Graphite negative electrode particles, preparation method therefor, battery, and energy storage apparatus

Abstract

The present application provides graphite negative electrode particles, a preparation method therefor, a battery, and an energy storage apparatus. The graphite negative electrode particles in the embodiments of the present application have a plurality of pores, the plurality of pores are strip-shaped, the maximum length direction of the pores is a first long diameter direction, the maximum length direction of the graphite negative electrode particles is a second long diameter direction, the range of an included angle α between the first long diameter direction and the second long diameter direction is 0°≤α≤30°, and the range of the porosity P1 of particles among the graphite negative electrode particles having a diameter greater than 10μm is 10%≤P1≤60%. The graphite negative electrode particles of the present application have a relatively high compaction density, and a relatively low expansion rate during lithium intercalation.

Description

Graphite anode particles, their preparation methods, batteries and energy storage devices

[0001] This application claims priority to Chinese Patent Application No. 202410977475.X, filed on July 19, 2024, entitled "Graphite Anode Particles, Preparation Method Thereof, Battery and Energy Storage Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of energy storage, specifically to a graphite anode particle, its preparation method, battery, and energy storage device. Background Technology

[0003] The energy efficiency requirements for lithium-ion batteries are becoming increasingly stringent, and improving energy efficiency mainly relies on enhancing the kinetics of the electrochemical system. Graphite is commonly used as the anode material in lithium-ion batteries; however, existing graphite materials struggle to achieve both a low expansion rate and a high compaction density. Summary of the Invention

[0004] This application provides a graphite anode particle with high compaction density and low expansion rate during lithium intercalation.

[0005] In a first aspect, embodiments of this application provide a graphite anode particle, the graphite anode particle having multiple pores, the multiple pores being elongated, the maximum length direction of the pores being a first major axis direction, the maximum length direction of the graphite anode particle being a second major axis direction, the range of the included angle α between the first major axis direction and the second major axis direction being 0°≤α≤30°, and the range of the porosity P1 of the particles with a diameter greater than 10μm in the graphite anode particle being 10%≤P1≤60%.

[0006] Secondly, embodiments of this application also provide a method for preparing graphite anode particles, the preparation method comprising:

[0007] A carbon source is provided, wherein the mass fraction of volatiles in the carbon source ranges from 3% to 15%;

[0008] The carbon source is pretreated at a first temperature to obtain intermediate particles; and

[0009] The intermediate particles are graphitized at a second temperature to obtain the graphite anode particles. The first temperature is lower than the second temperature. The graphite anode particles have multiple pores, which are elongated. The maximum length direction of the pores is the first major axis direction, and the maximum length direction of the graphite anode particles is the second major axis direction. The angle α between the first and second major axis directions is in the range of 0°≤α≤30°. The porosity P1 of the particles with a diameter greater than 10μm in the graphite anode particles is in the range of 10%≤P1≤60%.

[0010] Thirdly, embodiments of this application also provide a battery, which includes:

[0011] Electrolyte;

[0012] Positive electrode sheet;

[0013] A separator, the separator being located on one side of the positive electrode, and

[0014] A negative electrode sheet is disposed on the side of the separator opposite to the positive electrode sheet. The negative electrode sheet includes a negative electrode active layer, which includes the graphite negative electrode particles described in the embodiments of this application.

[0015] Fourthly, embodiments of this application also provide an energy storage device, which includes:

[0016] include:

[0017] Box; and

[0018] Multiple batteries as described in the embodiments of this application are housed within the casing.

[0019] In this embodiment of the application, the porosity P1 of the graphite anode particles with a diameter greater than 10 μm ranges from 10% to 60%, thereby giving the graphite anode particles a low expansion rate during lithium intercalation. The graphite anode particles have multiple pores, which are elongated. The maximum length direction of the pores is the first major axis direction, and the maximum length direction of the graphite anode particles is the second major axis direction. The angle α between the first and second major axis directions ranges from 0° to 30°. This allows the graphite anode particles to have a high compaction density. Through the design of the porosity and the angle between the major axis of the pores and the major axis of the graphite anode particles, the graphite anode particles can have a low expansion rate while also having a high compaction density. Therefore, when applied to batteries, the batteries can have a high energy density. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 is a schematic diagram of the structure of a graphite negative electrode particle according to an embodiment of this application.

[0022] Figure 2 is a scanning electron microscope image of the graphite anode particles prepared in Example 2 of this application.

[0023] Figure 3 is a schematic flowchart of a method for preparing graphite anode particles according to an embodiment of this application.

[0024] Figure 4 is a schematic diagram of the structure of a battery according to an embodiment of this application.

[0025] Figure 5 is a cross-sectional view of a battery according to an embodiment of this application along the AA direction in Figure 4.

[0026] Figure 6 is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application.

[0027] Figure 7 is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application.

[0028] Figure 8 is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0029] Explanation of reference numerals in the attached drawings: 100-graphite negative electrode particles, 10-pores, 300-battery, 310-positive electrode sheet, 311-positive electrode current collector, 312-positive electrode active layer, 320-separator, 330-negative electrode sheet, 331-negative electrode current collector, 332-negative electrode active layer, 340-shell, 350-end cap assembly, 400-energy storage device, 410-box. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0031] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0032] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0033] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0034] The energy efficiency requirements for lithium-ion batteries are becoming increasingly stringent, and improving energy efficiency mainly relies on enhancing the kinetics of the electrochemical system. Graphite is commonly used as the anode material in lithium-ion batteries; however, existing graphite materials struggle to achieve both a low expansion rate and a high compaction density.

