Polymer, preparation method, dispersant, positive electrode slurry, positive electrode sheet, secondary battery and electric device

Abstract

The present application provides a polymer, a preparation method, a dispersant, a positive electrode slurry, a positive electrode sheet, a secondary battery, and an electric device, the polymer comprising a structure represented by formula (I), wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X′ comprises a non-polar group; and L comprises a constitutional unit represented by formula (II), wherein R1 is C 1-12 Alkylene, C 6-12 arylene, or formula (A), wherein R2 is C 1-12 Alkylene, C 6-12 arylene, or formula (B), wherein R3 is hydrogen or C 1-3 In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, m1 and m2 each independently represent an integer of 3 to 60, and n1 and n2 each independently represent an integer of 0 to 60. JPEG2026507325000158.jpg4541

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application cites Chinese Patent Application No. 202310864261.7, filed on July 14, 2023, entitled "Polymer, Preparation Method, Dispersant, Positive Electrode Slurry, Positive Electrode Sheet, Secondary Battery and Electrical Device," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of secondary batteries, and in particular to polymers, preparation methods, dispersants, positive electrode slurries, positive electrode sheets, secondary batteries, and electrical devices. [Background technology]

[0003] In recent years, secondary batteries have been widely applied to various fields such as energy storage power supply systems for hydroelectric power, thermal power, wind power, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] As a key component of secondary batteries, positive electrode sheets directly affect the battery's performance. They typically consist of a current collector, positive electrode active material, conductive agent, and binder. However, positive electrode active materials are typically nanoscale materials with large specific surface areas and high surface activity. This leads to aggregation during the homogenization process of positive electrode slurries, resulting in the formation of large aggregates that affect the electrode coating efficiency, lower the conductivity of the resulting electrode sheets, and directly affect the electrochemical performance of the battery. In conventional technologies, dispersants are typically added to improve the dispersibility of slurries. However, these dispersants are incompatible with slurries containing positive electrode active materials with different degrees of graphitization produced by different manufacturing processes. This makes these dispersants less versatile and less effective for reducing manufacturing costs. Therefore, there is a need to develop new dispersants suitable for slurries containing positive electrode active materials produced by different manufacturing processes. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and its object is to provide a polymer as a dispersant that is suitable for positive electrode active materials with different degrees of graphitization, which can improve the dispersibility of a slurry system containing positive electrode active materials with different degrees of graphitization, effectively increase the solid content of the slurry, reduce the gelation phenomenon of the slurry, reduce the film resistance of the electrode sheet, improve the toughness of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0006] A first aspect of the present application is a polymer comprising a structure shown in Formula I: [ka] wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; L comprises a constitutional unit of formula II, [ka] In the formula, R1 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R2 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R3 is hydrogen or C 1-3 wherein EO represents —CH—CH—O—, PO represents —CH(CH)—CH—O—, m1 and m2 are each independently an integer of 3 to 60, and n1 and n2 are each independently an integer of 0 to 60.

[0007] The polymer has a non-polar end group at one end, exhibiting lipophilicity, and a polar end group at the other end, exhibiting hydrophilicity, including at least one of carboxyl, ester, sulfonic acid, sulfonate, phosphate, and phosphate groups. When the polymer is added to a slurry system, the carboxyl, ester, sulfonic acid, sulfonate, phosphate, or phosphate group at one end acts as an anchor site for adsorption onto the surface of solid particles, while the non-polar group at the other end forms a steric hindrance in the slurry. When the solid particles approach each other, this steric hindrance generates a strong repulsive force, preventing particle aggregation and forming a uniformly dispersed, stable slurry. At the same time, the amide group contained in the structural unit of formula II is a polar group, generating a strong intermolecular inductive force, further improving the dispersion effect of the polymer. In addition, the L segment has few branched chains and a relatively fixed bond angle, exhibiting a constant linear structure in the slurry system. The segments are fully extended in the slurry system, making it difficult for entanglement to occur between the segments. The resulting steric hindrance ensures that the solid particles are sufficiently separated, further improving the dispersion effect.

[0008] Furthermore, the structural unit represented by Formula II in the L segment contains an amide group. Due to the p-π conjugation effect, the lone pair charges of the oxygen and nitrogen atoms on the amide group are delocalized to a C-N single bond. At the same time, the amide group, as a carboxylic acid derivative, undergoes enol tautomerization under either acidic or basic conditions, and its α-C forms an instantaneous double bond with the C on the carbonyl group, resulting in the entire L segment containing partial double bonds. The L segment tends to be linear, which reduces the sliding resistance between the positive electrode active material during the cold-pressing process and improves the flexibility and toughness of the electrode sheet.

[0009] As described above, compared with conventional dispersants, the polymer dispersant of the present application is more versatile and suitable for slurry systems containing positive electrode active materials with different degrees of graphitization. Compared with conventional dispersants, the polymer dispersant of the present application has improved polymer dispersion ability due to the combined action of the terminal X group, amide group, and L segment, improving the applicability of the polymer dispersant to positive electrode active materials with different degrees of graphitization, thereby contributing to reduced production costs and improved production efficiency.

[0010] In any embodiment, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4: [ka] [ka] [ka] [ka] In the formula, a1 and a2 each independently represent an integer of 2 to 12, and R4 and R5 each independently represent hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, [ka] R6, R7, and R8 each independently represent hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, [ka] wherein R9, R 10 are each independently C 1-12 Contains alkylene, R 11 is C 1-12 Alkyl or C 6-30 Contains aryl.

[0011] In any embodiment, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4: [ka] [ka] [ka] In the formula, a1 and a2 each independently represent an integer of 2 to 12, and R4 and R5 each independently represent C 1-12 alkyl alcohols, [ka] and R8 is hydrogen, C 1-12 alkyl alcohols, [ka] wherein R9, R 10 are each independently C 1-12 Contains alkylene, R 11 is C 1-12 Alkyl or C 6-30 Contains aryl.

[0012] In any embodiment, R3 in the building block of formula II comprises hydrogen.

[0013] R3 in the structural unit represented by formula II contains hydrogen, which can form a hydrogen bond with the oxygen atoms on the surface of the positive electrode active material, further enhancing the slurry dispersion effect of the polymer, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature storage performance of the battery.

[0014] In any embodiment, R1 is [ka] and R2 is [ka] In the formula, n1 or n2 is 0, and m1 and m2 each independently represent an integer of 3 to 60.

[0015] The polymer contains polyethylene oxide segments or polyethylene oxide-propylene oxide segments, which improves the flexibility of the polymer, reduces the sliding resistance between particles during the cold pressing process of the electrode sheet, improves the toughness of the electrode sheet, and can improve the initial coulombic efficiency and high-temperature storage performance of the battery.

[0016] In any embodiment, R1 is [ka] and R2 is [ka] In the formula, n1 and n2 each independently represent an integer of 1 to 60, and m1 and m2 each independently represent an integer of 3 to 30.

[0017] The polymer contains polyethylene oxide-propylene oxide segments, which further improves the flexibility of the polymer, reduces the sliding resistance between particles during the cold pressing process of the electrode sheet, improves the toughness of the electrode sheet, reduces the film resistance of the electrode sheet, and improves the initial coulombic efficiency and high-temperature storage performance of the battery.

[0018] In any embodiment, the number of repeating units of formula II in L is 3 to 100.

[0019] By controlling the repeating number of the structural unit represented by formula II within an appropriate range, it is possible to ensure that the polymer has a sufficient number of amide groups, and that the polymer generates sufficient intermolecular inductive force to form sufficient intermolecular interaction force with the solid particles in the slurry system, thereby improving the dispersing ability of the polymer. At the same time, the appropriate number of structural units represented by formula II allows the polymer to have excellent solubility in the slurry system, and the polymer can be sufficiently spread out in the slurry system, so that the polymer can act as a dispersant.

[0020] In any embodiment, X' is C 3-30 Alkyl, C 6-30 aryl.

[0021] In any embodiment, the weight average molecular weight of the polymer is from 1500 g / mol to 70000 g / mol.

[0022] In any embodiment, the glass transition temperature of the polymer is between 50°C and 200°C.

[0023] In any embodiment, the polymer has a melting point of between 70°C and 300°C at 1 standard atmosphere.

[0024] In any embodiment, the polymer has a hydrophilic-lipophilic balance value of 6-16.

[0025] In any embodiment, the polymer has a hydrophilic-lipophilic balance value of 10-12.

[0026] A second aspect of the present application provides a method for preparing a polymer, comprising the steps of: 1) Polycondensation reaction: preparing an intermediate polymer comprising the structure shown in Formula III by polymerizing at least one dibasic acid and at least one diamine; [ka] In the formula, Y′ and Y each independently contain a carboxyl group or an amino group. 2) End group reaction: reacting the end groups of the intermediate polymer to obtain a polymer containing the structure shown in Formula I; [ka] wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; L comprises a constitutional unit of formula II, [ka] In the formula, R1 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R2 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R3 is hydrogen or C 1-3 In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, m1 and m2 each independently represent an integer of 3 to 60, and n1 and n2 each independently represent an integer of 0 to 60.

[0027] The preparation method of the present application can produce a polymer having a carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate group at one end, a non-polar group at the other end, and an amide group in the backbone, which can be used as a dispersant for positive electrode active materials with different degrees of graphitization to improve the dispersibility of slurry systems containing positive electrode active materials with different degrees of graphitization, increase the solid content of the slurry, reduce the gelation phenomenon of the slurry, reduce the film resistance of the electrode sheet, improve the toughness of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0028] In any embodiment, the preparation method specifically comprises: reacting a catalyst, at least one dibasic acid, and at least one diamine with stirring at 20°C to 300°C for 2 hours to 35 hours to obtain an intermediate polymer having the same terminal groups at both ends; and reacting the end groups at both ends of the intermediate polymer to obtain a polymer.

[0029] The present application uses polycondensation reaction and end group reaction to prepare the polymer, which simplifies the preparation method and improves production efficiency.

[0030] In a third aspect of the present application, there is provided a dispersant comprising a polymer of the first aspect or a polymer prepared by the preparation method of the second aspect.

[0031] In a fourth aspect of the present application, there is provided the use of the polymer of the first aspect in a secondary battery.

[0032] In a fifth aspect of the present application, there is provided a positive electrode slurry comprising a positive electrode active material, a conductive agent, a binder, and a dispersant, the dispersant comprising the polymer of the first aspect.

