Positive electrode composition, positive electrode slurry, positive electrode sheet, secondary battery, battery module, battery pack, and power using device

Abstract

This application provides a positive electrode composition, a positive electrode slurry, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. The positive electrode composition includes a positive electrode active material and an anti-agglomeration agent, wherein the positive electrode active material includes a lithium phosphate, and the anti-agglomeration agent includes a polymer whose molecular chain contains phosphorous groups and ether bonds.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a positive electrode composition, positive electrode slurry, positive electrode sheet, secondary battery, battery module, battery pack and electrical device. Background Technology

[0002] In recent years, as the application scope of secondary batteries has become increasingly wide, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, transportation vehicles, military equipment, and aerospace.

[0003] With the rising market position of rechargeable batteries, people not only expect rechargeable batteries to have higher energy density and better cycle performance, but also lower manufacturing costs and higher production capacity.

[0004] However, in the current industrial production process of secondary batteries, some material loss is inevitable, which leads to an increase in the manufacturing cost of secondary batteries and a reduction in the production capacity of secondary batteries. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode composition that enables a secondary battery to have both low cost and good electrochemical performance.

[0006] To achieve the above objectives, this application provides a positive electrode composition, a positive electrode slurry, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device.

[0007] The first aspect of this application provides a cathode composition for a lithium battery cathode, comprising a cathode active material and an anti-agglomeration agent, wherein the cathode active material comprises a lithium phosphate, and the anti-agglomeration agent comprises a polymer containing phosphite groups and ether bonds in its molecular chain.

[0008] The cathode composition of this application includes a lithium phosphate and the aforementioned anti-agglomeration agent. The phosphite group in the anti-agglomeration agent can interact with the phosphate group in the lithium phosphate through hydrogen bonding, thereby "anchoring" the lithium phosphate to the anti-agglomeration agent molecular chain. Other parts of the anti-agglomeration agent molecular chain can generate strong charge interactions with other molecular chains, causing mutual repulsion between the anti-agglomeration agent molecular chains. This allows the anti-agglomeration agent molecular chains, linked to the lithium phosphate, to be independently and stably dispersed in the solvent of the cathode slurry. Therefore, when the cathode composition of this application is used in the cathode slurry of a secondary battery, it can effectively reduce the agglomeration of the cathode active material, alleviate the gelation phenomenon of the cathode slurry, thereby reducing the amount of solvent used and the re-stirring process, and increasing the solid content of the cathode slurry. Thus, when the cathode composition of this application is used in a secondary battery, it can reduce the manufacturing cost of the secondary battery, increase the production capacity of the secondary battery, and maintain good electrochemical performance of the secondary battery.

[0009] In any embodiment of the first aspect of this application, the lithium-containing phosphate includes lithium iron phosphate, and optionally, the particle size D of the lithium iron phosphate is... 10 The particle size D of the lithium iron phosphate is 100nm to 800nm. More preferably, the particle size D of the lithium iron phosphate is... 10 The wavelength is 200nm to 300nm, D 50 The particle size is 400nm to 600nm. The cathode composition of this application includes an anti-agglomeration agent, which, when applied to the cathode slurry, effectively reduces the risk of gelation in the cathode slurry even if the lithium iron phosphate particle size is within the aforementioned small range. Therefore, when the cathode composition of this application is applied to a secondary battery, it not only ensures that the secondary battery possesses good low-temperature power performance, kinetic performance, and fast charge / discharge performance, but also reduces the manufacturing cost of the secondary battery and increases its production capacity.

[0010] In any embodiment of the first aspect of this application, the number average molecular weight of the anti-agglomerate is 1000 to 10000, optionally 3000 to 8000. When the number average molecular weight of the anti-agglomerate is within the aforementioned suitable range, it ensures that the anti-agglomerate molecular chains linked with lithium phosphate are independently and stably dispersed in the solvent of the positive electrode slurry, thereby preventing gelation of the positive electrode slurry, and thus reducing the manufacturing cost of the secondary battery and increasing its production capacity.

[0011] In any embodiment of the first aspect of this application, the anti-coagulant comprises a compound represented by Formula 1.

[0012]

[0013] In Formula 1, m is selected from 20 to 180, and may be an integer from 60 to 150, and n is selected from 25 to 150, and may be an integer from 50 to 120. In the compound shown in Formula 1, the phosphite group is located at the end group, and the volume of the molecular chain and the proportion of ether bonds in the molecular chain are within a suitable range. Therefore, the molecular chains of the anti-coagulation agent can repel each other through charge interaction, thereby stably dispersing in the solvent of the positive electrode slurry. The anti-coagulation agent of this application includes the compound shown in Formula 1, which can further reduce the risk of gel formation in the positive electrode slurry, thereby improving the power output of the secondary battery.

[0014] In any embodiment of the first aspect of this application, the cathode composition further includes carbon nanotubes. Optionally, the carbon nanotubes are single-walled carbon nanotubes. When the cathode composition of this application includes carbon nanotubes, its application in the cathode slurry enables the prepared secondary battery to not only have high power output and low cost, but also excellent low-temperature power performance.