[0035] Please refer to Figures 1 and 2. This application embodiment provides a graphite anode particle 100, which has a plurality of pores 10. The plurality of pores 10 are elongated. The maximum length direction of the pores 10 is the first major axis direction (as shown by the dashed line OO in Figure 1), and the maximum length direction of the graphite anode particle 100 is the second major axis direction (as shown by the dashed line PP in Figure 1). The range of the angle α between the first major axis direction and the second major axis direction is: 0°≤α≤30°. The porosity P1 of the particles with a diameter greater than 10μm in the graphite anode particle 100 is in the range of 10%≤P1≤60%.

[0036] The graphite anode particles 100 of this application embodiment can be used as, but are not limited to, as a negative electrode active material for lithium-ion batteries.

[0037] Understandably, the pore 10 is an elongated structure, that is, the length of the pore 10 is greater than the width of the pore 10.

[0038] It should be noted that the graphite negative electrode particles 100 in this embodiment of the application have a slender or elongated structure; in other words, the length of the graphite negative electrode particles 100 is greater than the width of the graphite particles.

[0039] It should be noted that, unless otherwise specified, the diameter of the graphite anode particle 100 mentioned in the embodiments of this application refers to the dimension in the major axis direction of the graphite anode particle 100, that is, the maximum length of the graphite anode particle 100.

[0040] Understandably, the range of the angle α between the major axis of the pore 10 and the major axis of the graphite negative electrode particle 100 is: 0°≤α≤30°.

[0041] Furthermore, the angle α between the first major axis direction and the second major axis direction can be, but is not limited to, less than or equal to 25°, less than or equal to 20°, less than or equal to 15°, less than or equal to 10°, etc.

[0042] Specifically, the angle α between the first major axis direction and the second major axis direction can be, but is not limited to, 0°, 3°, 5°, 8°, 10°, 13°, 15°, 18°, 20°, 23°, 25°, 28°, 30°, etc. The larger the angle α between the first major axis and the second major axis, the lower the powder compaction density of the graphite anode particles 100. This is because during the cold pressing process in the preparation of the anode sheet, the orientation of the graphite anode particles 100 makes the second major axis of the graphite anode particles 100 more inclined to be arranged parallel to the plane of the anode current collector. The larger the angle α between the first major axis and the second major axis, the stronger the suppression effect of the cold pressing external force, and the smaller the compaction density of the graphite anode particles 100. However, the expansion force of the graphite anode particles 100 during the lithium intercalation process is mainly monitored in the thickness direction of the anode sheet (also known as the Z direction). The larger the angle α between the first major axis and the second major axis, the smaller the expansion force of the graphite anode particles 100 during the lithium intercalation process. The smaller the angle α between the first and second major axes, the greater the compaction density of the graphite anode particles 100, and the greater the expansion force of the graphite anode particles 100 during lithium intercalation. In this embodiment, by ensuring that the angle α between the first and second major axes is ≤30°, the graphite anode particles 100 can have a high compaction density and a low expansion force. This reduces the risk of solid electrolyte interface (SEI) film rupture caused by the expansion of the graphite anode particles 100 during lithium intercalation, thereby reducing the repeated consumption of active lithium during the cycling process and improving the cycling performance of the graphite anode particles 100.

[0043] Furthermore, the angle α between the first major axis direction and the second major axis direction is in the range of 0°≤α≤15°. This allows the graphite anode particles 100 to have both higher compaction density and lower expansion force.

[0044] Optionally, in the graphite anode particles 100, at least 50% of the particles with a diameter greater than 10 μm have a porosity ranging from 10% to 60%.

[0045] Specifically, the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. If the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm is too small, the graphite anode particles 100 are prone to expansion during lithium intercalation, increasing the expansion rate of the graphite anode particles 100. If the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm is too large, on the one hand, it will increase the number of grain boundaries in the graphite anode particles 100, significantly reducing the compaction density and specific capacity of the graphite anode particles 100. On the other hand, due to the increased number of grain boundaries in the graphite anode particles 100, there will also be more defects, which will trigger more side reaction products, causing by-products to accumulate on the surface of the graphite anode particles 100, increasing the size of the graphite anode particles 100, and significantly deteriorating the expansion force of the battery using the graphite anode particles 100.

[0046] In this embodiment of the application, the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm ranges from 10% to 60%, thereby giving the graphite anode particles 100 a low expansion rate during lithium intercalation. The graphite anode particles 100 have multiple pores 10, which are elongated. The maximum length direction of the pores 10 is the first major axis direction, and the maximum length direction of the graphite anode particles 100 is the second major axis direction. The angle α between the first major axis direction and the second major axis direction ranges from 0° to 30°. This allows the graphite anode particles 100 to have a high compaction density. Through the design of the porosity and the angle between the major axis of the pores 10 and the major axis of the graphite anode particles 100, the graphite anode particles 100 have a low expansion rate and a high compaction density, thus enabling the battery to have a high energy density when applied to a battery.

[0047] In some embodiments, within the same graphite anode particle 100, the range of the included angle β in the first major axis direction of any two pores 10 is: 0°≤β≤20°.

[0048] Understandably, within the same graphite anode particle 100, the first major axis direction of multiple pores 10 tends to extend in the same direction. That is, the extension direction of multiple pores 10 tends to be consistent. The pores 10 tend to be arranged in parallel.

[0049] Specifically, within the same graphite negative electrode particle 100, the included angle β of the first major axis direction of any two pores 10 can be, but is not limited to, 0°, 2°, 4°, 6°, 8°, 10°, 12°, 14°, 16°, 18°, 20°, etc.

