Negative electrode active particle and preparation method therefor, negative electrode sheet and battery

Abstract

Provided are a negative electrode active particle and a preparation method therefor, a negative electrode sheet and a battery. Provided in the embodiments is a negative electrode active particle, which has a plurality of pores, wherein the length-diameter ratio α of the pores falls within the following range: 1≤α≤8. When the negative electrode active particle provided by the embodiments is applied to a battery, the battery is enabled to have a relatively high cycling capacity retention rate.

Description

Negative electrode active particles and preparation method thereof, negative electrode sheet and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 1, 2024, with application number 2024101420441 and application name “Negative electrode active particles and preparation method thereof, negative electrode sheet and battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of energy storage, and specifically to a negative electrode active particle and a preparation method thereof, a negative electrode plate and a battery. Background Art

[0003] With the continuous development of lithium-ion battery technology, lithium-ion batteries have advantages over other types of batteries such as lead-acid and nickel-cadmium batteries, such as high specific capacity, no memory effect, high operating voltage, fast charging speed, wide operating temperature range, long cycle life, small size, and light weight. Currently, lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles, energy storage cabinets and other fields, and their application range is becoming increasingly wider.

[0004] However, the cycle capacity retention rate of existing lithium-ion batteries still needs to be improved.

[0005] Summary of the Invention

[0006] The negative electrode active particles provided in the embodiments of the present application, when applied to a battery, enable the battery to have a higher cycle capacity retention rate.

[0007] In a first aspect, an embodiment of the present application provides a negative electrode active particle having a plurality of pores, wherein the aspect ratio α of the pores is in the range of 1≤α≤8.

[0008] In a second aspect, an embodiment of the present application further provides a method for preparing negative electrode active particles, the preparation method comprising:

[0009] Provide carbon source;

[0010] Pre-treating the carbon source to obtain intermediate particles; and

[0011] The intermediate particles are graphitized to obtain negative electrode active particles, wherein the negative electrode active particles have a plurality of pores, and the aspect ratio α of the pores is in the range of 1≤α≤8.

[0012] In a third aspect, an embodiment of the present application further provides a negative electrode sheet, comprising:

[0013] a negative electrode current collector; and

[0014] A negative electrode active layer is provided on the surface of the negative electrode current collector, and the negative electrode active layer includes the negative electrode active particles described in the embodiment of the present application.

[0015] In a fourth aspect, an embodiment of the present application provides a battery, comprising:

[0016] electrolyte;

[0017] A positive electrode sheet, the positive electrode sheet is immersed in the electrolyte;

[0018] a diaphragm, located on one side of the positive electrode sheet and immersed in the electrolyte, and

[0019] The negative electrode plate described in the embodiment of the present application is arranged on the side of the separator away from the positive electrode plate and immersed in the electrolyte.

[0020] The negative electrode active particles of the present application are designed to have a pore aspect ratio α in the range of 1≤α≤8, thereby enabling a battery using the negative electrode active particles to have higher kinetic performance and higher initial efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] FIG1 is a diagram showing an application scenario of an energy storage system according to an embodiment of the present application.

[0023] FIG2 is a schematic structural diagram of an energy storage system according to an embodiment of the present application.

[0024] FIG3 is a circuit block diagram of an energy storage system according to an embodiment of the present application.

[0025] FIG4 is a partial perspective structural diagram of an electric power system according to an embodiment of the present application.

[0026] FIG5 is a schematic structural diagram of an energy storage device according to an embodiment of the present application.

[0027] FIG6 is a schematic structural diagram of a battery according to an embodiment of the present application.

[0028] FIG. 7 is a schematic cross-sectional view of a battery according to an embodiment of the present application along the AA position in FIG. 6 .

[0029] FIG8 is a schematic cross-sectional view of the positive electrode sheet according to an embodiment of the present application along the AA position in FIG6 .

[0030] FIG9 is a schematic cross-sectional view of the negative electrode sheet along the AA position in FIG6 according to an embodiment of the present application.

[0031] FIG10 is a schematic diagram of the structure of negative electrode active particles according to an embodiment of the present application.

[0032] FIG11 is an enlarged view of the dotted frame I in FIG10 .

[0033] FIG12 is a schematic flow chart of a method for preparing negative electrode active particles according to an embodiment of the present application.

[0034] FIG13 is a schematic diagram of a flow chart of graphitization treatment during the preparation of negative electrode active particles according to an embodiment of the present application.

[0035] FIG14 is a scanning electron microscope image (SEM image) of a cross section of the negative electrode active particles of Example 5 of the present application.

[0036] FIG15 is an impedance-state-of-charge curve diagram of the batteries of Example 5 and Comparative Example 2 of the present application.

[0037] Description of reference numerals:

[0038] 100-Energy storage system, 110-Electric energy conversion device, 130-Electric load, 200-Energy storage device, 210-Case, 300-Electric system, 310-Electric equipment, 400-Battery, 410-Positive electrode sheet, 411-Positive current collector, 412-Positive active layer, 420-Separator, 430-Negative electrode sheet, 431-Negative current collector, 432-Negative active layer, 440-Case, 500-Negative active particles, 510-Pores. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0040] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0041] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0042] It should be noted that, for the convenience of explanation, in the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0043] Currently, the generation of green electricity generally relies on photovoltaics, wind power, and hydropower. However, wind and solar energy are generally intermittent and highly volatile, which can cause grid instability, insufficient electricity during peak hours, and excessive electricity during off-peak hours. Unstable voltage can also damage electricity. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar power curtailment". To solve these problems, we must rely on energy storage. This means converting electrical energy into other forms of energy through physical or chemical means and storing them. When needed, this energy is converted into electrical energy and released. Simply put, energy storage is like a large "power bank", storing electricity when photovoltaic and wind energy are sufficient and releasing the stored electricity when needed.

