Negative active material, negative electrode sheet, secondary battery, and electric device

Abstract

The application discloses a negative electrode active material, a negative electrode sheet, a secondary battery and an electric device. The negative electrode active material comprises a first carbon-based material and a second carbon-based material. The first carbon-based material comprises regenerated graphite, and the second carbon-based material comprises artificial graphite secondary particles. The mass proportion of the regenerated graphite in the negative electrode active material is greater than or equal to 30%. Through cooperation of the regenerated graphite and the artificial graphite secondary particles, the expansion of the negative electrode sheet can be reduced, and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to negative electrode active materials, negative electrode sheets, secondary batteries, and electrical devices. Background Technology

[0002] Graphite is one of the main negative electrode active materials in batteries. Regenerated graphite is produced by recycling and regenerating waste graphite negative electrodes, which is beneficial to saving resources and protecting the environment. However, during the charging and discharging process of batteries, recycled graphite has the problem of large volume expansion, which leads to the expansion of large negative electrode sheets and lower battery cycle performance. Summary of the Invention

[0003] This application is made in view of the above-mentioned problems, and its purpose is to provide a negative electrode active material that can reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery.

[0004] To achieve the above objectives, embodiments of this application provide a negative electrode active material, a negative electrode sheet, a secondary battery, and an electrical device.

[0005] In a first aspect, embodiments of this application propose a negative electrode active material, which includes a first carbon-based material and a second carbon-based material, wherein the first carbon-based material includes recycled graphite, the second carbon-based material includes artificial graphite secondary particles, and the recycled graphite accounts for more than or equal to 30% of the mass of the negative electrode active material.

[0006] Therefore, in the technical solution of this application embodiment, the negative electrode active material includes recycled graphite and artificial graphite secondary particles. The artificial graphite secondary particles have high isotropy. By mixing recycled graphite and artificial graphite secondary particles and making the mass ratio of recycled graphite in the negative electrode active material greater than or equal to 30%, the expansion of the negative electrode sheet during cycling can be effectively reduced while reducing the amount of artificial graphite secondary particles, thereby improving the cycle performance of the battery.

[0007] In any embodiment, the recycled graphite accounts for 50% to 80% of the mass of the negative electrode active material. When the recycled graphite accounts for 50% to 80% of the mass of the negative electrode active material, it can effectively reduce the expansion of the negative electrode sheet, improve the cycle performance of the battery, and further reduce the amount of artificial graphite secondary particles. Optionally, the recycled graphite accounts for 60% to 80% of the mass of the negative electrode active material. A suitable range of recycled graphite mass percentage can effectively reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery while further reducing the amount of artificial graphite secondary particles.

[0008] In any embodiment, the recycled graphite does not have a coating layer. When the recycled graphite does not have a coating layer, the expansion of the negative electrode sheet can be reduced, improving the cycle performance of the battery; and / or,

[0009] The artificial graphite secondary particles do not have a coating layer. When the artificial graphite secondary particles do not have a coating layer, the expansion of the negative electrode sheet can be reduced, thereby improving the cycle performance of the battery.

[0010] In any embodiment, the OI value of the recycled graphite is less than or equal to 20. When the OI value of the recycled graphite is less than or equal to 20, it is beneficial to improve the adhesion between the negative electrode active material and the negative electrode current collector. At the same time, the recycled graphite also has high isotropy, which can reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery. Optionally, the OI value of the recycled graphite is 12 to 18, which is a more suitable range for the OI value of the recycled graphite, which is beneficial to reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery.

[0011] In any embodiment, the specific capacity of the recycled graphite is greater than or equal to 340 mAh / g. When the specific capacity of the recycled graphite is greater than or equal to 340 mAh / g, the energy density and cycle performance of the battery can be improved; optionally, the specific capacity of the recycled graphite is 340 mAh / g to 353 mAh / g, which is a suitable range for the specific capacity of the recycled graphite and is beneficial to improving the energy density and cycle performance of the battery.