[0050] In this embodiment, the smaller the angle β between the first major axis of any two pores 10 within the same graphite anode particle 100, the better it is to increase the compaction density of the graphite anode particle 100; if the angle β between the first major axis of any two pores 10 within the same graphite anode particle 100 is too large, it indicates that the isotropy of the single crystal within the graphite anode particle 100 is relatively high and the anisotropy is reduced, thereby reducing the compaction density of the graphite anode particle 100 and reducing the energy density of the battery.

[0051] In some embodiments, within the same graphite anode particle 100, the minimum distance d between two adjacent pores 10 is in the range of 0.5μm≤d≤5μm.

[0052] Specifically, within the same graphite negative electrode particle 100, the minimum spacing d between two adjacent pores 10 can be, but is not limited to, 0.5μm, 0.8μm, 1.0μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc.

[0053] In this embodiment, if the minimum distance d between two adjacent pores 10 within the same graphite anode particle 100 is too small, then there are too many pores 10 within the graphite anode particle 100, which greatly increases the compaction density of the graphite anode particle 100. If the minimum distance d between two adjacent pores 10 within the same graphite anode particle 100 is too large, then there are too few pores 10 within the graphite anode particle 100, which reduces the buffering capacity of the graphite anode particle 100 during the lithium intercalation process, increases the expansion force of the graphite anode particle 100 during the lithium intercalation process, and increases the expansion rate of the graphite anode particle 100.

[0054] In some embodiments, the minimum length direction of the pore 10 is the minor axis direction, the size of the pore 10 along the first major axis direction is smaller than the size of the pore 10 along the minor axis direction, and the size w1 of the pore 10 along the minor axis direction is in the range of 0.5μm≤w1≤1μm.

[0055] Understandably, the minor axis direction is perpendicular to the first major axis direction.

[0056] Specifically, the dimension w1 of the pore 10 along the minor axis can be, but is not limited to, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 8μm, 0.85μm, 0.9μm, 0.95μm, 1μm, etc. If the dimension w1 of the pore 10 along the minor axis is too small, the porosity of the graphite anode particles 100 is reduced, thereby increasing the expansion force of the graphite anode particles 100 during the lithium intercalation process. If the dimension w1 of the pore 10 along the minor axis is larger, the space in the thickness direction of the anode sheet is larger when the graphite anode particles 100 are used in the battery, thereby reducing the compaction density of the graphite anode particles 100. However, during the lithium intercalation process of the graphite anode particles 100, the space for lattice expansion to release force is larger, and the reduction in expansion force is more significant. When the size w1 of the pore 10 along the minor axis is in the range of 0.5μm≤w1≤1μm, the graphite anode particles 100 can have a high compaction density and a high stress relief space when lithium is inserted into the graphite anode particles 100, thereby also making the graphite anode particles 100 have a low expansion force.

[0057] Optionally, the size w2 of the pore 10 along the first major axis direction is in the range of 3μm≤w1≤20μm.

[0058] Specifically, the size w2 of the pore 10 along the first major axis direction can be, but is not limited to, 3μm, 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, etc.

[0059] In this embodiment, if the size w2 of the pore 10 along the first major axis is too small, the porosity of the graphite anode particles 100 will be reduced, thereby increasing the expansion force of the graphite anode particles 100 during the lithium intercalation process; if the size w2 of the pore 10 along the first major axis is too large, the compaction density and specific capacity of the graphite anode particles 100 will be reduced.

[0060] In some embodiments, the porosity P2 of the graphite anode particles 100 with a diameter greater than or equal to 6 μm and less than or equal to 10 μm ranges from 5% to 20%; the porosity P3 of the graphite anode particles 100 with a diameter greater than or equal to 1 μm and less than 6 μm ranges from 3% to 5%.

[0061] Specifically, the porosity P2 of the particles with a diameter greater than or equal to 6 μm and less than or equal to 10 μm in the graphite anode particles 100 can be, but is not limited to, 5%, 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, etc. If the porosity P2 of the particles with a diameter greater than or equal to 6 μm and less than or equal to 10 μm in the graphite anode particles 100 is too small, the graphite anode particles 100 are prone to expansion during lithium intercalation, increasing the expansion rate of the graphite anode particles 100; if the porosity P2 of the particles with a diameter greater than or equal to 6 μm and less than or equal to 10 μm in the graphite anode particles 100 is too large, the specific capacity and compaction density of the graphite anode particles 100 are reduced.

[0062] Specifically, the porosity P3 of the particles with a diameter greater than or equal to 1 μm and less than 6 μm in the graphite anode particles 100 can be, but is not limited to, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, etc. If the porosity P3 of the particles with a diameter greater than or equal to 1 μm and less than 6 μm in the graphite anode particles 100 is too small, the graphite anode particles 100 are prone to expansion during lithium intercalation, increasing the expansion rate of the graphite anode particles 100; if the porosity P3 of the particles with a diameter greater than or equal to 1 μm and less than 6 μm in the graphite anode particles 100 is too large, the specific capacity and compaction density of the graphite anode particles 100 will be reduced.

[0063] In some embodiments, the graphite anode particles 100 include multiple layers of sheets stacked sequentially, and the first major axis direction of the pores 10 is parallel to the sheets.

[0064] Understandably, the pores 10 extend within the sheets of the graphite anode particles 100. The direction of extension of the pores 10 is parallel to the direction of extension of the sheets of the graphite anode particles 100.

[0065] In this embodiment, during the lithium intercalation process of the graphite anode particles 100, the graphite lattice expands, and the pores 10 extend within the sheets of the graphite anode particles 100, which can play a certain buffering role, reducing the expansion force of the graphite anode particles 100 during lithium intercalation, thereby reducing the risk of SEI film rupture caused by the expansion of the graphite anode particles 100 during lithium intercalation, reducing the repeated consumption of active lithium during the cycling process of the graphite anode particles 100, and thus improving the cycling performance of the graphite anode particles 100.