[0044] Taking electrochemical energy storage as an example, the present application provides an energy storage device, which is equipped with a chemical battery. The chemical elements in the battery are mainly used as energy storage media. The charging and discharging process is accompanied by chemical reactions or changes in the energy storage medium. Simply put, the electricity generated by wind and solar energy is stored in the chemical battery. When the use of external electricity reaches its peak, the stored electricity is released for use, or transferred to places where electricity is scarce for use.

[0045] Currently, energy storage (i.e., energy storage) has a wide range of application scenarios, including power generation-side energy storage, grid-side energy storage, renewable energy grid-connected energy storage, and user-side energy storage. The corresponding types of energy storage devices include:

[0046] (1) Large energy storage containers used in grid-side energy storage scenarios can serve as high-quality active and reactive power regulation power sources in the grid, achieving load matching of electricity in time and space, enhancing the ability to absorb renewable energy, and are of great significance in grid system backup, alleviating peak load power supply pressure, and peak and frequency regulation.

[0047] (2) The main operating mode of small and medium-sized energy storage cabinets used in industrial and commercial energy storage scenarios (banks, shopping malls, etc.) on the user side and small household energy storage boxes used in home energy storage scenarios on the user side is "peak shaving and valley filling". Since there is a large price difference in electricity prices at peak and valley locations according to electricity demand, after users have energy storage equipment, in order to reduce costs, they usually charge the energy storage cabinets / boxes during the low electricity price period; during the peak electricity price period, the electricity in the energy storage equipment is discharged for use to achieve the purpose of saving electricity bills. In addition, in remote areas and areas with high incidence of natural disasters such as earthquakes and hurricanes, the existence of household energy storage devices is equivalent to users providing themselves and the power grid with backup power, eliminating the inconvenience caused by frequent power outages due to disasters or other reasons.

[0048] Figure 1 is a diagram illustrating an application scenario of an energy storage system 100 provided in an embodiment of the present application. The embodiment of Figure 1 of the present application uses a household energy storage scenario in user-side energy storage as an example. The energy storage device 200 of the present application is not limited to household energy storage scenarios. Figure 2 is a schematic diagram illustrating the structure of the energy storage system 100 according to an embodiment of the present application. Figure 3 is a circuit block diagram of the energy storage system 100 according to an embodiment of the present application.

[0049] Please refer to Figures 1 to 3. The present application provides an energy storage system 100, which is a household energy storage system 100. The energy storage system 100 includes an electric energy conversion device 110, an energy storage device 200, and an electrical load 130. The electric energy conversion device 110 is used to convert other forms of energy into electric energy; the energy storage device 200 is electrically connected to the electric energy conversion device 110 and is used to store the electric energy of the electric energy conversion device 110; the electric load 130 is electrically connected to the electric energy conversion device 110 and the energy storage device 200, respectively, and is used to use the electric energy of the electric energy conversion device 110 or the energy storage device 200 to work. It can be understood that part of the electric energy converted by the electric energy conversion device 110 is stored in the energy storage device 200, and part is used to power the electric load 130. The energy storage device 200 is used to store electric energy and supply the electric load 130 when the electricity price is peak. The energy storage system 100 can convert other generated energy into electrical energy and store the electrical energy in the energy storage device 200 to supply sufficient electrical energy to the electrical load 130 .

[0050] Optionally, the electric energy conversion device 110 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electric energy, providing a stable power supply for the electrical load 130 and the energy storage device 200.

[0051] Optionally, the power conversion device 110 may be a photovoltaic panel, which can convert solar energy into electrical energy during periods of low electricity prices and store the energy in the energy storage device 200. In other embodiments, the power conversion device 110 may be at least one of a wind power generation device, a thermal power generation device, a tidal power generation device, a biomass power generation device, and a mechanical power generation device.

[0052] Optionally, the energy storage device 200 is a small energy storage box that can be mounted on an outdoor wall. In other embodiments, the energy storage device 200 can also be a large energy storage container, a battery used in electronic equipment, etc.

[0053] Optionally, the electrical load 130 may be a street lamp, household appliance, motor vehicle, etc. The energy storage device 200 is used to store the electrical energy and supply it to street lamps and household appliances for use when electricity prices are high, or to supply power when the grid is out of power.

[0054] It is understood that the energy storage device 200 may include but is not limited to at least one of a single cell, a battery module, a battery pack, a battery system, etc. The single cell may be but is not limited to at least one of a cylindrical battery, a square battery, etc.

[0055] It is understandable that the drawings in this embodiment illustrate only one form of the energy storage system 100 and should not be understood as limiting the energy storage system 100 provided in this application, nor should they be understood as limiting the energy storage device 200 provided in each embodiment of this application.

[0056] 4 is a partial perspective structural diagram of an electric system 300 according to an embodiment of the present application. This embodiment of the present application further provides an electric system 300 comprising: an electric device 310 and an energy storage device 200 , wherein the energy storage device 200 supplies power to the electric device 310 .

[0057] The power-consuming device 310 in the embodiments of the present application may be, but is not limited to, a portable electronic device such as a mobile phone, tablet computer, laptop computer, desktop computer, smart bracelet, smart watch, e-reader, game console, or the like. It may also be a vehicle such as a car, truck, sedan, van, lorry, train, high-speed train, electric vehicle, or other vehicle. Furthermore, it may be various household appliances such as refrigerators, electric lights, and air conditioners. It should be understood that the power-consuming device 310 illustrated in the drawings of this application is merely one embodiment of the power-consuming device 310 and should not be construed as limiting the power-consuming device 310 provided herein.