[0033] The positive electrode slurry has excellent dispersibility and a high solid content, and can produce an electrode sheet with excellent performance.

[0034] In any embodiment, the positive electrode active material comprises lithium iron phosphate having a carbon coating layer on the surface thereof.

[0035] In any embodiment, the degree of graphitization of the lithium iron phosphate having a carbon coating layer on its surface is 10% to 30%.

[0036] The polymer dispersant of the present application can be applied to slurry systems that use lithium iron phosphate with different degrees of graphitization as the positive electrode active material, and is versatile, contributing to reduced production costs and improved production efficiency.

[0037] In any embodiment, the mass fraction of the dispersant is 0.01% to 3% based on the total mass of the solid materials in the positive electrode slurry.

[0038] By setting the mass fraction of the dispersant within an appropriate range, the slurry has a high solid content, the electrode sheet has excellent toughness, and the battery has excellent initial coulombic efficiency and high-temperature storage performance.

[0039] In any embodiment, the mass fraction of the dispersant is 0.03% to 2% based on the total mass of the solid materials in the cathode slurry.

[0040] By setting the mass fraction of the dispersant within an appropriate range, the toughness of the electrode sheet can be further improved, and the high-temperature storage performance of the battery can be improved.

[0041] In a sixth aspect of the present application, there is provided a positive electrode sheet including a positive electrode current collector and a positive electrode film provided on at least one surface of the positive electrode current collector, wherein the positive electrode film is produced from the positive electrode slurry of the fifth aspect.

[0042] The positive electrode sheet of the present application has excellent toughness and low film resistance, and the electrode sheet has excellent usage performance.

[0043] In a seventh aspect of the present application, there is provided a secondary battery comprising a separator, a negative electrode sheet, an electrolyte, and the positive electrode sheet of the sixth aspect.

[0044] In an eighth aspect of the present application, there is provided an electrical device comprising the secondary battery of the seventh aspect. [Brief explanation of the drawings]

[0045] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Figure 2] FIG. 2 is an exploded view of the secondary battery shown in FIG. 1 according to the embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of an electrical device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the polymer, preparation method, dispersant, positive electrode slurry, positive electrode sheet, secondary battery, and electric device of the present application will be described in detail, but unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid unnecessary redundancy in the following description so as to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the scope of the claims.

[0047] The "ranges" disclosed herein are defined by lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of that particular range. Such defined ranges may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit and any upper limit can be combined to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, the ranges of 60 to 110 and 80 to 120 are also understood to be contemplated. Furthermore, if the minimum range values ​​are 1 and 2 and the maximum range values ​​are 3, 4, and 5, the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range of "a to b" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed in this specification, and "0 to 5" is merely shorthand for combinations of these numbers. Note that when a parameter is described as an integer of 2 or greater, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments in this application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all steps in this application may be performed in order or randomly, preferably in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when the method further includes step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), or may be otherwise.

[0051] Unless otherwise specified, the terms "comprise" and "comprises" in this application are open-ended but may also be closed-ended. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0052] In this application, the term "or" is inclusive unless otherwise specified. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": 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).

[0053] Positive electrode slurries are solid-liquid mixtures primarily consisting of a positive electrode active material, a conductive agent, a binder, and a solvent. In conventional technologies, dispersants are often added to improve the dispersibility of the slurry. However, conventional dispersants are generally only suitable for slurry systems with fixed components, resulting in limited versatility. Changing physical properties of the components in the slurry generally necessitates the adjustment of the dispersant. For example, in conventional technologies, lithium iron phosphates manufactured under different manufacturing process conditions have different degrees of surface carbon coating and different degrees of graphitization. Therefore, a single dispersant cannot be applied to lithium iron phosphates with different degrees of graphitization. When conventional dispersants are used in slurry systems containing lithium iron phosphates with different degrees of graphitization as positive electrode active materials, the dispersibility of the slurry system is not ideal, making it difficult to meet the performance requirements of the electrode sheet and battery.

[0054] [Dispersant] Based on this, the present application provides a polymer comprising a structure shown in formula I, [ka] wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; and L comprises a constitutional unit represented by formula II: [ka] In the formula, R1 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R2 is C 1-12 Alkylene, C 6-12 arylene, or [ka] and R3 is hydrogen or C 1-3 Contains alkyl, In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, m1 and m2 each independently represent an integer of 3 to 60, and n1 and n2 each independently represent an integer of 0 to 60.

[0055] As used herein, the term "polymer" includes, on the one hand, chemically homogeneous macromolecular assemblies prepared by polymerization reactions, but which differ in terms of degree of polymerization, molar mass and chain length, and, on the other hand, the term also includes derivatives of such macromolecular assemblies formed by polymerization reactions, i.e., compounds obtained by reactions, for example addition or substitution, of functional groups in the macromolecules, which compounds may be chemically homogeneous or heterogeneous.

[0056] As used herein, the term "carboxyl" refers to --COOH.

[0057] As used herein, the term "ester group" means [ka] refers to R 12 is a group other than hydrogen.

[0058] As used herein, the term "sulfonic acid group" refers to -SO3H.

[0059] As used herein, the term "sulfonate group" means [ka] refers to R 13 is a group other than hydrogen.

[0060] As used herein, the term "phosphate group" means [ka] Refers to...

[0061] As used herein, the term "phosphate group" means [ka] refers to R 14 is a group other than hydrogen.

[0062] As used herein, the term "amide group" means [ka] refers to R 15 , R 16 are each independently hydrogen or a group other than hydrogen.

[0063] As used herein, the term "amino group" means [ka] refers to R 17 , R 18 are each independently hydrogen or a group other than hydrogen.

[0064] As used herein, the term "non-polar group" refers to groups with coincident centers of positive and negative charge, including, but not limited to, alkyl and aryl.

[0065] As used herein, the term "alkyl" refers to a straight or branched hydrocarbon chain radical composed solely of carbon and hydrogen atoms and containing no unsaturation.

[0066] As used herein, the term "aryl" refers to an aromatic ring system in which at least one ring is aromatic.

[0067] In some embodiments, the non-polar group is C 3-30 Alkyl or C 6-30 Contains aryl.

[0068] In some embodiments, X' is C 3-30 Alkyl, C 6-30 aryl.

[0069] As used herein, the term "C 3-30"Alkyl" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, having from 3 to 30 carbon atoms, and attached to the rest of the molecule by a single bond. 1-3 Alkyl" and "C 1-12 "Alkyl" should be construed accordingly.

[0070] As used herein, the term "C 6-30 "Aryl" refers to a monovalent functional group formed by removing one hydrogen atom from an aromatic hydrocarbon ring containing 6 to 30 carbon atoms, such as a phenyl group or a naphthyl group. Aromatic hydrocarbons refer to hydrocarbons having an aromatic ring, and include monocyclic and polycyclic hydrocarbons, in which the other ring may be aromatic or non-aromatic.

[0071] As used herein, the term "C 1-12 "Alkylene" refers to branched and straight-chain saturated aliphatic divalent hydrocarbon groups having the specified number of carbon atoms, containing no unsaturation, having from 1 to 12 carbon atoms and attached to the remainder of the molecule by a single bond.

[0072] As used herein, the term "C 6-12 "Arylene" refers to a divalent functional group formed by removing two hydrogen atoms from an aromatic hydrocarbon ring containing 6 to 12 carbon atoms, such as a phenylene group or naphthylenediyl.

[0073] In this specification, [ka] The EO and PO units therein may be arranged randomly or in blocks.

[0074] As used herein, the term "dispersant" refers to a substance that prevents solid particles in a solid-liquid dispersion from agglomerating with each other and keeps the solid particles uniformly dispersed in the liquid phase for a long period of time.

[0075] In some embodiments, the dispersion medium of the dispersant is an aqueous solvent such as water, i.e., the dispersant is dissolved in the aqueous solvent.

[0076] In some embodiments, the dispersion medium of the dispersant is an oil-based solvent, examples of which include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate, i.e., the dispersant is dissolved in the oil-based solvent.

[0077] In some embodiments, the dispersant is used as a positive electrode slurry dispersant to disperse the positive electrode active material, the conductive agent, and the binder to form a positive electrode slurry.

[0078] In some embodiments, the dispersant is used as a negative electrode slurry dispersant to disperse the negative electrode active material, the conductive agent, and the binder to form a negative electrode slurry.

[0079] In some embodiments, the X group comprises a carboxyl, sulfonic acid, or phosphate group.

[0080] The carboxyl, sulfonic acid, or phosphate groups can be ionized to generate negative ions, which are mainly adsorbed onto the surfaces of the positive electrode active material particles in the slurry system by electrostatic action, and one end of the polymer is anchored to the surfaces of the positive electrode active material particles.

[0081] In some embodiments, the X group comprises an ester group, a sulfonate group, or a phosphate group.

[0082] The ester group, sulfonate group or phosphate group is adsorbed onto the surface of the positive electrode active material particles in the slurry system by intermolecular action, and one end of the polymer is anchored to the surface of the positive electrode active material particles.

[0083] One end group of the polymer contains a nonpolar group, exhibiting lipophilicity, while the other end group contains at least one polar group selected from the group consisting of carboxyl, ester, sulfonic acid, sulfonate, phosphate, and phosphate, exhibiting hydrophilicity. When the polymer is added to a slurry system, the carboxyl, ester, sulfonic acid, sulfonate, phosphate, or phosphate group at one end is adsorbed onto the surface of the positive electrode active material particles as an anchor site, while the other end is suspended in the slurry, forming steric hindrance. When the particles approach each other, this steric hindrance generates strong repulsive forces, preventing particle aggregation and forming a uniformly dispersed, stable slurry. The amide group contained in the structural unit represented by Formula II is a polar group, generating strong intermolecular inductive forces, which can form strong intermolecular interactions with the particles, further improving the dispersion ability of the polymer. Furthermore, the oxygen and nitrogen atoms in the amide groups can form hydrogen bonds with the hydroxyl and / or carboxyl groups on the surface of the positive electrode active material. At the same time, the nitrogen and oxygen atoms can coordinate with the positive electrode active material, synergistically improving the dispersion effect of the polymer dispersant on particles in the slurry system. The L segments have few branched chains and relatively fixed bond angles, exhibiting a consistent linear structure in the slurry system. The segments are fully extended in the slurry system, reducing inter-segment entanglement. The resulting steric hindrance ensures sufficient separation of the solid particles. At the same time, the L segments are sufficiently extended and spread, allowing the amide groups to fully interact with different particles, further improving the dispersion effect. The polymer dispersant of the present application can achieve multi-site adsorption on the surface of positive electrode active materials with different degrees of graphitization, enhancing the adsorption effect and strengthening the dispersion effect of the polymer dispersant on the slurry.

