Polymers, methods for preparing the same, positive electrode sheets, secondary batteries, electrical devices

Abstract

This application provides a polymer, a method for preparing the same, a cathode sheet, a secondary battery, and an electrical device. The polymer comprises a structure represented by formula I, where X comprises a phosphate group or phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, or a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment. The polymer provided in this application can effectively increase the maximum solid content of the cathode slurry, shorten the filtration time, improve the production efficiency and quality of the electrode sheet, and improve the flexibility of the electrode sheet.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application incorporates by reference to Chinese Patent Application No. 202310961340.X, filed on August 1, 2023, titled "Polymer, Method for Preparing the Same, Cathode Sheet, Secondary Battery, Electrical Device," and Chinese Patent Application No. 202311098921.1, filed on August 29, 2023, both of which are incorporated into this application by reference.

[0002] This application relates to the technical field of secondary batteries, and more particularly to polymers, methods for preparing the same, positive electrode sheets, secondary batteries, and electrical devices. [Background technology]

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

[0004] Electrode sheets in secondary batteries are generally made by coating a current collector with a slurry containing an active material and drying it. Increasing the solvent content in the slurry and decreasing the solid content is an effective way to optimize the dispersion uniformity of the slurry and improve the coating quality of the slurry. However, slurries with a high solvent content require longer drying times and have higher manufacturing costs. How to increase the solid content of the slurry while ensuring dispersion uniformity and effectively increasing the maximum solid content of the slurry is a technical challenge that needs to be addressed urgently in this field. [Overview of the project]

[0005] This application has been made in view of the above-mentioned problems, and aims to provide a dispersant that can increase the maximum solid content of a slurry.

[0006] In a first aspect of this application, a polymer comprising the structure represented by formula I, [ka] The present invention provides a polymer in which X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment.

[0007] This polymer can effectively increase the maximum solid content of the positive electrode slurry, shorten the filtration time, improve the production efficiency and quality of the electrode sheet, and improve the flexibility of the electrode sheet.

[0008] In any embodiment, the organic segment of R2 includes at least one of an amide group, an amino group, or an aryl group.

[0009] Nitrogen-containing groups or aryl groups in the polymer help improve the anchoring action between the polymer and the cathode active material. This makes the polymer particularly suitable for carbon-coated cathode active materials, further increasing its versatility as a dispersant. By increasing the anchoring sites of the dispersant, the polymer exhibits a more effective dispersing action, thereby further increasing the maximum solid content of the slurry, improving the molding quality of the electrode sheet, reducing costs, and enhancing effectiveness.

[0010] In any embodiment, the organic segment of R2 contains C 2-12 It also contains hydrocarbon groups.

[0011] In polymers, C 2-12The inclusion of hydrocarbon groups helps to further improve the anchoring and fixation of the polymer to the carbon-modified cathode active material. The hydrocarbon groups can effectively anchor and fix to the carbon on the cathode active material, increasing the dispersibility of the polymer's anchoring sites on the cathode active material. This further improves the applicability of the polymer dispersant, increases the maximum solid content of the slurry, optimizes the molding quality of the electrode sheet, reduces costs, and improves effectiveness.

[0012] In any embodiment, R2 includes the structure shown in formula II, [ka] In the formula, R4 and R5 copolymerize randomly, and R4 is C 2-12 Hydrocarbylene group, C 3-13 It contains at least one of the amide groups, and R5 is [ka] It includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R6 a R6 b is hydrogen, C 1-4 It contains at least one alkyl group, and satisfies 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10.

[0013] The organic segment with the above structure exhibits a more effective anchoring effect through copolymerization of nitrogen-containing groups and hydrocarbon groups, improving the dispersion of the polymer and effectively increasing the solid content of the slurry.

[0014] In any embodiment, R2 includes the structure shown in formula III, [ka] In the formula, R6 is C 2-12 It contains a hydrocarbylene group, and R7 is [ka] It contains at least one of the following, and q5 and q6 each independently contain any integer from 0 to 4, and 1 ≤ n ≤ 6.

[0015] The organic segment with the above structure exhibits more effective anchor fixation through alternating copolymerization of nitrogen-containing groups and hydrocarbon groups, improving polymer dispersion and effectively increasing the solid content of the slurry.