[0058] 5 , an embodiment of the present application further provides an energy storage device 200 , which includes a box 210 and a plurality of batteries 400 . The plurality of batteries 400 are stacked and accommodated in the box 210 .

[0059] Optionally, the battery 400 may be, but is not limited to, a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery or a magnesium-ion battery, an energy storage battery, or the like.

[0060] The term "plurality" means greater than or equal to two.

[0061] It can be understood that the multiple batteries 400 of the energy storage device 200 can be connected in parallel with each other; or in series with each other; 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 400 of the same energy storage device 200.

[0062] It is understood that the housing 210 has a receiving cavity, and multiple batteries 400 are received in the receiving cavity. In some embodiments, each receiving cavity receives one battery 400. In other embodiments, each receiving cavity receives multiple batteries 400.

[0063] Referring to Figures 6 and 7 , an embodiment of the present application further provides a battery 400, which includes an electrolyte (not shown), a positive electrode sheet 410, a separator 420, and the negative electrode sheet 430. The positive electrode sheet 410 is immersed in the electrolyte; it is located on one side of the positive electrode sheet 410 and immersed in the electrolyte; and the negative electrode sheet 430 is disposed on a side of the separator 420 facing away from the positive electrode sheet 410 and immersed in the electrolyte.

[0064] It is understood that the positive electrode sheet 410, the separator 420 and the negative electrode sheet 430 are stacked in sequence to form an electrode assembly. The electrode assembly can be, but is not limited to, a wound structure, a laminated structure, etc., which is not specifically limited in this application.

[0065] Optionally, the electrolyte includes an electrolyte salt, an additive, and an organic solvent.

[0066] Optionally, the electrolyte salt is a lithium salt, which may be, but is not limited to, at least one of lithium hexafluorophosphate (LIFP6) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0067] Optionally, the organic solvent may include but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethylene glycol dimethyl ether (DEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), etc.

[0068] Optionally, the additive may include but is not limited to at least one of vinylene carbonate (abbreviated as VC), fluoroethylene carbonate (abbreviated as FEC), and the like.

[0069] 8 , optionally, the positive electrode sheet 410 includes a positive electrode current collector 411 and a positive electrode active layer 412 , wherein the positive electrode active layer 412 is disposed on the surface of the positive electrode current collector 411 . It is understood that the positive electrode active layer 412 may cover one surface or two opposite surfaces of the positive electrode current collector 411 .

[0070] Optionally, the positive electrode current collector 411 may be, but is not limited to, an aluminum sheet.

[0071] Optionally, the positive electrode active layer 412 includes positive electrode active particles, a first conductive agent, and a first binder. Optionally, the positive electrode active particles may be, but are not limited to, lithium iron phosphate. The first conductive agent may be, but are not limited to, conductive carbon black. The first binder may be, but are not limited to, polyvinylidene fluoride (PVDF).

[0072] Optionally, the diaphragm 420 may be, but is not limited to, at least one of a polypropylene film (PP film for short), a polyethylene film (PE film for short), a ceramic diaphragm 420 , and the like.

[0073] Optionally, the battery 400 further includes a housing 440 , and the housing 440 is used to accommodate the electrolyte, the positive electrode plate 410 , the separator 420 and the negative electrode plate 430 .

[0074] Referring to FIG9 , the embodiment of the present application further provides a negative electrode plate 430 , which includes a negative electrode current collector 431 and a negative electrode active layer 432 . The negative electrode active layer 432 is disposed on the surface of the negative electrode current collector 431 , and the negative electrode active layer 432 includes negative electrode active particles 500 (as shown in FIG10 ).

[0075] It can be understood that the negative electrode active layer 432 can cover one surface or two opposite surfaces of the negative electrode current collector 431 .

[0076] Optionally, the negative electrode current collector 431 may be, but is not limited to, a copper sheet.

[0077] Optionally, the negative electrode active layer 432 further includes a second conductive agent, a second binder, and a thickener. Optionally, the second conductive agent may be, but is not limited to, conductive carbon black (SP). The second binder may be, but is not limited to, styrene-butadiene latex or styrene-butadiene rubber (SBR). The thickener may be, but is not limited to, sodium carboxymethyl cellulose (CMC).

[0078] In some embodiments, the compaction density ρ of the negative electrode active layer 432 is in the range of 1.4 g / cm 3 ≤ρ≤1.7g / cm 3 Specifically, the compaction density ρ of the negative electrode active layer 432 may be, but is not limited to, 1.4 g / cm3 , 1.45g / cm 3 , 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 If the compaction density of the negative electrode active layer 432 is too high, the negative electrode active layer 432 is difficult to be infiltrated by the electrolyte, and the electrolyte infiltration is difficult, which easily causes lithium precipitation, thereby causing the cycle life of the battery 400 to decay rapidly; if the compaction density of the negative electrode active layer 432 is too low, the energy density of the battery 400 is reduced, and the unit manufacturing cost of the battery 400 is increased. When the compaction density ρ of the negative electrode active layer 432 is 1.4 g / cm 3 ≤ρ≤1.7g / cm 3 When the battery 400 is subjected to the above conditions, it can have a higher cycle capacity retention rate and a lower unit manufacturing cost.