[0084] Furthermore, the structural unit of formula II in the L segment contains an amide group, and due to the p-π conjugation effect, the lone pair charge of the nitrogen atom on the amide group is delocalized to a C-N single bond. At the same time, the amide group, as a carboxylic acid derivative, undergoes enol tautomerization under either acidic or basic conditions, and its α-C forms an instantaneous double bond with the C on the carbonyl group. Therefore, the entire L segment contains partial double bonds and tends to be linear, which reduces the sliding resistance between the positive electrode active materials during the cold-pressing process and improves the softness and toughness of the electrode sheet.

[0085] As a result, the polymer of the present application as a dispersant can improve the dispersibility of slurries containing positive electrode active materials with different graphitization degrees through the action of multi-site adsorption, increase the solid content of the slurry, reduce the gelation of the slurry, reduce the film resistance of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery. At the same time, it can also improve the toughness of the electrode sheet, providing a basis for the subsequent production of thickly coated, high-density electrode sheets.

[0086] While conventional dispersants have poor compatibility and are unable to adapt to differences in cathode active materials due to different manufacturing process conditions in the slurry, the present application improves the dispersing ability of the polymer through the combined action of the terminal X group, amide group, and L segment, improving the applicability of the polymer dispersant to cathode active materials with different degrees of graphitization, improving the versatility of the polymer dispersant, and contributing to reduced manufacturing costs and improved production efficiency.

[0087] In some embodiments, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4: [ka] [ka] [ka] [ka] In the formula, a1 and a2 each independently represent an integer of 2 to 12, and R4 and R5 each independently represent hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, [ka] R6, R7, and R8 each independently represent hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, [ka] wherein R9, R 10 are each independently C 1-12 Contains alkylene, R 11 is C 1-12 Alkyl or C 6-30 Contains aryl.

[0088] As used herein, the term "C 1-12 "Alkyl alcohol" refers to a monovalent atomic group in which an alkylene group is bonded to one hydroxyl group (-OH), and "-C n H 2n -OH" (where n is a natural number from 1 to 12).

[0089] In some embodiments, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4: [ka] [ka] [ka] In the formula, a1 and a2 each independently represent an integer of 2 to 12, and R4 and R5 each independently represent C 1-12 alkyl alcohols, [ka] and R8 is hydrogen, C 1-12 alkyl alcohols, [ka] wherein R9, R 10 are each independently C 1-12 Contains alkylene, R 11 is C 1-12 Alkyl or C 6-30 Contains aryl.

[0090] In some embodiments, L is [ka] [ka] [ka] [ka] [ka] Further comprising one or more of:

[0091] In some embodiments, R4 in the structure of formula I-1 comprises hydrogen.

[0092] Because R4 contains hydrogen, the polymer can be ionized to generate negative ions, which can be electrostatically adsorbed onto the surface of the positive electrode active material particles in the slurry system, strengthening the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, and improving the use performance of the slurry and electrode sheet.

[0093] In some embodiments, R4 in the structure of formula I-1 is C 1-12 Alkyl alcohol or [ka] Includes.

[0094] R4 is C 1-12 Alkyl alcohol or [ka] By including the polymer dispersant, the amino group or hydroxy group therein can generate an adsorption force with the positive electrode active material particles in the slurry system, thereby enhancing the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, and improving the use performance of the slurry.

[0095] In some embodiments, R5 in the structure of formula I-2 comprises hydrogen.

[0096] Because R5 contains hydrogen, the polymer can be ionized to generate negative ions, which can be electrostatically adsorbed onto the surface of the positive electrode active material particles in the slurry system, strengthening the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0097] In some embodiments, R5 in the structure of formula I-2 is C 1-12 Alkyl alcohol or [ka] Includes.

[0098] R5 is C 1-12 Alkyl alcohol or [ka] By including the polymer dispersant, the amino group or hydroxy group therein can generate an adsorption force with the positive electrode active material particles in the slurry system, thereby strengthening the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0099] In some embodiments, R6 or R7 in the structure of formula I-3 comprises hydrogen.

[0100] When R6 or R7 contains hydrogen, the polymer can be ionized to generate negative ions, which can be electrostatically adsorbed onto the surface of the positive electrode active material particles in the slurry system, thereby enhancing the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0101] In some embodiments, R6 or R7 in the structure of formula I-3 is C 1-12 alkyl alcohols, [ka] Includes.

[0102] R6 or R7 is C 1-12 alkyl alcohols, [ka] By including the polymer dispersant, the amino group or hydroxy group therein can generate an adsorption force with the positive electrode active material particles in the slurry system, thereby strengthening the dispersing effect of the polymer dispersant, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0103] In some embodiments, R8 in the structure of formula I-4 comprises hydrogen.

[0104] Because R8 contains hydrogen, the polymer can be ionized to generate negative ions, which can be electrostatically adsorbed onto the surface of the positive electrode active material particles in the slurry system, enhancing the dispersing effect of the polymer dispersant, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature storage performance of the battery.

[0105] In some embodiments, R8 in the structure of formula I-4 is C 1-12 alkyl alcohols, [ka] It includes at least one of the following:

[0106] R8 is C 1-12 alkyl alcohols, [ka] By including the above, the amino group, hydroxy group, and ester group therein can generate an adsorption force with the positive electrode active material particles in the slurry system, thereby strengthening the dispersing effect of the polymer dispersant, improving the toughness of the electrode sheet, and improving the high-temperature storage performance of the battery.

[0107] In some embodiments, the polymer comprises a structure shown in formula I-4.

[0108] Compared with the structure represented by formula I-3, which contains one L segment, the structure represented by formula I-4 contains two L segments, which can enhance the dispersing effect of the polymer dispersant, thereby resulting in a slurry with a higher solids content, which in turn improves the initial coulombic efficiency and high-temperature cycling performance of the battery, and improves the electrochemical performance of the battery.

[0109] In some embodiments, R3 in the building block of formula II comprises hydrogen.

[0110] R3 in the structural unit represented by formula II contains hydrogen, which can form a hydrogen bond with the oxygen atoms on the surface of the positive electrode active material, further improving the dispersibility of the slurry, increasing the solid content of the slurry, reducing the gelling phenomenon of the slurry, improving the toughness of the electrode sheet, reducing the film resistance of the electrode sheet, and improving the initial coulombic efficiency and high-temperature storage performance of the battery.

[0111] In some embodiments, R is C 1-12 alkylene or [ka] and R2 is C 1-12 alkylene or [ka] In the formula, m1 and m2 each independently represent an integer of 3 to 60, and n1 and n2 each independently represent an integer of 0 to 60.

[0112] By introducing a longer alkyl segment or a polyether flexible segment into the L segment, the toughness of the electrode sheet can be improved.

[0113] In some embodiments, R1 is [ka] and R2 is [ka] In the formula, n1 or n2 is 0, and m1 and m2 each independently represent an integer of 3 to 60.

[0114] As used herein, the term "polyoxyethylene segment" refers to a polymer segment that includes a -CH2-CH2-O- unit.

[0115] As used herein, the term "polyoxyethylene-propylene oxide segment" refers to a polymer segment containing -CH2-CH2-O- and -CH(CH3)-CH2-O- units.

[0116] The polymer contains polyethylene oxide segments or polyethylene oxide-propylene oxide segments, which can improve the flexibility of the polymer, reduce the sliding resistance between particles during the cold pressing process of the electrode sheet, improve the toughness of the electrode sheet, and improve the use performance of the electrode sheet.

[0117] In some embodiments, R1 is [ka] and R2 is [ka] In the formula, n1 and n2 each independently represent an integer of 1 to 60, and m1 and m2 each independently represent an integer of 3 to 30.

[0118] The polymer contains polyethylene oxide-propylene oxide segments, which further improves the flexibility of the polymer, reduces the sliding resistance between particles during the cold pressing process of the electrode sheet, improves the toughness of the electrode sheet, improves the use performance of the electrode sheet, and improves the high-temperature storage performance of the battery.

[0119] In some embodiments, the number of repeating units of formula II in L is 3 to 100.

[0120] In some embodiments, the number of repeating units of formula II in L is optionally any value of 3, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a range consisting of any two of these values.

[0121] In some embodiments, the number of repeating units of formula II in L is 8 to 80.

[0122] In some embodiments, the number of repeating units of formula II in L is optionally any value of 8, 10, 20, 30, 40, 50, 60, 70, 80, or a range consisting of any two of these values.

[0123] By controlling the repeating number of the structural unit represented by formula II within an appropriate range, it is possible to ensure that the polymer has a sufficient number of amide groups, and that the polymer generates sufficient intermolecular inductive force to form sufficient intermolecular interaction force with the solid particles in the slurry system, thereby improving the dispersing ability of the polymer. At the same time, the appropriate number of structural units represented by formula II allows the polymer to have excellent solubility in the slurry system, and the polymer can be sufficiently spread out in the slurry system, so that the polymer can act as a dispersant.

[0124] In some embodiments, the weight percentage of X in the polymer is from 0.5% to 20% based on the weight of the polymer.

[0125] In some embodiments, the total weight percentage of R1 and R2 in the polymer is 20% to 80% based on the weight of the polymer.

[0126] In some embodiments, in the polymer [ka] The mass percentage of is 0.5% to 50% based on the mass of the polymer.

[0127] By controlling the mass percentages of the X group, R1 and R2, and amide group within an appropriate range, the X anchor group, L segment, and amide group can fully utilize their respective advantages, and through their synergistic action, the polymer has excellent dispersing ability and improves the dispersibility of the slurry.

[0128] In some embodiments, the weight average molecular weight of the polymer is from 1500 g / mol to 70000 g / mol.

