrode active material includes a core containing graphite and a coating layer containing hard carbon located on at least a portion of the surface of the core, and the negative electrode active material has an R value R50 of 0.15 to 0.40, where the cumulative distribution from the lower limit is 50%, in a cumulative distribution curve of R values ​​obtained using a laser microscopic confocal Raman spectroscopy in area scanning mode.

[0082] In this application, the R values ​​of the negative electrode active material, core, and coating layer refer to the peak intensity ratio of the D band (D-band) and the G band (G-band) in the Raman spectrum, and the position of the D band is 1350±50 cm -1 The G band is located at 1585±50cm -1 The R value can characterize the degree of defect and disorder of each carbon material, with the higher the value, the more defect and disorder the carbon material.

[0083] The Raman spectrum of each carbon material can be obtained using a laser microscope confocal Raman spectrometer, with a laser wavelength of 532 nm. During testing, an appropriate amount of sample is taken and its surface is scanned in all directions, with a scanning area of ​​100 μm x 100 μm, a step size of 2 μm, and a total of 2,500 scanning points. This allows for the acquisition of all R values ​​and R value cumulative distribution curves. R50 is the R value at which the cumulative distribution from the lower limit reaches 50%. The 2,500 R values ​​obtained are sorted in ascending order, and R50 is the R value corresponding to the 50th highest value. The testing device can be a high-precision Renishaw laser microscope confocal Raman spectrometer.

[0084] The negative electrode active material sample can be obtained by sampling during the battery manufacturing process or by disassembling the manufactured battery. For example, the battery cell is discharged (for safety reasons, the battery cell is generally fully discharged), the negative electrode sheet is removed after disassembly, and the negative electrode sheet is immersed in dimethyl carbonate for a certain period of time (e.g., 2 to 10 hours). The negative electrode sheet is then removed and dried at a certain temperature for a certain period of time (e.g., 60°C for 4 hours or more). After drying, the negative electrode sheet is removed and baked at a certain temperature for a certain period of time (e.g., 400°C for 2 hours or more). The baked negative electrode sheet is then sampled from an arbitrary region of the baked negative electrode sheet (e.g., by scraping off the powder with a blade). The collected negative electrode active material can then be crushed and sieved (e.g., through a 200-mesh sieve) to obtain a negative electrode active material sample for testing.

[0085] The core material sample may be obtained by sampling during the manufacturing process of the negative electrode active material.

[0086] The R value and R value concentration of the coating layer refer to the properties of the hard carbon material itself, which is formed by carbonizing the precursor compound used to prepare the coating layer material. A coating layer material sample can be obtained as follows: An appropriate amount of the precursor compound (e.g., the liquid-phase hard carbon coating agent described below) is taken and carbonized under the same carbonization conditions as those used to prepare the negative electrode active material coating layer. The resulting material is then crushed and sieved to obtain a coating layer material sample.

[0087] The R value of a negative electrode active material can characterize the degree of defects and disorder in the negative electrode active material. The R value (R50) at which the cumulative distribution of the negative electrode active material is 50% correlates with the R value (R50) at which the cumulative distribution of the core is 50%, the R value (R50) at which the cumulative distribution of the coating layer is 50%, the thickness of the coating layer, and the uniformity of the coating layer. For example, when other conditions are the same, a larger R value (R50) at which the cumulative distribution of the core is 50% corresponds to a larger R value (R50) at which the cumulative distribution of the negative electrode active material is 50%, and a larger coating layer thickness corresponds to a larger R value (R50) at which the cumulative distribution of the negative electrode active material is 50%.

[0088] When the R value (R50) at which the cumulative distribution of the negative electrode active material is 50% is high, the negative electrode active material has a high degree of defects, ionic charge exchange on the surface of the negative electrode active material is fast, the negative electrode active material has excellent dynamic properties, and lithium deposition on the negative electrode during rapid charging of the battery is less likely to occur. However, a high degree of defects in the negative electrode active material increases side reactions on the surface of the negative electrode active material, such as side reactions at the anode-electrolyte interface, which increases irreversible capacity loss and reduces capacity retention after cycling.

[0089] When the R value R50, at which the cumulative distribution of the negative electrode active material is 50%, is 0.15 to 0.40, not only can the charge exchange ability of ions on the surface of the negative electrode active material be improved, but also side reactions on the surface of the negative electrode active material particles can be reduced to a low level. Therefore, the negative electrode active material provided by the examples of the present application can enable batteries to have both high energy density and good dynamic and cycle characteristics.

[0090] The R value R50 at which the cumulative distribution of the negative electrode active material becomes 50% may be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, or a range consisting of any of the above numerical values.

[0091] Alternatively, the R value R50 at which the cumulative distribution of the negative electrode active material is 50% may be 0.20 to 0.39, 0.20 to 0.38, 0.20 to 0.37, 0.20 to 0.36, 0.20 to 0.35, 0.20 to 0.34, 0.20 to 0.33, 0.20 to 0.32, 0.20 to 0.31, or 0.20 to 0.30, thereby enabling the battery to have a high energy density, good dynamic characteristics, and good cycle characteristics.

[0092] The critical charge rate of the battery of the present invention without lithium deposition is 3C or higher, i.e., the battery of the present invention is a fast charge battery with a charge rate of 3C or higher, and the time required for charging the battery from 0% SOC to 100% SOC is within 20 minutes, which meets the current needs for fast charging.

[0093] By further limiting the R values ​​of the negative electrode active material, the core, and the coating layer, it is possible to improve at least one of the energy density, dynamic characteristics, and cycle characteristics of the battery.

[0094] In some embodiments, the percentage of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the cores is 50% may be 10% or less.

[0095] The percentage of R values ​​obtained by a negative electrode active material that are less than the R value R50, where the cumulative core distribution is 50%, can more accurately indicate the degree of uncoated area of ​​the negative electrode active material. The smaller this value, the less uncoated area of ​​the negative electrode active material and the higher the degree of isotropy of the negative electrode active material. This increases the number of active sites on the negative electrode active material, thereby enhancing the ionic charge exchange capacity on the surface of the negative electrode active material and further improving the dynamic properties of the negative electrode active material and the battery. Furthermore, a smaller degree of uncoated area of ​​the negative electrode active material can further reduce the co-intercalation phenomenon of the electrolyte solvent during cycling, resulting in better cycle performance for the battery.

[0096] Alternatively, the proportion of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the cores is 50% may be 8% or less, and more preferably 6% or less.

[0097] This can further improve the dynamic and cycle characteristics of the battery.

[0098] In some embodiments, the R value R50 at which the cumulative distribution of the core of the negative electrode active material is 50% is smaller than the R value R50 at which the cumulative distribution of the coating layer is 50%.

[0099] When the coating layer of the negative electrode active material has a large R50 (50% cumulative distribution) and high disorder, the negative electrode active material and the battery can have good dynamic properties. When the core of the negative electrode active material has a small R50 (50% cumulative distribution) and low disorder, the negative electrode active material as a whole can have a high specific capacity, and the battery can have a high energy density.

[0100] In some embodiments, the R value (R50) at which the cumulative distribution of the coating layer reaches 50% may be 0.9 to 1.4, such as 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.4, or any range thereof. Optionally, the R value (R50) at which the cumulative distribution of the coating layer reaches 50% may be 0.95 to 1.25. When the R value (R50) at which the cumulative distribution of the coating layer reaches 50% falls within the above range, the coating layer itself has good dynamic properties, which can improve the dynamic properties of the negative electrode active material and the battery. Furthermore, the negative electrode active material can have a small specific surface area, which can reduce side reactions in the battery and result in good cycle performance.

[0101] In some embodiments, the R value R50 at which the cumulative distribution of the core reaches 50% may be 0.06 to 0.13, such as 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, or any range thereof.

