Battery cell, negative electrode material and preparation method therefor, battery device, and electric device

Abstract

Provided in the present application are a battery cell, a negative electrode material, a method for preparing the negative electrode material, a battery device, and an electric device. The battery cell comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode material, the negative electrode material comprises a negative electrode active material, the negative electrode active material comprises secondary particles, and the secondary particles comprise primary particles and a one-dimensional carbon material and / or a two-dimensional carbon material. The volume-average particle size Dv50 of the secondary particles is 7-23 μm, and the volume-average particle size Dv50 of the primary particles is 0.5-5 μm. The primary particles comprise a porous carbon material, and silicon particles are distributed on the surface and / or pore channels of the porous carbon material. The battery cell of the present application has a high energy density, and also has both good dynamic performance and stable cycle performance.

Description

Battery cells, negative electrode materials and their preparation methods, battery devices and electrical devices

[0001] This application is based on and claims priority to Chinese Patent Application No. 202411591632.X, filed on November 8, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, a negative electrode material, a method for preparing the negative electrode material, a battery device, and an electrical device. Background Technology

[0003] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant advancements in battery technology, higher requirements have been placed on their energy density, cycle performance, and kinetic performance. Summary of the Invention

[0004] This application addresses the aforementioned issues and aims to provide a battery cell, a negative electrode material, a method for preparing the negative electrode material, a battery device, and an electrical device. The battery cell of this application exhibits high energy density, along with good kinetic performance and stable cycle performance.

[0005] To achieve the above objectives, a first aspect of this application provides a battery cell including a negative electrode sheet, the negative electrode sheet including a negative electrode material, the negative electrode material including a negative electrode active material, the negative electrode active material including secondary particles, the secondary particles including primary particles, and one-dimensional carbon material and / or two-dimensional carbon material; the volume average particle size Dv50 of the secondary particles is 7-23 μm; the volume average particle size Dv50 of the primary particles is 0.5-5 μm; the primary particles include porous carbon material, and silicon particles are distributed on the surface and / or in the pores of the porous carbon material.

[0006] Therefore, this application shortens the solid-phase mass transfer distance of lithium ions by using primary particles of a certain size while maintaining the secondary particle size of the negative electrode material; the silicon particles on the surface and / or in the channels of the porous carbon material in the primary particles improve the energy density of the battery cell; and the simultaneous use of two-dimensional carbon materials and / or one-dimensional carbon materials provides space for the volume expansion of silicon, stabilizes the material structure, improves the material conductivity, and reduces the DCR of the battery cell; thereby improving the energy density, kinetic performance and cycle stability of the battery cell.

[0007] In any embodiment, the (Dv90-Dv10) / Dav50 value of the secondary particles is 0.8-1.9 or 1.1-1.8. This improves the uniformity of the secondary particle size, increases the tap density of the negative electrode material, and thus improves the kinetic performance and energy density of the battery cell.

[0008] In any embodiment, the average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm. This is beneficial for increasing silicon deposition and lithium-ion transport, while controlling the degree of silicon-induced expansion, thereby improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0009] In any embodiment, the pore volume of the negative electrode material is 0.7-1.6 cm³. 3 / g or 1.05-1.6cm 3 / g. This is beneficial for increasing silicon deposition and lithium-ion transport, while controlling the degree of silicon-induced expansion, thereby improving the energy density, kinetic performance, and cycle stability of individual battery cells.

[0010] In any embodiment, the BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g. Therefore, the BET specific surface area of ​​the negative electrode material affects its pore volume and average pore size, thereby improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0011] In any embodiment, the (Dv90-Dv10) / Dv50 value of the primary particle is 3.4-5.

[0012] As a result, the uniform particle size of the primary particles shortens the solid-phase mass transfer distance of lithium ions, and the primary particles expose more reactive sites, reducing the DCR of the battery cell and thus improving the kinetic performance of the battery cell.

[0013] In any embodiment, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g.

[0014] In any embodiment, the average pore size of the porous carbon material is 0.8-5 nm.

[0015] In any embodiment, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g.

[0016] Therefore, the BET specific surface area, average pore size, and pore volume of the porous carbon material are within the above range, providing a larger space for silicon particles and improving the energy density of the battery cell; furthermore, it suppresses the side reactions of the negative electrode and improves the cycle stability of the battery cell.

[0017] In any embodiment, the secondary particles comprise one-dimensional carbon material, which is entangled with the primary particles; or,

[0018] When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

[0019] This provides space for the volume expansion of silicon in the negative electrode material, improves the structural stability of the material, and enhances the cycle stability of the battery cell.

[0020] In any embodiment, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or,

[0021] The two-dimensional carbon material includes graphene.

[0022] In any embodiment, the silicon content in the negative electrode material is 30%-60% by mass. This is beneficial for improving the energy density of the battery cell.

[0023] In any embodiment, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm.

[0024] In any embodiment, the two-dimensional carbon material includes graphene, and the number of graphene sheets is 1-8.

[0025] In any embodiment, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000.

[0026] Therefore, the graphene and carbon nanotubes with the above parameters provide space for silicon volume expansion, stabilize the material structure, improve the material conductivity, and can effectively reduce the DCR of the battery cell, thereby improving the kinetic performance and cycle stability of the battery cell.

[0027] In any embodiment, the surface of the primary particle is further coated with a coating layer containing carbon.

[0028] In any embodiment, the average thickness of the primary particle surface coating layer is greater than 0 and less than or equal to 5 nm.

[0029] Therefore, the coating layer on the surface of the primary particles helps to improve the conductivity between the primary particles, and at the same time plays a physical adhesion role between the primary particles, thereby improving the mechanical strength of the negative electrode material.

[0030] In any embodiment, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5); and / or,

[0031] The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015).

[0032] In any embodiment, the surface of the secondary particles is coated with a coating layer comprising carbon.

[0033] In any embodiment, the average thickness of the coating layer on the surface of the secondary particles is 2-10 nm.

[0034] Therefore, the carbon coating layer on the surface of secondary particles is beneficial to improving the conductivity of the negative electrode material.

[0035] A second aspect of this application also provides a negative electrode material comprising secondary particles, the secondary particles comprising primary particles, and one-dimensional carbon materials and / or two-dimensional carbon materials; the average particle size of the secondary particles is 7-23 μm; the volume average particle size Dv50 of the primary particles is 0.5-5 μm; the primary particles comprise porous carbon materials, and silicon particles are distributed on the surface and / or within the pores of the porous carbon materials.

[0036] Therefore, this application, while maintaining the secondary particle size of the negative electrode material, uses primary particles of a certain size to shorten the solid-phase mass transfer distance of lithium ions; the silicon particles on the surface and / or in the channels of the porous carbon material in the primary particles improve the energy density of the battery cell; and, at the same time, the use of two-dimensional carbon materials and / or one-dimensional carbon materials provides space for the volume expansion of silicon, stabilizes the material structure, improves the material conductivity, and reduces the DCR of the battery cell; thereby improving the energy density, kinetic performance and cycle stability of the battery cell.