[0016] In any embodiment, the terminal group of R2 includes at least one of -C(O)-NH2 and -CH2-NH2.

[0017] Polymers containing terminal groups -C(O)-NH2 and -CH2-NH2 can exhibit more effective dispersion, increase the maximum solid content of the slurry, and further improve the molding quality and efficiency of electrode sheets.

[0018] In any embodiment, at least one of R1 and R3 includes a polyether segment, and selectively, both R1 and R3 include a polyether segment.

[0019] In any embodiment, at least one of R1 and R3 includes a polyether segment represented by formula IV, [ka] In the formula, EO represents -CH2-CH2-O- and PO represents -CH(CH3)-CH2-O-, and 4≦m1≦50 and 4≦n1≦50.

[0020] The polyether segment having the above structure possesses appropriate steric hindrance and a low glass transition temperature, which more effectively reduces the order and glass transition temperature of the binder crystals in the positive electrode slurry, thereby lowering the crystallinity of the binder and improving the flexibility of the electrode sheet. Through dispersion and flexibility, it improves the uniformity and flexibility of the electrode sheet, thereby improving the safety and critical pressure density of the battery, increasing the load of the positive electrode active material in the battery, and contributing to a further improvement in the energy density of the battery.

[0021] In any embodiment, the terminal groups of the polyether segment include aryl groups.

[0022] The aryl groups and the carbon layer on the surface of the cathode active material exhibit excellent compatibility, further improving the anchoring and fixation of the polymer and the carbon-modified cathode active material. The effective anchoring and fixation of the aryl groups and carbon on the cathode active material increases the dispersibility of the anchoring sites of the polymer on the cathode active material, thereby further improving the applicability of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the molding quality of the electrode sheet, reducing costs, and improving effectiveness.

[0023] In any embodiment, X includes a phosphate group.

[0024] Phosphate polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode sheet. Furthermore, phosphate polymers possess higher stability and, in addition to improving slurry dispersibility, can effectively improve the battery's cycle capacity retention rate.

[0025] In any embodiment, the polymer is a polymer represented by the following formula, [ka] Includes at least one of the following: In the formula, at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV, [Chemical formula] In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4 ≤ m1 ≤ 15, 4 ≤ n1 ≤ 15, and R6 and R4 are each independently C 4-8 alkylene group, C 4-8 including at least one of alkenylene groups.

[0026] In any embodiment, the polymer is as shown by the following formula: [Chemical formula] In the formula, R2 includes at least one of hydrogen, an aryl group, a substituted or unsubstituted alkyl group, an amino group, or an organic segment containing an amide group. At least one of R1 and R3 includes a block copolymer polyether segment represented by Formula IV. [Chemical formula] In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4 ≤ m1 ≤ 50, 4 ≤ n1 ≤ 50, and the end group of the polyether segment contains a phenyl group.

[0027] In any embodiment, the weight-average molecular weight of the polymer is 1000 - 10000, and optionally 2000 - 5000.

[0028] A polymer with a weight-average molecular weight within the above range exhibits excellent dispersibility, can further increase the solid content of the slurry, endows the slurry with excellent fluidity performance, reduces the coating time, and improves the coating uniformity and speed. When the weight-average molecular weight of the polymer is 2000 - 5000, the dispersion effect can be more effectively achieved, the maximum solid content of the slurry can be increased, and the filtration time can be shortened.

[0029] In the second aspect of this application, A method for preparing a polymer, comprising the step of reacting a compound represented by formula VI with a polymerization monomer containing R3OH, R1OH, water, and an unsaturated bond to prepare a polymer having the structure represented by formula I, [ka] The present invention provides a method for preparing a polymer, wherein in the formula, X comprises a phosphate group or a phosphite group, X1, X2, and X3 all comprise a halogen, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment.

[0030] In any embodiment, the preparation method is The first step involves reacting the compound represented by formula VI with R3OH, R1OH, and water to prepare the intermediate product represented by formula VII. [ka] The process includes the step of reacting the intermediate product with a polymerization monomer containing at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer.