[0129] In some embodiments, the weight average molecular weight of the polymer is optionally 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, 6000 g / mol, 6500 g / mol, 7000 g / mol, 7500 g / mol, 8000 g / mol, 8500 g / mol, 9000 g / mol, 1000 g / mol, 1100 g / mol, 1200 g / mol, 1300 g / mol, 1400 g / mol, 1500 g / mol, 1600 g / mol, 1700 g / mol, 1800 g / mol, 1900 g / mol, 2000 g / mol, 2100 g / mol, 2200 g / mol, 2300 g / mol, 2400 g / mol, 2500 g / mol, 2600 g / mol, 2700 g / mol, 2800 g / mol, 2900 g / mol, 3000 g / mol, 3100 g / mol, 3200 g / mol, 3300 g / mol, 3400 g / mol, 3500 g / mol, 3600 g / mol, 3700 g / mol, 3800 g / mol, 3900 g / mol, 4000 g / mol, 4100 g / mol, 4200 g / mol, 4300 g / mol, 4400 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, 6000 g / mol, 6 g / mol, 9500 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, 25000 g / mol, 30000 g / mol, 35000 g / mol, 40000 g / mol, 45000 g / mol, 50000 g / mol, 55000 g / mol, 60000 g / mol, 65000 g / mol, and 70000 g / mol, or a range consisting of any two of these values.

[0130] As used herein, the term "weight average molecular weight" refers to the sum of the products of the weight fractions of molecules of different molecular weights in a polymer and the corresponding molecular weights.

[0131] In this application, the weight-average molecular weight of a polymer can be measured by any method known in the art, such as gel chromatography, using a Waters 2695 Isocratic HPLC-type gel chromatograph (differential refractive index detector 2141). In some embodiments, the measurement method is as follows: A 3.0% mass fraction polystyrene solution sample is used as the reference, and a matching chromatographic column (oil-based: Styragel HT5 DMF 7.8 * 300 mm + Styragel HT4) is selected. A 3.0% fluorine-containing polymer solution is prepared in purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day before use. During measurement, tetrahydrofuran is first aspirated into a syringe, followed by washing and repeated several times. Then, 5 ml of the experimental solution is aspirated, the air in the syringe is removed, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the injection port. After the displayed value has stabilized, data is acquired and the weight average molecular weight is read.

[0132] If the weight-average molecular weight of the polymer is too large, the polymer is difficult to dissolve and cannot function as a dispersant, whereas if the weight-average molecular weight of the polymer is too small, the polymer cannot achieve an effective dispersing effect, which is unfavorable for the formation of a conductive network, increases the film resistance of the electrode sheet, and reduces the initial coulombic efficiency and high-temperature storage performance of the battery.

[0133] In some embodiments, the glass transition temperature of the polymer is between 50°C and 200°C.

[0134] In some embodiments, the glass transition temperature of the polymer is any value, or a range consisting of any two of the following: 50°C, 60°C, 90°C, 100°C, 120°C, 140°C, 150°C, 170°C, 180°C, 190°C, 200°C.

[0135] As used herein, the term "glass transition temperature" refers to the temperature at which an amorphous polymer (including the amorphous portion in a crystalline polymer) transitions from a glassy state to a highly elastic state, or from a highly elastic state to a glassy state, and is the lowest temperature at which the macromolecular segments of the amorphous polymer are free to move.

[0136] As used herein, the term "glassy state" refers to a state in which an amorphous polymer is subject to very little deformation due to external force, is proportional to the magnitude of the applied force, and is quickly restored when the external force is removed. In the glassy state, the energy of molecular motion is so small that it is not enough to overcome the rotational barrier of the main chain and excite the motion of the segments, and the segments are in a frozen state. For example, when an external force is applied, only slight changes occur in the bond length and bond angle of the main chain because the motion of the segments is frozen. Therefore, from a macroscopic perspective, the deformation of the polymer after the force is applied is very small.

[0137] As used herein, the term "highly elastic state" refers to an amorphous polymer that undergoes large deformation with a very small external force. In a highly elastic state, when an amorphous polymer is subjected to an external force, the molecular chains adapt to the action of the external force through internal rotation of single bonds and conformational changes of segments. For example, when subjected to a tensile force, the molecular chains can change from a contracted state to an extended state, resulting in large macroscopic deformation. When the external force is removed, the molecular chains also return to their original contracted state through internal rotation of single bonds and segmental movement, which is macroscopically referred to as elastic contraction.

[0138] In the present application, the glass transition temperature of a polymer can be measured by selecting a method known in the art, for example, a differential scanning calorimeter (Q1000 model) manufactured by TA Corp. A 6 to 9 g polymer sample is taken, heated from room temperature to 200°C at a heating rate of 10°C / min, and the obtained differential scanning calorimetry curve is analyzed to obtain the glass transition temperature of the polymer, expressed in °C.

[0139] In some embodiments, the polymer has a melting point of between 70°C and 300°C at 1 standard atmosphere.

[0140] In some embodiments, the melting point of the polymer at 1 standard atmosphere is any value, or a range consisting of any two of: 70°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C.

[0141] As used herein, the term "1 standard atmosphere" refers to the sea level pressure at standard atmospheric conditions, which has a value of 101.325 kPa, and is the unit of atmosphere, recorded as atm.

[0142] In this application, the melting point of a polymer at 1 standard atmospheric pressure can be measured by any method known in the art, for example, using a precision microscope melting point analyzer (X-5 model). At 1 standard atmospheric pressure, 0.01 mg of a uniformly polished sample is placed on a glass slide, covered with another glass slide and lightly pressed down, and placed in the center of the hot stage. After covering with an insulating plate, the focal length of the microscope is adjusted until the sample can be clearly observed. Then, the temperature knob is adjusted to rapidly increase the temperature until the polymer is slightly melted, and the heating rate is slowly adjusted until the sample is completely melted. The temperature at which the polymer completely melts is recorded as the melting point of the polymer, expressed in °C.

[0143] In some embodiments, the polymer has a hydrophilic-lipophilic balance value of 6-16.

[0144] In some embodiments, the hydrophilic-lipophilic balance value of the polymer is optionally any value of 6, 8, 10, 12, 14, 16, or a range consisting of any two of these values.

[0145] The term "hydrophilic-lipophilic balance value" is used herein to characterize the overall hydrophilic-lipophilic tendency of a polymer. A higher hydrophilic-lipophilic balance value indicates a more hydrophilic polymer, and conversely, a lower hydrophilic-lipophilic balance value indicates a less hydrophilic and more lipophilic polymer.

[0146] In this specification, the hydrophilic-lipophilic balance (HLB) of a polymer can be measured by any method known in the art, for example, by using an emulsification method. The principle is that when an oily medium is emulsified using a polymer, if the HLB value of the polymer is the same as the HLB value required for the oily medium, the resulting emulsion will be most stable. The ideal HLB value can be obtained by mixing standard samples with known HLB values ​​in proportion, and the prepared oily phase is emulsified with the polymer and allowed to stand for 24 hours. The HLB value required for the oily phase in the sample with the highest stability is the HLB value of the polymer.

[0147] In some embodiments, the polymer has a hydrophilic-lipophilic balance value of 10-12.

[0148] In some embodiments, the hydrophilic-lipophilic balance value of the polymer is optionally any value of 10, 11, 12, or a range consisting of any two of these values.

[0149] One embodiment of the present application provides a method for preparing a polymer, comprising the steps of: 1) Polycondensation reaction: preparing an intermediate polymer comprising the structure shown in Formula III by polymerizing at least one dibasic acid and at least one diamine; [ka] In the formula, Y′ and Y each independently contain a carboxyl group or an amino group. 2) End group reaction: reacting the end groups of the intermediate polymer to obtain a polymer comprising the structure of formula I; [ka] wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; L comprises a constitutional unit of formula II, [ka] In the formula, R1 is C 1-12 Alkylene, C 6-12 arylene or [ka] and R2 is C 1-12 Alkylene, C 6-12 arylene or [ka] and R3 is hydrogen or C 1-3 In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, m1 and m2 each independently represent an integer of 3 to 60, and n1 and n2 each independently represent an integer of 0 to 60.

[0150] As used herein, the term "diamine" refers to an amine containing two amino groups.

[0151] As used herein, the term "diacid" refers to an acid that contains two carboxyls.

[0152] In some embodiments, the diamine has a structure according to formula IV: [ka] In the formula, R2 is C 1-12 Alkylene, C 6-12 Arylene, [ka] and R3 is hydrogen or C 1-3It contains alkyl, m2 is any integer from 3 to 60, and n2 is any integer from 0 to 60.

[0153] In some embodiments, the diamine is [ka] [ka] [ka] [ka] [ka] [ka] Contains one of the following:

[0154] In some embodiments, the diacid has a structure according to Formula V: [ka] In the formula, R1 is C 1-12 Alkylene, C 6-12 Arylene, [ka] wherein m1 is an integer of 3 to 60, and n1 is an integer of 0 to 60.

[0155] In some embodiments, the diacid is [ka] [ka] [ka] Contains one of the following:

[0156] This preparation method uses inexpensive raw materials, reduces costs, reduces environmental pollution, and contributes to an improved yield of polymer dispersants. At the same time, this preparation method can produce polymers that contain a polar group, such as a carboxyl, ester, sulfonic acid, sulfonate, phosphate, or phosphate group, at one end and a non-polar group at the other end, with an amide group in the backbone. The polymers can be used as dispersants for positive electrode active materials with different degrees of graphitization, improving the dispersibility of slurry systems containing positive electrode active materials with different degrees of graphitization, increasing the solids content of the slurry, reducing the gelation phenomenon of the slurry, reducing the film resistance of the electrode sheet, improving the toughness of the electrode sheet, and improving the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0157] In some embodiments, the preparation method specifically comprises: reacting a catalyst, at least one dibasic acid, and at least one diamine with stirring at 20°C to 300°C for 2 hours to 35 hours to obtain an intermediate polymer having the same terminal groups at both ends; and reacting the end groups at both ends of the intermediate polymer to obtain the polymer.

[0158] In some embodiments, the end groups of the intermediate polymer are both carboxyl.

[0159] In some embodiments, the terminal groups of the intermediate polymer are both amino groups.