[0037] In any embodiment, the (Dv90-Dv10) / Dv50 value of the secondary particles is 0.8-1.9 or 1.1-1.8.

[0038] In any embodiment, the average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm.

[0039] In any embodiment, the pore volume of the negative electrode material is 0.7-1.6 cm³. 3 / g or 1.05-1.6cm 3 / g.

[0040] In any embodiment, the BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g.

[0041] In any embodiment, the (Dv90-Dv10) / Dv50 value of the primary particle is 3.4-5.

[0042] In any embodiment, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g.

[0043] In any embodiment, the average pore size of the porous carbon material is 0.8-5 nm.

[0044] In any embodiment, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g.

[0045] In any embodiment, the secondary particles comprise one-dimensional carbon material, which is entangled with the primary particles; or,

[0046] When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

[0047] In any embodiment, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or,

[0048] The two-dimensional carbon material includes graphene.

[0049] In any embodiment, the silicon content in the negative electrode material is 30%-60% by mass.

[0050] In any embodiment, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm.

[0051] In any embodiment, the two-dimensional carbon material includes graphene, and the number of graphene sheets is 1-8.

[0052] In any embodiment, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000.

[0053] In any embodiment, the surface of the primary particle is further coated with a coating layer containing carbon.

[0054] In any embodiment, the average thickness of the primary particle surface coating layer is greater than 0 and less than or equal to 5 nm.

[0055] In any embodiment, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5); and / or,

[0056] The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015).

[0057] In any embodiment, the surface of the secondary particles is coated with a coating layer comprising carbon.

[0058] In any embodiment, the average thickness of the coating layer on the surface of the secondary particles is 2-10 nm.

[0059] A third aspect of this application provides a method for preparing a negative electrode material, comprising the following steps:

[0060] Primary particles, as well as one-dimensional carbon materials and / or two-dimensional carbon materials, are mixed with a solvent, granulated, and calcined for the first time to obtain a negative electrode material; wherein, the primary particles include porous carbon materials and silicon particles distributed on the surface and / or in the pores of the porous carbon materials; the negative electrode material includes a negative electrode active material, the negative electrode active material includes secondary particles, the volume average particle size Dv50 of the secondary particles is 7-23 μm, and the volume average particle size Dv50 of the primary particles is 0.5-5 μm.

[0061] In any embodiment, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5).

[0062] In any embodiment, the mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015).

[0063] In any embodiment, the mixing temperature is 70-90°C.

[0064] In any embodiment, the temperature of the first calcination is 400-650°C.

[0065] In any embodiment, the first roasting time is 4-9 hours.

[0066] In any embodiment, the first calcination is carried out in an inert atmosphere.

[0067] In any embodiment, the negative electrode material is the negative electrode material of the second aspect of this application.

[0068] In any embodiment, during the mixing step, the primary particles, binder, and the one-dimensional carbon material and / or the two-dimensional carbon material are mixed with the solvent.

[0069] In any embodiment, the binder accounts for 20%-40% of the total mass of raw materials excluding solvents; and / or,

[0070] The binder includes one or more of sucrose, glucose, and fructose.

[0071] In any embodiment, the method further includes: coating the surface of the calcined product with carbon to obtain a negative electrode material with a carbon coating layer.

[0072] In any embodiment, the steps for preparing the negative electrode material with a carbon coating layer include:

[0073] The carbon source and the calcination product are mixed at the melting temperature of the carbon source, and then calcined a second time.

[0074] In any embodiment, in the step of preparing the negative electrode material with a carbon coating, the mass ratio of the carbon source to the calcination product is 1:(4-99).

[0075] In any embodiment, in the step of preparing the negative electrode material with a carbon coating, the temperature of the second calcination is 150-400°C.

[0076] In any embodiment, in the step of preparing the negative electrode material with a carbon coating, the second calcination time is 1-10 hours.

[0077] In any embodiment, the primary particles are prepared by the following steps:

[0078] A resin containing a ring structure is calcined to create pores, resulting in a porous carbon material.

[0079] Using the porous carbon material as a substrate, a silicon source is used for vapor deposition to obtain primary particles.

[0080] In any embodiment, during the step of preparing the primary particles, carbon is coated onto the surface of the vapor-deposited product to obtain primary particles including a carbon coating layer.

[0081] In any embodiment, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g.

[0082] In any embodiment, the average pore size of the porous carbon material is 0.8-5 nm.

[0083] In any embodiment, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g.

[0084] In any embodiment, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods.

[0085] In any embodiment, the two-dimensional carbon material includes graphene.

[0086] In any embodiment, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm.

[0087] In any embodiment, the two-dimensional carbon material includes graphene, and the average number of graphene sheets is 1-8.

[0088] In any embodiment, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000.

[0089] The fourth aspect of this application provides a battery device, including a battery cell according to the first aspect of this application, a negative electrode material according to the second aspect of this application, or a negative electrode material prepared by the method according to the third aspect of this application.

[0090] The fifth aspect of this application provides an electrical device, including the battery device of the fourth aspect of this application. Attached Figure Description

[0091] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0092] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0093] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0094] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0095] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0096] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0097] Figure 7A is a SEM image of the negative electrode active material of Example 1 of this application.

[0098] Figure 7B is a SEM image of the secondary particles in the negative electrode active material of Example 1 of this application.

[0099] Figure 7C is a magnified SEM image of the secondary particles in the negative electrode active material of Example 1 of this application.

[0100] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0101] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0102] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0103] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0104] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0105] [Battery cell]

[0106] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0107] The battery cell can be a lithium-ion battery.

[0108] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0109] One embodiment of this application provides a battery cell including a negative electrode sheet, the negative electrode sheet including a negative electrode material, the negative electrode material including a negative electrode active material, the negative electrode active material including secondary particles, the secondary particles including primary particles, and one-dimensional carbon materials and / or two-dimensional carbon materials; the volume average particle size Dv50 of the secondary particles is 7-23μm (e.g., 7μm, 8μm, 10μm, 12μm, 14μm, 15μm, 17μm, 19μm, 20μm, 20μm, 22μm). The primary particles have a volume average particle size Dv50 of 0.5-5 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.1 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm or any of the above values); the primary particles comprise porous carbon materials, and silicon particles are distributed on the surface and / or within the pores of the porous carbon materials.