[0079] In some embodiments, the porosity P of the negative electrode active layer 432 is in the range of 10% ≤ P ≤ 42%. Specifically, the porosity P of the negative electrode active layer 432 may be, but is not limited to, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 42%, and the like. If the porosity of the negative electrode active layer 432 is too low, the negative electrode active layer 432 is difficult to be infiltrated by the electrolyte, which makes it difficult for the electrolyte to infiltrate the negative electrode active layer 432, and lithium plating is likely to occur, thereby rapidly reducing the cycle life of the battery 400. If the porosity of the negative electrode active layer 432 is too high, the energy density of the battery 400 is reduced, and the unit manufacturing cost of the battery 400 is increased. When the porosity P of the negative electrode active layer 432 is 10% ≤ P ≤ 42%, the battery 400 can have a high cycle capacity retention rate while having a low unit manufacturing cost.

[0080] Furthermore, the porosity P of the negative electrode active layer 432 is in the range of 15%≤P≤37%. When the porosity P of the negative electrode active layer 432 is within this range, the battery 400 can have a high cycle capacity retention rate and a low unit manufacturing cost.

[0081] In some embodiments, the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is in the range of 5 N / m ≤ σ ≤ 20 N / m. Specifically, the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 can be, but is not limited to, 5 N / m, 8 N / m, 10 N / m, 12 N / m, 14 N / m, 16 N / m, 18 N / m, 20 N / m, etc. If the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is too small, the negative electrode active layer 432 may easily shed powder or residue during use, causing the cycle life of the battery 400 to decline rapidly. If the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is too large, a large amount of binder is required. Excessive use of binder increases the internal resistance of the battery 400, thereby reducing the cycle life of the battery 400. When the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is 5 N / m≤σ≤20 N / m, the battery 400 is unlikely to slag during use and has a higher cycle capacity retention rate.

[0082] In some embodiments, the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is in the range of 7 N / m ≤ σ ≤ 16 N / m. When the peel strength σ between the negative electrode active layer 432 and the negative electrode current collector 431 is within this range, the battery 400 is less likely to slag during use and has a higher cycle capacity retention rate.

[0083] 10 , an embodiment of the present application further provides a negative electrode active particle 500 , wherein the negative electrode active particle 500 has a plurality of pores 510 , and the aspect ratio α of the pores 510 is in the range of 1≤α≤8.

[0084] It can be understood that the plurality of pores 510 are randomly or irregularly distributed in the negative electrode active particles 500 .

[0085] It should be noted that the aspect ratio of the pore 510 is the ratio of the length to the width of the pore 510. The length of the pore 510 refers to the maximum length L of the pore 510, and the width of the pore 510 refers to the maximum width w of the pore 510 in a direction parallel to the direction perpendicular to the maximum length of the pore 510, that is, α = L / w.

[0086] Optionally, the negative electrode active particles 500 may be, but are not limited to, graphite particles.

[0087] Specifically, the aspect ratio α of the pores 510 can be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, etc. If the aspect ratio α of the pores 510 is too small, the kinetic performance of the negative electrode active particles 500 is reduced, thereby reducing the kinetic performance of the battery 400. If the aspect ratio α of the pores 510 is too large, the specific surface area of ​​the negative electrode active particles 500 is too high, reducing the initial efficiency of the battery 400. When the aspect ratio α of the pores 510 is between 1 and 8, the battery 400 can have higher kinetic performance and higher initial efficiency.

[0088] The negative electrode active particles 500 of the present application are designed to have an aspect ratio of the pores 510 such that the aspect ratio α of the pores 510 is in the range of 1≤α≤8, thereby enabling the battery 400 using the negative electrode active particles 500 to have higher dynamic performance and higher initial efficiency.

[0089] 11 , in some embodiments, the maximum length L of the pore 510 is in the range of 0.1 μm ≤ L ≤ 2.5 μm. Specifically, the maximum length L of the pore 510 may be, but is not limited to, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.5 μm, etc. If the maximum length L of the pores 510 is too long, the negative electrode active particles 500 are easily crushed when the negative electrode active layer 432 is compacted. Reducing the compaction pressure of the negative electrode active layer 432 reduces the compaction density of the negative electrode active layer 432, thereby reducing the energy density of the battery 400 and increasing the unit manufacturing cost of the battery 400. If the maximum length L of the pores 510 is too short, the pores 510 of the negative electrode active particles 500 are mostly nanoscale pores 510, which increases the specific surface area of ​​the negative electrode active particles 500. During the film formation reaction, more active lithium is consumed, thereby increasing the active lithium consumption of the negative electrode active particles 500 and reducing the initial efficiency of the battery 400. When the maximum length L of the pores 510 is between 0.1 μm and 2.5 μm, the negative electrode active layer 432 of the battery 400 can have a more suitable compaction density, thereby reducing the unit manufacturing cost, while also preventing the battery 400 from consuming excessive active lithium during the film formation reaction.

[0090] Unless otherwise specified, the “film formation” mentioned in this application refers to the formation of a solid electrolyte interface film (SEI film).

[0091] In some embodiments, the maximum width w of the pore 510 along a direction parallel to a direction perpendicular to the maximum length direction of the pore 510 is in a range of 0.1 μm ≤ w ≤ 2.5 μm. Specifically, along a direction parallel to the direction perpendicular to the maximum length direction of the pore 510, the maximum width w of the pore 510 may be, but is not limited to, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.5 μm, etc. If the maximum width w of the pores 510 is too long, the negative electrode active particles 500 are easily crushed when the negative electrode active layer 432 is compacted. Reducing the compaction pressure of the negative electrode active layer 432 reduces the compaction density of the negative electrode active layer 432, thereby reducing the energy density of the battery 400 and increasing the unit manufacturing cost of the battery 400. If the maximum width w of the pores 510 is too short, it means that the pores 510 of the negative electrode active particles 500 are mostly nanoscale pores 510, which will increase the specific surface area of ​​the negative electrode active particles 500. During the film formation reaction, more active lithium is consumed, thereby increasing the active lithium consumption of the negative electrode active particles 500. When the maximum width w of the pores 510 is between 0.1 μm and 2.5 μm, the negative electrode active layer 432 of the battery 400 can have a more suitable compaction density, thereby reducing the unit manufacturing cost, while also preventing the battery 400 from consuming excessive active lithium during the film formation reaction.