[0102] When the R value R50 at which the cumulative distribution of the core is 50% is large, the dynamic properties of the negative electrode active material are excellent, and when the R value R50 at which the cumulative distribution of the core is 50% is small, the specific capacity of the negative electrode active material is high. When the R value R50 at which the cumulative distribution of the core is 50% is within the above range, the battery can have both high energy density and good dynamic properties.

[0103] In some embodiments, the weight of the coating layer may be 0.3% to 4.5% of the weight of the core, such as 0.3%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.4%, 2.8%, 3.2%, 3.6%, 4%, 4.5%, or any range thereof. Optionally, the weight of the coating layer may be 1% to 3.2% of the weight of the core.

[0104] The mass of the coating layer affects the thickness of the coating layer, and further affects the R value R50 at which the cumulative distribution of the negative electrode active material becomes 50% and the degree of uncoated portion of the coating layer.

[0105] Coating the core surface with a single coating layer can reduce contact between the core and the electrolyte, thereby reducing the co-intercalation of the electrolyte solvent during cycling and improving the cycle characteristics of the battery. However, as the thickness of the coating layer continues to increase, the coating layer itself has many voids, which increases side reactions at the anode-electrolyte interface, increases irreversible capacity loss, and causes a certain degree of deterioration in the cycle characteristics of the battery.

[0106] The mass fraction of the coating layer within the above range can reduce the degree of non-coating of the coating layer, improve the charge exchange ability of ions on the surface of the negative electrode active material, and further reduce side reactions on the surface of the negative electrode active material particles, thereby providing the negative electrode active material with a high specific capacity. The mass fraction of the coating layer within the above range is advantageous for the battery to have a high energy density, good dynamic characteristics, and a long cycle life.

[0107] In some embodiments, the difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core may be 1 μm to 5.5 μm, such as 1 μm, 1.4 μm, 1.8 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 5 μm, 5.5 μm, or any range thereof. Optionally, the difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core may be 1.5 μm to 4.2 μm, or 2 μm to 4 μm.

[0108] When the difference between the volume-based particle size distribution Dv50 of the negative electrode active material and the volume-based particle size distribution Dv50 of the core is within the above range, not only can the charge exchange ability of ions on the surface of the negative electrode active material be improved, but side reactions on the surface of the negative electrode active material particles can be reduced to a low level, and the negative electrode active material can have a high specific capacity, which is advantageous for the battery to have a high energy density, good dynamic properties, and a long cycle life.

[0109] In some embodiments, the volumetric particle size distribution Dv50 of the negative electrode active material may be 8 μm to 25 μm, or optionally 12 μm to 17 μm. When the volumetric particle size distribution Dv50 of the negative electrode active material is within this range, lithium ions can have good solid-state conductivity within the negative electrode active material particles, and the negative electrode active material can have a small specific surface area, which is advantageous for the battery to have both good cycle characteristics and dynamic characteristics. When the volumetric particle size distribution Dv50 of the negative electrode active material is within this range, the negative electrode paste can also have good dispersibility.

[0110] The volumetric particle size distribution Dv50 of a material has a meaning known in the art, which indicates the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. It can be measured using devices and methods known in the art. For example, see GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, which can be easily measured using a laser particle size analyzer. The testing device can be a Mastersizer 3000 laser particle size analyzer manufactured by Malvern Instruments, UK.

[0111] The graphite is an artificial graphite. The core contains artificial graphite, which allows the battery to have high energy density and good cycle characteristics.

[0112] In some embodiments, the graphite may be in the form of secondary particles, which increases the degree of isotropy of the graphite, favoring rapid intercalation of lithium ions, thereby helping the battery to have good dynamic properties and further improving the specific capacity of the negative electrode active material and the energy density of the battery.

[0113] In some embodiments, the graphite may have an intensity ratio C(004) / C(110) of the 004 plane diffraction peak to the 110 plane diffraction peak of 5.5 to 6.5 as measured by X-ray diffraction.

[0114] The intensity ratio of the 004 diffraction peak to the 110 diffraction peak measured by X-ray diffraction of graphite can indicate the degree of isotropy of graphite. A small value indicates a high degree of isotropy of graphite, and all directions of the graphite particles have lithium ion insertion ports, which is favorable for the rapid insertion of lithium ions and favorable dynamic properties of the battery.

[0115] For example, the intensity ratio C(004) / C(110) of the 004 diffraction peak to the 110 diffraction peak, measured by X-ray diffraction of graphite, can be measured using an X-ray diffractometer (such as a Bruker D8 Discover). The test is performed according to JIS K 0131-1996 and JB / T 4220-2011, and the X-ray diffraction spectrum of the powder sample can be obtained. C(004) / C(110) represents the ratio of the integrated area of ​​the 004 diffraction peak to the integrated area of ​​the 110 diffraction peak of crystalline carbon in the powder sample. In X-ray diffraction analysis, a copper target can be used as the anode target, with CuKα radiation as the radiation source, a radiation wavelength λ = 1.5418 A, a scanning 2θ angle range of 20° to 80°, and a scanning speed of 4° / min.

[0116] In some embodiments, the specific capacity of the negative electrode active material may be 354 mAh / g to 361 mAh / g.

[0117] The specific capacity of the negative electrode active material can be obtained by assembling a button battery and conducting a charge / discharge test. For example, a negative electrode active material sample, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) are uniformly mixed with the solvent N-methylpyrrolidone (NMP) in a mass ratio of 91.6:1.8:6.6 to produce a paste. The paste is applied to a copper foil current collector, dried in an oven, and cold-pressed to prepare it for use. The green density is 1.4 g / cm. 3 ~1.6g / cm 3The battery was then placed in an argon-protected glove box. The electrolyte solution was then injected into a metal lithium piece as a counter electrode and a polyethylene film as a separator. The battery was then assembled into a CR2430 button cell in an argon-protected glove box. The electrolyte formulation was as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DEC) were mixed in a 1:1:1 volume ratio, and thoroughly dried lithium salt LiPF6 was dissolved in the mixed solvent at a ratio of 1 mol / L to produce the electrolyte. The resulting button cell was then left at 25°C for 12 hours, then discharged at a constant current of 0.05 C to 0.005 V, allowed to stand for 10 minutes, discharged at a constant current of 50 μA to 0.005 V, allowed to stand for 10 minutes, and discharged at a constant current of 10 μA to 0.005 V. The sum of the discharge capacities for these three cycles was used as the first-cycle discharge capacity of the button cell. Then, the battery is charged at a constant current of 0.1 C to 2.0 V, and the first cycle charge capacity of the button battery is recorded. The ratio of the first cycle charge capacity of the button battery to the mass of the negative electrode active material sample is the specific capacity of the negative electrode active material.

[0118] In some embodiments, the negative electrode active material has a green density of 1.68 g / cm at a pressure of 20,000 N. 3 ~1.78g / cm 3 may be.

[0119] For example, an appropriate amount of negative electrode active material powder is placed in a special compaction mold, the mold is placed in a compaction density instrument, different pressures are set, the powder thickness (here, the thickness after pressure release) at different pressures is read by the instrument, and the compaction density ρ of the negative electrode active material at the corresponding pressure is calculated by ρ = m / (s * h). The pressure is set to 20,000 N. m represents the mass of the negative electrode active material powder sample, expressed in g. s is the base area of ​​the special compaction mold, here 1.327 cm 2 h is the compaction thickness of the negative electrode active material powder sample, and the unit is cm.

[0120] In some embodiments, the specific surface area of ​​the negative electrode active material is 1.5 m 2 / g~4.5m 2 / g.

[0121] When the specific surface area of ​​the negative electrode active material is within the above range, side reactions at the negative electrode-electrolyte interface can be reduced, irreversible consumption of lithium ions can be reduced, and the cycle life of the battery can be improved.