[0160] In some embodiments, the polymer is synthesized by polymerizing at least one dibasic acid and at least one diamine under the action of a catalyst to produce an intermediate polymer, resulting in an excess of dibasic acid or diamine, and an intermediate polymer having both end groups, either amino or carboxyl. The amino or carboxyl group at one end undergoes a functional group reaction with an activated monomer containing an X' group, and the amino or carboxyl group at the other end undergoes a functional group reaction with an activated monomer containing an X group, to produce a polymer having an X group at one end and an X' group at the other end. It is understood that an activated monomer containing an X' group refers to a monomer containing an X' group and an active functional group capable of reacting with the amino or carboxyl group at one end of the intermediate polymer, and an activated monomer containing an X group refers to a monomer containing an X group and an active functional group capable of reacting with the carboxyl or amino group at one end of the intermediate polymer. The active functional group that reacts with the amino group is optionally one of an epoxy group, a carboxyl group, an acid anhydride group, an isocyanate group, a carbonyl chloride group, and a halogen atom, and the active functional group that reacts with the carboxyl group is optionally a hydroxyl group or an amino group.

[0161] The present application uses polycondensation reaction and end group reaction to prepare the polymer, which simplifies the preparation method and improves production efficiency.

[0162] In some embodiments, the terminal group of the intermediate polymer is an amino group, and the activated monomer containing an X′ group refers to an activated monomer that contains an X′ group and a halogen atom.

[0163] In some embodiments, the terminal group of the intermediate polymer is an amino group, and the activated monomer containing an X group refers to an activated monomer that contains an X group and a halogen atom.

[0164] In some embodiments, the terminal group of the intermediate polymer is an amino group, and the activated monomer containing an X′ group refers to X′—(CH 2 )mA, where m is an integer from 1 to 12, and A is F, Cl, Br, or I.

[0165] In some embodiments, the terminal group of the intermediate polymer is an amino group, and the activated monomer containing an X group refers to X—(CH)B, where n is an integer from 1 to 12, and B is F, Cl, Br, or I.

[0166] In some embodiments, the preparation of the polymer is as shown in the following diagram. [ka] .

[0167] In some embodiments, the preparation of the polymer is as shown in the following diagram. [ka] .

[0168] In some embodiments, the catalyst comprises sodium hypophosphite.

[0169] In some embodiments, a dispersant is provided that includes a polymer of any embodiment or a polymer prepared by the preparation method of any embodiment.

[0170] In some embodiments, there is provided the use of the polymer of any embodiment in a secondary battery.

[0171] [Positive electrode slurry] In some embodiments, a positive electrode slurry is provided that includes a positive electrode active material, a conductive agent, a binder, and a dispersant, the dispersant including the polymer of any embodiment.

[0172] The positive electrode slurry has excellent dispersibility and a high solid content, which is advantageous for producing an electrode sheet with excellent performance.

[0173] In some embodiments, the positive electrode active material may be any positive electrode active material known in the art for batteries. For example, the positive electrode active material may include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound of each of these. However, the present application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries 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 lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel manganese cobalt oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (can also be abbreviated as LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (can also be abbreviated as LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (can also be abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (can also be abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0174] In some embodiments, the positive electrode slurry includes a conductive agent. By way of example, 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.

[0175] In some embodiments, the active cathode material comprises lithium iron phosphate having a carbon coating layer on the surface thereof.

[0176] On the one hand, the structural unit represented by formula II in the L segment contains an amide group, and the oxygen and nitrogen atoms on the amide group can form coordination interactions with the iron atoms in the lithium iron phosphate. On the other hand, the oxygen and nitrogen atoms on the amide group can form hydrogen bonds with the carboxyl or hydroxyl groups in the carbon coating layer. The combined effect of these two factors improves the dispersibility of the polymer in the slurry, and the polymer dispersant has excellent dispersibility for slurry systems that use lithium iron phosphate having a carbon coating layer on its surface as the positive electrode active material.

[0177] In some embodiments, the degree of graphitization of the lithium iron phosphate having a carbon coating layer on its surface is 10% to 30%.

[0178] In some embodiments, the degree of graphitization of the lithium iron phosphate having a carbon coating layer on its surface is optionally any value of 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of these values.

[0179] In the present application, the term "degree of graphitization" refers to the degree of graphitization of the carbon component, and reflects the degree of perfection of the graphite crystal structure in the carbon-coated lithium iron phosphate, particularly in the carbon coating layer, i.e., the degree of regularity of the carbon atom arrangement in the graphite structure.

[0180] In this specification, the graphitization degree of lithium iron phosphate can be measured by any method known in the art. For example, the characteristics are evaluated using a Raman spectrometer. Specifically, the graphitization degree is evaluated using a high-resolution Raman spectrometer manufactured by HORIBA Jobin Yvon, France, model LabRAM HR Evlution. After subtracting the detection background, the following Gaussian function is used for fitting. Raman spectrum measurement conditions: wavelength 532 nm, scanning range 200-4000 cm -1 Stack two measurements, measure 10 points for each sample, and take the average value for fitting.

[0181]

number

[0182] In the prior art, carbon coating is applied to the surface of lithium iron phosphate cathode active materials to improve their electronic and ionic conductivity. However, the coating processes for lithium iron phosphate available on the market today are diverse, resulting in varying degrees of carbon coating on the surface and varying degrees of graphitization of the lithium iron phosphate. Therefore, conventional dispersants are incompatible with slurries containing lithium iron phosphate cathode active materials with different degrees of graphitization. The polymer dispersant disclosed herein is versatile and can improve the dispersibility of slurries containing lithium iron phosphate cathode active materials with different degrees of graphitization, increase the solids content of the slurries, reduce the gelation phenomenon of the slurries, reduce the film resistance of the electrode sheet, improve the toughness of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery. The polymer dispersant is versatile and can be used with cathode slurries containing lithium iron phosphate with different degrees of graphitization manufactured using different manufacturing processes, thereby reducing manufacturing costs and improving production efficiency.

[0183] In some embodiments, the mass fraction of the dispersant is 0.01% to 3% based on the total mass of solid materials in the positive electrode slurry.

[0184] In some embodiments, the mass fraction of the dispersant is, based on the total mass of solid materials in the cathode slurry, optionally any value of 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or a range consisting of any two of these values.

[0185] By setting the mass fraction of the dispersant within an appropriate range, the slurry has a high solid content, the electrode sheet has excellent toughness, and the battery has excellent initial coulombic efficiency and high-temperature storage performance.

[0186] In some embodiments, the mass fraction of the dispersant is 0.03% to 2% based on the total mass of solid materials in the positive electrode slurry.

[0187] In some embodiments, the mass fraction of the dispersant is, based on the total mass of solid materials in the cathode slurry, optionally any value of 0.03%, 0.1%, 0.5%, 1%, 1.5%, 2%, or a range consisting of any two of these values.

[0188] By setting the mass fraction of the dispersant within an appropriate range, the toughness of the electrode sheet can be further improved, and the high-temperature storage performance of the battery can be improved.

[0189] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector and a positive electrode film provided on at least one surface of the positive electrode current collector, and the positive electrode film is produced from the positive electrode slurry of any embodiment.

[0190] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film is provided on either one or both of the two facing surfaces of the positive electrode current collector.

[0191] In some embodiments, the positive electrode 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 polymeric substrate layer and a metal layer formed on at least one surface of the polymeric substrate layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0192] In some embodiments, the positive electrode sheet can be produced as follows: The components for producing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, dispersant, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then applied to a positive electrode current collector, followed by oven drying, cold pressing, and other processes to obtain a positive electrode sheet.

[0193] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0194] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two facing surfaces of the negative electrode current collector.

[0195] 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 polymeric substrate layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0196] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from silicon elemental, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from tin elemental, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials usable 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.

[0197] In some embodiments, the negative electrode membrane layer optionally further comprises a binder, which may be at least one selected from 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).

[0198] In some embodiments, the negative electrode film layer optionally further includes a conductive agent, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0199] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents such as a thickener (eg, carboxymethylcellulose sodium (CMC-Na)).

[0200] In some embodiments, the negative electrode sheet can be produced as follows: The components for producing the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, followed by oven drying, cold pressing, and other processes to obtain a negative electrode sheet.

[0201] [Electrolytes] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. In this application, the type of electrolyte is not specifically limited and can be selected as needed. For example, the electrolyte may be liquid, gel, or all solid.

[0202] In some embodiments, the electrolyte uses an electrolytic solution, which includes an electrolyte salt and a solvent.

[0203] In some embodiments, the electrolyte salt may be at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0204] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene 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, ethyl methyl sulfone, and diethyl sulfone.

[0205] In some embodiments, the electrolyte solution optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some battery performance, such as an additive that can improve the overcharge performance of the battery or an additive that can improve the high-temperature or low-temperature performance of the battery.

[0206] [Separator] In some embodiments, the secondary battery further includes a separator. In the present application, the type of separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0207] In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the layers may be the same or different, and are not particularly limited.

[0208] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly by a winding process or a lamination process.

[0209] In some embodiments, the secondary battery may include an exterior body that can be used to encapsulate the electrode assembly and electrolyte.

[0210] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may be a soft pack, such as a pouch-type soft pack. The soft pack may be made of plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0211] [Secondary battery] In the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows a secondary battery 5 having a rectangular structure as an example. The secondary battery may be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.

[0212] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround the case 51 to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is sealed in the receiving cavity. The electrode assembly 52 is impregnated with an electrolyte. The secondary battery 5 may include one or more electrode assemblies 52, and this can be selected by those skilled in the art according to specific actual needs.

[0213] [Battery module] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by a person skilled in the art depending on the application and capacity of the battery module.

[0214] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fastening members.

[0215] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0216] [Battery pack] In some embodiments, the above battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0217] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box 2 and a lower box 3, and the upper box 2 is covered by the lower box 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0218] [Electrical Equipment] In one embodiment of the present application, there is provided an electric device including at least one of the secondary battery of any of the embodiments, the battery module of any of the embodiments, or the battery pack of any of the embodiments.

[0219] The electric device includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric 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.), trains, ships, satellites, energy storage systems, etc.

[0220] The electrical device can be selected from a secondary battery, a battery module, or a battery pack depending on the needs of the use.

[0221] 6 shows an example of an electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, which can use a battery pack or a battery module to meet the high power and high energy density requirements of secondary batteries.

[0222] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. Such devices are generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0223] Example Examples of the present application are described below. The examples described below are illustrative and are intended only to interpret the present application, and should not be understood as limiting the present application. In the examples, specific techniques or conditions are not specified, and the techniques or conditions are carried out in accordance with the techniques or conditions described in the literature in the field, or the product specifications. Unless the manufacturer is specified, the reagents or equipment used are ordinary products available commercially.