[0092] In some embodiments, the negative electrode active particle 500 has a predetermined cross-section, where the area of ​​the predetermined cross-section of the negative electrode active particle 500 is s. The total area s' covered by the plurality of pores 510 in the predetermined cross-section satisfies the following equation: 0.01 ≤ s' / s ≤ 0.06. Specifically, s' / s may be, but is not limited to, 0.01, 0.01, 0.01, 0.01, 0.01, 0.06, etc. If s' / s is too large, the distribution of pores at the predetermined cross-section is relatively dense, indicating that the specific surface area of ​​the negative electrode active particle 500 is large. This increases the consumption of active lithium during the film formation reaction, reducing the initial efficiency of the battery 400. If s' / s is too small, the distribution of pores 510 at the predetermined cross-section of the negative electrode active particle 500 is relatively sparse, resulting in too few channels for lithium ion movement and a reduced lithium ion migration rate, thereby reducing the kinetic performance of the negative electrode active layer 432. This insufficient kinetic performance of the negative electrode active layer 432 may lead to lithium deposition. When the ratio of the total porous coverage area on the preset cross section to the area of ​​the preset cross section is 0.01 to 0.06, the battery 400 using the negative electrode active particles 500 has better kinetic performance, is less prone to lithium plating, and has a higher initial efficiency.

[0093] It is understood that in this embodiment, the predetermined cross-section of the negative electrode active particle 500 can be a cross-section of the negative electrode active particle 500 along any direction and at any angle, which satisfies the condition 0.01 ≤ s' / s ≤ 0.06 in this embodiment. In other words, the predetermined cross-section is any cross-section or profile of the negative electrode active particle 500.

[0094] In some embodiments, the area s of the predetermined cross section is in the range of 0.5 μm 2 ≤s≤400μm 2 Specifically, the area s of the preset cross section may be, but is not limited to, 0.5 μm 2 , 1μm 2 , 3μm 2 , 5μm 2 , 10μm 2 , 30μm 2 , 50μm 2 , 80μm 2 , 100μm 2 , 150μm 2 , 200μm 2 , 250μm 2 , 300μm 2 , 350μm 2 , 400μm 2 If the area s of the preset cross section is too small, it indicates that there are fine powders with too small a particle size in the negative electrode active particles 500, which will reduce the initial efficiency of the battery 400 using the negative electrode active particles 500 and deteriorate the high-temperature electrical performance of the battery 400 using the negative electrode active particles 500; if the area s of the preset cross section is too large, it indicates that there are particles with too large a particle size in the negative electrode active particles 500, which will cause difficulties in the processing of the negative electrode plate 430 (such as easy to produce coating scratches, rolling dark marks, etc.). When the area s of the preset cross section is between 0.5 μm 2 Up to 400 μm 2 In this way, the battery 400 using the negative electrode active particles 500 can have a higher initial efficiency and better high-temperature performance, and the negative electrode sheet 430 using the negative electrode active particles 500 can have better processing performance.

[0095] Furthermore, the area s of the preset cross section is in the range of 5 μm 2 ≤s≤350μm 2 When the area s of the predetermined cross section is within this range, the battery 400 using the negative electrode active particles 500 can have higher initial efficiency and better high-temperature performance, and the negative electrode sheet 430 using the negative electrode active particles 500 can have better processing performance.

[0096] Furthermore, the area s of the preset cross section is in the range of 15 μm 2 ≤s≤300μm 2 When the area s of the predetermined cross section is within this range, the battery 400 using the negative electrode active particles 500 can have higher initial efficiency and better high-temperature performance, and the negative electrode sheet 430 using the negative electrode active particles 500 can have better processing performance.

[0097] Furthermore, the area s of the preset cross section is in the range of 30 μm 2 ≤s≤200μm 2 When the area s of the predetermined cross section is within this range, the battery 400 using the negative electrode active particles 500 can have higher initial efficiency and better high-temperature performance, and the negative electrode sheet 430 using the negative electrode active particles 500 can have better processing performance.

[0098] In some embodiments, the total area s' covered by the plurality of pores 510 on the predetermined cross section is in the range of 0.005 μm 2 ≤s'≤24μm 2 Specifically, on the preset cross section, the total area s' covered by the plurality of pores 510 may be, but is not limited to, 0.005 μm 2 , 0.01μm 2 , 0.05μm 2 , 0.1μm 2 , 0.5μm 2 , 1μm 2 , 2μm 2 , 5μm 2 , 8μm 2 , 10μm 2 , 12μm 2 , 15μm 2 , 18μm 2 , 20μm 2 , 22μm 2 , 24μm 2 Etc. On the preset cross section, the total area s' covered by the multiple pores 510 is too small, indicating that the pores 510 distributed in the negative active particles 500 are few, affecting the kinetic performance of the negative active particles 500; on the preset cross section, the total area s' covered by the multiple pores 510 is too large, indicating that the pores 510 distributed in the negative active particles are many, resulting in excessive consumption of active lithium during SEI film formation in the battery 400 using the negative active particles 500, affecting the initial efficiency of the battery 400 and reducing the electrical performance of the battery 400. When the total area s' covered by the multiple pores 510 on the preset cross section is in the range of 0.005μm2 to 24μm 2 When the negative electrode active particles 500 are used, the battery 400 can have better kinetic performance and higher initial efficiency.