[0122] The specific surface area of ​​a material has a meaning known in the art and can be measured using devices and methods known in the art. For example, it can be measured using the test method for analyzing specific surface area by nitrogen adsorption method in accordance with GB / T 19587-2017, and calculated by the Brunauer Emmett Teller (BET) method. The test for analyzing specific surface area by nitrogen adsorption method can be performed using a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, USA.

[0123] The present embodiment further provides a method for manufacturing a negative electrode active material, which can manufacture the negative electrode active material according to the present embodiment.

[0124] The method includes the steps of preparing a coke raw material, crushing, shaping, and classifying the coke raw material to obtain aggregate, mixing the obtained aggregate with a binder and sequentially granulating and graphitizing the aggregate to obtain graphite, solid-liquid mixing the obtained graphite with a liquid-phase hard carbon coating agent, and carbonizing the solid-liquid mixed product in a protective gas atmosphere to carbonize the liquid-phase hard carbon coating agent into hard carbon and coat at least a portion of the surface of the graphite to obtain a negative electrode active material. The negative electrode active material includes a core containing graphite and a coating layer containing hard carbon located on at least a portion of the surface of the core, and the negative electrode active material has an R50 of 0.15 to 0.40, where R50 is the cumulative distribution curve of R values ​​obtained using a laser microscopic confocal Raman spectroscopy in area scanning mode, at which the cumulative distribution from the lower limit reaches 50%.

[0125] The particle size of coke raw materials is generally large, and crushing can reduce the particle size of the coke raw materials. Optionally, the crushing process may include two steps: coarse crushing and fine pulverization. Coarse crushing can break down the coke raw materials into agglomerated particles on the order of millimeters. Fine pulverization can reduce the particle size from the order of millimeters to tens of micrometers. After crushing, the surface of the coke raw materials is not flat, and a shaping process can make the coke raw material particles round. Classification can reduce the content of particles that are too large or too small, and further adjust the particle size and particle size distribution of the coke raw materials.

[0126] The coke raw material may include one or more of petroleum-based needle coke and coal-based needle coke, which are anisotropic materials and are advantageous in reducing the disorder of the core material, improving the specific capacity of the core material and the specific capacity of the entire negative electrode active material, and further improving the energy density of the battery.

[0127] The manufacturing method provided by the present embodiment employs a solid-liquid mixing step of a liquid hard carbon coating agent and graphite. The liquid hard carbon coating agent has good fluidity, allowing it to be uniformly distributed on the surface of the graphite particles, improving the coating effect and reducing the degree of uncoated particles. Furthermore, the carbonization of the liquid hard carbon coating agent reduces the R50 of the anode active material, thereby improving the ionic charge exchange capacity on the surface of the anode active material and improving the dynamic properties of the anode active material and the battery. Reducing the degree of uncoated particles in the anode active material further reduces side reactions on the surface of the anode active material particles, further contributing to the battery's excellent cycling performance. Therefore, the anode active material manufactured by the manufacturing method provided by the present embodiment can enable batteries to combine high energy density with excellent dynamic and cycling performance.

[0128] Alternatively, the weight of the binder may be 6% to 12% of the weight of the aggregate obtained by the classification treatment, and optionally 8% to 10%, which allows the graphite to have a good secondary particle morphology.

[0129] Optionally, the binder may include asphalt.

[0130] The equipment employed for the granulation process may include either a horizontal reactor or a vertical reactor.

[0131] Alternatively, the granulation process may be a step-up and temperature-holding process, which allows the graphite to have good secondary particle morphology and high capacity.

[0132] Optionally, 2 to 4 programmable heating plates can be installed during the heating process.

[0133] Generally, the surfaces of coke raw materials from different batches and from different sources are uneven and have many defects. Graphitization treatment can significantly repair the defects on the material surface, thereby improving the concentration of Raman values ​​in the area scanning mode of the core material and improving the consistency of the performance of graphite products.

[0134] The equipment employed for the graphitization process may include at least one of an Acheson graphitization furnace, a box furnace, or a shaft furnace.

[0135] Alternatively, the graphitization temperature may be 2800°C to 3800°C, such as 2800°C, 2850°C, 2900°C, 3000°C, 3100°C, 3200°C, 3300°C, 3400°C, 3500°C, 3600°C, 3700°C, 3800°C, or any range of the above values. Also, the graphitization temperature may be 2850°C to 3300°C. The specific graphitization time may be reasonably selected based on the equipment used.

[0136] When the graphitization temperature is high, the graphitization time is long, and the specific capacity of graphite is high, the disorder is small, and the R value R50 at which the cumulative distribution of graphite is 50% is small.

[0137] By selecting an appropriate graphitization temperature, the battery can combine high energy density with good dynamic properties.

[0138] In some embodiments, the coke yield of the liquid-phase hard carbon coating agent may be 35% to 50%, and optionally 38% to 48%.

[0139] The coke yield of a liquid hard carbon coating is the percentage of the mass of residual carbon remaining after heating a specified amount of a liquid hard carbon coating sample under specified conditions to the mass of the liquid hard carbon coating sample, and can be tested in accordance with GB / T 8727-2008.

[0140] In some embodiments, the mass of the liquid hard carbon coating agent may be 0.7% to 10% of the mass of the graphite, such as 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range thereof. Optionally, the mass of the liquid hard carbon coating agent may be 3% to 7% of the mass of the graphite.

[0141] As the mass ratio of the liquid-phase hard carbon coating agent increases, the R value R50 at which the cumulative distribution of the negative electrode active material becomes 50% increases, and the disorder on the surface of the negative electrode active material particles increases.

[0142] When the mass of the liquid-phase hard carbon coating agent is within the above range, the degree of non-coating of the negative electrode active material can be narrowed, which not only improves the ionic charge exchange ability on the surface of the prepared negative electrode active material but also reduces side reactions on the particle surface of the prepared negative electrode active material. Furthermore, the prepared negative electrode active material can have a high specific capacity, which is advantageous for a battery having a high energy density, good dynamic characteristics, and a long cycle life.

[0143] In some embodiments, the liquid-phase hard carbon coating agent includes a liquid resin that is a hard carbon precursor material. When the coating layer includes hard carbon, the negative electrode active material and the battery have better dynamic properties.

[0144] The liquid resin is commercially available or can be synthesized by a method known in the art, or can be obtained by uniformly mixing and stirring a resin powder and a solvent.

[0145] In some embodiments, the liquid resin may have a viscosity at 25° C. of 150 mPa·s to 2000 mPa·s, such as 150 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1050 mPa·s, 1200 mPa·s, 1400 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, or any range thereof. Optionally, the liquid resin may have a viscosity at 25° C. of 300 mPa·s to 900 mPa·s.

[0146] The viscosity of the liquid resin can be tested in accordance with GB / T 14074-2017. The test temperature is 25°C, and the test equipment can be an NDJ-1 type rotational viscometer.

[0147] When the viscosity of the liquid resin is within the above range, the liquid resin not only has good fluidity and diffusibility, but also has good curing and coating effects, which allows the liquid resin to be uniformly dispersed on the surface of the graphite particles, which is advantageous for improving the coating effect and reducing the degree of non-coating, and further improving the coating uniformity on the surface of the graphite particles, which is advantageous for the battery to have both good dynamic properties and a long cycle life.

[0148] In some embodiments, the solids content of the liquid resin may be between 50% and 85%, and optionally between 60% and 82%.

[0149] The solid content of liquid hard carbon coatings can be tested by a drying method in accordance with GB / T 14074-2017. The free components and moisture in the liquid hard carbon coating evaporate at high temperatures, and the solid content of the liquid hard carbon coating refers to the percentage of the remaining mass after drying under specified conditions. The oven temperature is set to 150°C and the coating is baked until a constant weight is reached.