[0224] 1. Manufacturing method Example 1 1) Preparation of intermediate polymer: Dibasic acid and diamine were weighed in a 1:1.2 molar ratio and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, after which the temperature was raised to 180°C and the reaction was continued at this temperature for 1 hour. The temperature was then raised to 230°C and the reaction was continued for 2 hours. The pressure was then reduced to 0.01 atm, and the temperature was raised to 270°C and the reaction was continued for 4 hours. The heat source was then removed, the vacuum was maintained, and the reactor was cooled. The product was removed, yielding an intermediate polymer with amino end groups. The structural formulas of the dibasic acid and diamine are shown below. [ka] [ka]

[0225] Two moles of the intermediate polymer with amino end groups and one mole of 1-chlorododecane were dissolved in 1,000 ml of methylene chloride and the halogenation reaction was carried out at room temperature. After 6 hours of reaction, 500 ml of deionized water was added to quench the reaction. The reaction mixture was extracted three times with methylene chloride, and the oil phase product was collected. It was then dried over magnesium sulfate and rotary evaporated to separate the product, which was then separated using a chromatography column to obtain the first product.

[0226] 1 mol of the first product and 1.5 mol of Cl-C4H8-COOH were dissolved in 1000 ml of methylene chloride and the halogenation reaction was carried out at room temperature. After 6 hours of reaction, 500 ml of deionized water was added to quench the reaction. The reaction mixture was extracted three times with methylene chloride, and the oil phase product was collected. It was then dried over magnesium sulfate and rotary evaporated to separate the product, which was finally separated using a chromatography column to obtain polymer dispersant P-1.

[0227] The reaction process for preparing polymer dispersant P-1 is as follows: [ka]

[0228] In the formula, R1 and R2 are [ka] is.

[0229] 2) Preparation of cathode slurry A cathode slurry was prepared by adding carbon-coated lithium iron phosphate (LFP@C), conductive agent acetylene black (SP), binder polyvinylidene fluoride (PVDF), and dispersant (P-1) to N-methylpyrrolidone (NMP) and stirring. The weight ratio of LFP@C, SP, and PVDF was 97:2:1. The mass fraction of the dispersant was 1.5% of the total mass of the cathode active material, conductive agent, binder, and dispersant. The theoretical solids content of the cathode slurry was 60%. After stirring, the viscosity of the slurry was measured and controlled to less than 20,000 mPa·s. If the viscosity was higher than 20,000 mPa·s, a minimum amount of NMP was added to maintain the viscosity below 20,000 mPa·s.

[0230] 3) Manufacturing of positive electrode sheets The positive electrode slurry was uniformly applied to two surfaces of the aluminum foil of the positive electrode current collector and then dried to obtain a film layer, which was then cold pressed and slit to obtain a positive electrode sheet.

[0231] 4) Manufacturing of negative electrode sheets The negative electrode active material, artificial graphite, conductive agent, carbon black, binder, styrene butadiene rubber (SBR), and thickener, sodium carboxymethyl cellulose (CMC-Na), were dissolved in deionized water in a weight ratio of 96:2:1:1 and mixed uniformly to form a negative electrode slurry. The negative electrode slurry was then uniformly applied multiple times to the two surfaces of the copper foil negative electrode current collector, followed by oven drying, cold pressing, and slitting to obtain a negative electrode sheet.

[0232] 5) Separator A polypropylene film was used as a separator.

[0233] 6) Electrolyte production In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3 / 7, and LiPF6 lithium salt was dissolved in the organic solvent to prepare a 12.5% ​​solution, obtaining the electrolyte.

[0234] 7) Secondary battery manufacturing The positive electrode sheet, separator, and negative electrode sheet prepared in Example 1 were stacked in this order with the separator separating the positive and negative electrode sheets, and then wound to obtain a bare cell. A tab was welded to the bare cell, which was then placed in an aluminum case and baked at 80°C to remove water. An electrolyte was then immediately injected and sealed to obtain an uncharged battery. The uncharged battery was then left to stand, and subsequently passed through processes such as hot pressing, cold pressing, chemical formation, molding, and capacity measurement to obtain the lithium-ion battery product of Example 1.

[0235] Examples 2 to 12 The batteries of Examples 2 to 12 were manufactured in the same manner as in Example 1, except that the type of anchor blocking agent was adjusted and the polymer structural formula was further adjusted. See Table 1 for specific adjustment parameters.

[0236] [Table 1-1] [Table 1-2]

[0237] Here, X' in the polymer structures of Examples 1 to 12 is -C 12 H 25 and the L segment includes: [ka] Includes.

[0238] Examples 13 to 16 Except for adjusting the types of dibasic acid and diamine, and further adjusting the structures of R1 and R2 in the polymer, the batteries of Examples 13 to 16 were manufactured in a similar manner to that of Example 1. The specific adjustment parameters are as shown in Table 2, and the corresponding R1 and R2 groups are as shown in Table 3.

[0239] [Table 2]

[0240] [Table 3]

[0241] Examples 17 to 22 Compared with Example 1, the preparation parameters of the polymer were adjusted, and further, the number of repeating units of the constitutional unit represented by Formula II was adjusted. The specific preparation method is as follows:

[0242] Example 17 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, then the temperature was raised to 100°C and the reaction was carried out at a constant temperature for 1 hour. The pressure was lowered to 0.01 atm, the temperature was raised to 120°C, and the reaction was carried out for 2 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0243] Example 18 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, then the temperature was raised to 100°C and the reaction was carried out at a constant temperature for 1 hour. The pressure was reduced to 0.01 atm, the temperature was raised to 120°C, and the reaction was carried out for 4 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0244] Example 19 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, after which the temperature was raised to 180°C and the reaction was carried out at a constant temperature for 2 hours. The temperature was then raised to 230°C and the reaction was carried out for 5 hours. The pressure was then lowered to 0.01 atm, and the temperature was raised to 300°C and the reaction was carried out for 12 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0245] Example 20 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, after which the temperature was raised to 180°C and the reaction was carried out at a constant temperature for 2 hours. The temperature was then raised to 230°C and the reaction was carried out for 5 hours. The pressure was then lowered to 0.01 atm, and the temperature was raised to 300°C and the reaction was carried out for 24 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0246] Example 21 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, then the temperature was raised to 180°C and the reaction was continued at a constant temperature for 1 hour. The temperature was then raised to 230°C and the reaction was continued for 2 hours. The pressure was then reduced to 0.01 atm, and the temperature was raised to 270°C and the reaction was continued for 3 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0247] Example 22 Compared with Example 1, the preparation process of the intermediate polymer was adjusted, specifically as follows: Dibasic acid and diamine were weighed in a molar ratio of 1:1.2 and added to a three-neck flask. Deionized water (8 times the weight of the monomer) and sodium hypophosphite (0.15% of the weight of the monomer) were added. The reactor was sealed, evacuated, and filled with nitrogen. This process was repeated three times, after which the temperature was raised to 180°C and the reaction was continued at a constant temperature for 1 hour. The temperature was then raised to 230°C and the reaction was continued for 5 hours. The pressure was then reduced to 0.01 atm, and the temperature was raised to 300°C and the reaction was continued for 8 hours. After that, the heat source was removed, the vacuum was maintained, and the reactor was cooled. The product was removed to obtain an intermediate polymer.

[0248] Examples 23 to 27 Compared with Example 1, the mass fraction of the polymer dispersant was adjusted, specifically see the examples in Table 5.

[0249] Examples 28 to 31 Compared with Example 1, the graphitization degree of lithium iron phosphate is adjusted, specifically see the examples in Table 5.

[0250] Example 32 Compared to Example 1, the positive electrode active material is carbon-coated LiNi 0.6 Co 0.2 Mn 0.2 Adjusted to O2 (NCM@C).

[0251] Example 33 Compared with Example 1, the structural formula of the diamine is adjusted, and the structural formula of the diamine is as follows: [ka]

[0252] Examples 34 to 36 Except for adjusting the types of dibasic acid and diamine, and further adjusting the structures of R1 and R2 in the polymer, the batteries of Examples 34 to 36 were manufactured in a similar manner to that of Example 1. The specific adjustment parameters are as shown in Table 4, and the corresponding R1 and R2 groups are as shown in Table 5. In Example 35, the diamine was paraphenylenediamine, and the dibasic acid in Example 36 was terephthalic acid.

[0253] [Table 4]

[0254] [Table 5]

[0255] Comparative Examples 1 to 4 Compared with Example 1, the dispersant was replaced with polyvinylpyrrolidone (PVP) dispersant, and the graphitization degree of lithium iron phosphate was adjusted.

[0256] Comparative Example 5 Compared with Example 1, the dispersant was replaced with polymer dispersant D-1, whose structural formula is C 12 H 25 -O-(EO) 80 -(PO) 40 It is -(CH2)4-COOH, and the specific preparation process is as follows: 1 mol of C 12 H 25Using -OH as the initiator and 0.5% KOH by weight of the initiator as the catalyst, the system was evacuated and filled with nitrogen, the reactor was heated to 130°C and evacuated, 85 mol of ethylene oxide gas was introduced, the pressure in the reactor was maintained at less than 0.3 MPa, and the reaction was carried out at that pressure and temperature for 1 hour, and then cooled to obtain the first product. Then, 0.5% KOH by weight of the initiator was added, the system was evacuated and filled with nitrogen, the reactor was heated to 130°C and evacuated, and 45 mol of propylene oxide gas was introduced, the reaction was carried out for 1 hour, and then cooled to obtain the first product. The product was then neutralized by acid washing, extracted three times with methylene chloride, dried, filtered, and rotary evaporated to obtain the intermediate product.

[0257] One mole of the intermediate product and 1.5 moles of the anchor blocking agent Cl-C4H8-COOH were dissolved in 1000 ml of methylene chloride and the halogenation reaction was carried out at room temperature. After 6 hours of reaction, 500 ml of deionized water was added to quench the reaction. The reaction mixture was extracted three times with methylene chloride, and the oil phase product was collected. It was then dried over magnesium sulfate and rotary evaporated to separate the product, which was then separated using a chromatography column to obtain polymer dispersant D-1.

[0258] Comparative Example 6 Compared with Example 1, the dispersant was replaced with polymer dispersant D-2, and the preparation process was compared with Example 1, except that the anchor blocking agent was adjusted to Cl—C4H8—CH3.