[0110] While porous carbon vapor-deposited silicon composite materials can improve the energy density of individual battery cells when used as negative electrode active materials, their long lithium-ion transport paths result in high impedance, leading to a higher DCR (discharge rate) and decreased kinetic performance. Furthermore, silicon easily expands during charge and discharge, causing volume changes in the negative electrode and worsening the cycle stability of the battery. Additionally, while reducing the particle size of silicon-carbon composite materials helps shorten the lithium-ion transport path, it increases the amount of gas generated by side reactions in the negative electrode, further deteriorating the cycle performance of the battery. Moreover, small-particle-size silicon-carbon composite materials are prone to uneven deposition and clogging of production pipelines, and the use of more binders during negative electrode fabrication also worsens the battery's kinetic performance.

[0111] Although the mechanism is not yet clear, the applicant unexpectedly discovered that, while maintaining the particle size of the secondary particles in the negative electrode material, the use of primary particles of a certain size shortens the solid-phase mass transfer distance of lithium ions; the silicon particles on the surface and / or in the channels of the porous carbon material in the primary particles improve the energy density of the battery cell; and, the simultaneous use of two-dimensional carbon materials and / or one-dimensional carbon materials provides space for the volume expansion of silicon, stabilizes the material structure, improves the material conductivity, and reduces the DCR of the battery cell; thereby improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0112] In some embodiments, the (Dv90-Dv10) / Dv50 value of the secondary particles is 0.8-1.9 or 1.1-1.8, for example, 0.8, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or any range of the above values. This improves the uniformity of the secondary particle size, increases the tap density of the negative electrode material, and thus improves the kinetic performance and energy density of the battery cell.

[0113] In some embodiments, the average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm, for example, 2 nm, 3 nm, 3.8 nm, 4 nm, 4.3 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or any combination thereof. This is beneficial for increasing silicon deposition and lithium-ion transport while controlling the degree of silicon-induced expansion, thereby improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0114] In some embodiments, the pore volume of the negative electrode material is 0.7-1.6 cm. 3 / g or 1.05-1.6cm 3 / g, for example, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.09cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.21cm 3 / g, 1.25cm 3 / g, 1.24cm 3 / g, 1.26cm 3 / g, 1.3cm 3 / g, 1.31cm 3 / g, 1.35cm 3 / g, 1.4cm 3 / g, 1.45cm 3 / g, 1.5cm 3 / g, 1.6cm 3 / g or any of the above values. This is beneficial for increasing silicon deposition and lithium-ion transport, while controlling the degree of silicon-induced expansion, thereby improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0115] In some embodiments, the BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g, for example 9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g、20m 2 / g、21m 2 / g、23m 2 / g、25m 2 / g、27m 2 / g、30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g or any of the above values. Therefore, the BET specific surface area of ​​the negative electrode material affects its pore volume and average pore size, thus improving the energy density, kinetic performance, and cycle stability of the battery cell.

[0116] In some embodiments, the (Dv90-Dv10) / Dv50 value of the primary particle is 3.4–5, for example, 3.4, 3.5, 3.7, 3.9, 4, 4.2, 4.5, 4.7, 4.9, 5 or any range of the above values.

[0117] As a result, the uniform particle size of the primary particles shortens the solid-phase mass transfer distance of lithium ions, and the primary particles expose more reactive sites, reducing the DCR of the battery cell and thus improving the kinetic performance of the battery cell.

[0118] In some embodiments, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g, for example 800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1790m 2 / g、1800m 2 / g、1810m 2 / g、1850m 2 / g、1900m 2 / g、2000m 2 / g or any range of the above values.

[0119] In some embodiments, the average pore size of the porous carbon material is 0.8-5 nm, for example, 0.8 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or any range of the above values.

[0120] In some embodiments, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g, for example, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.05cm 3 / g or any range of the above values.

[0121] Therefore, the BET specific surface area, average pore size, and pore volume of the porous carbon material are within the above range, providing a larger space for silicon particles and improving the energy density of the battery cell; furthermore, it suppresses the side reactions of the negative electrode and improves the cycle stability of the battery cell.

[0122] In some embodiments, the secondary particles comprise one-dimensional carbon material, which is entangled with the primary particles; or,

[0123] When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

[0124] This provides space for the volume expansion of silicon in the negative electrode material, improves the structural stability of the material, and enhances the cycle stability of the battery cell.

[0125] In some embodiments, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or,

[0126] The two-dimensional carbon material includes graphene.

[0127] In some embodiments, the silicon content in the negative electrode material is 30%-60% by mass, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination of the above values. This is beneficial for improving the energy density of the battery cell.

[0128] In some embodiments, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any range of the above values.

[0129] In some embodiments, the two-dimensional carbon material includes graphene, and the number of graphene sheets is 1-8, for example, 1, 2, 3, 4, 5, 6, 7, 8 layers or any range of the above values.

[0130] In some embodiments, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000, such as 3000, 4000, 6000, 8000, 9000, 10000 or any range of the above values.

[0131] Therefore, the graphene and carbon nanotubes with the above parameters provide space for the volume expansion of silicon, stabilize the material structure, improve the material conductivity, and can effectively reduce the DCR of the battery cell, thereby improving the kinetic performance and cycle stability of the battery cell.

[0132] In some embodiments, the surface of the primary particles is further coated with a coating layer containing carbon.

[0133] In some embodiments, the average thickness of the primary particle surface coating is greater than 0 and less than or equal to 5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or any range of the above values.

[0134] This helps to improve the conductivity between primary particles and also plays a physical adhesion role between primary particles, thereby improving the mechanical strength of the negative electrode material.

[0135] In some embodiments, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or any range of the above values; and / or,

[0136] The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015), for example, 1:0.005, 1:0.008, 1:0.01, 1:0.012, 1:0.015 or any range of the above values.

[0137] In some embodiments, the surface of the secondary particles is coated with a coating layer comprising carbon.

[0138] In some embodiments, the average thickness of the coating layer on the surface of the secondary particles is 2-10 nm, for example, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm or any of the above values.

[0139] Therefore, the carbon coating layer on the surface of secondary particles is beneficial to improving the conductivity of the negative electrode material.

[0140] This application also provides a method for preparing a negative electrode material, comprising the following steps:

[0141] Primary particles, as well as one-dimensional and / or two-dimensional carbon materials, are mixed with a solvent, granulated, and subjected to a first calcination to obtain a negative electrode material. The primary particles comprise porous carbon materials and silicon particles distributed on the surface and / or within the pores of the porous carbon materials. The negative electrode material comprises a negative electrode active material, which includes secondary particles with a volume average particle size (Dv50) of 7-23 μm (e.g., 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, 1...). The volume average particle size Dv50 of the primary particles is 0.5-5 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.1 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm, or any range of the above values).

[0142] In some embodiments, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5 or any range of the above values.

[0143] In some embodiments, the mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015), for example 1:0.005, 1:0.008, 1:0.01, 1:0.012, 1:0.015 or any range of the above values.