[0066] Optionally, the D10 of the graphite anode particles 100 is in the range of 2μm≤D10≤9μm, where D10 refers to the particle size corresponding to the cumulative particle size distribution percentage of the graphite anode particles 100 reaching 10%. Specifically, the D10 of the graphite anode particles 100 can be, but is not limited to, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc.

[0067] Optionally, the D50 of the graphite anode particles 100 is in the range of 8 μm ≤ D50 ≤ 18 μm, where D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the graphite anode particles 100 reaches 50%. Specifically, the D50 of the graphite anode particles 100 can be, but is not limited to, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 17 μm, 18 μm, etc.

[0068] Optionally, the D90 of the graphite anode particles 100 ranges from 20 μm to 35 μm, where D90 refers to the particle size corresponding to the cumulative particle size distribution percentage of the graphite anode particles 100 reaching 90%. Specifically, the D90 of the graphite anode particles 100 can be, but is not limited to, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 35 μm, etc.

[0069] Optionally, the D99 of the graphite anode particles 100 is in the range of D99 ≤ 58 μm, where D99 refers to the particle size corresponding to the cumulative particle size distribution percentage of the graphite anode particles 100 reaching 99%. Specifically, the D99 of the graphite anode particles 100 can be, but is not limited to, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 56 μm, 58 μm, etc.

[0070] The graphite anode particles 100 of this application embodiment can be prepared by the methods described in the following embodiments of this application. In addition, they can also be prepared by other methods. The preparation methods of this application embodiment are merely one or more preparation methods of the graphite anode particles 100 of this application and should not be construed as limiting the graphite anode particles 100 provided in the embodiments of this application.

[0071] Please refer to Figure 3. This application also provides a method for preparing graphite anode particles 100, the preparation method comprising:

[0072] S201, providing a carbon source, wherein the mass fraction of volatile matter in the carbon source ranges from 3% to 15%;

[0073] Optionally, the carbon source may be, but is not limited to, at least one of petroleum coke, pitch coke, coal coke, metallurgical coke, etc.

[0074] Specifically, the mass fraction of volatiles in the carbon source can be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. If the mass fraction of volatiles in the carbon source is too low, the porosity of the resulting graphite anode particles 100 will be too low, increasing the impedance of the graphite anode particles 100, reducing the kinetic performance of the graphite anode particles 100, and increasing the expansion force of the graphite anode particles 100 during lithium intercalation, thus reducing the cycle performance of the graphite anode particles 100. If the mass fraction of volatiles in the carbon source is too high, the compaction density of the resulting graphite anode particles 100 will be reduced, thus reducing the specific capacity and energy density of the graphite anode particles 100.

[0075] S202, the carbon source is pretreated at a first temperature to obtain intermediate particles; and

[0076] S203, the intermediate particles are graphitized at a second temperature to obtain the graphite anode particles 100, wherein the first temperature is lower than the second temperature, and the graphite anode particles 100 have a plurality of pores 10, the plurality of pores 10 being elongated, the maximum length direction of the pores 10 being a first major axis direction, the maximum length direction of the graphite anode particles 100 being a second major axis direction, the range of the angle α between the first major axis direction and the second major axis direction being 0°≤α≤30°, and the range of the porosity P1 of the particles with a diameter greater than 10μm in the graphite anode particles 100 being 10%≤P1≤60%.

[0077] For a detailed description of other features of the graphite anode particles 100, please refer to the description of the corresponding part of the above embodiments, which will not be repeated here.

[0078] The graphite anode particles 100 prepared by the method of this application have a porosity P1 in the range of 10% ≤ P1 ≤ 60% for particles with a diameter greater than 10 μm, thereby giving the graphite anode particles 100 a low expansion rate during lithium intercalation. The graphite anode particles 100 have multiple pores 10, which are elongated. The maximum length direction of the pores 10 is the first major axis direction, and the maximum length direction of the graphite anode particles 100 is the second major axis direction. The angle α between the first major axis direction and the second major axis direction is in the range of 0° ≤ α ≤ 30°. This allows the graphite anode particles 100 to have a high compaction density. By designing the porosity and the angle between the major axis of the pores 10 and the major axis of the graphite anode particles 100, the graphite anode particles 100 can have a low expansion rate and a high compaction density, thereby giving the battery a high energy density when applied to a battery.

[0079] Optionally, in S201, providing the carbon source includes: pulverizing the carbon source.

[0080] Optionally, the carbon source is coarsely crushed by a jaw crusher and then ground into fine powder by an air jet mill to obtain aggregate particles of carbon source with a median particle size Dv50 ranging from 6μm to 18μm.

[0081] Specifically, the median particle size Dv50 of the carbon source aggregate particles can be, but is not limited to, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, etc. The larger the median particle size Dv50 of the carbon source aggregate particles, the larger the range of spacing between two adjacent pores 10 in the multiple pores 10 of the resulting graphite anode particles 100. However, this results in too few pores 10 within the graphite anode particles 100, which reduces the buffering capacity of the graphite anode particles 100 during the lithium intercalation process, increases the expansion force during lithium intercalation, and increases the expansion rate of the graphite anode particles 100.

[0082] Furthermore, the median particle size (Dv50) of the carbon source aggregate particles ranges from 8 μm to 123 μm. This allows the prepared graphite anode particles 100 to have a high compaction density while also having good buffering capacity during lithium intercalation, thus better reducing the expansion rate of the graphite anode particles 100 during lithium intercalation.