[0031] In any embodiment, the second reaction is specifically: The intermediate product is subjected to an addition reaction with at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond, and then further subjected to a substitution reaction with a halogen-substituted organic alcohol. The process includes preparing the polymer by sequentially repeating the above addition reaction and substitution reaction multiple times, R2 includes the structure shown in Equation III, [ka] In the formula, R6 is C 2-12 It contains a hydrocarbon group, and R7 is [ka] It contains at least one of the following, and q5 and q6 each independently contain any integer from 0 to 4, and 1 ≤ n ≤ 6.

[0032] In any embodiment, the preparation method is The process further comprises the step of a third reaction in which the intermediate product is reacted with (i) at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond or a cyclic amide monomer, thereby preparing the polymer, wherein R2 comprises the structure shown in formula II. [ka] In the formula, R4 and R5 copolymerize randomly, and R4 is C 2-12 hydrocarbon group, C 3-13 It contains at least one of the amide groups, and R5 is [ka] It includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R6 a R6 b is hydrogen, C 1-4 It contains at least one alkyl group, and satisfies 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10.

[0033] Another aspect of this application relates to a method for preparing a polymer, comprising the step of reacting a compound represented by formula VI with a starting material containing R3OH and R1OH to prepare a polymer having a structure represented by formula I, [ka] The present invention provides a method for preparing a polymer, wherein in the formula, X comprises a phosphate group or a phosphite group, X1, X2, and X3 all comprise a halogen, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment, at least one terminal group of the polyether segment comprises an aryl group, and R2 comprises an organic segment.

[0034] A third aspect of this application provides for use as a dispersant for polymers or polymers prepared by the preparation method of any embodiment.

[0035] A fourth aspect of this application provides a cathode slurry comprising a dispersant containing the polymer of the first aspect of the claims or the polymer prepared by the preparation method of the second aspect.

[0036] The positive electrode slurry has a high solid content, which improves the molding efficiency and quality of the positive electrode film layer, and helps to enhance the electrochemical expression and processing efficiency of the battery.

[0037] In any embodiment, the positive electrode slurry includes a positive electrode active material comprising at least one lithium-containing phosphate and a carbon-modified material thereof, and selectively comprising at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, and lithium manganese iron phosphate and its doping material.

[0038] The polymer exhibits electronegative properties and can further strengthen its mutual anchoring with lithium-containing phosphate, which exhibits weak acidity, through electrostatic action, thereby improving the dispersive effect of the polymer with respect to lithium-containing phosphate. Furthermore, since lithium-containing phosphate has poor conductivity, its conductivity is often improved during the preparation of the positive electrode active material by sintering organic materials such as glucose and sucrose and coating them with a carbon layer. The polymer simultaneously possesses groups that anchor and fix to the carbon coating layer, and also exhibits excellent dispersive properties with respect to carbon-modified lithium-containing phosphate, further improving the dispersibility of the slurry and increasing the maximum solid content of the slurry.

[0039] In any embodiment, the positive electrode active material includes a core and a carbon coating layer, the carbon coating layer covers at least a portion of the surface of the core, and sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is 0.2 or higher, selectively 0.5 or higher, and selectively 0.8 or higher.

[0040] By forming a carbon coating layer on the core surface, the conductivity of the positive electrode active material can be improved, and sp in the carbon coating layer on the core surface 2 When the molar ratio of hybridized carbon atoms to sp3 hybridized carbon atoms is 0.5 or higher, the carbon coating layer structure of the positive electrode active material exhibits high regularity, and the pore structure of the carbon coating layer has high density and a small pore size distribution range. During the battery production process, external moisture has difficulty entering the pores of the carbon coating layer, thereby effectively reducing the water absorption and water storage performance of the positive electrode active material, improving battery safety and cycle performance, effectively saving energy consumption during the drying process, and significantly reducing production costs.

[0041] However, sp 2 Hybrid carbon atoms and sp 3Because the carbon coating layer has a high degree of graphitization due to a molar ratio of 0.5 or more of mixed carbon atoms, the positive electrode active material tends to aggregate, making it difficult to effectively disperse during the slurry preparation process. The dispersant provided in the embodiment of this application has abundant anchor groups for carbon coating layers with a high degree of graphitization, and is particularly suitable for dispersing positive electrode active material with a high degree of graphitization of the coating layer. The combination of the two can simultaneously improve the battery's performance and processing performance.