[0144] In some embodiments, the mass ratio of the primary particles to the solvent is 1:5–15.

[0145] In some embodiments, the mixing temperature is 70°C-90°C, for example 70°C, 75°C, 80°C, 85°C, 90°C or any combination of the above values.

[0146] In some embodiments, the granulation is spray drying granulation.

[0147] In some embodiments, the temperature of the first firing is 400°C-650°C, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or any range of the above values.

[0148] In some embodiments, the first roasting time is 4-9 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or any range of the above values.

[0149] In some embodiments, the first calcination is carried out in an inert atmosphere.

[0150] In some embodiments, the negative electrode material is the negative electrode material described above in this application.

[0151] In some embodiments, during the mixing step, the primary particles, binder, and the one-dimensional carbon material and / or the two-dimensional carbon material are mixed with the solvent.

[0152] In some embodiments, the binder comprises 20%-40% of the total mass of raw materials excluding solvents, for example, 20%, 23%, 25%, 27%, 29%, 30%, 32%, 34%, 35%, 37%, 39%, 40%, or any range of the above values; and / or,

[0153] The binder includes one or more of sucrose, glucose, and fructose.

[0154] In some embodiments, the method further includes: coating the surface of the calcined product with carbon to obtain a negative electrode material with a carbon coating layer.

[0155] In some embodiments, the steps for preparing the negative electrode material with a carbon coating include:

[0156] The carbon source and the calcination product are mixed at the melting temperature of the carbon source, and then calcined a second time.

[0157] In some embodiments, in the step of preparing the negative electrode material with a carbon coating, the mass ratio of the carbon source to the calcined product is 1:(4-99), for example, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:99, or any range of the above values.

[0158] In some embodiments, in the step of preparing the negative electrode material with a carbon coating, the temperature of the second calcination is 150-400°C, for example, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C or any combination of the above values.

[0159] In some embodiments, in the step of preparing the negative electrode material with a carbon coating, the second calcination time is 1-10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0160] In some implementations, the carbon source is coal tar pitch.

[0161] In some embodiments, the carbon source in the step of preparing the negative electrode material with a carbon coating is coal tar pitch.

[0162] In some embodiments, the primary particles are prepared by the following steps:

[0163] A resin containing a ring structure is calcined to create pores, resulting in a porous carbon material.

[0164] Using the porous carbon material as a substrate, a silicon source is used for vapor deposition to obtain primary particles.

[0165] In some embodiments, the calcination temperature in the step of preparing the primary particles is 850-1100°C, for example, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C or any combination of the above values.

[0166] In some embodiments, the calcination time in the step of preparing the primary particles is 4-15 hours, for example, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 15 hours or any range of the above values.

[0167] In some embodiments, the calcination is carried out in an inert atmosphere during the step of preparing the primary particles.

[0168] In some embodiments, the pore-forming process in the step of preparing the primary particles is steam pore-forming.

[0169] In some embodiments, during the step of preparing the primary particles, the steam flow rate for steam pore formation is 0.1-0.5 L / min, for example, 0.1 L / min, 0.15 L / min, 0.2 L / min, 0.25 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.5 L / min, or any range of the above values.

[0170] In some embodiments, during the step of preparing the primary particles, the controlled pressure for steam pore formation is 5-30 MPa, for example, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, or any combination of the above values.

[0171] In some embodiments, the steam pore-forming time in the step of preparing the primary particles is 6-16 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 13 hours, 14 hours, 15 hours, 16 hours or any range of the above values.

[0172] In some embodiments, the silicon source in the step of preparing the primary particles is a silicon-containing gas.

[0173] In some embodiments, the silicon source in the step of preparing the primary particles includes one or more of silanes and halosilanes.

[0174] In some embodiments, the silicon source in the step of preparing the primary particles includes one or more of silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0175] In some embodiments, during the step of preparing the primary particles, the silicon source flow rate of the vapor deposition is 0.5-5 L / min, for example, 0.5 L / min, 0.8 L / min, 1.0 L / min, 1.5 L / min, 2 L / min, 2.5 L / min, 3 L / min, 4 L / min, 5 L / min or any range of the above values.

[0176] In some embodiments, during the step of preparing the primary particles, the temperature of the vapor deposition is 550-600°C, for example, 550°C, 580°C, 590°C, 600°C, or any combination of the above values.

[0177] In some embodiments, the vapor deposition time in the step of preparing the primary particles is 6-12 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours or any range of the above values.

[0178] In some embodiments, during the step of preparing the primary particles, the protective gas for the vapor deposition is an inert gas and / or nitrogen.

[0179] In some embodiments, during the step of preparing the primary particles, the protective gas flow rate for the vapor deposition is 0.5-30 L / min.

[0180] In some embodiments, in the step of preparing the primary granules, the resin is crushed and sieved before the calcination.

[0181] In some embodiments, during the step of preparing the primary particles, carbon is coated onto the surface of the vapor-deposited product to obtain primary particles comprising a carbon coating layer.

[0182] In some embodiments, the step of preparing the primary particles including the carbon coating layer involves coating the surface of the vapor-deposited product with carbon using vapor-phase precipitation or solid-phase synthesis.

[0183] In some embodiments, the vapor deposition temperature is 550-600°C during the step of preparing the primary particles including the carbon coating.

[0184] In some embodiments, the vapor deposition time is 2-8 hours in the step of preparing the primary particles including the carbon coating.

[0185] In some embodiments, the carbon source used in the step of preparing the primary particles including the carbon coating layer includes one or more of alkanes, alkenes, and alkynes in the vapor deposition.

[0186] In some embodiments, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g, for example 800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1790m 2 / g、1800m 2 / g、1810m 2 / g、1850m 2 / g、1900m 2 / g、2000m 2 / g or any range of the above values.

[0187] In some embodiments, the average pore size of the porous carbon material is 0.8-5 nm, for example, 0.8 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or any range of the above values.

[0188] In some embodiments, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g, for example, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.05cm 3 / g or any range of the above values.

[0189] In some embodiments, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods.

[0190] In some embodiments, the two-dimensional carbon material includes graphene.

[0191] In some embodiments, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any range of the above values.

[0192] In some embodiments, the two-dimensional carbon material includes graphene, and the average number of graphene sheets is 1-8 layers, for example, 1, 2, 3, 4, 5, 6, 7, 8 layers or any range of the above values.

[0193] In some embodiments, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000, such as 3000, 4000, 6000, 8000, 9000, 10000 or any range of the above values.

[0194]

Positive Electrode

[0195] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0196] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0197] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0198] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0199] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0200] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0201] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0202] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0203] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0204] [Negative electrode plate]

[0205] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative current collector.

[0206] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0207] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode material disposed on at least one surface of the negative electrode current collector.