[0150] When the solids content of the liquid resin is within the above range, the liquid resin not only has good fluidity and diffusibility, but also has good curing and coating effects. This allows the liquid resin to be uniformly dispersed on the surface of the graphite particles, which is beneficial for improving the coating effect and reducing the degree of uncoated particles. Furthermore, it allows the R value (R50) at which the cumulative distribution of the negative electrode active material is 50% to be adjusted, which increases the disorder on the surface of the negative electrode active material particles and improves the charge exchange ability of ions on the surface of the negative electrode active material, which is beneficial for the battery to have both good dynamic properties and a long cycle life.

[0151] In some embodiments, the liquid resin may include at least one of a liquid phenolic resin, a liquid epoxy resin, a liquid vinyl ester resin, a liquid unsaturated polyester resin, a liquid furan resin, and derivatives of each, which generally refer to products derived from a polymer by replacing hydrogen atoms or atomic groups with other atoms or atomic groups.

[0152] The liquid resin is a good hard carbon precursor material, and as a liquid-phase hard carbon coating agent, it can better improve the dynamic properties of the battery, so that the battery can have good cycle properties.

[0153] In some embodiments, the liquid hard carbon coating agent includes a liquid phenolic resin, and the solid content of the liquid phenolic resin may be 60% to 82% and the weight average molecular weight may be 300 to 800.

[0154] Alternatively, the liquid phenolic resin may have a solid content of 68%-78% and a weight average molecular weight of 450-700.

[0155] Compared to other liquid resins, the hard carbon formed by carbonizing and coking the liquid phenolic resin itself has better performance.

[0156] By further adjusting the solid content and weight average molecular weight of the liquid phenolic resin to fall within the above ranges, the hard carbon formed by carbonizing the liquid phenolic resin can have better dynamic properties, improve the coating effect, and reduce the degree of non-coating, thereby improving the charge exchange ability of ions on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material.

[0157] The weight average molecular weight of the liquid-phase hard carbon coating agent can be tested by gel permeation chromatography. The test equipment can be an Agilent 1290 Infinity II GPC system. The eluent can be tetrahydrofuran, and polystyrene standards can be used for calibration.

[0158] The liquid phenolic resin may be a phenolic compound, an aldehyde compound, or the like, and is formed by polycondensation in the presence of an alkaline catalyst, initiating the polycondensation reaction to produce a liquid substance. The liquid phenolic resin described in the examples of this application is a resol type phenolic resin.

[0159] The phenolic compound may include one or more of phenol, cresol, dimethylphenol, nonylphenol, bisphenol A, bisphenol F, resorcinol, propylphenol, ethylphenol, and cardanol, and may alternatively be phenol. The aldehyde compound may include one or more of formaldehyde, acetaldehyde, butylaldehyde, paraformaldehyde, and furfural, and may alternatively be formaldehyde. The alkaline catalyst may include one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, magnesium hydroxide, aqueous ammonia, sodium carbonate, and tertiary amines.

[0160] In some embodiments, the device for solid-liquid mixing of graphite and a liquid-phase hard carbon coating agent may be a mixer.

[0161] Alternatively, the stirring rotation speed of the mixer may be 350 r / min to 1000 r / min, for example, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 850 r / min, 900 r / min, 1000 r / min, or a range consisting of any of the above values. Further alternatively, the stirring rotation speed of the mixer may be 450 r / min to 850 r / min.

[0162] Increasing the stirring rotation speed of the mixer is beneficial for improving the coating effect and reducing the degree of uncoated area, thereby improving the ionic charge exchange ability on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material. However, if the stirring rotation speed of the mixer is too high, the outer surface structure of the core will be destroyed, and strong centrifugal separation will cause mass loss of the liquid-phase hard carbon coating agent.

[0163] Alternatively, the stirring time for solid-liquid mixing may be 4 to 10 minutes, for example, 4, 5, 6, 7, 8, 9, 10 minutes, or any range of the above values.More preferably, the stirring time for solid-liquid mixing may be 6 to 8 minutes.

[0164] Increasing the stirring time of the solid-liquid mixture is beneficial for improving the coating effect and reducing the degree of non-coating, thereby improving the charge exchange ability of ions on the surface of the negative electrode active material and improving the dynamic properties of the negative electrode active material. However, if the stirring time is too long, the improvement in the coating effect will not be obvious and will also increase energy consumption.

[0165] In some embodiments, the carbonization device may be a shuttle kiln.

[0166] In some embodiments, the temperature for the carbonization treatment may be between 900°C and 1500°C, such as 900°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1500°C, or any range thereof. Optionally, the temperature for the carbonization treatment may be between 1050°C and 1350°C.

[0167] In some embodiments, the incubation time for the carbonization treatment may be 2 hours to 10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any range thereof. Optionally, the incubation time for the carbonization treatment may be 5 hours to 8 hours. The incubation time for the carbonization treatment refers to the residence time at the incubation temperature.

[0168] In some embodiments, the manufacturing method may further include the steps of depolymerizing, sieving, and demagnetizing the carbonized material.

[0169] Depolymerization can be carried out in a depolymerizer, which can remove weak adhesion on the surface of the coating layer and eliminate the problem of excessive particle agglomeration in the resulting product. Sieving can reduce the content of large particles and fine powder in the resulting product, which is advantageous for achieving a desired particle size and particle size distribution. Demagnetization can reduce the content of magnetic impurities in the resulting product, which increases battery self-discharge and reduces battery performance.

[0170] [Negative electrode sheet] The battery cell includes a negative electrode sheet.

[0171] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector. 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 opposing surfaces of the negative electrode current collector.

[0172] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, copper foam, nickel foam, and aluminum foam. The composite current collector may include a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal material may include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, aluminum, aluminum alloy, silver, and silver alloy. For example, the polymer substrate layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0173] The negative electrode film layer includes the above-described negative electrode active material or the negative electrode active material prepared by the above-described method, which allows the battery to have high energy density, good dynamic characteristics, and good cycle characteristics.

[0174] In some embodiments, the negative electrode film layer may further include other negative electrode active materials known in the art, including, but not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0175] In some embodiments, the negative electrode film layer optionally further comprises a negative electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] In some embodiments, the negative electrode film layer optionally further comprises a negative electrode binder. For example, the negative electrode binder may include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0177] In some embodiments, the negative electrode film layer optionally further comprises other additives, such as, but not limited to, thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0178] In some embodiments, the thickness of the negative electrode film layer may be 45 μm to 100 μm, or alternatively 55 μm to 100 μm, or 70 μm to 100 μm. The thickness of the negative electrode film layer is the thickness of the negative electrode film layer on one side of the negative electrode current collector. The thickness of the negative electrode film layer can be measured with a micrometer.

[0179] The thickness of the negative electrode film layer is related to the rate of ion intercalation and the magnitude of negative electrode polarization, so differences in thickness affect the dynamic properties of the negative electrode sheet. Generally, the thicker the negative electrode film layer, the more difficult it is for ions to diffuse into the liquid phase inside the negative porous electrode under the same conditions.

[0180] By adjusting the thickness of the negative electrode film layer within the above range, it is possible to ensure that the battery has good dynamic properties under the premise of high energy density.

[0181] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer located between the first negative electrode film layer and the negative electrode current collector, the thickness of the first negative electrode film layer being 30% to 60% of the thickness of the negative electrode film layer, and the thickness of the second negative electrode film layer being 70% to 40% of the thickness of the negative electrode film layer. Optionally, the thickness of the first negative electrode film layer is 30% to 40% of the thickness of the negative electrode film layer, and the thickness of the second negative electrode film layer is 70% to 60% of the thickness of the negative electrode film layer.

[0182] The first negative electrode film layer includes a first negative electrode active material, and the second negative electrode film layer includes a second negative electrode active material, the first negative electrode active material including the above-described negative electrode active material or the negative electrode active material prepared by the above-described method, thereby enabling the battery to have high energy density, good dynamic characteristics, and good cycle characteristics.