[0083] In some embodiments, when the carbon source is pretreated at the first temperature or before the carbon source is pretreated at the first temperature, the method further includes: grinding the carbon source to perform a rounding process, wherein the rotational speed during the rounding process is in the range of 40 r / min to 50 r / min.

[0084] Optionally, the carbon source is rounded in a horizontal reactor.

[0085] Specifically, the rotation speed during the corner rounding process can be, but is not limited to, 40 r / min, 42 r / min, 44 r / min, 46 r / min, 48 r / min, 50 r / min, etc. Grinding the carbon source to achieve corner rounding improves the edge sharpness of the resulting graphite anode particles 100, increases their compaction density, and enhances their processing performance. If the rotation speed during corner rounding is too low, it will not effectively shape the edge sharpness of the carbon source, resulting in a lower compaction density during rolling. Conversely, if the rotation speed is too high, the angle α between the first and second major axes of the resulting graphite anode particles 100 will be too large, similarly reducing the compaction density, but also decreasing the expansion force of the graphite anode particles 100 during lithium intercalation. When the rotation speed during the rounding process is in the range of 40 r / min to 50 r / min, the resulting graphite anode particles 100 can have a higher compaction density and a lower expansion force during the lithium intercalation process.

[0086] It should be noted that the carbon source is polished to round the corners, which can be done before the carbon source is pretreated at the first temperature, or it can be done simultaneously with the pretreatment step. In other words, the pretreatment process can be carried out in a horizontal reactor, and this application does not make any specific limitations.

[0087] Optionally, in S201, the range of the first temperature T1 is 500℃≤T1≤800℃. That is, the range of the pretreatment temperature T1 is 500℃≤T1≤800℃.

[0088] Specifically, the first temperature T1 can be, but is not limited to, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, etc. In this embodiment, if the pretreatment temperature is too low, it will not have a significant effect on the volatilization of volatiles, and will not play a role in creating internal pores, thus reducing the porosity of the obtained graphite anode particles 100 and increasing the expansion force of the graphite anode particles 100 during the lithium intercalation process; if the pretreatment temperature is too high, it will increase the preparation cost of the graphite anode particles 100, and will also increase the minor diameter of the internal pores 10 of the obtained graphite anode particles 100, reducing the compaction density of the graphite anode particles 100.

[0089] Optionally, the pretreatment time can range from 2 hours to 4 hours. Specifically, the pretreatment time can be, but is not limited to, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc. If the pretreatment time is too short, too little volatile matter will be removed; if the pretreatment time is too long, the preparation cost of the graphite anode particles 100 will increase.

[0090] Optionally, in S203, the graphitization treatment of the intermediate particles at a second temperature includes: placing the intermediate particles in a graphite crucible and performing graphitization treatment in a graphitization furnace at a second temperature T2 ranging from 2800℃ to 3500℃, wherein the height of the graphite crucible ranges from 100cm to 140cm, and the filling height of the intermediate particles in the graphite crucible is 70% to 90% of the height of the graphite crucible.

[0091] Optionally, the height of the graphite crucible can be, but is not limited to, 100cm, 105cm, 110cm, 115cm, 120cm, 125cm, 130cm, 135cm, 140cm, etc. Increasing the height of the graphite crucible is beneficial to improving the porosity of the obtained graphite anode particles 100.

[0092] Optionally, the filling height of the intermediate particles in the graphite crucible is 70%, 75%, 80%, 85%, 90%, etc., of the height of the graphite crucible. The smaller the proportion of the filling height of the intermediate particles in the graphite crucible, the more beneficial it is to improving the porosity of the obtained graphite anode particles 100.

[0093] Optionally, in S202, the range of the second temperature T2 is 2800℃≤T2≤3500℃. That is, the range of the graphitization treatment temperature is 2800℃≤T2≤3500℃. Specifically, the second temperature T2 can be, but is not limited to, 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, 3050℃, 3100℃, 3150℃, 3200℃, 3250℃, 3300℃, 3350℃, 3400℃, 3450℃, 3500℃, etc. If the graphitization treatment temperature is too low, the degree of graphitization of the graphite anode particles 100 will be reduced, the conductivity of the graphite anode particles 100 will be reduced, and thus the kinetic performance of the graphite anode particles 100 will be reduced; if the graphitization treatment temperature is too high, the preparation cost of the graphite anode particles 100 will be increased.

[0094] Optionally, the holding time for the graphitization treatment ranges from 12 hours to 24 hours. Specifically, the holding time for the graphitization treatment can be, but is not limited to, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc. If the holding time for the graphitization treatment is too short, the degree of graphitization of the resulting graphite anode particles 100 will be too low, reducing the conductivity of the graphite anode particles 100 and thus reducing the kinetic performance of the graphite anode particles 100; if the holding time for the graphitization treatment is too long, it will increase the preparation cost of the graphite anode particles 100.

[0095] Please refer to Figures 4 to 6. This application embodiment also provides a battery 300, which includes an electrolyte, a positive electrode 310, a separator 320, and a negative electrode 330. The separator 320 is located on one side of the positive electrode 310, and the negative electrode 330 is disposed on the side of the separator 320 opposite to the positive electrode 310. The negative electrode 330 includes a negative electrode active layer 332, and the negative electrode active layer 332 includes the graphite negative electrode particles 100 described in this application embodiment.

[0096] Understandably, the positive electrode 310, the separator 320, and the negative electrode 330 are all at least partially immersed in the electrolyte.

[0097] Understandably, the positive electrode 310, the separator 320, and the negative electrode 330 are sequentially stacked to form an electrode assembly. The electrode assembly can be, but is not limited to, a wound structure, a stacked structure, etc., and this application does not specifically limit it in this regard.