[0015] In any embodiment of the first aspect of this application, the positive electrode composition further includes a binder and a conductive agent. Optionally, based on the total mass of the positive electrode composition, the mass percentage of the positive electrode active material is 93wt% to 96.9wt%, the mass percentage of the anti-agglomeration agent is 0.1wt% to 0.5wt%, optionally 0.3wt% to 0.5wt%, the mass percentage of the binder is 1wt% to 2wt%, and the mass percentage of the conductive agent is 2wt% to 4.5wt%. When the mass percentages of the positive electrode active material, anti-agglomeration agent, binder, and conductive agent are within the above ranges, their application in the positive electrode slurry can effectively prevent the formation of gelation; when applied in a secondary battery, they can enable the positive electrode sheet to have good electronic conductivity and active ion transport capabilities, as well as good structural stability.

[0016] In any embodiment of the first aspect of this application, the positive electrode composition further includes a binder, a conductive agent, and carbon nanotubes. Optionally, based on the total mass of the positive electrode composition, the mass percentage of the positive electrode active material is 93wt% to 96wt%, the mass percentage of the anti-agglomeration agent is 0.1wt% to 0.5wt%, optionally 0.3wt% to 0.5wt%, the mass percentage of the carbon nanotubes is 0.1wt% to 1wt%, the mass percentage of the binder is 1wt% to 2wt%, and the mass percentage of the conductive agent is 2wt% to 4wt%. When the mass percentages of the positive electrode active material, anti-agglomeration agent, carbon nanotubes, binder, and conductive agent in the positive electrode composition are within the above ranges, their application in the positive electrode slurry can effectively prevent the formation of gelation; when applied in a secondary battery, they can further improve the electronic conductivity, active ion transport capacity, and structural stability of the positive electrode sheet.

[0017] In any embodiment of the first aspect of this application, the mass ratio of lithium phosphate to carbon nanotubes in the positive electrode composition is 1:0.003 to 1:0.01. A mass ratio of lithium phosphate to carbon nanotubes within this range can effectively improve the conductivity of the positive electrode composition, thereby enabling secondary batteries using the positive electrode composition of this application to have low DC resistance (DCR) and long cycle life.

[0018] In any embodiment of the first aspect of this application, the mass ratio of lithium phosphate to anti-coagulation agent in the cathode composition is 1:0.003 to 1:0.006. Within this range, the mass ratio of lithium phosphate to anti-coagulation agent effectively reduces gelation of the cathode slurry while simultaneously enabling the cathode composition to possess higher energy density, lower cost, and good electrochemical performance. Therefore, when applied to secondary batteries, it ensures that the secondary battery has high energy output, low cost, and good electrochemical performance.

[0019] A second aspect of this application provides a positive electrode slurry, including a solvent and a positive electrode composition according to a first aspect of this application.

[0020] The positive electrode slurry of this application includes the positive electrode composition of this application. Therefore, the positive electrode slurry of this application is less prone to gelation due to the agglomeration of the positive electrode active material, thereby reducing the amount of solvent used and the need for re-stirring, and increasing the solid content of the positive electrode slurry. Thus, when the positive electrode slurry of this application is applied to secondary batteries, it can reduce the manufacturing cost of secondary batteries, increase the production capacity of secondary batteries, and enable secondary batteries to maintain good electrochemical performance.

[0021] In any embodiment of the second aspect of this application, the positive electrode slurry satisfies at least one of the following (1) to (3).

[0022] (1) The solvent is N-methylpyrrolidone.

[0023] (2) The solid component content of the positive electrode slurry is 55wt% to 65wt%. When the solid component content of the positive electrode slurry is within a suitable range, it is easy to control the coating weight and film thickness of the positive electrode sheet, thereby taking into account the energy density, electrolyte wetting rate and electron conduction energy of the positive electrode sheet, and thus improving the electrochemical performance of the secondary battery.

[0024] (3) The viscosity of the positive electrode slurry is 7000 mPa·s to 15000 mPa·s. The positive electrode slurry has a suitable viscosity, which is conducive to forming a coating of uniform thickness on the surface of the positive electrode current collector, thereby improving the yield of the positive electrode sheet and increasing the production capacity of the secondary battery.

[0025] A third aspect of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector. The positive electrode film layer comprises a positive electrode composition according to a first aspect of this application, or the positive electrode film layer is a layer formed by drying a positive electrode slurry according to a second aspect of this application.

[0026] In the positive electrode sheet of this application, the positive electrode film layer includes the positive electrode composition of this application, or is formed by drying the positive electrode slurry of this application, which can achieve low preparation cost, high production capacity and good electrochemical performance. Therefore, when the positive electrode sheet of this application is applied to secondary batteries, it can reduce the manufacturing cost of secondary batteries, increase the production capacity of secondary batteries, and enable secondary batteries to maintain good electrochemical performance.

[0027] A fourth aspect of this application provides a secondary battery, including the positive electrode sheet of the third aspect of this application.

[0028] The secondary battery of this application includes the positive electrode sheet of this application, thereby enabling it to have low manufacturing cost, high production capacity and good electrochemical performance.

[0029] The fifth aspect of this application provides a battery module, including the secondary battery of the fourth aspect of this application.

[0030] A sixth aspect of this application provides a battery pack that includes the battery module of the fifth aspect of this application.

[0031] A seventh aspect of this application provides an electrical device comprising at least one selected from the fourth aspect of this application, the fifth aspect of this application, or the sixth aspect of this application.