[0259] 2. Performance measurement 1. Polymer characterization 1) Weight average molecular weight A Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141) was used. A 3.0% mass fraction polystyrene solution sample was used as a reference, and a matching chromatography column (oil-based: Styragel HT5 DMF 7.8*300mm + Styragel HT4) was selected. A 3.0% polymer solution was prepared in N-methylpyrrolidone (NMP) solvent and allowed to stand for one day before use. For measurement, tetrahydrofuran was first aspirated into the syringe, followed by washing, and this was repeated several times. Then, 5 ml of the experimental solution was aspirated, the air in the syringe was removed, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the injection port. Data was acquired after the displayed value stabilized.

[0260] 2) Glass transition temperature The glass transition temperature was measured using a differential scanning calorimeter (Q1000 model) manufactured by TA Co., Ltd. 6 to 9 g of polymer sample was taken, and the temperature was raised from room temperature to 200°C at a heating rate of 10°C / min. The obtained differential scanning calorimetric curve was analyzed to obtain the glass transition temperature of the polymer, expressed in °C.

[0261] 3) Melting point The melting point is measured using a precision microscope melting point analyzer (X-5 model). Measure at 1 standard atmospheric pressure. Place 0.01 mg of a uniformly polished sample on a glass slide, cover it with another glass slide, lightly press it down, and place it in the center of the hot stage. Cover it with an insulating plate and adjust the focal length of the microscope until the sample can be clearly observed. Then, adjust the temperature knob to rapidly increase the temperature until the polymer is slightly melted, and slowly adjust the heating rate until the sample is completely melted. The temperature at which the sample is completely melted is recorded as the polymer's melting point, expressed in °C.

[0262] 4) Hydrophilic-Lipophilic Balance (HLB) This is measured using an emulsification method, and its principle is that when an oily medium is emulsified using a polymer, the resulting emulsion will have the highest stability if the polymer's HLB value is the same as the HLB value required for the oily medium.The ideal HLB value can be obtained by mixing standard samples with known HLB values ​​in proportion, and the prepared oily phase is emulsified with the polymer and left to stand for 24 hours.The HLB value required for the oily phase in the sample with the highest stability is the HLB value of the polymer.

[0263] 2, positive electrode active material 1) Degree of graphitization The graphitization degree was characterized using a high-resolution Raman spectrometer manufactured by HORIBA Jobin Yvon, France, model LabRAM HR Evlution. After subtracting the detection background, the Raman spectrum was fitted using the following Gaussian function. Raman spectrum measurement conditions: wavelength 532 nm, scanning range 200–4000 cm -1 Two measurements were stacked, and 10 points were measured for each sample, and the average value was taken and fitted.

[0264]

number

[0265] 3. Cathode slurry 1) Solid content The copper foil was removed, weighed on a weight loss measuring device, recorded as M0, and set to zero. A small amount of the positive electrode slurry was taken, applied to a copper foil, placed in a moisture meter, weighed, and recorded as M1. The apparatus was closed and oven drying commenced. After completion, the weighing data is recorded and recorded as M2, and the solid content is calculated, which is (M2-M0) / (M1-M0).

[0266] 2) Slurry stability measurement After stirring the slurry for another 30 minutes, a certain amount of the slurry was poured into the stability tester's sample bottle. After the sample bottle was filled, the lid of the test tower was closed. The lid of the test tower was opened, and a scanning curve began to appear on the test interface. The stability test of the sample was started, and the test was continued for more than 72 hours until the test was completed.

[0267] 4. Positive electrode sheet 1) Brittleness measurement A defect-free positive electrode sheet was taken and cut lengthwise into samples measuring 20 cm in length and 2.5 cm in width. There were at least eight samples. After pre-folding, the film was placed on a measuring table and roll-pressed once with a 2 kg cylindrical press roller. If light was transmitted, the number of times of light transmission for brittleness was one. If light was not transmitted, the folding and roll-pressing were repeated in the opposite direction. The folds were observed under light to see if light was transmitted or if they were cracked. The actual number of times of folding was recorded, and the average value was used as the measurement result.

[0268] 2) Film resistor The oven-dried positive electrode slurry (film layer) was cut into small circular electrode sheets with a diameter of 3 mm from the left, middle, and right sides of the positive electrode sheet. The IEST sheet resistance meter was turned on, the probe was placed in the appropriate position, the "start" button was pressed, and the reading was read once it stabilized. Two measurements were taken for each small circular electrode sheet, and the average of the six measurements was calculated as the resistance of the electrode sheet film layer.

[0269] 5, secondary battery 1) First Coulomb Efficiency At 25°C, the batteries of the above examples and comparative examples were charged to a voltage of 4.3 V at a constant current of 0.1 C rate, and the charge capacity at this time was recorded as the initial charge capacity of the secondary battery. After leaving the battery standing for 5 minutes, the battery was discharged to a voltage of 2.0 V at a constant current of 0.1 C rate and left standing for 5 minutes, which constituted one charge-discharge cycle. The discharge capacity this time was recorded as the initial discharge capacity of the secondary battery, i.e., the initial capacity of the secondary battery.

[0270] Initial coulombic efficiency (%) of secondary battery = initial discharge capacity / initial charge capacity × 100%.

[0271] 2) 45℃ cycle capacity retention rate At 45°C, the batteries of the examples and comparative examples were charged to 3.65 V at a constant current of 1 / 3 C, then charged to a current of 0.05 C at a constant voltage of 3.65 V, left for 10 minutes, and then discharged to 2.5 V at 1 / 3 C, and the resulting capacity was designated as the initial capacity C0. The above steps were repeated for the same batteries, and the discharge capacity Cn of the batteries after n cycles was recorded. The battery capacity retention rate after each cycle is as follows:

number

[0272] In this measurement process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2, ... the 100th cycle corresponds to n = 100. The battery capacity retention rate data for Example 1 in Table 5 was measured after repeating 300 cycles under the above measurement conditions, and was the value P300.

[0273] 3. Analysis of the measurement results of each example and comparative example [Table 6-1] [Table 6-2]

[0274] [Table 7-1] [Table 7-2] [Table 7-3]

[0275] As can be seen from the above results, the polymers of Examples 1 to 36 contain X'-LX, where X' is -C 12 H 25 X comprises any one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; L comprises a constitutional unit of formula II, [ka] In the formula, R1 is [ka] [ka] [ka] or [ka] and R2 is [ka] [ka] [ka] or [ka] and R3 comprises hydrogen or methyl.

[0276] As can be seen from comparisons of Examples 1 to 22 and 33 to 36 with Comparative Example 3, Example 28 with Comparative Example 1, Example 29 with Comparative Example 2, and Example 30 with Comparative Example 4, compared with conventional PVP dispersants, the polymer dispersant of the present application is versatile and can improve the dispersibility of slurries containing lithium iron phosphates with different degrees of graphitization as the positive electrode active material, increase the solids content of the slurries, reduce the gelation phenomenon of the slurries, reduce the film resistance of the electrode sheets, improve the toughness of the electrode sheets, and improve the initial coulombic efficiency and high-temperature cycling performance of the batteries. The polymer dispersant is versatile and can be used with positive electrode slurries containing lithium iron phosphates with different degrees of graphitization produced by different manufacturing processes, contributing to reduced manufacturing costs and improved production efficiency.

[0277] As can be seen from a comparison between Example 1 and Comparative Example 5, the amide group in the structural unit represented by Formula II in the polymer dispersant of the present application can effectively increase the solids content of the slurry, reduce the gelling phenomenon of the slurry, improve the toughness of the electrode sheet, reduce the film resistance of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery. As can be seen from a comparison between Examples 1 to 12 and Comparative Example 6, the X group including a carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate group in the polymer dispersant of the present application can effectively increase the solids content of the slurry, reduce the gelling phenomenon of the slurry, improve the toughness of the electrode sheet, reduce the film resistance of the electrode sheet, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery.

[0278] As can be seen from the comparison of Examples 1, 9 and 10 with Example 5, compared with the case where the X group is -C4H8-COO-C3H7, the polymer dispersant containing the X group -C4H8-COOH, -C4H8-COO-C3H6-OH or -C4H8-COO-NH-C3H6-OH can further improve the dispersibility of the slurry, increase the solid content of the slurry, and improve the use performance of the slurry. As can be seen from a comparison between Example 1 and Examples 5, 9, and 10, compared with polymer dispersants containing an X group of -C4H8-COO-C3H7, -C4H8-COO-C3H6-OH, or -C4H8-COO-NH-C3H6-OH, the polymer dispersant containing an X group of -C4H8-COOH further improves the dispersion effect of the slurry, increases the solids content of the slurry, reduces the gelation phenomenon of the slurry, improves the toughness of the electrode sheet, reduces the film resistance of the electrode sheet, and improves the service performance of the slurry and electrode sheet, as well as improving the initial coulombic efficiency and high-temperature storage performance of the battery. As can be seen from a comparison between Example 2 and Example 6, compared to the case where the X group of -C4H8-SO3-C3H7 is included, the polymer dispersant containing the X group of -C4H8-SO3H further improves the dispersion effect of the slurry, increases the solid content of the slurry, reduces the gelling phenomenon of the slurry, improves the toughness of the electrode sheet, reduces the film resistance of the electrode sheet, and improves the initial coulombic efficiency and high-temperature cycle performance of the battery. As can be seen from a comparison between Examples 4, 11, and 12 and Example 8, [ka] Compared to polymeric dispersants containing [ka] [ka] or [ka] The polymer dispersant containing the compound can further improve the toughness of the electrode sheet and improve the high-temperature storage performance of the battery. As can be seen from the comparison between Example 4 and Examples 8, 11 and 12, [ka] [ka] or [ka] Compared to polymeric dispersants containing [ka] The polymer dispersant containing the compound can further improve the solid content of the slurry, reduce the gelling phenomenon of the slurry, improve the toughness of the electrode sheet, reduce the film resistance of the electrode sheet, and improve the initial coulomb efficiency and high-temperature storage performance of the battery. [ka] Compared to polymers containing [ka] The polymer dispersant containing the compound can further reduce the gelling phenomenon of the slurry, improve the toughness of the electrode sheet, and improve the initial coulomb efficiency and high-temperature cycle performance of the battery. [ka] Compared to polymers containing [ka] The polymer dispersant containing the compound can improve the initial coulombic efficiency and high-temperature cycling performance of the battery, and can improve the electrochemical performance of the battery. [ka] Compared to polymers containing [ka] The polymer dispersant containing the compound (I) can further increase the solid content of the slurry, improve the flexibility of the electrode sheet, and improve the initial coulombic efficiency and high-temperature storage performance of the battery.