[0098] Optionally, the negative electrode 330 further includes a negative electrode current collector 331, and the negative electrode active layer 332 is disposed on the surface of the negative electrode current collector 331. It can be understood that the negative electrode active layer 332 may cover one surface or both opposite surfaces of the negative electrode current collector 331.

[0099] Optionally, the negative electrode current collector 331 can be, but is not limited to, a copper sheet.

[0100] Optionally, the negative electrode active layer 332 further includes a negative electrode conductive agent, a negative electrode binder, and a negative electrode thickener.

[0101] Referring to Figure 7, optionally, the positive electrode 310 includes a positive current collector 311 and a positive active layer 312, wherein the positive active layer 312 is disposed on the surface of the positive current collector 311. It can be understood that the positive active layer 312 may cover one surface or both opposite surfaces of the positive current collector 311.

[0102] Optionally, the positive current collector 311 can be, but is not limited to, an aluminum sheet.

[0103] Optionally, the positive electrode active layer 312 includes a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode thickener.

[0104] Optionally, the positive electrode active material can be, but is not limited to, lithium iron phosphate.

[0105] Optionally, the diaphragm 320 can be, but is not limited to, at least one of polypropylene membrane (PP membrane), polyethylene membrane (PE membrane), ceramic diaphragm 320, etc.

[0106] Optionally, the battery 300 further includes a housing 340 and an end cap assembly 350, the housing 340 and the end cap assembly 350 forming a closed receiving cavity for housing the electrolyte, the positive electrode 310, the separator 320, and the negative electrode 330. Understandably, the end cap assembly 350 electrically connects the positive electrode 310 and the negative electrode 330, respectively, and leads out the positive electrode 310 and the negative electrode 330 for electrical connection to external devices or other batteries 300.

[0107] The graphite anode particles 100 and battery 300 of this application will be further described below through specific embodiments.

[0108] Example 1

[0109] The graphite anode particles 100 in this embodiment are prepared through the following steps:

[0110] (1) Provide petroleum coke with a volatile matter mass fraction of 5%, and crush the petroleum coke into fine powder by passing it through a jaw crusher and then grinding it into fine powder by an air jet mill to obtain carbon source aggregate, wherein the Dv50 of the carbon source aggregate is 8um.

[0111] (2) The aggregate containing the carbon source was placed in a horizontal reactor and pretreated at 600℃ to obtain intermediate particles, wherein the rotation speed of the horizontal reactor was 40 r / min; and

[0112] (3) The intermediate particles are placed in a graphite crucible with a height of 100cm. The height of the intermediate particles is 90% of the height of the graphite crucible. The graphitization process is carried out in a graphite furnace at 3100℃ to obtain graphite anode particles 100.

[0113] Example 2

[0114] The difference between this embodiment and Embodiment 1 is that the volatile matter content of the stone tar is 10% by mass.

[0115] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0116] Example 3

[0117] The difference between this embodiment and Embodiment 1 is that the volatile matter content of the stone tar is 15% by mass.

[0118] During the graphitization process, the height of the graphite crucible is 140 cm, and the height of the intermediate particles is 70% of the height of the graphite crucible.

[0119] Example 4

[0120] The difference between this embodiment and Embodiment 1 is that the rotational speed of the horizontal reactor is 0.

[0121] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0122] Example 5

[0123] The difference between this embodiment and Embodiment 1 is that the rotation speed of the horizontal reactor is 45 r / min.

[0124] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0125] Example 6

[0126] The difference between this embodiment and Embodiment 1 is that the pretreatment temperature is 700°C.

[0127] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0128] Example 7

[0129] The difference between this embodiment and Embodiment 1 is that the pretreatment temperature is 800℃.

[0130] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0131] Example 8

[0132] The difference between this embodiment and Embodiment 1 is that the Dv50 of the carbon source aggregate is 10µm.

[0133] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0134] Example 9

[0135] The difference between this embodiment and Embodiment 1 is that the Dv50 of the carbon source aggregate is 15µm.

[0136] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0137] Comparative Example 1

[0138] The difference between this comparative example and Example 1 is that the volatile matter content of the stone tar is 18% by mass, and the Dv50 of the carbon source aggregate is 18 μm.

[0139] During the graphitization process, the height of the graphite crucible is 150cm, and the height of the intermediate particles is 65% of the height of the graphite crucible.

[0140] Comparative Example 2

[0141] The difference between this comparative example and Example 1 is that the rotation speed of the horizontal reactor is 55 r / min.

[0142] During the graphitization process, the height of the graphite crucible is 120cm, and the height of the intermediate particles is 80% of the height of the graphite crucible.

[0143] The graphite negative electrode particles 100 of each embodiment and comparative example are assembled into a square battery 300: negative electrode sheets 330 are prepared by using the graphite negative electrode particles 100 prepared by each embodiment and comparative example, and the negative electrode sheet 330, polypropylene separator 320, lithium iron phosphate positive electrode sheet 310 and lithium hexafluorophosphate electrolyte with a concentration of 1 mol / L are assembled into a soft pack battery 300.

[0144] Various performance tests were conducted on the graphite anode particles 100 and the assembled battery 300 of each embodiment and comparative example. The test results are shown in Table 1 below.

[0145] (1) Porosity Test: After disassembling battery 300, the outermost, middle, and innermost folds of negative electrode sheet 330 were selected. Further, the tab side, middle position, and opposite side of each fold of negative electrode sheet 330 were selected for ion polishing-scanning electron microscopy (CP+SEM test). Five images from different field positions were selected at 1KX magnification. The porosity of each image was measured using Nano Measurer software. Finally, the internal porosity of the graphite negative electrode particles 100 was statistically analyzed. The diameter of the graphite negative electrode particles 100 was measured using the same software, specifically the longest diameter (i.e., maximum length) of the particles.