[0012] In any embodiment, the average particle size D of the recycled graphite v 50 is greater than or equal to 12 μm. When the average particle size D of the recycled graphite is... v When the particle size of the recycled graphite is greater than or equal to 12 μm, the energy density of the battery can be improved; optionally, the average particle size D of the recycled graphite... v 50 represents an average particle size D of 12μm to 25μm, which is considered suitable for recycled graphite. v A range of 50 is beneficial for improving the energy density of batteries.

[0013] In any embodiment, the initial weight loss temperature of the recycled graphite is 610℃~715℃. When the initial weight loss temperature of the recycled graphite is 610℃~715℃, the recycled graphite has a relatively stable structure, which can improve the cycle performance of the battery; optionally, the initial weight loss temperature of the recycled graphite is 620℃~710℃, and a more suitable initial weight loss temperature range for the recycled graphite is beneficial to improving the cycle performance of the battery.

[0014] In any embodiment, the resistivity of the recycled graphite powder is 0.005 Ω / cm to 0.025 Ω / cm. When the resistivity of the recycled graphite powder is 0.005 Ω / cm to 0.025 Ω / cm, it is beneficial to improve the electrical contact between particles in the negative electrode sheet, thereby improving the kinetic performance of the battery. Optionally, the resistivity of the recycled graphite powder is 0.005 Ω / cm to 0.020 Ω / cm, which is a suitable range for the resistivity of the recycled graphite powder and is beneficial to improving the kinetic performance of the battery.

[0015] In any embodiment, the surface of the recycled graphite has conductive carbon, which can improve the cycle performance of the battery.

[0016] In any embodiment, the OI value of the artificial graphite secondary particles is less than or equal to 18. When the OI value of the artificial graphite secondary particles is less than or equal to 18, the OI value is relatively small, the isotropy is relatively high, and the volume expansion during cycling can effectively release stress and strain from all directions, thereby reducing the expansion of the negative electrode sheet and improving the cycle performance of the battery. Optionally, the OI value of the artificial graphite secondary particles is 6 to 15, which is a more suitable range for OI values, which is beneficial for reducing the expansion of the negative electrode sheet and improving the cycle performance of the battery.

[0017] In any embodiment, the specific capacity of the artificial graphite secondary particles is greater than or equal to 350 mAh / g. When the specific capacity of the artificial graphite secondary particles is greater than or equal to 350 mAh / g, the energy density and cycle performance of the battery can be improved. Optionally, the specific capacity of the artificial graphite secondary particles is 350 mAh / g to 360 mAh / g, which is a suitable range for the specific capacity of the artificial graphite secondary particles and is beneficial to improving the energy density and cycle performance of the battery.

[0018] In any embodiment, the average particle size D of the artificial graphite secondary particles v 50 is greater than or equal to 12 μm. When the average particle size D of the artificial graphite secondary particles... v When the particle size is greater than or equal to 12 μm, the energy density of the battery can be improved; optionally, the average particle size D of the artificial graphite secondary particles... v 50 represents an average particle size D of 12μm to 18μm, which is considered suitable for artificial graphite secondary particles. v A range of 50 is beneficial for improving the energy density of batteries.

[0019] In any embodiment, the compacted density of the artificial graphite secondary particles under a pressure of 50,000 N is less than or equal to 2.00 g / cm³. 3 When the compaction density of artificial graphite secondary particles under a pressure of 50,000 N is less than or equal to 2.00 g / cm³. 3This can improve the energy density of the battery; optionally, the compaction density of the artificial graphite secondary particles under a pressure of 50000N is 1.75g / cm³. 3 ~2.00g / cm 3 The appropriate compaction density range of artificial graphite secondary particles under 50,000 N pressure is beneficial to improving the energy density of the battery.

[0020] Secondly, embodiments of this application provide a negative electrode sheet, including the negative electrode active material of the first aspect of this application.