[0279] As can be seen from a comparison between Example 1 and Example 33, compared with R3 in the structural unit represented by Formula II containing methyl, R3 containing hydrogen can further improve the dispersibility of the slurry, increase the solids content of the slurry, reduce the gelling phenomenon of the slurry, improve the toughness of the electrode sheet, reduce the film resistance of the electrode sheet, and improve the initial coulombic efficiency and high-temperature storage performance of the battery.

[0280] As can be seen from the comparison between Examples 1 and 13 and Examples 14 and 36, the comparison between Examples 1 and 16 and Examples 15 and 35, and the comparison between Example 15 and Example 34, R1 and R2 are [ka] [ka] By including R1 and R2, the solid content of the slurry can be increased, the gelling phenomenon of the slurry can be reduced, the toughness of the electrode sheet can be improved, and the initial coulomb efficiency and high-temperature storage performance of the battery can be improved. [ka] By including the above, the solid content of the slurry can be further improved, gelation of the slurry can be reduced, the toughness of the electrode sheet can be improved, the film resistance of the electrode sheet can be reduced, and the initial coulombic efficiency and high-temperature storage performance of the battery can be improved.

[0281] As can be seen from Examples 1 and 17-22, when the repeating number of the structural unit represented by Formula II is 3-100, the slurry has a high solids content, the electrode sheet has excellent toughness, and the battery has excellent initial coulombic efficiency and high-temperature storage performance. As can be seen from comparing Examples 1, 18-19, and 21-22 with Examples 17 and 20, when the repeating number of the structural unit represented by Formula II is 8-80, the solids content of the slurry is further increased, the gelling phenomenon of the slurry is reduced, the softness of the electrode sheet is improved, and the usability of the slurry and electrode sheet is improved. As can be seen from comparing Examples 1, 21-22 with Examples 17-20, when the repeating number of the structural unit represented by Formula II is 15-50, the solids content of the slurry is further increased, the gelling phenomenon of the slurry is reduced, the softness of the electrode sheet is improved, and the initial coulombic efficiency and high-temperature storage performance of the battery are improved.

[0282] The positive electrode slurries of Examples 1 to 36 contain a positive electrode active material, a conductive agent, a binder, and a dispersant, where the dispersant is the polymer of the present application, and the positive electrode active material contains lithium iron phosphate without a carbon coating layer on its surface, lithium iron phosphate with a carbon coating layer on its surface, or lithium nickel cobalt manganese with a carbon coating layer on its surface.

[0283] As can be seen from a comparison between Example 1 and Example 32, compared with the case where the positive electrode active material is lithium nickel cobalt manganese with a carbon coating layer on its surface, the polymer dispersant of the present application is more suitable for lithium iron phosphate with a carbon coating layer on its surface, and can further increase the solids content of the lithium iron phosphate with a carbon coating layer on its surface slurry, improve the toughness of the electrode sheet, reduce the film resistance, and improve the use performance of the slurry and the electrode sheet.

[0284] As can be seen from Examples 1 and 29 to 31, the polymer dispersant of the present application is versatile and suitable for slurry systems using lithium iron phosphate with a graphitization degree of 10% to 30% as the positive electrode active material. As can be seen from a comparison of Examples 1 and 29 to 31 with Example 28, the use of lithium iron phosphate with a graphitization degree of 10% to 30% further improves the toughness of the electrode sheet, reduces the film resistance of the electrode sheet, and improves the usability of the electrode sheet.

[0285] As can be seen from Examples 1 and 23 to 27, by setting the mass fraction of the polymer dispersant to 0.01% to 3% based on the total mass of the solid materials in the positive electrode slurry, the slurry has a high solid content, the electrode sheet has excellent toughness, and the battery has excellent initial coulombic efficiency and high-temperature storage performance. A comparison of Examples 1 and 24 to 26 with Examples 23 and 27 shows that by setting the mass fraction of the polymer dispersant to 0.03% to 2% based on the total mass of the solid materials in the positive electrode slurry, the high-temperature storage performance of the battery can be improved and the operating temperature of the battery can be expanded.

[0286] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and all embodiments that have substantially the same technical ideas and provide the same functions and effects within the scope of the technical solution of the present application are included in the technical scope of the present application. Furthermore, various modifications that a person skilled in the art may make to the embodiments and other forms formed by combining some of the components of the embodiments are also included in the scope of the present application, as long as they do not deviate from the gist of the present application. [Explanation of symbols]

[0287] 1 battery pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Secondary battery 51 cases 52 Electrode assembly 53 Lid plate.

Claims

1. A polymer comprising a structure according to formula I: 【Chemistry 1】 wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; L comprises a constitutional unit of formula II: 【Chemistry 2】 In the formula, R 1 is C 1-12 Alkylene, C 6-12 arylene, or 【Transformation 3】 and R 2 is C 1-12 Alkylene, C 6-12 arylene, or 【Chemistry 4】 Including, In the formula, EO is —CH 2 -CH 2 -O-, and PO represents -CH(CH 3 )-CH 2 represents —O—, m1 and m2 each independently represent an integer from 3 to 60, and n1 and n2 each independently represent an integer from 0 to 60. R 3 is hydrogen or C 1-3 A polymer comprising an alkyl group of the formula:

2. The polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4, 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 In the formula, a1 and a2 each independently represent an integer of 2 to 12; 4 , R 5 are each independently hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, 【Chemistry 9】 and R 6 , R 7 , R 8 are each independently hydrogen, C 1-12 Alkyl, C 1-12 alkyl alcohols, 【Chemistry 10】 wherein R 9 , R 10 are each independently C 1-12 alkylene, R 11 is C 1-12 Alkyl or C 6-30 The polymer of claim 1 , characterized in that it contains an aryl.

3. The polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4: 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 In the formula, a1 and a2 each independently represent an integer of 2 to 12; 4 , R 5 are each independently C 1-12 alkyl alcohols, 【Chemistry 14】 and R 8 is hydrogen, C 1-12 alkyl alcohols, 【Chemistry 15】 wherein R 9 , R 10 are each independently C 1-12 alkylene, R 11 is C 1-12 Alkyl or C 6-30 3. The polymer according to claim 1 or 2, characterized in that it contains an aryl.

4. R in the structural unit represented by formula II 3 4. The polymer according to claim 1, wherein R is a hydrogen atom.

5. The R 1 teeth 【Chemistry 16】 and R 2 teeth 【Chemistry 17】 wherein n1 or n2 is 0, and m1 and m2 are each independently an integer from 3 to 60.

6. The R 1 teeth [Chemistry 18] and R 2 teeth 【Chemistry 19】 Including, In the formula, n1 and n2 each independently represent an integer of 1 to 60, and m1 and m2 each independently represent an integer of 3 to 30. The polymer according to any one of claims 1 to 4.

7. 7. The polymer according to claim 1, wherein the number of repeating units of the structural unit represented by formula II in L is 3 to 100.

8. The X' is C 3-30 Alkyl, C 6-30 8. The polymer according to claim 1, characterized in that it comprises at least one of the following: aryl.

9. 9. The polymer according to claim 1, wherein the weight average molecular weight of the polymer is between 1500 g / mol and 70000 g / mol.

10. 10. The polymer according to claim 1, wherein the polymer has a glass transition temperature of from 50°C to 200°C.

11. 11. The polymer according to claim 1, wherein the melting point at 1 standard atmosphere is between 70°C and 300°C.

12. 12. The polymer according to claim 1, wherein the polymer has a hydrophilic-lipophilic balance value of 6 to 16.

13. 1. A method for preparing a polymer, comprising the steps of: 1) Polycondensation reaction: preparing an intermediate polymer comprising the structure shown in Formula III by polymerizing at least one dibasic acid and at least one diamine; 【Chemistry 20】 In the formula, Y′ and Y each independently contain a carboxyl group or an amino group. 2) End group reaction: reacting the end groups of the intermediate polymer to obtain a polymer comprising the structure of Formula I; 【Chemistry 21】 wherein X comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group, and a phosphate group; X' comprises a non-polar group; L comprises a constitutional unit of formula II: 【Chemistry 22】 In the formula, R 1 is C 1-12 Alkylene, C 6-12 arylene, or 【Chemistry 23】 and R 2 is C 1-12 Alkylene, C 6-12 arylene, or 【Chemistry 24】 Including, In the formula, EO is —CH 2 -CH 2 -O-, and PO represents -CH(CH 3 )-CH 2 represents —O—, m1 and m2 each independently represent an integer from 3 to 60, and n1 and n2 each independently represent an integer from 0 to 60. R 3 is hydrogen or C 1-3 Including alkyl.

14. The preparation method specifically includes: reacting a catalyst, at least one dibasic acid, and at least one diamine with stirring at 20°C to 300°C for 2 hours to 35 hours to obtain the intermediate polymer having the same end groups at both ends; and reacting the end groups at both ends of the intermediate polymer to obtain the polymer.

15. A dispersant comprising a polymer according to any one of claims 1 to 12 or a polymer prepared by the method according to claim 13 or 14.

16. Use of a polymer according to any one of claims 1 to 12 in a secondary battery.

17. A positive electrode slurry comprising a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant contains the polymer according to claim 1 .

18. The positive electrode slurry according to claim 17, wherein the positive electrode active material comprises lithium iron phosphate having a carbon coating layer on its surface.

19. The positive electrode slurry according to claim 18, wherein the graphitization degree of the lithium iron phosphate having a carbon coating layer on its surface is 10% to 30%.

20. The cathode slurry according to any one of claims 17 to 19, wherein the mass fraction of the dispersant is 0.01% to 3%, and optionally 0.03% to 2%, based on the total mass of the solid materials in the cathode slurry.

21. 21. A positive electrode sheet including a positive electrode current collector and a positive electrode film provided on the positive electrode current collector, wherein the positive electrode film is produced from the positive electrode slurry according to claim 17.

22. A secondary battery comprising a separator, a negative electrode sheet, an electrolyte, and the positive electrode sheet of claim 21.

23. An electrical device comprising the secondary battery of claim 22.

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