[0042] In any embodiment, the thickness of the carbon coating layer is 15 nm or less, selectively 10 nm or less, selectively 4 nm to 8 nm. A carbon coating layer within the above thickness range can effectively improve the conductivity of the positive electrode active material by forming a thin carbon coating layer on the surface of the core, and can also improve the compaction performance when manufacturing the electrode sheet of the battery using the positive electrode active material.

[0043] In any embodiment, the mass content of the polymer in the total mass of the dry material of the positive electrode slurry is 0.1% to 2.0%, and selectively 0.2% to 1.0%.

[0044] Polymers within the above range can not only perform effective dispersion but also maintain the battery's volumetric energy density without seriously negatively impacting the battery's electrochemical expression.

[0045] In any embodiment, the positive electrode slurry comprises a binder, the binder comprising a vinylidene fluoride polymer having a weight-average molecular weight of 300,000 or more, and selectively, the weight-average molecular weight of the binder is between 700,000 and 9,000,000.

[0046] Vinylidene fluoride polymers with a weight-average molecular weight in this range possess excellent binding properties and electrochemical stability. By using vinylidene fluoride polymers with a weight-average molecular weight of 700,000 to 9,000,000, the amount of vinylidene fluoride used can be further reduced, decreasing the rigidity of the positive electrode film layer, improving the flexibility of the electrode sheet, and further increasing the critical pressure density of the battery, thus contributing to an improvement in the battery's energy density.

[0047] In any embodiment, the maximum solid content of the positive electrode slurry is 60% or more, and selectively 60% to 80%.

[0048] A fifth aspect of this application provides a positive electrode sheet including a positive electrode film layer, wherein the positive electrode film layer is prepared from a positive electrode slurry of any embodiment, or the positive electrode film layer contains a dispersant, the dispersant containing a polymer of the first aspect, or a polymer prepared by the preparation method of the second aspect.

[0049] In any embodiment, the pressure density of the positive electrode sheet is 2.6 g / cm³. 3 In this case, the number of times it is folded in half is 2 or more, selectively 3 to 6 times.

[0050] The polymer can not only effectively increase the solid content of the slurry, but also act as a flexuring agent, improving the flexibility of the positive electrode sheet and further enhancing the safety and electrochemical performance of the battery.

[0051] In any embodiment, the surface density of the positive electrode sheet is 300 mg / 1540.25 cm². 2 The above is a selective 300 mg / 1540.25 cm³. 2 ~600 mg / 1540.25 cm 2 That is the case.

[0052] The polymer can effectively increase the maximum solid content of the slurry, thereby accelerating the coating speed by more than 30%, making it particularly suitable for high-speed coating and thick coating molding methods. It effectively solves the problem of electrode sheets being prone to cracking during the thick coating process, and its high flexibility helps in the production of crack-free positive electrode sheets after winding molding.

[0053] In any embodiment, the positive electrode film layer comprises a dispersant, the dispersant comprising a structure represented by formula I, [ka] In the formula, X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, or a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, R2 comprises an organic segment, selectively comprising at least one of an amide group or an amino group in the organic segment of R2, selectively comprising an aryl group as the terminal group of the polyether segment, the positive electrode active material comprises at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, and selectively comprising at least one of lithium manganese iron phosphate and its doping material, and the mass content of the dispersant in the total mass of the positive electrode film layer is 0.1% to 2.0%, selectively 0.2% to 1.0%.

[0054] The positive electrode film layer has good dispersibility and processability, which is advantageous for improving manufacturing efficiency and battery performance.

[0055] A sixth aspect of this application provides a secondary battery including the positive electrode sheet of the fifth aspect.

[0056] A seventh aspect of this application provides an electrical device including a secondary battery according to the sixth aspect. [Brief explanation of the drawing]

[0057] [Figure 1] This is a schematic diagram of a polymer dispersion mechanism according to one embodiment of this application. [Figure 2] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 3] Figure 2 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 4] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 5]This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 6] Figure 5 is an exploded view of a battery pack according to one embodiment of this application. [Figure 7] This is a schematic diagram of an electrical device using a secondary battery as a power source according to one embodiment of this application. [Modes for carrying out the invention]

[0058] The following describes in detail embodiments specifically disclosing the polymer, its preparation method, cathode sheet, secondary battery, and electrical device of this application, with appropriate reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical components may be omitted. This is to avoid unnecessarily verbose descriptions, making them easily understandable to those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the intent of the claims.