[0208] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0209] This application provides a negative electrode material, comprising secondary particles, which include primary particles, one-dimensional carbon material, and / or two-dimensional carbon material; the average particle size of the secondary particles is 7-23 μm (e.g., 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 19 μm, 20 μm, 20 μm, 22 μm, 23 μm, or any range of the above values); the volume average particle size Dv50 of the primary particles is 0.5-5 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.1 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm, or any range of the above values); the primary particles comprise porous carbon material, and silicon particles are distributed on the surface and / or within the pores of the porous carbon material.

[0210] Therefore, this application, while maintaining the secondary particle size of the negative electrode material, uses primary particles of a certain size to shorten the solid-phase mass transfer distance of lithium ions; the silicon particles on the surface and / or in the channels of the porous carbon material in the primary particles improve the energy density of the battery cell; and, at the same time, the use of two-dimensional carbon materials and / or one-dimensional carbon materials provides space for the volume expansion of silicon, stabilizes the material structure, improves the material conductivity, and reduces the DCR of the battery cell; thereby improving the energy density, kinetic performance and cycle stability of the battery cell.

[0211] In some embodiments, the (Dv90-Dv10) / Dv50 value of the secondary particles is 0.8-1.9 or 1.1-1.8, for example, 0.8, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or any range of the above values.

[0212] In some embodiments, the average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm, for example, 2 nm, 3 nm, 3.8 nm, 4 nm, 4.3 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or any combination of the above values.

[0213] In some embodiments, the pore volume of the negative electrode material is 0.7-1.6 cm. 3 / g or 1.05-1.6cm 3 / g, for example, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.09cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.21cm 3 / g, 1.25cm 3 / g, 1.24cm 3 / g, 1.26cm 3 / g, 1.3cm 3 / g, 1.31cm 3 / g, 1.35cm 3 / g, 1.4cm 3 / g, 1.45cm 3 / g, 1.5cm 3 / g, 1.6cm 3 / g or any range of the above values.

[0214] In some embodiments, the BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g, for example 9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m2 / g、18m 2 / g、19m 2 / g、20m 2 / g、21m 2 / g、23m 2 / g、25m 2 / g、27m 2 / g、30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g or any range of the above values.

[0215] In some embodiments, the (Dv90-Dv10) / Dv50 value of the primary particle is 3.4-5, for example, 3.4, 3.5, 3.7, 3.9, 4, 4.2, 4.5, 4.7, 4.9, 5 or any range of the above values.

[0216] In some embodiments, the BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g, for example 800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1790m 2 / g、1800m 2 / g、1810m 2 / g、1850m 2 / g、1900m 2 / g、2000m 2 / g or any range of the above values.

[0217] In some embodiments, the average pore size of the porous carbon material is 0.8-5 nm, for example, 0.8 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or any range of the above values.

[0218] In some embodiments, the pore volume of the porous carbon material is 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g, for example, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, 1.05cm 3 / g or any range of the above values.

[0219] In some embodiments, the secondary particles comprise one-dimensional carbon material, which is entangled with the primary particles; or,

[0220] When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

[0221] In some embodiments, the one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or,

[0222] The two-dimensional carbon material includes graphene.

[0223] In some embodiments, the silicon content in the negative electrode material is 30%-60% by mass, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any range of the above values.

[0224] In some embodiments, the two-dimensional carbon material includes graphene, wherein the average diameter of the graphene sheets is 3-8 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any range of the above values.

[0225] In some embodiments, the two-dimensional carbon material includes graphene, and the number of graphene sheets is 1-8, for example, 1, 2, 3, 4, 5, 6, 7, 8 layers or any range of the above values.

[0226] In some embodiments, the one-dimensional carbon material includes carbon nanotubes with an aspect ratio of 3000–10000, such as 3000, 4000, 6000, 8000, 9000, 10000 or any range of the above values.

[0227] In some embodiments, the surface of the primary particles is further coated with a coating layer containing carbon.

[0228] In some embodiments, the average thickness of the primary particle surface coating is greater than 0 and less than or equal to 5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or any range of the above values.

[0229] In some embodiments, the mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or any range of the above values; and / or,

[0230] The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015), for example, 1:0.005, 1:0.008, 1:0.01, 1:0.012, 1:0.015 or any range of the above values.

[0231] In some embodiments, the surface of the secondary particles is coated with a coating layer comprising carbon.

[0232] In some embodiments, the average thickness of the coating layer on the surface of the secondary particles is 2-10 nm, for example, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm or any of the above values.

[0233] As an example, the negative electrode material may also include other negative electrode active materials known in the art for use in battery cells. As an example, the negative electrode active material may also include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-nitrogen compounds, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used.

[0234] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0235] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0236] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0237] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0238] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0239] Electrolytes

[0240] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0241] Liquid electrolytes include electrolyte salts and solvents.

[0242] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0243] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0244] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0245] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0246] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0247] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0248] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0249] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0250]

Isolation Components

[0251] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0252] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0253] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0254] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0255] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0256] [Structure of the Electrode Assembly]

[0257] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0258] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0259] In some implementations, the electrode assembly is a stacked structure.

[0260] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0261] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0262] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0263] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0264] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0265] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0266] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0267]

shell

[0268] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0269] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0270] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also be provided one or more.

[0271] Electrode terminals

[0272] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0273] Pressure relief mechanism

[0274] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0275] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0276] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0277] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0278] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0279] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0280] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0281] [Battery Device]

[0282] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0283] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0284] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0285] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0286] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0287] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0288] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0289] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0290] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0291] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0292] Figure 1 shows a square-structured battery cell 5 as an example.

[0293] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0294] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0295] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0296] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0297] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0298] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0299] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0300] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0301] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0302] [Example]

[0303] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0304] Example 1

[0305] (1) Preparation of negative electrode active material:

[0306] ① 100g of epoxy resin E51 was crushed, ground, and sieved to obtain powder. The powder was calcined at 950℃ for 12h to obtain calcined product. The calcined product was then subjected to steam pore formation at a steam flow rate of 0.2L / min and a controlled pressure of 20MPa for 6h to obtain porous carbon material.

[0307] ② Using porous carbon material as the substrate, SiH4 gas as the silicon source, and argon gas as the protective gas, vapor deposition was carried out in a fluidized bed apparatus. The flow rate of SiH4 gas was 0.8 L / min, the flow rate of the protective gas was 2 L / min, the vapor deposition temperature was 580℃, and the time was 8 h, to obtain porous carbon material with silicon particles distributed on the surface and / or in the pores.

[0308] ③ Using acetylene gas as a carbon source, a carbon layer was deposited onto the surface of the obtained porous carbon material via vapor deposition. The vapor deposition temperature was 600℃, and the time was 8 hours. The gas source was then turned off for cooling. After airflow classification, sieving, and demagnetization, porous carbon material coated with a carbon layer, i.e., primary particles, was obtained, with an average carbon layer thickness of 1 nm.