[0021] In any embodiment, the compaction density of the negative electrode sheet is greater than or equal to 1.50 g / cm³. 3 When the compaction density of the negative electrode sheet is greater than or equal to 1.50 g / cm³ 3 This can improve the energy density of the battery; optionally, the compaction density of the negative electrode sheet is 1.55 g / cm³. 3 ~1.70g / cm 3 A suitable range of compaction density for the negative electrode sheet is beneficial for improving the energy density of the battery.

[0022] Thirdly, embodiments of this application propose a secondary battery, including the negative electrode sheet of the second aspect of this application.

[0023] Fourthly, embodiments of this application provide an electrical device including a secondary battery as described in the third aspect of this application. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0025] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0026] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0027] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0028] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0029] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0032] The following details embodiments of the positive electrode material, its preparation method, the positive electrode sheet, the battery, and the power device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually 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.

[0033] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in 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.

[0037] Graphite is one of the main negative electrode active materials in batteries. Regenerated graphite is produced by recycling and regenerating waste graphite negative electrodes, which is beneficial to saving resources and protecting the environment. However, during the charging and discharging process of batteries, recycled graphite has the problem of large volume expansion, which leads to large cell expansion and low battery cycle life.

[0038] Based on this, in the first aspect, this application proposes a negative electrode active material that can reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery.

[0039] Surprisingly, in one aspect, embodiments of this application propose a negative electrode active material, which includes a first carbon-based material and a second carbon-based material, wherein the first carbon-based material includes recycled graphite, the second carbon-based material includes artificial graphite secondary particles, and the recycled graphite accounts for more than or equal to 30% of the mass of the negative electrode active material.

[0040] In the technical solution of this application embodiment, the negative electrode active material includes recycled graphite and artificial graphite secondary particles. The artificial graphite secondary particles have high isotropy. By mixing recycled graphite and artificial graphite secondary particles and making the mass ratio of recycled graphite in the negative electrode active material greater than or equal to 30%, the expansion of the negative electrode sheet during cycling can be effectively reduced while reducing the amount of artificial graphite secondary particles, thereby improving the cycle performance of the battery. The mass ratio of recycled graphite in the negative electrode active material can be 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

[0041] In any embodiment, the recycled graphite accounts for 50% to 80% of the mass of the negative electrode active material. When the recycled graphite accounts for 50% to 80% of the mass of the negative electrode active material, it can effectively reduce the expansion of the negative electrode sheet, improve the cycle performance of the battery, and further reduce the amount of artificial graphite secondary particles. Optionally, the recycled graphite accounts for 60% to 80% of the mass of the negative electrode active material. A suitable range of recycled graphite mass percentage can effectively reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery while further reducing the amount of artificial graphite secondary particles.

[0042] In any embodiment, the recycled graphite does not have a coating layer. When the recycled graphite does not have a coating layer, the expansion of the negative electrode sheet can be reduced, improving the cycle performance of the battery; and / or,

[0043] The artificial graphite secondary particles do not have a coating layer. When the artificial graphite secondary particles do not have a coating layer, the expansion of the negative electrode sheet can be reduced, thereby improving the cycle performance of the battery.

[0044] In any embodiment, the OI value of the recycled graphite is less than or equal to 20. When the OI value of the recycled graphite is less than or equal to 20, it is beneficial to improve the adhesion between the negative electrode active material and the negative electrode current collector. At the same time, the recycled graphite also has high isotropy, which can reduce the expansion of the negative electrode sheet. The OI value of the recycled graphite can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20. Optionally, the OI value of the recycled graphite is 12 to 18. A suitable range of OI values ​​for recycled graphite is beneficial to reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery.

[0045] In any embodiment, the specific capacity of the recycled graphite is greater than or equal to 340 mAh / g. When the specific capacity of the recycled graphite is greater than or equal to 340 mAh / g, the energy density and cycle performance of the battery can be improved. The specific capacity of the recycled graphite can be 340 mAh / g, 343 mAh / g, 347 mAh / g, 350 mAh / g, 353 mAh / g, or 357 mAh / g. Optionally, the specific capacity of the recycled graphite is between 340 mAh / g and 353 mAh / g, which is a suitable range for improving the energy density and cycle performance of the battery.