[0183] Optionally, in some embodiments, the second negative electrode active material may include the above-described negative electrode active material or the negative electrode active material prepared by the above-described method, and the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and the mass content of the negative electrode binder in the first negative electrode film layer is less than the mass content of the negative electrode binder in the second negative electrode film layer.

[0184] If the negative electrode binder floats up during the drying process of the paste, the content of the negative electrode binder on the outer surface of the negative electrode film layer will increase, which will be unfavorable to the liquid phase conduction of ions inside the negative electrode porous electrode and the charge exchange of ions on the surface of the negative electrode active material.

[0185] By partitioning the negative electrode film layers, and ensuring that the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and that the mass content of the negative electrode binder in the first negative electrode film layer is less than the mass content of the negative electrode binder in the second negative electrode film layer, the problem of the negative electrode binder floating up during the paste drying process can be reduced, and the content of the negative electrode binder on the outer surface of the negative electrode film layer can be reduced, which is beneficial to the liquid phase conduction of ions inside the negative electrode porous electrode and the charge exchange of ions on the surface of the negative electrode active material, and further improves the dynamic properties of the battery.

[0186] Alternatively, the mass content w1 of the second negative electrode active material in the first negative electrode film layer may be 96.9% or more, and may be 96.9% to 97.4%.

[0187] Alternatively, the mass content w2 of the second negative electrode active material in the second negative electrode film layer may be less than 96.9%, and may be optionally 96.4% to 96.8%.

[0188] In some alternative embodiments, the second negative electrode active material may include graphite, the graphite being in the form of secondary particles, and the R value (R50) at which the cumulative distribution of graphite is 50% is 0.06 to 0.13. The second negative electrode active material may be the core of the negative electrode active material according to the above embodiments of the present application, i.e., graphite. The second negative electrode active material does not have a coating layer, thereby providing a battery with a higher energy density.

[0189] Optionally, the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and the mass content of the negative electrode binder in the first negative electrode film layer is less than the mass content of the negative electrode binder in the second negative electrode film layer.

[0190] By partitioning the negative electrode film layers, and ensuring that the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and that the mass content of the negative electrode binder in the first negative electrode film layer is less than the mass content of the negative electrode binder in the second negative electrode film layer, the problem of the negative electrode binder floating up during the paste drying process can be reduced, and the content of the negative electrode binder on the outer surface of the negative electrode film layer can be reduced, which is beneficial to the liquid phase conduction of ions inside the negative electrode porous electrode and the charge exchange of ions on the surface of the negative electrode active material, and further improves the dynamic properties of the battery.

[0191] Alternatively, the mass content w1 of the second negative electrode active material in the first negative electrode film layer may be 96.9% or more, and may be 96.9% to 97.4%.

[0192] Alternatively, the mass content w2 of the second negative electrode active material in the second negative electrode film layer may be less than 96.9%, and may be optionally 96.4% to 96.8%.

[0193] In some embodiments, the negative electrode film layer has a green density of 1.62 g / cm 3 ~1.80g / cm 3 and optionally 1.65 g / cm 3 ~1.80g / cm 3 The negative electrode active material according to the embodiment of the present application or the negative electrode active material manufactured by the manufacturing method according to the embodiment of the present application may allow the negative electrode film layer to have a high green density.

[0194] The green density of the negative electrode film layer refers to the ratio of the areal density of the negative electrode film layer to the thickness of the negative electrode film layer, and the areal density of the negative electrode film layer refers to the ratio of the weight of the negative electrode film layer after coating, drying, and roll pressing to the coating area.

[0195] The negative electrode film layer is typically formed by applying a negative electrode paste onto a negative electrode current collector, drying it, and cold-pressing it. The negative electrode paste is typically formed by dispersing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional auxiliary agents in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0196] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In some embodiments, the negative electrode sheet may further include a protective layer covering the surface of the negative electrode film layer.

[0197] [Positive electrode sheet] The battery cell includes a positive electrode sheet.

[0198] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on one or both of the opposing surfaces of the positive electrode current collector.

[0199] The positive electrode film layer includes a positive electrode active material, which may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds.

[0200] As an example, the lithium transition metal oxide may include, but is not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. In some embodiments, the lithium transition metal oxide may include Li a Ni b Co c M d O e A f where 0 < a ≤ 1.2, 0.8 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1. M may include, but is not limited to, one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B. A may include, but is not limited to, one or more of N, F, S, and Cl. This can further improve the energy density of the battery cell. Optionally, the lithium transition metal oxide may be LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.06 Mn 0.04 O2, LiNi 0.92 Co 0.06 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, etc., and may include one or more of them, but is not limited to these.

[0201] During the charge and discharge process of the battery cell, as Li desorbs and is consumed, the molar content of Li discharged when the battery cell is in different states is different. In the description of the positive electrode active material of the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before the material is introduced. When the positive electrode active material is applied in the battery cell and the charge and discharge cycles elapse, the molar content of Li may change.

[0202] In the description of the positive electrode active material in the examples of the present application, the molar content of O is merely a theoretical value, and the release of lattice oxygen brings about a change in the molar content of O, and the molar content of O actually fluctuates.

[0203] By way of example, the lithium-containing phosphate may include, but is not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composite, lithium manganese phosphate, lithium manganese phosphate and carbon composite, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite, and respective modified compounds.

[0204] The modifying compounds for the positive electrode active material can perform doping modification and / or surface coating modification on the positive electrode active material.

[0205] In some embodiments, the positive electrode film layer may optionally further include a positive electrode conductive agent, such as, but not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0206] In some embodiments, the positive electrode film layer may optionally further include a positive electrode binder. For example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylic resin, styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0207] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, aluminum foil. The composite current collector may include a polymeric substrate layer and a metal material layer formed on at least one surface of the polymeric substrate layer. For example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric substrate layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0208] The positive electrode film layer is typically formed by applying a positive electrode paste to a positive electrode current collector, drying it, and cold pressing it. The positive electrode paste is typically formed by dispersing a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and other optional components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0209] [Electrolytes] The battery cell includes an electrolyte. The present application does not particularly limit the type of electrolyte, and it can be selected as needed. For example, the electrolyte may include one or more of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

[0210] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0211] In some embodiments, by way of example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0212] In some embodiments, the solvent may include, but is not limited to, one or more of an ester-based solvent, a sulfone-based solvent, and an ether-based solvent. By way of example, the solvent may include, but is not limited to, one or more of 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), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), methylsulfonylmethane (MSM), ethyl methanesulfonate (EMS), and diethylsulfone (ESE).

[0213] In some embodiments, the electrolyte solution may further include optional additives, such as a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve specific battery performance, such as an additive that improves the overcharge characteristics of the battery, an additive that improves the high-temperature characteristics of the battery, or an additive that improves the low-temperature power output characteristics of the battery.

[0214] [Separator] Both liquid electrolyte and solid electrolyte battery cells further include a separator, which is placed between the positive and negative electrode sheets and primarily serves to prevent internal short circuits.

[0215] The present application does not particularly limit the type of separator, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0216] In some embodiments, the separator material may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. The separator may be a monolayer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0217] Methods for manufacturing battery cells are well known. In some embodiments, a battery cell can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed from a positive electrode sheet, a separator, and a negative electrode sheet through a winding process and / or a lamination process. The electrode assembly can then be placed in a housing, dried, and then the electrolyte can be injected. The battery cell can then be obtained through processes such as encapsulation, standing, and chemical formation. Multiple battery cells can be further connected in series, parallel, or series-parallel to form a battery module. Multiple battery modules can be further connected in series, parallel, or series-parallel to form a battery pack. In some embodiments, multiple battery cells can be further connected directly to form a battery pack.