[0032] The battery module, battery pack, and power device of this application include the secondary battery provided in this application, and therefore have at least the same advantages as the secondary battery of this application. Attached Figure Description

[0033] Figure 1 This is a schematic diagram showing the state in which the positive electrode composition exists in the positive electrode slurry in one embodiment of the positive electrode composition of this application.

[0034] Figure 2 This is a schematic diagram illustrating an embodiment of the secondary battery of this application.

[0035] Figure 3 yes Figure 2 An exploded view of an embodiment of the secondary battery of this application is shown.

[0036] Figure 4 This is a schematic diagram of one embodiment of the battery module of this application.

[0037] Figure 5This is a schematic diagram of one embodiment of the battery pack of this application.

[0038] Figure 6 yes Figure 5 The diagram shown is an exploded view of an embodiment of the battery pack of this application.

[0039] Figure 7 This is a schematic diagram of an embodiment of the secondary battery of this application used as a power source for an electrical device.

[0040] Figure 8 This is a low-temperature power test diagram of the secondary battery of Embodiment 1 of this application.

[0041] Figure 9 This is a low-temperature power test diagram of the secondary battery of Comparative Example 1 of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 01 Positive electrode active material; 02 Anti-agglomeration agent; 03 Carbon nanotubes; 021 Phosphite group; 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery; 51 Shell; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0044] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the positive electrode composition, positive electrode slurry, positive electrode sheet, secondary battery, battery module, battery pack, and power supply 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.

[0045] 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 also 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.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] 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.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0051] With the development of rechargeable batteries, there is a growing expectation that they will possess excellent electrochemical performance while also achieving lower manufacturing costs and higher production capacity. From a manufacturing perspective, each step in the process significantly impacts the manufacturing cost and production capacity of rechargeable batteries.

[0052] The inventors discovered through research that existing positive electrode manufacturing processes suffer from significant raw material losses and low production efficiency. Specifically, they found that in the industrial production of secondary batteries, after the positive electrode slurry is prepared, it typically needs to be left to stand for a period of time before being transported through pipelines for coating to form the positive electrode film. Due to the small particle size of the positive electrode material, the prepared positive electrode slurry contains a large number of nanoparticles, which are prone to agglomeration and gel formation.

[0053] Currently, to alleviate the gelation phenomenon in cathode slurry, the slurry is typically placed in a mixing tank and continuously stirred slowly. Once gelation occurs, solvent is added for re-stirring and viscosity adjustment. However, re-stirring of the cathode slurry is impossible in the delivery pipeline, where gelation is more likely to occur. Furthermore, re-stirring and viscosity adjustment increase solvent usage, thereby increasing the manufacturing cost of secondary batteries.

[0054] In view of this, the inventors, after in-depth consideration, have provided a positive electrode composition, a positive electrode slurry, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device.

[0055] Positive electrode composition

[0056] The first aspect of this application discloses a positive electrode composition that can be used in lithium batteries. The positive electrode composition includes a positive electrode active material and an anti-agglomeration agent. The positive electrode active material includes a lithium phosphate, and the anti-agglomeration agent includes a polymer whose molecular chain contains phosphite groups and ether bonds.

[0057] In the molecular chain of the aforementioned anti-coagulant, there can be one or more phosphorous groups, which can be terminal groups or groups in the side chains; there can be one or more ether bonds, which can be located at the chain ends, in segments of the main chain, or in the side chains. Optionally, the ether bonds can be included in the repeating units of the molecular chain.

[0058] Although the mechanism is not yet clear, the applicant has unexpectedly discovered that the positive electrode composition of this application includes lithium phosphate and the above-mentioned anti-coagulation agent, which can effectively prevent the formation of gelation in the positive electrode slurry during the standing process and in the conveying pipeline when applied to the positive electrode slurry.

[0059] Specifically, not intended to be limited to any theory or explanation, the inventors discovered that in the anti-coagulation agent of this application, the phosphite group can interact with the phosphate group in the lithium phosphate through hydrogen bonds, thereby "anchoring" the lithium phosphate to the anti-coagulation agent molecular chain. Other parts of the anti-coagulation agent molecular chain, especially the ether bonds, generate strong charge interactions with other molecular chains, causing mutual repulsion between the anti-coagulation agent molecular chains. This allows the anti-coagulation agent molecular chains linked with the lithium phosphate to be independently and stably dispersed in the solvent of the positive electrode slurry, thus preventing gelation of the positive electrode slurry. In some embodiments, when the positive electrode composition of this application is applied to the positive electrode slurry, the resulting positive electrode slurry does not exhibit gelation even after standing for 48 hours. Furthermore, when the anti-coagulation agent of this application is applied to the positive electrode slurry, the electrochemical performance of the prepared secondary battery is almost unaffected, enabling the secondary battery to maintain good electrochemical performance.

[0060] The cathode composition of this application includes lithium phosphate and an anti-agglomeration agent. When applied to the cathode slurry of a secondary battery, it can effectively reduce the agglomeration of the cathode active material and alleviate the gelation phenomenon of the cathode slurry. This reduces the amount of solvent used and the need for re-stirring, while increasing the solid content of the cathode slurry. Therefore, the cathode composition of this application, when applied to secondary batteries, can reduce the manufacturing cost of secondary batteries, increase the production capacity of secondary batteries, and enable secondary batteries to maintain good electrochemical performance.