[0059] The “range” disclosed in this application is limited to a lower and upper limit, and a given range is limited by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundary of a special range. Such limited ranges may or may not include endpoint values ​​and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a single range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, the ranges 60-110 and 80-120 are also understood to be predictable. Similarly, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all predictable. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated representation of combinations of these numbers. Furthermore, when a parameter is described as being an integer of 2 or more, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0060] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technological solutions.

[0061] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0062] Unless otherwise specified, all steps of this application may be performed sequentially 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 steps (b) and (a) performed in order. For example, when the method further includes step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), or otherwise.

[0063] Unless otherwise specified, descriptions such as "includes" and "inclusive" in this application are open, but may also be closed. For example, such descriptions as "includes" and "inclusive" may further include or include other components not listed, or may include or include only the listed components.

[0064] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the "A or B" condition: 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).

[0065] To improve the kinetic and electrochemical performance of batteries, the synthesis of positive electrode active materials tends towards nanotechnology and denser carbon coating. This results in positive electrode active materials having a larger specific surface area, requiring more solvent for effective dispersion during the slurry mixing process, which reduces the solid content of the slurry. Slurries with low solid content require longer drying times during the electrode sheet coating and drying process, leading to lower production efficiency and higher energy consumption. Furthermore, during the prolonged heating and drying process, low solid content slurries can cause problems such as warping, dry cracking, and binder lifting of the electrode sheets, degrading the quality of the electrode sheets.

[0066] Based on this, a first aspect of this application provides a polymer comprising a structure represented by formula I, [ka] In the formula, X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, or a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment.

[0067] In this specification, polymers include chemically homogeneous aggregates of polymers with different degrees of polymerization, molar masses and chain lengths, prepared by polymerization reactions, as well as derivatives of such polymer aggregates formed by polymerization reactions, i.e., polymers obtained by reactions of functional groups in the polymers, such as addition or substitution, which may be chemically homogeneous or chemically heterogeneous.

[0068] In some embodiments, the polymer includes a phosphate-based polymer. The structure of the phosphate-based polymer is shown in formula V. [ka]

[0069] In some embodiments, the polymer includes a phosphite polymer. The structural formula of the phosphite polymer is shown in V'. [ka]

[0070] In this specification, a polyether segment refers to a polymer segment that contains an ether bond (-COC-) in its structural unit.

[0071] In this specification, a polyester segment refers to a polymer segment that contains an ester group (-COO-) in its structural unit.

[0072] In this specification, a hydrocarbon group refers to a group containing carbon and hydrogen atoms, and includes, but is not limited to, alkyl groups, alkenyl groups, and alkynyl groups.

[0073] In this specification, the organic segment may be a polymer of repeating structural units or an organic group consisting of small molecule monomers. The dispersion mechanism of the polymer provided in the examples of this application is shown in Figure 1. The polymer 6 comprises an anchor group 61 and a soft segment 62, the anchor group 61 at one end of the polymer 6 acting on the surface of the positive electrode active material 7, and the dispersion objective is achieved by the steric hindrance effect of the soft segment 62. The phosphate group or phosphite group in the polymer 6 can be effectively anchored to the surface of the positive electrode active material 7 by intermolecular forces or electrostatic action, and thus plays the role of anchor fixing group 61. The anchoring action of the anchoring groups on the surface of the positive electrode active material allows the steric hindrance effect of the soft segments 62, such as polyether segments and polyester segments, to be effectively exerted on the surface of the positive electrode active material particles, thereby preventing aggregation of the positive electrode active material 7. Furthermore, it increases the amount of positive electrode active material 7 that can be effectively dispersed in a unit volume of solvent, mitigating gelation and aggregation of the slurry during the homogenization process, reducing the viscosity of the slurry, significantly increasing the effective solids content of the slurry, reducing the slurry filtration time, and improving the molding efficiency and quality of the electrode sheet. The polymer provided in the embodiments of this application allows the slurry to be applied to thick coating processes, which helps to improve the energy density of the battery.