[0218] power consumption equipment

[0010] The present invention also provides a power consuming device, including a battery according to the present invention, for use in supplying electrical energy. The battery may be used as a power source for the power consuming device or as an energy storage element for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0219] A power consuming device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, depending on its usage requirements.

[0220] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the power consuming device, a battery pack or battery module can be used.

[0221] Other examples of power consuming devices include mobile phones, tablet computers, laptop computers, etc. Such power consuming devices are generally required to be lightweight and thin, and can use battery cells as a power source.

[0222] Example The following examples more specifically describe the contents disclosed herein, but since various modifications and variations within the scope of the contents disclosed herein will be apparent to those skilled in the art, these examples are for illustrative purposes only. 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 treatment, and all equipment used in the examples is commercially available.

[0223] Example 1 (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0224] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. The product was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0225] (2) Manufacturing of negative electrode sheets The negative electrode active material, the thickener sodium carboxymethyl cellulose, the negative electrode binder styrene butadiene rubber (SBR), and the negative electrode conductive agent Super P are mixed in a mass ratio of 97.3:1.1:0.8:0.8, and deionized water as a solvent is added. The mixture is stirred uniformly using a vacuum stirrer to prepare a first negative electrode paste.

[0226] The negative electrode active material, the thickener sodium carboxymethyl cellulose, the negative electrode binder styrene butadiene rubber (SBR), and the negative electrode conductive agent Super P were mixed in a mass ratio of 96.5:1.1:2.0:0.4, and deionized water as a solvent was added. The mixture was uniformly stirred using a vacuum stirrer to prepare a second negative electrode paste.

[0227] The second negative electrode paste was evenly applied to both surfaces of the negative electrode current collector copper foil, and the first negative electrode paste was applied to the second negative electrode paste. The coated negative electrode current collector was then dried at room temperature and then transferred to an oven for drying. It was then cold pressed and cut to obtain a negative electrode sheet. The thickness of the negative electrode film layer on one side of the negative electrode current collector was 58 μm. The ratio of the thickness of the first negative electrode paste to the thickness of the second negative electrode paste was 4:6.

[0228] (3) Manufacturing of positive electrode sheets Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1O2, the positive electrode conductive agent Super P, and the positive electrode binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, and the solvent N-methylpyrrolidone (NMP) is added. The mixture is stirred using a vacuum mixer until the mixture becomes uniform and transparent, producing a positive electrode paste. The positive electrode paste is then evenly applied to the two surfaces of the positive electrode current collector aluminum foil. The positive electrode current collector with the applied paste is then dried at room temperature and then transferred to an oven for drying. It is then cold pressed and cut to obtain a positive electrode sheet.

[0229] (4) Electrolyte production Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then thoroughly dried lithium salt LiPF6 is dissolved in the mixed solvent at a ratio of 1 mol / L to prepare an electrolyte solution.

[0230] (5) Separator manufacturing A 12 micrometer polyethylene film is selected.

[0231] (6) Battery (full battery) manufacturing The positive electrode sheet, separator, and negative electrode sheet are stacked in this order (the separator serves to separate the positive and negative electrode sheets), and then wound to obtain an electrode assembly. The electrode assembly is placed in a housing, and the prepared electrolyte is injected into the dried electrode assembly. A battery is then obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0232] Comparative Example 1 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0233] (1) Manufacturing of negative electrode active material Petroleum-based needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used, with program heating plates set at 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours. It is then cooled for 3 hours and removed. The granulated material is then placed in an Acheson graphitization furnace for graphitization at 3000°C for approximately 50 hours, followed by sieving and demagnetization to obtain the negative electrode active material.

[0234] Comparative Example 2 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0235] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 2850°C for 45 hours to obtain graphite.

[0236] A VC mixer was used to mix the graphite and solid coating agent in a mass ratio of 100:5, with the solid coating agent being asphalt with a softening point of 270°C. The product of the solid mixing was placed in a shuttle kiln and heated to 1150°C under a nitrogen atmosphere for carbonization, held at that temperature for 6 hours, then cooled to 50°C before being removed and subjected to depolymerization, sieving, and demagnetization to obtain the negative electrode active material.

[0237] Performance test of liquid phase hard carbon coating agent The viscosity of the liquid hard carbon coating agent is tested in accordance with GB / T 14074-2017. The test temperature is 25°C, and the test equipment is a NDJ-1 type rotational viscometer.

[0238] The solid content of the liquid hard carbon coating agent is tested by the dry method in accordance with GB / T 14074-2017. The oven temperature is set to 150°C and the coating is baked until a constant weight is reached.

[0239] Exam section (1) Raman spectrum test of negative electrode active material The test equipment is a high-precision Renishaw laser microscope confocal Raman spectrometer with a laser wavelength of 532 nm.

[0240] During the test, an appropriate amount of negative electrode active material sample was taken and its surface was scanned in all directions. The scanning area was 100 μm × 100 μm, the step size was 2 μm, and the total number of scanning points was 2500. The R value and the R value cumulative distribution curve were obtained at different positions. The R value refers to the peak intensity ratio of the D band and the G band in the Raman spectrum. The D band position was 1350 ± 50 cm. -1 The G band is located at 1585±50cm -1 R50 is the R value at which the cumulative distribution from the lower limit is 50%.

[0241] Raman spectroscopy of graphite and coating materials is performed in the same manner as described above. Coating material samples can be obtained as follows: An appropriate amount of liquid-phase hard carbon coating agent or solid-phase coating agent is taken and carbonized under the same carbonization conditions as in each example and comparative example. The resulting material is then crushed and sieved to obtain a coating material sample.

[0242] The proportion of all R values ​​of the obtained negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of graphite is 50% is defined as the degree of uncoated negative electrode active material X.

[0243] (2) Battery mass energy density test At 25°C, the batteries manufactured in each example and comparative example were fully charged at a rate of 0.33C and fully discharged at a rate of 0.33C. After three charge / discharge cycles, the actual discharge energy D0 of the battery was recorded. The charge / discharge voltage range of the battery was 2.5V to 4.25V. The batteries were weighed at 25°C using an electronic balance. The ratio of the actual discharge energy D0 of the battery to the mass of the battery was the mass energy density of the battery.

[0244] (3) Battery cycle characteristic test The batteries manufactured in each example and comparative example were fully charged at 35°C at a rate of 1C and fully discharged at a rate of 0.5C, and the charge-discharge cycle was repeated, with the charge-discharge voltage range of the battery being 2.5V to 4.25V. The battery's cycle characteristics were expressed by the capacity retention rate after 2000 cycles, with the higher this value, the better the battery's cycle characteristics. The battery's capacity retention rate after 2000 cycles = discharge capacity after 2000 cycles / discharge capacity after the first cycle.

[0245] (4) Battery critical charge rate test At 25°C, the batteries manufactured in each example and comparative example were fully charged at an equivalent charge rate of xC and fully discharged at 1C. This cycle was repeated 10 times, and then the batteries were fully charged at an equivalent charge rate of xC. The negative electrode sheet was removed and the state of lithium deposition on the surface was observed. The charge / discharge voltage range of the batteries was 2.5V to 4.25V. If lithium was not deposited on the negative electrode surface, the equivalent charge rate xC was gradually increased at a rate of 0.1C until lithium was deposited on the negative electrode surface, and the test was then stopped. The equivalent charge rate xC at this point was recorded, and (x-0.1)C was designated as the critical charge rate of the battery.

[0246] [Table 1]

[0247] As can be seen from the test results of Example 1 and Comparative Example 1, by providing a coating layer on the graphite surface and ensuring that the R value (R50) at which the cumulative distribution of the negative electrode active material after coating is 50% is greater than 0.15, the battery can have a higher critical charge rate, and thus better fast charging performance.