[0099] Furthermore, on the preset cross section, the total area s' covered by the plurality of pores 510 is in the range of 0.05 μm 2 ≤s'≤20μm 2 In this way, the battery 400 using the negative electrode active particles 500 can have both good kinetic performance and high initial efficiency.

[0100] Furthermore, on the predetermined cross section, the total area s' covered by the plurality of pores 510 is in the range of 1 μm 2 ≤s'≤17μm 2 In this way, the battery 400 using the negative electrode active particles 500 can have both good kinetic performance and high initial efficiency.

[0101] Optionally, the particle size of the negative electrode active particles 500 is 8 μm to 13 μm. Specifically, the particle size of the negative electrode active particles 500 can be, but is not limited to, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, etc. If the particle size of the negative electrode active particles 500 is too small, the initial efficiency of the battery 400 using the negative electrode active particles 500 will be reduced, and the high-temperature electrical performance of the battery 400 using the negative electrode active particles 500 will be deteriorated. If the particle size of the negative electrode active particles 500 is too large, it will cause difficulties in processing the negative electrode sheet 430 (such as easily causing coating scratches and rolling dark marks).

[0102] The negative electrode active particles 500 of the embodiments of the present application can be prepared by the methods described in the following embodiments of the present application. In addition, they can also be prepared by other methods. The preparation methods of the embodiments of the present application are merely one or more preparation methods of the negative electrode active particles 500 of the present application and should not be understood as limiting the negative electrode active particles 500 provided in the embodiments of the present application.

[0103] Referring to FIG. 12 , the present embodiment further provides a method for preparing negative electrode active particles 500 , which includes:

[0104] S601, providing a carbon source;

[0105] Optionally, the carbon source may be, but is not limited to, at least one of petroleum coke, coal coke, and the like.

[0106] Optionally, the mass fraction of sulfur (S) in the carbon source ranges from 1.5% to 2.0%. Specifically, the mass fraction of sulfur (S) in the carbon source can be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, etc. When the mass fraction of sulfur in the carbon source is too low, the length of the pores 510 of the negative electrode active particles 500 formed is too large, and the aspect ratio of the pores 510 is too large, thereby causing the specific surface area of ​​the negative electrode active particles 500 to be too high, reducing the initial efficiency of the battery 400; when the mass fraction of sulfur in the carbon source is too high, the length of the pores 510 of the negative electrode active particles 500 formed is too small, and the aspect ratio of the pores 510 is too small, which reduces the kinetic performance of the negative electrode active particles 500, thereby reducing the kinetic performance of the battery 400.

[0107] In the embodiments of the present application, when a numerical range from a to b is involved, unless otherwise specified, it means that the numerical value can be any numerical value between a and b, including the endpoint numerical value a, and including the endpoint numerical value b.

[0108] Optionally, the carbon source is in a granular form, and the particle size of the carbon source is 8 μm to 13 μm. Specifically, the particle size of the carbon source can be, but is not limited to, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, etc. If the particle size of the carbon source is too small, the particle size of the negative electrode active particles 500 produced is too small, which will reduce the initial efficiency of the battery 400 using the negative electrode active particles 500 and deteriorate the high-temperature electrical performance of the battery 400 using the negative electrode active particles 500. If the particle size of the carbon source is too large, the particle size of the negative electrode active particles 500 produced is too large, which will cause difficulties in processing the negative electrode sheet 430 (such as easily generating coating scratches, rolling dark marks, etc.).

[0109] S602, pre-treating the carbon source to obtain intermediate particles; and

[0110] Optionally, pretreatment is performed at a temperature of 400° C. to 600° C. for 4 to 6 hours.

[0111] Optionally, the pretreatment temperature may be, but is not limited to, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 550°C, 560°C, 580°C, 600°C, etc. If the pretreatment temperature is too low, the light components in the carbon source cannot be vaporized well, resulting in too few pores 510 in the formed negative electrode active particles 500 and uneven distribution of the pores 510 in the negative electrode active particles 500, thereby reducing the cycle capacity retention rate of the battery 400 using the negative electrode active particles 500. If the pretreatment temperature is too high, the intermediate particles formed are easily pre-oxidized, resulting in more severe oxidation during graphitization, and the resulting negative electrode active particles 500 have too many pores 510, thereby reducing the initial efficiency of the battery 400 using the negative electrode active particles 500.

[0112] Optionally, the pretreatment time can be, but is not limited to, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.

[0113] S603 , graphitizing the intermediate particles to obtain negative electrode active particles 500 , wherein the negative electrode active particles 500 have a plurality of pores 510 , and the aspect ratio α of the pores 510 is in the range of 1≤α≤8.

[0114] Referring to FIG. 13 , optionally, the graphitization treatment of the intermediate particles to obtain negative electrode active particles 500 includes:

[0115] S6031, placing the intermediate particles in a graphitization furnace having a reaction chamber, and ensuring that the distance between the intermediate particles and an opening of the reaction chamber is in a range of 70 cm to 120 cm; and

[0116] Specifically, the distance between the intermediate particles and the opening of the reaction chamber can be, but is not limited to, 70 cm, 75 cm, 80 cm, 85 cm, 90 cm, 95 cm, 100 cm, 105 cm, 110 cm, 115 cm, 120 cm, etc. If the distance between the intermediate particles and the opening of the reaction chamber is too small, the oxidation of the intermediate particles will be too intense, increasing the density of the pores 510 of the negative electrode active particles 500 and reducing the initial efficiency and cycle capacity retention rate of the battery 400 using the negative electrode active particles 500. If the distance between the intermediate particles and the opening of the reaction chamber is too large, the pores 510 of the produced negative electrode active particles 500 will be too few, the gram capacity of the produced negative electrode active particles 500 will be too high, and the kinetics of the battery 400 using the negative electrode active particles 500 will be insufficient.