[0046] In any embodiment, the average particle size D of the recycled graphite v 50 is greater than or equal to 12 μm. When the average particle size D of the recycled graphite is... v When the particle size of 50 is greater than or equal to 12 μm, the energy density of the battery can be improved; the average particle size D of recycled graphite v50 can be 12μm, 15μm, 19μm, 22μm, 25μm, or 28μm; optionally, the average particle size D of the recycled graphite v 50 represents an average particle size D of 12μm to 25μm, which is considered suitable for recycled graphite. v A range of 50 is beneficial for improving the energy density of batteries.

[0047] In any embodiment, the initial weight loss temperature of the recycled graphite is 610℃~715℃. When the initial weight loss temperature of the recycled graphite is 610℃~715℃, the recycled graphite has a relatively stable structure, which can improve the cycle performance of the battery. The initial weight loss temperature of the recycled graphite can be 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, or 715℃. Optionally, the initial weight loss temperature of the recycled graphite is 620℃~710℃, which is a more suitable range for the initial weight loss temperature of the recycled graphite and is beneficial to improving the cycle performance of the battery.

[0048] In any embodiment, the powder resistivity of the recycled graphite is 0.005 Ω / cm to 0.025 Ω / cm. When the powder resistivity of the recycled graphite is 0.005 Ω / cm to 0.025 Ω / cm, it is beneficial to improve the electrical contact between particles in the negative electrode sheet, thereby improving the kinetic performance of the battery. The powder resistivity of the recycled graphite can be 0.005 Ω / cm, 0.08 Ω / cm, 0.012 Ω / cm, 0.016 Ω / cm, 0.020 Ω / cm, or 0.025 Ω / cm. Optionally, the powder resistivity of the recycled graphite is 0.005 Ω / cm to 0.020 Ω / cm, which is a suitable range for improving the kinetic performance of the battery.

[0049] In any embodiment, the surface of the recycled graphite has conductive carbon, which can improve the cycle performance of the battery.

[0050] In any embodiment, the OI value of the artificial graphite secondary particles is less than or equal to 18. When the OI value of the artificial graphite secondary particles is less than or equal to 18, the OI value is small, the isotropy is high, and the volume expansion during cycling can effectively release stress and strain from all directions, thereby reducing the expansion of the negative electrode and improving the cycle performance of the battery. The OI value of the artificial graphite secondary particles can be 4, 6, 8, 10, 12, 15, or 18. Optionally, the OI value of the artificial graphite secondary particles is 6 to 15, which is a more suitable range for OI value, which is beneficial for reducing the expansion of the negative electrode and improving the cycle performance of the battery.

[0051] In any embodiment, the specific capacity of the artificial graphite secondary particles is greater than or equal to 350 mAh / g. When the specific capacity of the artificial graphite secondary particles is greater than or equal to 350 mAh / g, the energy density and cycle performance of the battery can be improved. The specific capacity of the artificial graphite secondary particles can be 350 mAh / g, 355 mAh / g, 360 mAh / g, or 365 mAh / g. Optionally, the specific capacity of the artificial graphite secondary particles is between 350 mAh / g and 360 mAh / g, which is a suitable range for improving the energy density and cycle performance of the battery.

[0052] In any embodiment, the average particle size D of the artificial graphite secondary particles v 50 is greater than or equal to 12 μm. When the average particle size D of the artificial graphite secondary particles... v When the particle size is greater than or equal to 12 μm, the energy density of the battery can be improved; the average particle size D of artificial graphite secondary particles v 50 can be 12μm, 15μm, 18μm, or 21μm; optionally, the average particle size D of the artificial graphite secondary particles is... v 50 represents an average particle size D of 12μm to 18μm, which is considered suitable for artificial graphite secondary particles. v A range of 50 is beneficial for improving the energy density of batteries.