[0061] In some embodiments, the lithium-containing phosphate may include lithium iron phosphate. Optionally, the particle size D of lithium iron phosphate... 10It can be 100nm~800nm, 100nm~700nm, 100nm~600nm, 100nm~500nm, 100nm~400nm, 100nm~300nm, 100nm~200nm, 200nm~800nm, 200nm~700nm, 200nm~600nm, 200nm~500nm, 200nm~400nm, 200nm~300nm, 300nm~800nm, 300nm~700nm, 300nm~600nm, 300nm~500nm, 300nm~400nm, 400nm~800nm, 400nm~700nm, 400nm~600nm, 400nm~500nm, 500nm~800nm. 500nm~700nm, 500nm~600nm, 600nm~800nm, 600nm~700nm, or 700nm~800nm. More optionally, the particle size D of lithium iron phosphate... 10 It can be 200nm~300nm, D 50 It can be 400nm~600nm, 450nm~600nm, 500nm~600nm, 550nm~600nm, 400nm~550nm, 450nm~550nm, 500nm~550nm, 400nm~500nm, 450nm~500nm, 400nm~450nm.

[0062] In this application, the particle size D of lithium iron phosphate is... 10 and D 50 Having the meaning known in the art, wherein D 10 This can refer to the particle size at which the cumulative particle distribution reaches 10%, meaning that particles smaller than this size account for 10% of the total particle volume. (D) 50 This can refer to the particle size where the cumulative particle distribution is 50%. (D) 10 and D 50 The particle size distribution can be determined using methods and instruments known in the art. For example, it can be determined using a laser particle size analyzer (e.g., Malvern Mastersizer 2000E) in accordance with GB / T 19077-2016, laser diffraction method.

[0063] Lithium iron phosphate (LFP) is used as a positive electrode active material in secondary batteries, enabling them to possess excellent low-temperature power performance, kinetic performance, and fast charge / discharge capabilities. Without intending to be limited by any theory or explanation, the inventors have discovered that the performance improvement of secondary batteries is more significant when the particle size of LFP is within the aforementioned smaller range. However, as the particle size of LFP decreases, the likelihood of LFP particles agglomerating in the positive electrode slurry also increases. The positive electrode composition of this application includes an anti-agglomeration agent, which, when applied to the positive electrode slurry, effectively reduces the risk of gelation even when the LFP particle size is within the aforementioned smaller range. Therefore, the positive electrode composition of this application, when applied to secondary batteries, not only ensures excellent low-temperature power performance, kinetic performance, and fast charge / discharge capabilities, but also reduces the manufacturing cost and increases the production capacity of secondary batteries.

[0064] In some embodiments, the number average molecular weight of the anti-coagulant can be 1000-10000, 2000-9000, 3000-8000, 4000-7000, or 5000-6000.

[0065] Not intending to be limited by any theory or explanation, the inventors discovered that when the number-average molecular weight of the anti-agglomerate is within the aforementioned suitable range, it not only facilitates the formation of hydrogen bonds between the phosphite groups in the anti-agglomerate and the lithium-containing phosphate, but also promotes the mutual dispersion of the anti-agglomerate molecular chains. This ensures that the anti-agglomerate molecular chains linked to the lithium-containing phosphate are independently and stably dispersed in the solvent of the positive electrode slurry, thereby preventing gelation of the positive electrode slurry, and ultimately reducing the manufacturing cost and increasing the production capacity of the secondary battery.

[0066] In some embodiments, the anti-coagulant may include a compound represented by Formula 1, in which m may be selected from integers of 20–180, 30–170, 40–160, 50–150, 60–150, 70–150, and 80–150, and n may be selected from integers of 25–150, 30–140, 40–130, and 50–120.

[0067]

[0068] The compound shown in Formula 1 can be obtained in a variety of ways. In some embodiments, the compound shown in Formula 1 can be prepared in-house. Specifically, the compound shown in Formula 1 can be prepared by the following steps:

[0069] S1, under reaction conditions, small molecule alcohols are polymerized with alkyl epoxides to obtain a polymer containing ether bonds in repeating units. Optionally, the alkyl epoxides include ethylene oxide.

[0070] S2, react the polymer containing ether bonds in the repeating unit with an amine polymer to obtain an amine polymer containing ether bonds in the repeating unit;

[0071] S3, the amine polymer containing ether bonds in the above repeating unit is mixed with phosphorous acid to react under the reaction conditions to obtain the compound shown in Formula 1.

[0072] It is easy to understand that the above steps are an example of the preparation of the compound shown in Formula 1, and are only for the purpose of explaining this application, and not for limiting this application.

[0073] Not intending to be limited by any theory or explanation, the inventors discovered that in the compound shown in Formula 1, the phosphite group is located at the end group, which is beneficial for forming hydrogen bonds with lithium-containing phosphates. Furthermore, in the compound shown in Formula 1, the values ​​of m and n within the aforementioned ranges ensure that the volume of the molecular chain and the proportion of ether bonds in the molecular chain are within suitable ranges. Therefore, the molecular chains of the anti-coagulation agent can repel each other through charge interactions, thereby stably dispersing in the solvent of the positive electrode slurry. The anti-coagulation agent of this application, including the compound shown in Formula 1, can further reduce the risk of gel formation in the positive electrode slurry, thereby improving the power output of the secondary battery.