[0309] ④ Take 1000g of primary particles with a volume average particle size Dv50 of 2.8μm, add 2000g of a graphene-carbon nanotube mixed solution (the mixed solution contains 9% graphene by mass, 0.4% carbon nanotubes by mass, and water as the solvent; the average diameter of the graphene sheets is 3μm, the average number of sheets is 5; the aspect ratio of the carbon nanotubes is 5000), 500g of sucrose, and 50g of polyvinylpyrrolidone, and stir and mix evenly at 80℃ to obtain a slurry. Spray dry the slurry to granulate (inlet air temperature 80℃, feed rate 1000mL / min, rotation speed 3000r / min), and calcine the granules at 450℃ in an argon atmosphere for 8h to obtain the calcined product.

[0310] ⑤ Add 800g of the calcined product and 114g of coal tar pitch to a mechanical fusion machine, melt and mix at 1500rpm for 30min, and calcine at 300℃ for 2h to obtain secondary particles coated with a carbon layer as the negative electrode active material. The parameters of the secondary particles are shown in Table 1, and the average thickness of the carbon layer is 2nm. The silicon content of the negative electrode material was measured to be 40%.

[0311] As shown in the SEM images in Figures 7A to 7C, carbon nanotubes are entangled and connected with porous carbon materials and graphene in the secondary particles of the negative electrode active material.

[0312] (2) Preparation of the positive electrode sheet:

[0313] LiNi, the positive electrode active material 0.96 Co 0.03 Mn 0.01O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1:2 and thoroughly mixed to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil, and subsequently dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0314] (3) Preparation of negative electrode sheet:

[0315] The negative electrode active material, conductive carbon black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na), and single-walled carbon nanotubes (SWCNT) were dissolved in deionized water at a mass ratio of 94.5:1:3:1:0.5 and thoroughly stirred to prepare a negative electrode slurry. The negative electrode slurry was coated onto a copper foil for the negative electrode current collector, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0316] (4) Separation membrane: Polypropylene membrane is used as the base membrane, coated with polyvinylidene fluoride (PVDF) with a thickness of 1μm, and then coated with polycarbosilane (PCS) with a thickness of 1μm.

[0317] (5) Preparation of electrolyte: Ethyl carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) were mixed in a volume ratio of 1:1:1:1. Then, LiPF6 was uniformly dissolved in the above solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0318] (6) Preparation of battery cell: The above positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain electrode assembly; the electrode assembly is placed in outer packaging, the electrolyte prepared above is added, and after encapsulation, standing, formation and aging processes, battery cell is obtained.

[0319] Examples 2-13 and Comparative Examples 1-5 are similar to the battery cell preparation methods in Example 1, with different product parameters detailed in Table 1-2.

[0320] Parameter testing

[0321] The testing method for the volume average particle size (Dv50), Dv10, and Dv90 of secondary particles is as follows: The negative electrode sheet is disassembled from the battery, thoroughly cleaned with DMC (dimethyl carbonate), and dried. The negative electrode material on the current collector is collected using a scraping method. The negative electrode material is scanned using SEM. Because the morphology of the secondary particles of the negative electrode active material differs from that of other components in the negative electrode material (conductive agents, binders, thickeners, etc.), the secondary particles of the negative electrode active material can be distinguished. The particle size of the secondary particles of the negative electrode active material is randomly measured in the SEM images. Then, multiple secondary particles of the negative electrode active material are selected, and the above test is repeated. The Dv10, Dv50, and Dv90 particle sizes of more than 50 secondary particles of the negative electrode active material are statistically analyzed.

[0322] Test methods for pore volume, average pore size, and BET specific surface area of ​​negative electrode materials: The negative electrode sheet is disassembled from the battery, thoroughly cleaned with DMC (dimethyl carbonate), and dried. The negative electrode material on the negative electrode current collector is collected by scraping. The pore volume, average pore size, and BET specific surface area of ​​the negative electrode material are measured using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA. Specifically, the nitrogen adsorption specific surface area analysis method is used according to GB / T 19587-2017, and the BET specific surface area is calculated using the BET (Brunauer Emmett Teller) method.

[0323] The testing method for the volume average particle size (Dv50), Dv10, and Dv90 of primary particles was as follows: The negative electrode sheet was disassembled from the battery, thoroughly cleaned with DMC (dimethyl carbonate), and dried. The negative electrode material on the current collector was collected by scraping, pulverized by airflow, and then scanned using SEM. The particle size of primary particles was randomly measured in the SEM images. The above test was then repeated for multiple primary particles, and the Dv10, Dv50, and Dv90 particle sizes of more than 50 primary particles were statistically analyzed.

[0324] BET specific surface area test method for primary particles: The BET specific surface area of ​​primary particles was tested using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA. Specifically, the nitrogen adsorption specific surface area analysis method was used according to GB / T 19587-2017, and the BET specific surface area was calculated using the BET (Brunauer Emmett Teller) method.

[0325] Methods for testing the pore volume and average pore size of porous carbon materials: The pore volume and average pore size of porous carbon materials were tested using a Tri-Star 3020 surface area and pore size analyzer from Micromeritics, USA.

[0326] Method for testing the average thickness of the coating layer of secondary particles: Disassemble the negative electrode sheet from the battery, thoroughly clean it with DMC (dimethyl carbonate), and dry it. Collect the negative electrode material on the negative electrode current collector using a scraping method. Scan the negative electrode material with SEM. Because the morphology of the secondary particles of the negative active material is different from that of other components (conductive agent, binder, thickener) in the negative electrode material, the secondary particles of the negative active material can be distinguished. Cut open the secondary particles of the negative active material, scan the cut surface with SEM, and measure the coating layer thickness of the secondary particles of the negative active material from multiple random directions in the SEM image. Then, repeat the above test with multiple secondary particles of the negative active material, and take the average value as the average thickness of the coating layer of the secondary particles.

[0327] Method for testing the average thickness of the coating layer of primary particles: Cut open a primary particle, scan the cut surface with SEM, and measure the coating layer thickness of the primary particle from multiple random directions in the SEM image. Then, repeat the above test with multiple primary particles and take the average value as the average thickness of the coating layer of the primary particle.

[0328] Test method for silicon content in negative electrode material: Disassemble the negative electrode sheet from the battery, thoroughly clean it with DMC (dimethyl carbonate) and dry it. Collect the negative electrode material on the negative electrode current collector using a scraping method. Test the silicon content of the negative electrode material using the ICP method.