[0146] (2) The angle α between the first major axis and the second major axis, the dimension w1 of the minor axis, and the distance d between two adjacent pores 10 were measured using a scanning electron microscope (SEM). The SEM image of the graphite anode particles 100 prepared in Example 2 is shown in Figure 2. In each embodiment and comparative example, when measuring the angle α between the first major axis and the second major axis, 100 graphite anode particles 100 were taken, and the average value of the first major axis and the second major axis on each graphite anode particle 100 was calculated. The average value of the angle α between the first major axis and the second major axis among the 100 particles was used as the angle α between the first major axis and the second major axis of the graphite anode particles 100 in this embodiment or comparative example. When measuring the dimension w1 of the minor axis, 100 pores 10 were taken, and the average value of the dimension w1 of the minor axis of each pore 10 was used as the w1 of the graphite anode particles 100 in this embodiment or comparative example. When measuring the distance d between two adjacent pores 10, 100 pores 10 are taken, and the average distance between any two adjacent pores 10 is taken as d of the graphite negative electrode particle 100 in this embodiment or comparative example.

[0147] (3) Powder compaction density test: Take 2g to 3g of graphite negative electrode particles 100 and add them into a mold with a diameter of 13mm. After pressing to 5 tons, hold the pressure for 10s and then release the pressure. Measure the mass and volume of the pressed cylinder and calculate the powder compaction density.

[0148] (4) Expansion force test after 500 cycles: During cycling, a fixture is installed on the battery 300. The fixture is a three-layer structure, with a stress sensor installed between the top two layers and the bottom two plates fixing the lithium-ion battery 300. When the lithium-ion battery 300 expands due to changes in thickness during cycling, the pressure sensor on the upper layer converts the position signal into a mechanical signal to obtain the magnitude of the expansion force at this time. The expansion force of the battery 300 is measured after 500 cycles.

[0149] Table 1 Performance parameters of each embodiment and comparative example

[0150] The test results from Examples 1 to 3 show that the higher the mass fraction of volatiles in the carbon source, the higher the height of the graphite crucible, and the smaller the proportion of intermediate particles filling the height, the greater the porosity of the resulting graphite anode particles 100. Furthermore, as the porosity P1 of particles with a diameter greater than 10 μm in the graphite anode particles 100 increases, the powder compaction density of the graphite anode particles 100 gradually decreases. This is because porosity occupies a certain volume space. Although the graphite anode particles 100 are soft, during cold pressing, they will be compressed to some extent along the thickness direction (also known as the Z-direction) of the anode sheet 330. However, the larger the porosity of the graphite anode particles 100, the larger the space occupied by the pores 10, resulting in a smaller mass for the same volume, thus affecting the use of the graphite anode particles 100 in high volumetric energy density systems. However, since porosity has a certain stress-relieving effect, during the cyclic lithium intercalation process of graphite anode particles 100, the lattice expansion caused by lithium intercalation will be partially relieved due to the presence of pores 10 inside the graphite anode particles 100, thus showing a trend that the expansion force of graphite anode particles 100 decreases significantly with the increase of pores 10.

[0151] The test results from Examples 2, 4, 5, and Comparative Example 2 show that when the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm remains constant, the powder compaction density of the graphite anode particles 100 gradually decreases as the angle α between the first and second major axes increases. This is because during cold pressing, the orientation of the graphite anode particles 100 makes the direction of their maximum length more parallel to the anode current collector 331. A larger angle α between the first and second major axes results in a stronger suppression of the cold pressing force, leading to a lower powder compaction density. Simultaneously, particles with a larger angle α between the first and second major axes exhibit relatively smaller forces in the Z-direction, resulting in a smaller expansion force in the battery 300 using the graphite anode particles 100. When the angle α between the first major axis direction and the second major axis direction is too large, the powder compaction density of the obtained graphite negative electrode particles 100 will be too low, which is not conducive to improving the energy density of the battery 300.

[0152] The test results of Examples 1, 6 and 7 show that as the pretreatment temperature increases, the porosity of the obtained graphite anode particles 100 gradually increases, the size w1 of the minor axis of the pores 10 also gradually increases, the compaction density of the graphite anode particles 100 gradually decreases, and the expansion force generated by the battery 300 using the graphite anode particles 100 during cycling also gradually decreases; however, the effect on the spacing between adjacent pores 10 is not significant.

[0153] As can be seen from the test results of Examples 2, 6 and 7, when the angle α between the first major axis direction and the second major axis direction of the graphite anode particle 100 remains unchanged, the powder compaction density of the graphite anode particle 100 gradually decreases as the size w1 of the pore 10 inside the graphite anode particle 100 along the minor axis direction increases. This is because the increase of the size w1 of the pore 10 along the minor axis direction means that the space in the Z direction is larger, and the powder compaction density is smaller. Since the Z direction space is larger, the space for lattice expansion caused by lithium intercalation is larger, and the reduction of expansion force is more significant.

[0154] The test results of Examples 2, 8, and 9 show that when the porosity P1 of the graphite anode particles with a diameter greater than 10 μm, the angle α between the first major axis and the second major axis, and the size w1 of the pores 10 along the minor axis remain unchanged, the powder compaction density of the graphite anode particles 100 gradually increases as the distance d between two adjacent pores 10 within the same graphite anode particle 100 increases. This is mainly reflected in the decrease in the number of pores 10 in the Z direction. The decrease in the number of pores 10 will affect the release of lattice expansion force, resulting in a larger expansion force.