[0074] In some embodiments, the cathode composition may further include carbon nanotubes (CNTs), specifically single-walled carbon nanotubes (SWCNTs) and / or multi-walled carbon nanotubes (MWCNTs). Optionally, the carbon nanotubes may be single-walled carbon nanotubes (SWCNTs).

[0075] In order to fully utilize the low-temperature power performance of lithium phosphate, the inventors conducted in-depth research after solving the problem of gelation that easily occurs when the positive electrode slurry is left to stand.

[0076] Not intended to be limited by any theory or explanation, the inventors unexpectedly discovered that including carbon nanotubes in the cathode composition of this application can significantly enhance the conductivity of the cathode composition, thereby reducing the impedance of the cathode composition and thus fully utilizing the low-temperature power performance of lithium phosphate. Specifically, as Figure 1As shown, when the cathode composition including carbon nanotubes is applied to the cathode slurry, the phosphite groups 021 in the anti-agglomeration agent 02 molecular chain can "anchor" the lithium phosphate molecules on the surface of the cathode active material 01. Adjacent "anchored" cathode active materials 01 exist stably and independently due to the repulsive effect between the anti-agglomeration agent 02 molecular chains. The molecular chains of carbon nanotubes 03 and anti-agglomeration agent 02 have a certain degree of flexibility. When dispersed in a solvent, carbon nanotubes 03 can disperse and entangle on the molecular chains of anti-agglomeration agent 02, thereby significantly improving the conductivity of the cathode composition. In particular, since single-walled carbon nanotubes have a larger aspect ratio than multi-walled carbon nanotubes, they are more easily entangled on the molecular chains of anti-agglomeration agent 02. Including single-walled carbon nanotubes in the cathode composition further enhances the conductivity of the cathode composition. Therefore, when the cathode composition of this application includes carbon nanotubes and is applied to the cathode slurry, the resulting secondary battery not only has high power output and low cost but also excellent low-temperature power performance.

[0077] In some embodiments, the positive electrode composition may further include a binder and a conductive agent. Optionally, based on the total mass of the positive electrode composition, the mass percentage of the positive electrode active material may be 93wt% to 96.9wt%, the mass percentage of the anti-agglomeration agent may be 0.1wt% to 0.5wt%, 0.2wt% to 0.5wt%, or 0.3wt% to 0.5wt%, the mass percentage of the binder may be 1wt% to 2wt%, and the mass percentage of the conductive agent may be 2wt% to 4.5wt%.

[0078] This application does not limit the types of binders and conductive agents, which can be commonly used in the art. For 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; the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0079] Not intended to be limited by any theory or explanation, when the mass ratios of the positive electrode active material, anti-agglomeration agent, binder, and conductive agent in the positive electrode composition are within the aforementioned range, their application in the positive electrode slurry can effectively prevent gelation; when applied to secondary batteries, they can give the positive electrode sheet good electronic conductivity, active ion transport capability, and good structural stability. This improves the production capacity of secondary batteries and ensures good electrochemical performance.

[0080] In some embodiments, the cathode composition further includes a binder, a conductive agent, and carbon nanotubes. Optionally, based on the total mass of the cathode composition, the mass percentage of the cathode active material can be 93wt% to 96wt%, the mass percentage of the anti-agglomeration agent can be 0.1wt% to 0.5wt%, 0.2wt% to 0.5wt%, or 0.3wt% to 0.5wt%, the mass percentage of the carbon nanotubes can be 0.1wt% to 1wt%, the mass percentage of the binder can be 1wt% to 2wt%, and the mass percentage of the conductive agent can be 2wt% to 4wt%.

[0081] Examples of adhesives and conductive agents are as described above and will not be repeated here.

[0082] Not intended to be limited by any theory or explanation, when the mass proportions of the positive electrode active material, anti-agglomeration agent, carbon nanotubes, binder, and conductive agent in the positive electrode composition are within the aforementioned range, their application in the positive electrode slurry can effectively prevent gelation. When applied to secondary batteries, this results in positive electrode sheets with good electronic conductivity, active ion transport capabilities, and good structural stability. Therefore, it can improve the production capacity of secondary batteries and ensure good electrochemical performance.

[0083] In some embodiments, the mass ratio of lithium phosphate to carbon nanotubes in the cathode composition is 1:0.003 to 1:0.01, for example, it can be 1:0.003, 1:0.004, 1:0.005, 1:0.006, 1:0.007, 1:0.008, 1:0.009, or 1:0.01.

[0084] Not intended to be limited by any theory or explanation, the mass ratio of lithium phosphate to carbon nanotubes within the above range can effectively improve the conductivity of the cathode composition, thereby enabling the secondary battery using the cathode composition of this application to have low DC resistance (DCR) and long cycle life.

[0085] In some embodiments, the mass ratio of lithium phosphate to anti-coagulant can be 1:0.003 to 1:0.006, for example, 1:0.003, 1:0.004, 1:0.005, or 1:0.006.