[0053] In any embodiment, the compacted density of the artificial graphite secondary particles under a pressure of 50,000 N is less than or equal to 2.00 g / cm³. 3 When the compaction density of artificial graphite secondary particles under a pressure of 50,000 N is less than or equal to 2.00 g / cm³. 3 This can increase the energy density of the battery; the compaction density of artificial graphite secondary particles can be 1.70 g / cm³. 3 1.75g / cm 3 1.81 g / cm 3 1.87 g / cm 3 1.93g / cm 3 Or 2.00g / cm 3 Optionally, the compaction density of the artificial graphite secondary particles under a pressure of 50,000 N is 1.75 g / cm³. 3 ~2.00g / cm 3 The appropriate compaction density range of artificial graphite secondary particles under 50,000 N pressure is beneficial to improving the energy density of the battery.

[0054] Secondly, embodiments of this application provide a negative electrode sheet, including the negative electrode active material of the first aspect of this application.

[0055] In any embodiment, the compaction density of the negative electrode sheet is greater than or equal to 1.50 g / cm³. 3 When the compaction density of the negative electrode sheet is greater than or equal to 1.50 g / cm³ 3 This can increase the energy density of the battery, and the compaction density of the negative electrode sheet can reach 1.50 g / cm³. 3 1.55g / cm 3 1.60g / cm 3 1.65g / cm 3 1.70g / cm 3 Or 1.75g / cm 3 Optionally, the compaction density of the negative electrode sheet is 1.55 g / cm³. 3 ~1.70g / cm 3 A suitable range of compaction density for the negative electrode sheet is beneficial for improving the energy density of the battery.

[0056] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including the negative electrode active material of the first aspect of this application.

[0057] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0058] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0059] In some embodiments, the negative electrode film layer may optionally include a binder. 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).

[0060] In some embodiments, the negative electrode film may optionally include a conductive agent. 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.

[0061] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0062] 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.

[0063] Thirdly, embodiments of this application propose a secondary battery, including the negative electrode sheet of the second aspect of this application.

[0064] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0065] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0066] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0067] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0068] In some embodiments, the secondary battery can be a lithium-ion battery, and the positive electrode active material can be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, 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 transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (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) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, 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 manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0069] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0070] 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.

[0071] 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.

[0072] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0073] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0074] 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.

[0075] 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.

[0076] 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 may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0077] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0078] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. 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.

[0079] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0080] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0081] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0082] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0083] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 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 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0084] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module 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 module.

[0085] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0086] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0087] 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.

[0088] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 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 body 2 and a lower body 3, with the upper body 2 covering the lower body 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.

[0089] Fourthly, embodiments of this application provide an electrical device, including the electrochemical device of the third aspect of this application.

[0090] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for 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.

[0091] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0092] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0093] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0094] Example

[0095] 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.

[0096] The method for preparing recycled graphite includes the following steps:

[0097] S1. The waste negative electrode sheet is crushed, graded, and sieved to separate the copper foil from the negative electrode material I, thus obtaining negative electrode material I.

[0098] S2. The negative electrode material I obtained in step S1 is fed into a rotary kiln for oxidation treatment to remove organic impurities, yielding negative electrode material II; wherein, the rotational speed of the rotary kiln tubes is 2 r / min to 6 r / min, and a gas is introduced into the rotary kiln, the gas including at least one of air, oxygen, and carbon dioxide, and the gas flow rate is 1 m³ / min. 3 / h~9m 3 / h, the oxidation treatment temperature is 300℃-800℃, and the time is 1h-5h;

[0099] S3. The negative electrode material II obtained in step S2 is mixed with acid solution and reacted for 0.5h to 6h. Then, it is filtered by pressure, washed with water and dried to obtain regenerated graphite. The acid solution includes at least one of hydrofluoric acid, nitric acid and hydrochloric acid.

[0100] Following step S3, the following may also be included:

[0101] S4. The recycled graphite obtained in step S3 is mixed with petroleum coke pitch with a thickness of 2.5μm to 5.0μm and carbonized under an inert gas to obtain recycled graphite with a carbon coating layer; wherein the carbonization treatment temperature is 1000℃ to 1300℃ and the time is 1h to 4h.