[0329] Battery test

[0330] (1) Energy density testing method for individual battery cells:

[0331] Incubate the battery cell at 25°C for 2 hours, ensuring the temperature remains at 25°C. Charge at 0.1C at 25°C until the charging cutoff voltage of 4.25V, then continue constant-voltage charging at this cutoff voltage until the current reaches 0.05C, at which point charging is complete (where C represents the battery's rated capacity). Incubate the battery cell at 25°C for 1 hour, then discharge at 0.1C at 25°C until the discharge cutoff voltage of 2.5V, recording the total discharge energy as E0. Place the battery cell on an electronic balance until its weight stabilizes, and read the battery weight value M0 (generally, the battery cell with its casing is weighed). Calculate the energy density of the battery cell using the following formula:

[0332] Energy density of a single battery cell = battery discharge energy E0 / battery weight M0.

[0333] (2) Test method for charging time of individual battery cells from 10% to 80% SOC:

[0334] Voltage calibration:

[0335] The battery cells were left to stand at 25°C for 30 minutes, then charged at 0.33C to the charging cutoff voltage of 4.25V. Constant voltage charging was continued at this charging cutoff voltage until the current reached 0.05C, at which point charging was stopped (where C represents the battery's rated capacity). After standing at 25°C for 1 hour, the battery cells were discharged at 0.33C to the discharge cutoff voltage of 2.5V at 25°C. The total discharge capacity C1 of the battery was recorded.

[0336] Charging test:

[0337] The battery cells were left to stand at 25°C for 30 minutes, then charged at 0.33C to 4.25V, and then charged at a constant voltage of 4.25V to 0.05C. They were then discharged at 0.33C to the discharge cutoff voltage of 2.5V. After standing for 5 minutes, the cells were charged with xC1 until the anode potential reached 0V, at which point the process proceeded to the next step (using a three-electrode monitoring system for the anode potential). This process of standing and charging was repeated 9 times, with x values ​​of 5, 4, 4.5, 3, 2, 1, 0.8, 0.5, and 0.33. The sum of all charging times was recorded as the 10%–80% SOC charging time.

[0338] (3) Cycle performance testing methods for individual battery cells:

[0339] Voltage calibration:

[0340] The battery cells were left to stand at 25°C for 2 hours to ensure the temperature remained at 25°C. At 25°C, the battery cells were charged at 0.33C to 4.25V, and then charged at a constant voltage of 4.25V until the current reached 0.05C. After standing for 1 hour, the cells were discharged at 0.33C to 0.95C at 25°C, and the voltage V1 was recorded. After standing for 5 minutes, the cells were discharged at 0.33C to 2.0V at 25°C. After standing for 5 minutes, the cells were charged at 0.33C to 0.97C at 25°C, and the voltage V2 was recorded.

[0341] Loop testing:

[0342] The individual battery cells were left to stand at 25°C for 2 hours to ensure the temperature remained at 25°C. At 25°C, the cells were charged to voltage V2 at 0.33C. After standing for 0.5 hours, the cells were discharged to voltage V1 at 0.33C at 25°C. The capacity at this point was recorded as C. n After resting for 0.5 hours, repeat the above charging and discharging operation and record the number of cycles when the battery reaches 80% SOC.

[0343] The test results are shown in Table 3-6.

[0344] Table 1: Differences in preparation methods between Examples 2-13, Comparative Examples 1-5, and Example 1 The "*" change steps also include adjusting the particle size parameters of the primary particles by controlling the degree of pulverization of the raw material resin.

[0345] Table 3: Comparison of test results between Examples 1-13 and Comparative Examples 1-5

[0346] It can be seen from the above table:

[0347] Compared with the excessively small Dv50 of the secondary particles in Comparative Example 1, the cycle life of the battery cells in Examples 1-13 of this application is significantly extended.

[0348] Compared with the excessively large Dv50 of the secondary particles in Comparative Example 2, the fast charging performance of the battery cells in Examples 1-13 of this application is significantly improved.

[0349] Compared with the small Dv50 of the primary particles in Comparative Example 3, the cycle life of the battery cells in Examples 1-13 of this application is significantly extended.

[0350] Compared with the excessively large Dv50 of the primary particles in Comparative Example 4, the fast charging performance of the battery cells in Examples 1-13 of this application is significantly improved.

[0351] Compared with Comparative Example 5, which does not use graphene and carbon nanotubes, the cycle life of the battery cells in Examples 1-13 of this application is significantly extended, and the energy density and fast charging performance of Example 1 of this application are improved.

[0352] Table 4: Comparison of test results between Examples 1, 7-8, 10-11 and Example 9

[0353] As can be seen from the table above, compared with the lower pore volume of the negative electrode material in Example 9, the energy density and fast charging performance of the battery cells in Examples 1, 7-8, and 10-11 of this application are significantly improved.

[0354] Table 5: Comparison of test results between Examples 1-6 and Example 12

[0355] As can be seen from the table above, compared with the excessively large BET specific surface area of ​​the negative electrode material in Example 12, the cycle life of the battery cells in Examples 1-6 of this application is significantly extended.

[0356] Table 6: Comparison of test results for Examples 1 and 13

[0357] As can be seen from the table above, compared with Example 13 which does not use carbon nanotubes, the energy density and fast charging performance of the battery cell in Example 1 of this application are significantly improved, and the cycle life is significantly extended.

[0358] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode material, the negative electrode material comprising a negative electrode active material, the negative electrode active material comprising secondary particles, the secondary particles comprising primary particles, and one-dimensional carbon material and / or two-dimensional carbon material; the volume average particle size Dv50 of the secondary particles is 7-23 μm; the volume average particle size Dv50 of the primary particles is 0.5-5 μm; the primary particles comprise porous carbon material, the porous carbon material having silicon particles distributed on its surface and / or within its pores.

2. The battery cell according to claim 1, characterized in that... One or more of the following: The (Dv90-Dv10) / Dv50 value of the secondary particles is 0.8-1.9 or 1.1-1.8; The average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm; The pore volume of the negative electrode material is 0.7-1.6 cm³. 3 / g or 1.05-1.6cm 3 / g; The BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g.

3. The battery cell according to claim 1 or 2, characterized in that... One or more of the following: The (Dv90-Dv10) / Dv50 value of the primary particles is 3.4-5; The BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g; The average pore size of the porous carbon material is 0.8-5 nm; The porous carbon material has a pore volume of 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g.

4. The battery cell according to any one of claims 1 to 3, wherein, When the secondary particles comprise one-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles; or, When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

5. The battery cell according to any one of claims 1 to 4, wherein, The one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or, The two-dimensional carbon material includes graphene.

6. The battery cell according to claim 5, characterized in that... One or more of the following: The silicon content in the negative electrode material is 30%-60% by mass; The two-dimensional carbon material includes graphene, and the average diameter of the graphene sheets is 3-8 μm. The two-dimensional carbon material includes graphene, and the average number of graphene sheets is 1-8. The one-dimensional carbon material includes carbon nanotubes, and the aspect ratio of the carbon nanotubes is 3000-10000. The surface of the primary particles is also coated with a coating layer containing carbon; The average thickness of the primary particle surface coating layer is greater than 0 and less than or equal to 5 nm.