[0155] As can be seen from the test results of Example 1 and Comparative Example 1, when the porosity P1 of the graphite anode particles 100 with a diameter greater than 10 μm is too large, this will increase the number of grain boundaries in the graphite anode particles 100, significantly reduce the compaction density of the graphite anode particles 100, and due to the increased number of grain boundaries in the graphite anode particles 100, there will also be more defects, which will trigger more side reaction products, causing by-products to accumulate on the surface of the graphite anode particles 100, increasing the size of the graphite anode particles 100, and significantly deteriorating the expansion force of the battery 300 using the graphite anode particles 100.

[0156] Please refer to Figure 8. This application embodiment also provides an energy storage device 400, which includes a housing 410 and the battery 300 described in this application embodiment, wherein the plurality of batteries 300 are housed in the housing 410.

[0157] The energy storage device 400 of this application can be applied to, but is not limited to, energy storage on the generation side, energy storage on the grid side, and energy storage on the consumption side.

[0158] The term "multiple" refers to two or more.

[0159] Understandably, the multiple batteries 300 of the energy storage device 400 can be connected in parallel, or in series, or partially in parallel and partially in series (in other words, mixed connection). This application does not specifically limit the connection method of the multiple batteries 300 of the same energy storage device 400.

[0160] Understandably, the housing 410 has accommodating cavities in which multiple batteries 300 are housed. In some embodiments, each accommodating cavity houses one battery 300. In other embodiments, each accommodating cavity houses multiple batteries 300.

[0161] Optionally, the energy storage device 400 may include, but is not limited to, a battery module 300, a battery pack 300, or a battery system 300. The actual application form of the energy storage device 400 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 400. This application embodiment only uses a multi-cell battery 300 as an example for illustration. When the energy storage device 400 is a single-cell battery 300, the energy storage device 400 may be at least one of cylindrical batteries 300, prismatic batteries 300, etc.

[0162] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various places in the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

A graphite negative electrode particle, wherein, The graphite negative electrode particle has a plurality of pores, the plurality of pores are long strips, a maximum length direction of the pores is a first long diameter direction, a maximum length direction of the graphite negative electrode particle is a second long diameter direction, an included angle a between the first long diameter direction and the second long diameter direction ranges from 0° to 30°, and a porosity P1 of particles with a diameter greater than 10 μm in the graphite negative electrode particle ranges from 10% to 60%. The graphite negative electrode particle according to claim 1, wherein, An included angle β of the first long diameter direction of any two pores in the same graphite negative electrode particle ranges from 0° to 20°. The graphite negative electrode particle according to claim 1, wherein A distance d between adjacent two pores in the same graphite negative electrode particle ranges from 0.5 μm to 5 μm. The graphite negative electrode particle according to claim 1, wherein A minimum length direction of the pores is a short diameter direction, a size of the pores along the first long diameter direction is smaller than a size of the pores along the short diameter direction, a size w1 of the pores along the short diameter direction ranges from 0.5 μm to 1 μm, and a size w2 of the pores along the first long diameter direction ranges from 3 μm to 20 μm. The graphite negative electrode particle according to claim 1, wherein A porosity P2 of particles with a diameter greater than or equal to 6 μm and less than or equal to 10 μm in the graphite negative electrode particle ranges from 5% to 20%, and a porosity P3 of particles with a diameter greater than or equal to 1 μm and less than 6 μm in the graphite negative electrode particle ranges from 3% to 5%. The graphite negative electrode particle according to any one of claims 1 to 5, wherein The graphite negative electrode particle comprises a plurality of layers of sheets stacked in sequence, and the first long diameter direction of the pores is parallel to the sheets. A method of producing a graphite negative electrode particle, wherein The preparation method comprises: providing a carbon source, wherein a mass fraction of volatile components in the carbon source ranges from 3% to 15%; pre-treating the carbon source at a first temperature to obtain intermediate-state particles; and graphitizing the intermediate-state particles at a second temperature to obtain the graphite negative electrode particle, wherein the first temperature is less than the second temperature, wherein the graphite negative electrode particle has a plurality of pores, the plurality of pores are long strips, a maximum length direction of the pores is a first long diameter direction, a maximum length direction of the graphite negative electrode particle is a second long diameter direction, an included angle a between the first long diameter direction and the second long diameter direction ranges from 0° to 30°, and a porosity P1 of particles with a diameter greater than 10 μm in the graphite negative electrode particle ranges from 10% to 60%. The method of producing graphite negative electrode particles according to claim 7, wherein Before or during the pre-treatment of the carbon source at the first temperature, the method further comprises: polishing the carbon source to perform a rounding treatment, wherein a rotating speed during the rounding treatment ranges from 40 r / min to 50 r / min. The method of claim 7, wherein the graphite negative electrode particle is prepared by a process comprising: The first temperature T1 ranges from 500 ℃ to 800 ℃. The graphitizing the intermediate state particles at the second temperature comprises: arranging the intermediate state particles in a graphite crucible, and performing graphitizing treatment in a graphitizing furnace at a second temperature T2 in a range of 2800℃≤T2≤3500℃, wherein a height of the graphite crucible is in a range of 100cm to 140cm, and a filling height of the intermediate state particles in the graphite crucible is 70% to 90% of the height of the graphite crucible. A battery, wherein, Comprising: an electrolyte; a positive electrode sheet; a separator, the separator being located on one side of the positive electrode sheet, and a negative electrode sheet, the negative electrode sheet being arranged on a side of the separator away from the positive electrode sheet, the negative electrode sheet comprising a negative electrode active layer, the negative electrode active layer comprising the graphite negative electrode particles according to any one of claims 1-6. An energy storage device, wherein, Comprising: Comprising: a box; and a plurality of the batteries according to claim 10, the plurality of batteries being housed in the box.

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