[0117] S6032 , performing graphitization treatment at a temperature of 2800° C. to 3200° C. to obtain the negative electrode active particles 500 .

[0118] Specifically, the temperature of the graphitization treatment may be, but is not limited to, 2800° C., 2850° C., 2900° C., 2950° C., 3000° C., 3050° C., 3150° C., 3200° C., etc. If the temperature of the graphitization treatment is too low, the gram capacity of the negative electrode active particles 500 produced is too low, which is not conducive to improving the energy density of the battery 400 using the negative electrode active particles 500. If the temperature of the graphitization treatment is too high, the gram capacity of the negative electrode active particles 500 produced is too high, thereby resulting in insufficient kinetics of the battery 400 using the negative electrode active particles 500.

[0119] Optionally, the graphitization treatment time is 24 hours to 48 hours. Specifically, the graphitization treatment time can be, but is not limited to, 24 hours, 27 hours, 30 hours, 33 hours, 36 hours, 39 hours, 42 hours, 45 hours, 48 ​​hours, etc.

[0120] The negative electrode active particles 500 of the present application are further described below through specific examples.

[0121] Example 1

[0122] The negative electrode active particles 500 of this embodiment are prepared by the following steps:

[0123] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 1.5% and the particle size of the petroleum coke is 9 μm;

[0124] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0125] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 70 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0126] Example 2

[0127] The negative electrode active particles 500 of this embodiment are prepared by the following steps:

[0128] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 1.6% and the particle size of the petroleum coke is 10 μm;

[0129] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0130] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 85 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0131] Example 3

[0132] The negative electrode active particles 500 of this embodiment are prepared by the following steps:

[0133] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 1.7% and the particle size of the petroleum coke is 11 μm;

[0134] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0135] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 96 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0136] Example 4

[0137] The negative electrode active particles 500 of this embodiment are prepared by the following steps:

[0138] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 1.8% and the particle size of the petroleum coke is 12 μm;

[0139] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0140] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 105 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0141] Example 5

[0142] The negative electrode active particles 500 of this embodiment are prepared by the following steps:

[0143] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 2.0% and the particle size of the petroleum coke is 12 μm;

[0144] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0145] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 120 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0146] Comparative Example 1

[0147] The negative electrode active particles 500 of this comparative example were prepared by the following steps:

[0148] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 2.2% and the particle size of the petroleum coke is 11 μm;

[0149] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0150] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 35 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0151] Comparative Example 2

[0152] The negative electrode active particles 500 of this comparative example were prepared by the following steps:

[0153] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 1.2% and the particle size of the petroleum coke is 11 μm;

[0154] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0155] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 160 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0156] Comparative Example 3

[0157] The negative electrode active particles 500 of this comparative example were prepared by the following steps:

[0158] (1) providing petroleum coke (carbon source), wherein the mass fraction of sulfur in the petroleum coke is 2.6% and the particle size of the petroleum coke is 11 μm;

[0159] (2) pre-treating the petroleum coke at a temperature of 500° C. to obtain intermediate petroleum coke (i.e., intermediate particles), wherein the pre-treatment time is 5 hours; and

[0160] (3) The intermediate petroleum coke was placed in a graphitization furnace so that the distance between the intermediate petroleum coke and the opening of the reaction chamber of the graphitization furnace was 15 cm. The intermediate petroleum coke was graphitized at a temperature of 3000° C. for 36 hours to obtain graphite particles (i.e., negative electrode active particles 500).

[0161] The negative electrode active particles 500 of each embodiment and comparative example were used to prepare a battery 400 .

[0162] The battery 400 of each embodiment and comparative example includes an electrolyte, a positive electrode sheet 410, a separator 420, and the negative electrode sheet 430. The positive electrode sheet 410, the separator 420, and the negative electrode sheet 430 constitute an electrode assembly, which is wound and immersed in the electrolyte.

[0163] The negative electrode sheet 430 includes a copper foil (negative electrode current collector 431) and a negative electrode active layer 432 disposed on opposite surfaces of the copper foil. The negative electrode active layer 432 includes graphite particles (negative electrode active particles 500), which have pores 510. The parameters of the graphite particles and pores 510 in each embodiment and comparative example are shown in Table 1 below. The thickness of the negative electrode sheet 430 is 119 μm, the thickness of the copper foil is 8 μm, and the thickness of each layer of the negative electrode active layer 432 is 55.5 μm.

[0164] The positive electrode sheet 410 includes an aluminum foil (positive electrode current collector 411) and a positive electrode active layer 412 disposed on two opposing surfaces of the aluminum foil. The positive electrode active layer 412 includes lithium iron phosphate (positive electrode active particles). The thickness of the positive electrode sheet 410 is 162 μm, the thickness of the aluminum foil is 13 μm, and each layer of the positive electrode active layer 412 is 74.5 μm thick.

[0165] The electrolyte includes LiPF6 (lithium salt) and an organic solvent. The molar concentration of LiPF6 in the electrolyte is 1 mol / L. The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1. The separator 420 is a PP separator 420.

[0166] The battery 400 prepared with the negative electrode active particles 500 of the above-mentioned embodiments and comparative examples was subjected to a cycle performance test.

[0167] (1) Cycling performance test: At 25°C, the batteries 400 of the above embodiments and comparative examples were charged to 3.65V at a constant power of 1P, and then discharged to 2.5V at a constant power of 1P. The discharge capacity was recorded as the initial capacity. The cycle was repeated until the capacity of the lithium battery 400 was less than 70% of the initial capacity. The number of cycles was recorded.