[0086] Not intended to be limited by any theory or explanation, the mass ratio of lithium phosphate to anti-coagulation agent within the above range can effectively reduce the gelation phenomenon of the positive electrode slurry, while enabling the positive electrode composition to have higher energy density, lower cost and good electrochemical performance. Therefore, when applied to secondary batteries, it can ensure that the secondary battery has high production capacity, low cost and good electrochemical performance.

[0087] Positive electrode slurry

[0088] A second aspect of this application provides a positive electrode slurry, including a solvent and the positive electrode composition of this application.

[0089] In some embodiments, the solvent may be N-methylpyrrolidone (NMP).

[0090] In some embodiments, the solid component content of the positive electrode slurry can be 55wt% to 65wt%. Having the solid component content of the positive electrode slurry within a suitable range allows for easy control of the coating weight and film thickness of the positive electrode sheet, thereby balancing the energy density, electrolyte wetting rate, and electron conduction energy of the positive electrode sheet, and ultimately improving the electrochemical performance of the secondary battery.

[0091] In some embodiments, the viscosity of the positive electrode slurry can be from 7000 mPa·s to 15000 mPa·s. A suitable viscosity in the positive electrode slurry facilitates the formation of a uniform coating on the surface of the positive electrode current collector, thereby improving the yield of the positive electrode and increasing the production capacity of the secondary battery.

[0092] Method for preparing positive electrode slurry

[0093] This application also provides a method for preparing the positive electrode slurry of this application, comprising: uniformly mixing a positive electrode material including the positive electrode composition of this application with a solvent to obtain a positive electrode slurry.

[0094] It should be noted that in the method of this application, the positive electrode material comprising the positive electrode composition of this application is mixed uniformly with a solvent. This may include mixing each component of the positive electrode composition uniformly before mixing with a solvent; or it may include mixing each component of the positive electrode composition with a solvent in a certain order. As an example, the positive electrode active material, conductive agent, binder and solvent can be mixed uniformly, carbon nanotubes and anti-agglomeration agent can be added, and then a solvent can be added to adjust the viscosity of the slurry.

[0095] In some embodiments, the solvent may be N-methylpyrrolidone (NMP).

[0096] In some embodiments, the solid component content of the positive electrode slurry can be 55wt% to 65wt%. Having the solid component content of the positive electrode slurry within a suitable range allows for easy control of the coating weight and film thickness of the positive electrode sheet, thereby balancing the energy density, electrolyte wetting rate, and electron conduction energy of the positive electrode sheet, and ultimately improving the electrochemical performance of the secondary battery.

[0097] In some embodiments, the viscosity of the positive electrode slurry can be from 7000 mPa·s to 15000 mPa·s. A suitable viscosity in the positive electrode slurry facilitates the formation of a uniform coating on the surface of the positive electrode current collector, thereby improving the yield of the positive electrode and increasing the production capacity of the secondary battery.

[0098] Positive electrode sheet

[0099] A third aspect of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, wherein the positive electrode film layer includes a positive electrode composition according to this application, or the positive electrode film layer is a layer formed by drying the positive electrode slurry of this application.

[0100] 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.

[0101] 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.).

[0102] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode composition of this application and optional other components in a solvent (e.g., NMP) to form a positive electrode slurry, or by directly using the positive electrode slurry of this application; 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.

[0103] It should be noted that the substances contained in the positive electrode film layer in the positive electrode sheet of this application can be sampled and tested during the battery preparation process or from the prepared secondary battery. The testing method can be a method known in the art, such as testing by scanning electron microscopy.

[0104] Secondary batteries

[0105] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0106] In one embodiment of this application, a secondary battery is provided.

[0107] 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.

[0108] [Positive electrode plate]

[0109] The positive electrode is selected from the positive electrode according to the third aspect of this application.

[0110] [Negative electrode plate]

[0111] 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 a negative electrode active material.

[0112] 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.

[0113] 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.).

[0114] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may 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. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material 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 batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0115] 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).

[0116] 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.

[0117] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0118] 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.

[0119] [Electrolytes]

[0120] 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.

[0121] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] [Isolation membrane]

[0126] 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.

[0127] 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.

[0128] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0129] 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.

[0130] 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.

[0131] 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 2 This is an example of a square-structured secondary battery 5.

[0132] In some implementations, refer to Figure 3 The outer packaging may include a housing 51 and a top cover assembly 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 top cover assembly 53 can cover the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 through 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 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.

[0133] 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.

[0134] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 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.

[0135] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0136] 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.

[0137] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 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.

[0138] 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.

[0139] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0140] Figure 7 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.

[0141] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0142] Example

[0143] 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.

[0144] Examples 1-17

[0145] Preparation of positive electrode slurry

[0146] Lithium iron phosphate, PVDF binder, and Super P conductive agent were added to a mixing tank in a certain mass ratio and stirred for 15 minutes at a revolution speed of 25 rpm and a rotation speed of 800 rpm to obtain a dry mixture.

[0147] The dry mixture was mixed evenly with the solvent NMP to obtain an initial positive electrode slurry with a solid component content of 60 wt%.

[0148] Add an anti-agglomeration agent and optional carbon nanotubes (CNTs) to the initial positive electrode slurry, stir evenly, and then adjust the viscosity to 7000 mPa·s to 15000 mPa·s to obtain the positive electrode slurry.