[0248] [Table 2]

[0249] As can be seen from the test results in Table 2, compared to the negative electrode active material prepared using the solid phase coating agent of Comparative Example 2, the use of the liquid phase hard carbon coating agent in Example 1 can reduce the R value R50, at which the cumulative distribution of the negative electrode active material reaches 50%, thereby enabling the battery to have better fast charging performance and a higher cycle capacity retention rate.

[0250] As can be seen from the test results in Table 2, compared to the negative electrode active material prepared using the solid phase coating agent of Comparative Example 2, the battery prepared using the liquid phase hard carbon coating agent of Example 1 can have a higher energy density.

[0251] Example 2 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0252] (1) Manufacturing of negative electrode active material Petroleum-based needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3200°C for approximately 55 hours to obtain graphite.

[0253] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. The product was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0254] Example 3 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0255] (1) Manufacturing of negative electrode active material Petroleum-based needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 2850°C for approximately 45 hours to obtain graphite.

[0256] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. The product was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0257] [Table 3]

[0258] As can be seen from the test results in Table 3, when other conditions are the same, the R value R50 at which the cumulative distribution of the negative electrode active material is 50% can be adjusted by adjusting the manufacturing process of the core graphite.

[0259] As can be further seen from the test results in Table 3, when the degree of uncoated negative electrode active material is the same, the rapid charging performance of the battery improves as the R value R50, at which the cumulative distribution of the negative electrode active material is 50%, increases.

[0260] Example 4 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0261] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0262] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:3 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized in a nitrogen atmosphere at 1150°C for 6 hours. It was then cooled to 50°C and removed. It was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0263] Example 5 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0264] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0265] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:7 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. It was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0266] Example 6 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0267] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0268] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:10 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. It was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0269] Example 7 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0270] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0271] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:0.7 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. The mixture was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0272] [Table 4]

[0273] As can be seen from the test results in Table 4, under the same conditions, the R value (R50) at which the cumulative distribution of the negative active material becomes 50% and the degree of uncoated negative active material can be adjusted by adjusting the mass ratio of graphite to the liquid hard carbon coating agent.

[0274] As can be further seen from the test results in Table 4, when the mass ratio of graphite to liquid phase hard carbon coating agent is between 100:3 and 100:7, the battery can exhibit a good combination of high energy density, high cycle capacity retention, and high critical charge rate.

[0275] As can be seen from the test results in Table 4, as the mass of the liquid hard carbon coating agent increases, the cycle performance of the battery initially improves, but as the mass of the liquid hard carbon coating agent increases, the cycle performance of the battery tends to decrease. This is because when the mass of the liquid hard carbon coating agent is small, the coating layer formed is thin, and at this time, the coating layer can reduce the co-intercalation phenomenon of the solvent, thereby improving the cycle performance of the battery. However, as the mass of the liquid hard carbon coating agent continues to increase, the thickness of the coating layer increases, resulting in more voids in the coating layer and more side reactions, which tends to decrease the cycle performance of the battery.

[0276] Example 8 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0277] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0278] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 800, a viscosity of 2000 mPa·s at 25°C, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. It was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0279] [Table 5]

[0280] As can be seen from the test results in Table 5, under the same conditions, the R value (R50) at which the cumulative distribution of the negative active material reaches 50% and the degree of uncoated negative active material can be adjusted by adjusting the weight-average molecular weight and / or viscosity of the liquid hard carbon coating agent. When the weight-average molecular weight and / or viscosity of the liquid hard carbon coating agent are within an appropriate range, the degree of uncoated negative active material is reduced, and the battery can have a higher critical charge rate, thereby providing better fast charging performance.

[0281] Example 9 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0282] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0283] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 350 r / min, and the mixing time was 7 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. It was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0284] Example 10 The battery manufacturing process was the same as in Example 1, except for the manufacturing process of the negative electrode active material.

[0285] (1) Manufacturing of negative electrode active material Petroleum needle coke is crushed, shaped, and classified to obtain aggregate. The resulting aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation. A step-by-step heating and granulation process is used during heating, with program heating plates set to 200°C, 300°C, and 600°C, respectively. The material is held at 200°C for 1 hour, 300°C for 2 hours, and 600°C for 2 hours, then cooled for 3 hours before being removed. The granulated material is then placed in an Acheson graphitization furnace and graphitized at 3000°C for approximately 50 hours to obtain graphite.

[0286] Graphite and liquid hard carbon coating agent were mixed in a solid-liquid mixture at a mass ratio of 100:5 using a mixer. The mixer's rotation speed was 600 r / min, and the mixing time was 5 minutes. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity at 25°C of 550 mPa·s, and a solids content of 70%-71%. The solid-liquid mixed product was placed in a shuttle kiln and carbonized at 1150°C under a nitrogen atmosphere for 6 hours. It was then cooled to 50°C and removed. The product was then depolymerized, sieved, and demagnetized to obtain the negative electrode active material.

[0287] [Table 6]

[0288] As can be seen from the test results in Table 6, under the same conditions, the degree of uncoated anode active material can be adjusted by adjusting the solid-liquid mixing parameters of graphite and liquid hard carbon coating agent. Keeping the solid-liquid mixing parameters of graphite and liquid hard carbon coating agent within an appropriate range can reduce the degree of uncoated anode active material. Under the same conditions, a smaller degree of uncoated anode active material can result in a higher critical charge rate, which in turn can improve fast charging performance.

[0289] Example 11 The manufacturing process of the battery was the same as in Example 1, except for the manufacturing process of the negative electrode sheet.

[0290] (2) Manufacturing of negative electrode sheets The negative electrode active material prepared in Example 1, the thickener sodium carboxymethyl cellulose, the negative electrode binder styrene butadiene rubber (SBR), and the negative electrode conductive agent Super P were mixed in a mass ratio of 96.9:1.1:1.5:0.5, and deionized water as a solvent was added. The mixture was uniformly stirred using a vacuum stirrer to prepare a negative electrode paste.

[0291] The negative electrode paste was evenly applied to both surfaces of the negative electrode current collector copper foil, and the coated negative electrode current collector was then dried at room temperature and then transferred to an oven for drying. It was then cold pressed and cut to obtain a negative electrode sheet. The thickness of the negative electrode film layer on one side of the negative electrode current collector was 58 μm.

[0292] [Table 7]

[0293] As can be seen from the test results in Table 7, by partitioning the negative electrode film layers and ensuring that the mass content of the first negative electrode active material in the first negative electrode film layer is greater than the mass content of the second negative electrode active material in the second negative electrode film layer and that the mass content of the negative electrode binder in the first negative electrode film layer is less than the mass content of the negative electrode binder in the second negative electrode film layer, the battery can have a higher critical charge rate and therefore better fast charging performance. This is because this setting reduces the problem of the negative electrode binder floating up during the paste drying process, which reduces the amount of negative electrode binder on the outer surface of the negative electrode film layer, which is favorable for liquid-phase ion conduction within the negative electrode porous electrode and ion charge exchange on the surface of the negative electrode active material, resulting in better fast charging performance.

[0294] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. Furthermore, various modifications conceivable by those skilled in the art to the embodiments, as well as other forms constructed by combining some of the components of the embodiments, are also included within the scope of the present application, as long as they do not deviate from the gist of the present application.

Claims

1. one or more battery cells including a negative electrode sheet; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector and including a negative electrode active material, and the negative electrode active material includes a core including graphite and a coating layer located on at least a portion of the surface of the core and including hard carbon. In this lithium ion battery, the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit reaches 50%, in a cumulative distribution curve of R values ​​obtained in an area scanning mode with a laser microscopic confocal Raman spectroscopy instrument.

2. The lithium ion battery according to claim 1, wherein the R value R50 at which the cumulative distribution of the negative electrode active material is 50% is 0.20 to 0.

30.

3. The lithium ion battery according to any one of claims 1 to 2, wherein the proportion of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the core is 50% is 10% or less.