[0102] The preparation method of artificial graphite secondary particles includes the following steps:

[0103] S1. The raw materials are crushed and shaped to obtain intermediate I; wherein the raw materials include at least one of petroleum coke, needle coke, pitch coke and metallurgical coke.

[0104] S2. Granulate the intermediate I obtained in step S1 to obtain intermediate II;

[0105] S3. The intermediate obtained in step S2 is subjected to graphitization treatment to obtain artificial graphite secondary particles; wherein the temperature of the graphitization treatment is 2800℃~3200℃ and the time is 2h~6h.

[0106] The parameters of the negative electrode active materials in Examples 1-18 and Comparative Examples 1-2 of this application are as shown in Table 1, wherein the average particle size D of the recycled graphite is used as the reference parameter. v The particle size of the 50-type artificial graphite secondary particles is 19 μm, the initial weight loss temperature is 660℃, the powder resistivity is 0.12 Ω / cm, the surface has conductive carbon, and the average particle size D is... v 50 has a thickness of 15 μm, and its compacted density under a pressure of 50,000 N is 1.87 g / cm³. 3 For example.

[0107] Table 1. Parameters and test results of the negative electrode active materials in Examples 1-18 and Comparative Examples 1-2.

[0108]

[0109] Performance testing:

[0110] The negative electrode active materials of Examples 1-18 and Comparative Examples 1-2 were used to prepare secondary batteries, and the preparation methods are as follows:

[0111] Preparation of negative electrode sheet

[0112] The negative electrode active materials of Examples 1-18 and Comparative Examples 1-2, conductive carbon black (Super P), thickener sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber (SBR) were mixed at a mass ratio of 96.4:1:1.2:1.4. Deionized water was added as a solvent, and the mixture was stirred under vacuum until the system was homogeneous to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of the negative electrode current collector copper foil, and after drying, cold pressing, and slitting, a negative electrode sheet was obtained.

[0113] Preparation of positive electrode sheet

[0114] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2(NCM 523 Conductive agent conductive carbon black (Super P) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, and solvent N-methylpyrrolidone (NMP) is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing and slitting, a positive electrode sheet is obtained.

[0115] Preparation of electrolyte

[0116] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Lithium hexafluorophosphate (LiPF6) was then dissolved in the organic solvent to obtain an electrolyte. The concentration of LiPF6 was 1 mol / L.

[0117] Separator: Polyethylene film is selected as the separator.

[0118] Preparation of secondary batteries

[0119] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain the battery cell. The battery cell is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0120] The following tests were conducted:

[0121] (1) Expansion rate test of negative electrode sheet

[0122] The thickness of the negative electrode sheet after cold pressing is recorded as H0; at 25℃, the secondary battery is subjected to 1C / 1C cycles at 100% DOD (100% depth of discharge, i.e., full charge followed by full discharge) using a Xinwei charge / discharge machine; the discharge capacity of the first cycle (i.e., the initial capacity) is recorded as 100%, and the cycle is stopped when the cycle capacity retention rate is 80% of the initial capacity; then, the secondary battery is charged to 100% SOC (State of Charge), the secondary battery is disassembled, and the thickness of the negative electrode sheet is measured and recorded as H1; the expansion rate of the negative electrode sheet is calculated, where the expansion rate (%) of the negative electrode sheet = (H1 / H0-1)×100%.

[0123] (2) Cycle performance test of secondary batteries

[0124] At 45℃, the secondary battery is charged at a constant current of 1C to the upper limit cutoff voltage (corresponding to 100% SOC), then charged at a constant voltage to a current of 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 1C to the lower limit cutoff voltage (corresponding to 0% SOC), and the discharge capacity at this time is recorded, which is the discharge capacity of the first cycle. The secondary battery is subjected to cyclic charge and discharge tests in the above manner, and the discharge capacity after each cycle is recorded. The capacity retention rate of the secondary battery after 1000 cycles at 45℃ is calculated, where the capacity retention rate (%) of the secondary battery after 1000 cycles at 45℃ is = discharge capacity after 1000 cycles / discharge capacity of the first cycle × 100%.