[0149] The anti-agglomeration agents used in each embodiment are selected from compounds shown in Formula 1. In each embodiment, the particle size D of lithium iron phosphate is... 10 The percentage of lithium iron phosphate in the solid components of the cathode slurry (w1), and the number-average molecular weight (M) of the anti-coagulant. n 1. The proportion of anti-coagulant in the solid components of the cathode slurry (w2); 2. The mass ratio of anti-coagulant to lithium iron phosphate. Types of CNTs, the percentage of CNTs in the solid components of the cathode slurry (w3), and the mass ratio of CNTs to lithium iron phosphate. As shown in Table 1.

[0150] Comparative Examples 1-3

[0151] Based on the preparation process of the cathode slurry in Examples 1 to 17, cathode slurries of Comparative Examples 1 to 3 were prepared according to the preparation parameters of the cathode slurry shown in Table 1.

[0152] Table 1: Preparation parameters of Examples 1-17 and Comparative Examples 1-3

[0153]

[0154] After the positive electrode slurries of Examples 1-17 and Comparative Examples 1-3 were left to stand at 25°C for 48 hours, the following tests were conducted, and the test results are shown in Table 2 below.

[0155] (1) Test of the penetration level of a 150-mesh sieve

[0156] The positive electrode slurry was sieved through a 150-mesh sieve to observe the degree of transmission of the positive electrode slurry through the 150-mesh sieve.

[0157] (2) Viscosity test of positive electrode slurry

[0158] Using a rotational viscometer, select the appropriate rotor based on the sample viscosity. Use the viscometer lifting frame to slowly lower the viscometer, immersing the rotor in the slurry until the mark on the rotor is level with the liquid surface. Test temperature: 25℃, rotation speed: 12rpm. Press the measurement button to start the measurement. After 5 minutes, once the data stabilizes, read the viscosity value.

[0159] Table 2: Test parameters of the cathode slurry of Examples 1-17 and Comparative Examples 1-3

[0160] Serial Number 150-mesh sieve transmittance Viscosity (mPa·s) Example 1 Completely through 21000 Example 2 Completely through 19500 Example 3 Completely through 17000 Example 4 Completely through 16000 Example 5 Completely through 14000 Example 6 Completely through 17000 Example 7 Completely through 17000 Example 8 Completely through 17000 Example 9 Incompletely transparent 17000 Example 10 Incompletely transparent 29000 Example 11 Completely through 16000 Example 12 Completely through 15000 Example 13 Incompletely transparent 31000 Example 14 Completely through 27000 Example 15 Completely through 19000 Example 16 Completely through 15000 Example 17 Completely through 18000 Comparative Example 1 Not through 50000 Comparative Example 2 Not through 50000 Comparative Example 3 Not through 50000

[0161] In addition, the positive electrode slurries obtained in Examples 1-17 and Comparative Examples 1-3 were used to prepare secondary batteries as shown below, and performance tests were conducted. The test results are shown in Table 3 below.

[0162] (1) Preparation of secondary batteries

[0163] Preparation of positive electrode sheet

[0164] The prepared positive electrode slurry is uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0165] Preparation of negative electrode sheet

[0166] The active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a weight ratio of 96.2:0.8:0.8:1.2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil once or multiple times, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0167] Preparation of electrolyte

[0168] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3 / 7. Then, 12.5% ​​LiPF6 lithium salt is added and dissolved in the organic solvent and stirred evenly to obtain the final product.

[0169] Separating membrane

[0170] Polypropylene film is used as the separator.

[0171] Preparation of secondary batteries

[0172] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrodes are then wound to form an electrode assembly, which is then fitted with tabs and placed in an aluminum casing. The casing is baked at 100°C to remove moisture, followed by the injection of electrolyte and sealing to obtain a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain a rechargeable battery.

[0173] (2) Low-temperature power test of secondary batteries

[0174] Place the secondary battery in a temperature chamber at 25°C and discharge it to 50% SOC at a rate of 1C. Then adjust the temperature chamber to -20°C and let it rest for 2 hours. Then discharge it at a rate of 3C for 120 seconds and let it rest for 30 minutes. Take the lowest voltage during the 120-second discharge process as the terminal voltage.

[0175] Furthermore, using the time and voltage values ​​during the aforementioned 120s discharge process as the horizontal and vertical axes respectively, the voltage value at each moment was recorded to obtain the low-temperature power test graph of the secondary battery. The low-temperature power test graphs of the secondary batteries in Example 1 and Comparative Example 1 are shown in Figure 8, respectively. Figure 9 As shown.

[0176] Table 3: Performance test results of Examples 1-17 and Comparative Examples 1-3

[0177] Serial Number Terminal voltage (V) Example 1 2.710 Example 2 2.680 Example 3 2.610 Example 4 2.600 Example 5 2.550 Example 6 2.610 Example 7 2.610 Example 8 2.610 Example 9 2.610 Example 10 2.615 Example 11 2.610 Example 12 2.605 Example 13 2.625 Example 14 2.630 Example 15 2.643 Example 16 2.650 Example 17 2.635 Comparative Example 1 2.610 Comparative Example 2 2.645 Comparative Example 3 2.645