4. 4. The lithium ion battery according to claim 3, wherein the proportion of all R values ​​obtained by the negative electrode active material that are smaller than the R value R50 at which the cumulative distribution of the core is 50% is 6% or less.

5. The R value R50 at which the cumulative distribution of the core is 50% is smaller than the R value R50 at which the cumulative distribution of the coating layer is 50%, and / or The R value R50 at which the cumulative distribution of the coating layer reaches 50% is 0.9 to 1.4, and / or The lithium ion battery according to any one of claims 1 to 4, wherein the R value R50 at which the cumulative distribution of the core is 50% is 0.06 to 0.

13.

6. The lithium ion battery according to any one of claims 1 to 5, wherein the mass of the coating layer is 0.3% to 4.5% of the mass of the core.

7. The lithium ion battery according to any one of claims 1 to 6, wherein the mass of the coating layer is 1% to 3.2% of the mass of the core.

8. The difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core is 1 μm to 5.5 μm, and / or The lithium ion battery according to any one of claims 1 to 7, wherein the negative electrode active material has a volumetric particle size distribution Dv50 of 8 µm to 25 µm.

9. The difference between the volumetric particle size distribution Dv50 of the negative electrode active material and the volumetric particle size distribution Dv50 of the core is 1.5 μm to 4.2 μm, and / or The lithium ion battery according to claim 8, wherein the negative electrode active material has a volumetric particle size distribution Dv50 of 12 μm to 17 μm.

10. the graphite is synthetic graphite, and / or the graphite is in the form of secondary particles; and / or The graphite has an intensity ratio C(004) / C(110) of a 004 plane diffraction peak to a 110 plane diffraction peak, as measured by an X-ray diffraction method, of 5.5 to 6.5, and / or The specific capacity of the negative electrode active material is 354 mAh / g to 361 mAh / g, and / or The powder density of the negative electrode active material at a pressure of 20,000 N is 1.68 g / cm ３ ~1.78g / cm ３ and / or The specific surface area of ​​the negative electrode active material is 1.5 m ２ / g to 4.5m ２ / g. The lithium ion battery according to any one of claims 1 to 9.

11. 11. The lithium ion battery according to claim 1, wherein the negative electrode layer comprises a first negative electrode layer and a second negative electrode layer located between the first negative electrode layer and the negative electrode current collector, the thickness of the first negative electrode layer being 30% to 60% of the thickness of the negative electrode layer, the first negative electrode layer comprising a first negative electrode active material, and the second negative electrode layer comprising a second negative electrode active material, the first negative electrode active material comprising the negative electrode active material according to claim 1.

12. 12. The lithium-ion battery of claim 11, wherein the second negative electrode active material comprises the negative electrode active material of any one of claims 1 to 10, and the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and / or the mass content w1 of the first negative electrode active material in the first negative electrode film layer is 96.9% or more, and the mass content w2 of the second negative electrode active material in the second negative electrode film layer is less than 96.9%.

13. 12. The lithium-ion battery of claim 11, wherein the second negative electrode active material comprises graphite, the graphite being in the form of secondary particles, and an R value R50 at which the cumulative distribution of the graphite is 50% is 0.06 to 0.

13.

14. 14. The lithium-ion battery of claim 13, wherein the mass content w1 of the first negative electrode active material in the first negative electrode film layer is greater than the mass content w2 of the second negative electrode active material in the second negative electrode film layer, and / or the mass content w1 of the first negative electrode active material in the first negative electrode film layer is 96.9% or more, and the mass content w2 of the second negative electrode active material in the second negative electrode film layer is less than 96.9%.

15. The negative electrode film layer has a green density of 1.62 g / cm ３ ~1.80g / cm ３ and / or the thickness of the negative electrode film layer is 45 μm to 100 μm.

16. The negative electrode film layer has a green density of 1.65 g / cm ３ ~1.80g / cm ３ and / or the thickness of the negative electrode film layer is 70 μm to 100 μm.

17. 17. A power consuming device comprising a lithium ion battery according to any one of claims 1 to 16 used to supply electrical energy.

18. A negative electrode active material comprising: a core containing graphite; and a coating layer containing hard carbon located on at least a portion of the surface of the core, wherein the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit becomes 50%, in a cumulative distribution curve of R values ​​obtained in an area scanning mode of a laser microscopic confocal Raman spectroscopy apparatus.

19. providing a coke feedstock; crushing, shaping and classifying the coke raw material to obtain aggregate; mixing the obtained aggregate and binder, and sequentially subjecting the mixture to a granulation process and a graphitization process to obtain graphite; a step of solid-liquid mixing the obtained graphite and a liquid-phase hard carbon coating agent; and carbonizing the solid-liquid mixed product in a protective gas atmosphere to carbonize the liquid-phase hard carbon coating agent into hard carbon and coat the hard carbon on at least a portion of the surface of the graphite, thereby obtaining a negative electrode active material, the negative electrode active material includes a core containing graphite and a coating layer containing hard carbon located on at least a part of the surface of the core, and the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit becomes 50%, in a cumulative distribution curve of R values ​​obtained in an area scanning mode of a laser microscopic confocal Raman spectroscopy apparatus.

20. The coke feedstock comprises one or more of petroleum-based needle coke, coal-based needle coke, and / or The graphitization temperature is between 2800°C and 3800°C, and / or 20. The method of claim 19, wherein the mass of the liquid-phase hard carbon coating agent is 0.7% to 10% of the mass of the graphite.

21. The graphitization temperature is between 2850°C and 3300°C, and / or The method according to claim 20, wherein the mass of the liquid-phase hard carbon coating agent is 3% to 7% of the mass of the graphite.

22. The method according to any one of claims 19 to 21, wherein the liquid-phase hard carbon coating agent contains a liquid resin, the liquid resin having a viscosity of 150 mPa·s to 2000 mPa·s at 25°C and a solid content of 50% to 85%.

23. The manufacturing method according to claim 22, wherein the viscosity of the liquid resin at 25°C is 300 mPa·s to 900 mPa·s, and the solid content of the liquid resin is 60% to 82%.

24. The method according to any one of claims 22 to 23, wherein the liquid resin comprises at least one of a liquid phenolic resin, a liquid epoxy resin, a liquid vinyl ester resin, a liquid unsaturated polyester resin, a liquid furan resin, and derivatives of each.

25. 25. The method according to claim 24, wherein the liquid-phase hard carbon coating agent contains a liquid phenolic resin, the solid content of the liquid phenolic resin being 60% to 82% and the weight-average molecular weight being 300 to 800.

26. The method of claim 25, wherein the liquid phenolic resin has a solid content of 68% to 78% and a weight average molecular weight of 450 to 700.

27. The device for solid-liquid mixing the graphite and the liquid-phase hard carbon coating agent is a mixer, the stirring rotation speed of the mixer is 350 r / min to 1000 r / min, and the stirring time of the solid-liquid mixing is 4 min to 10 min, and / or The temperature of the carbonization treatment is 900°C to 1500°C, and / or The manufacturing method according to any one of claims 19 to 26, wherein the heat retention time for the carbonization treatment is 2 hours to 10 hours.

28. The method according to claim 27, wherein the stirring rotation speed of the mixer is 450 r / min to 850 r / min, and the stirring time for solid-liquid mixing is 6 min to 8 min.

29. a negative electrode sheet comprising: a negative electrode current collector; and a negative electrode film layer located on at least one surface of the negative electrode current collector and including a negative electrode active material, wherein the negative electrode active material comprises a core including graphite and a coating layer located on at least a portion of the surface of the core and including hard carbon, wherein the negative electrode active material has an R value R50 of 0.15 to 0.40, at which a cumulative distribution from a lower limit becomes 50%, in a cumulative distribution curve of R values ​​obtained in an area scanning mode of a laser microscopic confocal Raman spectroscopy apparatus.

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