[0168] (2) Measurement of the Length L and Aspect Ratio α of the Pores 510 of the Negative Electrode Active Particles 500: A scanning electron microscope (SEM) image of a cross section of the negative electrode active particle 500 was obtained. The SEM image was imported into Nano Measurer software, and the corresponding scale length was read. The longest and widest distances L of the pores of the negative electrode active particle 500 were measured to calculate the range of the aspect ratio α of the negative electrode material. An SEM image of a cross section of the negative electrode active particle 500 of Example 5 is shown in FIG.

[0169] Table 1 Performance parameters of each embodiment and comparative example

[0170] It can be seen from the test data of Examples 1 to 5 in Table 1 that when the aspect ratio of the pores 510 of the negative electrode active particles 500 (graphite particles) is between 1 and 8 and the preset cross-section of the graphite particles satisfies 0.01≤s' / s≤0.06, the battery 400 using the graphite particles has a high cycle capacity retention rate. After 500 cycles, the cycle capacity retention rate is still above 98.3%.

[0171] It can be seen from the test data of Comparative Example 1 that when the length of the pores 510 of the graphite particles is too large, the cycle capacity retention rate of the battery 400 decreases.

[0172] It can be seen from the test data of Comparative Example 2 that when the length of the pores 510 of the graphite particles is relatively large and s′ / s is relatively small, the cycle capacity retention rate of the battery 400 decreases.

[0173] It can be seen from the test data of Comparative Example 3 that when the length of the pores 510 of the graphite particles is relatively long and s′ / s is relatively large, the cycle capacity retention rate of the battery 400 will also decrease.

[0174] (3) Impedance test: Battery 400 is fully charged and discharged twice at its rated capacity, with the last discharge capacity recorded as C0. The fully discharged battery 400 is charged nine times at a current of 0.1C0 to a state of charge of 90%, and the corresponding resistance value is recorded.

[0175] The battery 400 of Example 5 and Comparative Example 2 was subjected to kinetic performance testing, and the resulting impedance-state-of-charge curve is shown in FIG15 . As shown in FIG15 , the battery 400 of Example 5 has lower impedance compared to the battery 400 of Comparative Example 2, indicating that when the size of the pores 510 of the graphite particles is designed within the range of this application, the battery 400 can have lower impedance and better kinetic cycling performance.

[0176] Mentioning "embodiments" and "implementation methods" in this application means that the specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, unless there is a contradiction between them.

[0177] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the above preferred implementation modes, ordinary technicians in this field should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A negative electrode active particle, wherein: The negative electrode active particles have a plurality of pores, and the aspect ratio α of the pores is in the range of 1≤α≤8.

2. The negative electrode active particle according to claim 1, wherein The maximum length L of the pores is in the range of 0.1 μm≤L≤2.5 μm.

3. The negative electrode active particle according to claim 1, wherein The maximum width w of the pore in a direction parallel to a direction perpendicular to a maximum length direction of the pore is in a range of 0.1 μm≤w≤2.5 μm.

4. The negative electrode active particle according to any one of claims 1 to 3, wherein: The negative electrode active particle has a preset cross section, the area of the preset cross section of the negative electrode active particle is s, and the total area covered by the plurality of pores on the preset cross section is s', then 0.01≤s' / s≤0.

06.

5. The negative electrode active particle according to claim 4, wherein The area s of the preset cross section is in the range of 0.5 μm 2 ≤s≤400μm 2 .

6. The negative electrode active particle according to claim 4, wherein On the preset cross section, the total area s' covered by the plurality of pores is in the range of 0.005 μm 2 ≤s'≤24μm 2 .

7. A method for preparing negative electrode active particles, wherein: The preparation method comprises: Provide carbon source; Pre-treating the carbon source to obtain intermediate particles; and The intermediate particles are graphitized to obtain negative electrode active particles, wherein the negative electrode active particles have a plurality of pores, and the aspect ratio α of the pores is in the range of 1≤α≤8.

8. The method for preparing negative electrode active particles according to claim 7, wherein: The mass fraction of sulfur in the carbon source ranges from 1.5% to 2.0%.

9. The method for preparing negative electrode active particles according to claim 7, wherein: The graphitizing the intermediate particles to obtain negative electrode active particles comprises: placing the intermediate particles in a graphitization furnace having a reaction chamber, wherein the distance between the intermediate particles and an opening of the reaction chamber is in a range of 70 cm to 120 cm; and The graphitization treatment is performed at a temperature of 2800° C. to 3200° C. to obtain the negative electrode active particles.

10. A negative electrode sheet, wherein: include: negative electrode current collector; as well as A negative electrode active layer is provided on the surface of the negative electrode current collector, and the negative electrode active layer comprises the negative electrode active particles according to any one of claims 1 to 6.

11. The negative electrode sheet according to claim 10, wherein: The compaction density ρ of the negative electrode active layer is in the range of 1.4 g / cm 3 ≤ρ≤1.7g / cm 3 The porosity P of the negative electrode active layer is in the range of 10%≤P≤42%.

12. The negative electrode sheet according to claim 10 or 11, wherein: The range of the peel strength σ between the negative electrode active layer and the negative electrode current collector is 5 N / m≤σ≤20 N / m.

13. A battery, wherein: include: electrolyte; A positive electrode sheet, the positive electrode sheet is immersed in the electrolyte; a diaphragm, located on one side of the positive electrode sheet and immersed in the electrolyte, and The negative electrode plate according to any one of claims 10 to 12 is arranged on a side of the diaphragm away from the positive electrode plate and immersed in the electrolyte.

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