[0125] The test results of Examples 1-18 and Comparative Examples 1-2 are shown in Table 1.

[0126] As can be seen from Table 1, through Examples 1-18 and Comparative Examples 1-2, mixing recycled graphite with artificial graphite secondary particles to prepare negative electrode active materials, and ensuring that the mass ratio of recycled graphite in the negative electrode active materials is greater than or equal to 30%, can effectively reduce the expansion of the negative electrode sheet and improve the cycle performance of the battery while reducing the amount of artificial graphite secondary particles.

[0127] Examples 4 and 7-9 show that an OI value of 20 or less for recycled graphite is beneficial for reducing the expansion of the negative electrode and improving the cycle performance of the battery. Examples 4 and 10-11 show that a specific capacity of 340 mAh / g or more for recycled graphite is beneficial for improving the cycle performance of the battery while ensuring the battery's energy density. Examples 4 and 12-14 show that an OI value of 18 or less for artificial graphite secondary particles is beneficial for reducing the expansion of the negative electrode and improving the cycle performance of the battery. Examples 4 and 15-16 show that a specific capacity of 350 mAh / g or more for artificial graphite secondary particles is beneficial for improving the cycle performance of the battery while ensuring the battery's energy density. Examples 4 and 17-18 show that when neither recycled graphite nor artificial graphite secondary particles have a carbon coating layer, it is beneficial for reducing the expansion of the negative electrode and improving the cycle performance of the battery.

[0128] 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 negative electrode active material, characterized in that, It includes a first carbon-based material and a second carbon-based material, wherein the first carbon-based material includes recycled graphite, and the second carbon-based material includes artificial graphite secondary particles, and the recycled graphite accounts for more than or equal to 30% of the mass of the negative electrode active material.

2. The negative electrode active material as described in claim 1, characterized in that, The recycled graphite accounts for 50% to 80% of the mass of the negative electrode active material.

3. The negative electrode active material as described in claim 1 or 2, characterized in that, The recycled graphite does not have a coating layer; and / or, The artificial graphite secondary particles do not have a coating layer.

4. The negative electrode active material as described in claim 1, characterized in that, The OI value of the recycled graphite is less than or equal to 20.

5. The negative electrode active material as described in claim 1, characterized in that, The specific capacity of the recycled graphite is greater than or equal to 340 mAh / g.

6. The negative electrode active material as described in claim 1, characterized in that, The average particle size D of the recycled graphite v 50 is greater than or equal to 12μm.

7. The negative electrode active material as described in claim 1, characterized in that, The initial weight loss temperature of the recycled graphite is 610℃~715℃.

8. The negative electrode active material as described in claim 1, characterized in that, The resistivity of the recycled graphite powder is 0.005Ω / cm to 0.025Ω / cm.

9. The negative electrode active material as described in claim 1, characterized in that, The surface of the recycled graphite has conductive carbon.

10. The negative electrode active material as described in claim 1, characterized in that, The OI value of the artificial graphite secondary particles is less than or equal to 18.

11. The negative electrode active material as described in claim 1, characterized in that, The specific capacity of the artificial graphite secondary particles is greater than or equal to 350 mAh / g.

12. The negative electrode active material as described in claim 1, characterized in that, The average particle size D of the artificial graphite secondary particles v 50 is greater than or equal to 12μm.

13. The negative electrode active material as described in claim 1, characterized in that, The compacted density of the artificial graphite secondary particles under a pressure of 50,000 N is less than or equal to 2.00 g / cm³. 3 .

14. A negative electrode sheet, characterized in that, Includes the negative electrode active material as described in any one of claims 1 to 13.

15. The negative electrode sheet as described in claim 14, characterized in that, The compacted density of the negative electrode sheet is greater than or equal to 1.50 g / cm³. 3 .

16. A secondary battery, characterized in that, Includes the negative electrode sheet as described in claim 14 or 15.

17. An electrical device, characterized in that, Includes the secondary battery as described in claim 16.

Images