[0178] As shown in Tables 1 to 3 above, including an anti-agglomeration agent in the positive electrode slurry can effectively reduce the gelation degree of the positive electrode slurry. Specifically, as shown in Examples 1 to 5, with the increase of lithium iron phosphate particle size D... 10 The smaller the particle size of lithium iron phosphate (LFP), the better the low-temperature power performance of the prepared secondary battery, but correspondingly, the greater the gelation degree of the positive electrode slurry. Including an anti-agglomeration agent in the positive electrode slurry helps to prevent this, even with a smaller LFP particle size. 10 With a molecular weight of 100 nm, the positive electrode slurry still maintains a low viscosity after standing for 48 hours. This allows for the reduction of gelation in the positive electrode slurry while fully utilizing the low-temperature power performance of lithium iron phosphate in secondary batteries. Examples 3, 7-9, and 10-12 demonstrate that the number-average molecular weight of the anti-agglomeration agent, within the range of this application, effectively reduces the gelation degree of the positive electrode slurry, and the gelation degree decreases with increasing anti-agglomeration agent content. Examples 3, 13-17 show that including carbon nanotubes, especially single-walled carbon nanotubes, in the positive electrode slurry significantly improves the low-temperature power performance of the secondary battery.

[0179] In contrast, the positive electrode slurry in Comparative Examples 1-3 does not include an anti-coagulation agent. After standing for 48 hours, the viscosity of the positive electrode slurry increases significantly. As a result, the production capacity and manufacturing cost of the secondary battery are not as ideal as those in Examples 1-17.

[0180] 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 cathode composition for use in lithium-ion batteries, characterized in that, The material includes a positive electrode active material, an anti-agglomeration agent, and carbon nanotubes. The positive electrode active material includes lithium phosphate, the anti-agglomeration agent includes a polymer containing phosphorous groups and ether bonds in its molecular chain, and the number average molecular weight of the anti-agglomeration agent is 1000~10000. The carbon nanotubes are single-walled carbon nanotubes.

2. The positive electrode composition according to claim 1, characterized in that, The lithium-containing phosphate includes lithium iron phosphate.

3. The positive electrode composition according to claim 2, characterized in that, The particle size D of the lithium iron phosphate is 100 nm to 800 nm. 10 is 100 nm to 800 nm.

4. The positive electrode composition according to claim 3, characterized in that, The particle size D of the lithium iron phosphate 10 For 200nm~300nm, D 50 The wavelength range is 400nm to 600nm.

5. The positive electrode composition according to claim 1, characterized in that, The number average molecular weight of the anti-coagulant is 3000~8000.

6. The positive electrode composition according to claim 1, characterized in that, The anti-coagulant includes the compound shown in Formula 1. Formula 1 In Equation 1, m is selected from integers from 20 to 180, and n is selected from integers from 25 to 150.

7. The positive electrode composition according to claim 1, characterized in that, m is selected from integers between 60 and 150.

8. The positive electrode composition according to claim 1, characterized in that, n is an integer selected from 50 to 120.

9. The positive electrode composition according to claim 1, characterized in that, The positive electrode composition also includes a binder.

10. The positive electrode composition according to claim 9, characterized in that, Based on the total mass of the cathode composition, the mass percentage of the cathode active material is 93wt%~96.9wt%, the mass percentage of the anti-agglomeration agent is 0.1wt%~0.5wt%, and the mass percentage of the binder is 1wt%~2wt%.

11. The positive electrode composition according to claim 10, characterized in that, Based on the total mass of the cathode composition, the anti-coagulation agent accounts for 0.3wt% to 0.5wt% of the mass.

12. The positive electrode composition according to claim 9, characterized in that, Based on the total mass of the cathode composition, the positive electrode active material accounts for 93wt%~96wt% of the mass, the anti-agglomeration agent accounts for 0.1wt%~0.5wt% of the mass, the carbon nanotubes account for 0.1wt%~1wt% of the mass, and the binder accounts for 1wt%~2wt% of the mass.

13. The positive electrode composition according to claim 12, characterized in that, Based on the total mass of the cathode composition, the anti-coagulation agent accounts for 0.3wt% to 0.5wt% of the mass.

14. The positive electrode composition according to claim 1, characterized in that, In the cathode composition, the mass ratio of the lithium phosphate to the carbon nanotube is 1:0.003 to 1:0.

01.

15. The positive electrode composition according to any one of claims 1-8, characterized in that, In the positive electrode composition, the mass ratio of the lithium phosphate to the anti-coagulation agent is 1:0.003 to 1:0.

006.

16. A positive electrode slurry, characterized in that, Includes solvents and the positive electrode composition according to any one of claims 1-15.

17. The positive electrode slurry according to claim 16, characterized in that, The positive electrode slurry satisfies at least one of the following: (1) The solvent is N-methylpyrrolidone; (2) The solid component content of the positive electrode slurry is 55wt%~65wt%; (3) The viscosity of the positive electrode slurry is 7000mPa·s~15000mPa·s.

18. A positive electrode plate, characterized in that, It includes a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, wherein the positive electrode film layer includes a positive electrode composition according to any one of claims 1-15, or the positive electrode film layer is a layer formed after drying the positive electrode slurry according to claim 16 or 17.

19. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 18.

20. A battery module, characterized in that, Includes the secondary battery as described in claim 19.

21. A battery pack, characterized in that, Includes the battery module as described in claim 20.

22. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 19, the battery module of claim 20, or the battery pack of claim 21.

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