7. The battery cell according to any one of claims 1 to 6, wherein, The mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5); and / or, The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015).

8. The battery cell according to any one of claims 1 to 7, wherein the surface of the secondary particles is coated with a coating layer, the coating layer comprising carbon.

9. The battery cell according to claim 8, wherein, The average thickness of the coating layer on the surface of the secondary particles is 2-10 nm.

10. A negative electrode material, comprising a negative electrode active material, the negative electrode active material comprising secondary particles, the secondary particles comprising primary particles, and one-dimensional carbon material and / or two-dimensional carbon material; the volume average particle size Dv50 of the secondary particles is 7-23 μm; the volume average particle size Dv50 of the primary particles is 0.5-5 μm; the primary particles comprise porous carbon material, the porous carbon material having silicon particles distributed on its surface and / or within its pores.

11. The negative electrode material according to claim 10, characterized in that... One or more of the following: The (Dv90-Dv10) / Dv50 value of the secondary particles is 0.8-1.9 or 1.1-1.8; The average pore size of the negative electrode material is 2-10 nm or 3.8-9 nm; The pore volume of the negative electrode material is 0.7-1.6 cm³. 3 / g or 1.05-1.6cm 3 / g; The BET specific surface area of ​​the negative electrode material is 9-70 m². 2 / g or 9-20m 2 / g.

12. The negative electrode material according to claim 10 or 11, characterized in that... One or more of the following: The (Dv90-Dv10) / Dv50 value of the primary particles is 3.4-5; The BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g; The average pore size of the porous carbon material is 0.8-5 nm; The porous carbon material has a pore volume of 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g.

13. The negative electrode material according to any one of claims 10 to 12, wherein, When the secondary particles comprise one-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles; or, When the secondary particles comprise one-dimensional carbon material and two-dimensional carbon material, the one-dimensional carbon material is entangled with the primary particles and / or the two-dimensional carbon material.

14. The negative electrode material according to any one of claims 10 to 13, wherein, The one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; and / or, The two-dimensional carbon material includes graphene.

15. The negative electrode material according to any one of claims 10 to 14, characterized in that... One or more of the following: The silicon content in the negative electrode material is 30%-60% by mass; The two-dimensional carbon material includes graphene, and the average diameter of the graphene sheets is 3-8 μm. The two-dimensional carbon material includes graphene, and the average number of graphene sheets is 1-8. The one-dimensional carbon material includes carbon nanotubes, and the aspect ratio of the carbon nanotubes is 3000-10000. The surface of the primary particles is also coated with a coating layer containing carbon; The average thickness of the primary particle surface coating layer is greater than 0 and less than or equal to 5 nm.

16. The negative electrode material according to any one of claims 10 to 15, wherein, The mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5); and / or, The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015).

17. The negative electrode material according to any one of claims 10 to 16, wherein the surface of the secondary particles is coated with a coating layer, the coating layer comprising carbon.

18. The negative electrode material according to claim 17, wherein, The average thickness of the coating layer on the surface of the secondary particles is 2-10 nm.

19. A method for preparing a negative electrode material, comprising the following steps: Primary particles, as well as one-dimensional carbon materials and / or two-dimensional carbon materials, are mixed with a solvent, granulated, and subjected to a first calcination to obtain the negative electrode material; wherein... The primary particles include porous carbon material and silicon particles distributed on the surface and / or within the pores of the porous carbon material; the negative electrode material includes a negative electrode active material, the negative electrode active material includes secondary particles, the volume average particle size Dv50 of the secondary particles is 7-23 μm, and the volume average particle size Dv50 of the primary particles is 0.5-5 μm.

20. The method according to claim 19, characterized in that... One or more of the following: The mass ratio of the primary particles to the two-dimensional carbon material is 1:(0.1–0.5); The mass ratio of the primary particles to the one-dimensional carbon material is 1:(0.001–0.015); The mixing temperature is 70-90℃; The temperature of the first roasting is 400-650℃; The first roasting time is 4-9 hours; The first calcination was carried out in an inert atmosphere; The negative electrode material is the negative electrode material according to any one of claims 10 to 18.

21. The method according to claim 19 or 20, wherein, In the mixing step, the primary particles, binder, and the one-dimensional carbon material and / or the two-dimensional carbon material are mixed with the solvent.

22. The method according to claim 21, wherein, The binder comprises 20%-40% of the total mass of raw materials excluding solvents; and / or, The binder includes one or more of sucrose, glucose, and fructose.

23. The method according to any one of claims 19 to 22, further comprising: Carbon is coated onto the surface of the calcined product to obtain a negative electrode material with a carbon coating layer.

24. The method according to claim 23, wherein the step of preparing the negative electrode material having a carbon coating layer comprises: The carbon source and the calcination product are mixed at the melting temperature of the carbon source, and then calcined a second time.

25. The method according to claim 24, wherein in the step of preparing the negative electrode material with the carbon coating layer, the characteristic is that... One or more of the following: The mass ratio of the carbon source to the roasting product is 1:(4-99); The temperature for the second roasting is 150-400℃; The second roasting time is 1-10 hours.

26. The method according to any one of claims 19 to 25, wherein, The primary particles are prepared through the following steps: The resin containing a ring structure is calcined to create pores, thus obtaining the porous carbon material. Using the porous carbon material as a substrate, the primary particles are obtained by vapor deposition using a silicon source.

27. The method according to claim 26, wherein, In the step of preparing the primary particles, carbon is coated on the surface of the vapor-deposited product to obtain primary particles including a carbon coating layer.

28. The method according to any one of claims 19 to 27, characterized in that... One or more of the following: The BET specific surface area of ​​the porous carbon material is 800-2000 m². 2 / g or 1000-2000m 2 / g; The average pore size of the porous carbon material is 0.8-5 nm; The porous carbon material has a pore volume of 0.3-1.05 cm³. 3 / g or 0.6-1.05cm 3 / g; The one-dimensional carbon material includes one or more of carbon nanotubes, carbon nanofibers, linear carbon, and carbon nanorods; The two-dimensional carbon material includes graphene; The two-dimensional carbon material includes graphene, and the average diameter of the graphene sheets is 3-8 μm. The two-dimensional carbon material includes graphene, and the average number of graphene sheets is 1-8. The one-dimensional carbon material includes carbon nanotubes, the aspect ratio of which is 3000–10000.

29. A battery device comprising a battery cell according to any one of claims 1 to 9, a negative electrode material according to any one of claims 10 to 18, or a negative electrode material prepared by any one of claims 19 to 28.

30. An electrical device comprising the battery device of claim 29.

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