[0074] Furthermore, soft segments in polymers, such as polyether segments and polyester segments, possess appropriate steric hindrance and low glass transition temperatures. The movement of these soft segments can improve the flexibility of the electrode sheet, while also performing dispersion and flexibility-enhancing effects.

[0075] In some embodiments, the organic segment of R2 includes at least one of an amide group, an amino group, or an aryl group.

[0076] In this specification, an amide group is defined as follows: [ka] This term refers to a group, and includes not only primary amides but also secondary and tertiary amides.

[0077] In this specification, the amino group is defined as: [ka] This term refers to a group, and includes not only primary amino groups but also secondary and tertiary amino groups.

[0078] In this specification, “aryl group” refers to an organic group derived from the removal of a hydrogen atom from a monocyclic or polycyclic aromatic hydrocarbon. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, and benzyl groups. The aryl group may be unsubstituted or substituted with one or more suitable substituents.

[0079] Furthermore, the aryl group may be monocyclic or polycyclic. In some embodiments, the aryl group contains at least 6, 7, 8, 9, or 10 carbon atoms. Polymers containing amide groups are characterized by infrared absorption spectroscopy, with the carbonyl group at 1900 cm². -1 ~1650cm -1 Absorption peaks located in the wavelength range, and the amide group at 3500 cm². -1 ~3100cm -1 A double absorption peak of intermediate intensity located in the wavelength range can be observed.

[0080] Nitrogen-containing groups or aryl groups in the polymer help improve the anchoring action between the polymer and the cathode active material. This makes the polymer particularly suitable for carbon-coated cathode active materials, further increasing its versatility as a dispersant. By increasing the anchoring sites of the dispersant, the polymer exhibits a more effective dispersing action, thereby further increasing the maximum solid content of the slurry, improving the molding quality of the electrode sheet, reducing costs, and enhancing effectiveness.

[0081] In some embodiments, the organic segment R2 contains C 2-12 It also contains hydrocarbon groups.

[0082] In this specification, "C 2-12 A "hydrocarbon group" refers to a linear or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, where unsaturation may or may not be present, and which has 2 to 12 carbon atoms, all bonded to the rest of the molecule by at least one single bond. 2-12 Examples of hydrocarbon groups include C 2-12 Alkyl alkyl group, C 2-12 Alkylene group, C 2-12 Alkenyl group, C 2-12 This includes, but is not limited to, alkenylene groups. Examples include ethylene, ethyl, n-propyl, 1-methylethyl (isopropyl), isopropylene, 1,3-propylene, butyl, isobutyl, tert-butyl, 1,4-butylene, 1,3-butylene, 2-butenylene, pentyl, isopentyl, neopentyl, hexyl, heptyl, and octyl groups. 2-12 The inclusion of hydrocarbon groups helps to further improve the anchoring and fixation of the polymer to the carbon-modified cathode active material. The hydrocarbon groups can effectively anchor and fix to the carbon on the cathode active material, increasing the dispersibility of the polymer's anchoring sites on the cathode active material. This further improves the applicability of the polymer dispersant, increases the maximum solid content of the slurry, optimizes the molding quality of the electrode sheet, reduces costs, and improves effectiveness.

[0083] In some embodiments, R2 includes the structure shown in formula II, [ka] In the formula, R4 and R5 copolymerize randomly, and R4 is C 2-12 Contains a hydrocarbylene group, C 3-13 It contains at least one of the amide groups, and R5 is [ka] It includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R6a R6 b is hydrogen, C 1-4 It contains at least one alkyl group, and satisfies 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10.

[0084] C 2-12 A hydrocarbylene group refers to a divalent hydrocarbon group having 2 to 12 carbon atoms. 2-12 Alkylene group, C 2-12 It contains an alkenylene group. For example, C 2-12The alkylene groups are 1,2-ethylene group, 1,2-propylene group, 1,3-propylene group, 1,3-butylene group, 1,4-butylene group, 2-methyl-1,3-propylene group, 1,1-dimethyl-1,2-ethylene group, 1,4-pentylene group, 1,5-pentylene group, 2-methyl-1,4-butylene group, 2,2-dimethyl-1,3-propylene group, 1,6-hexylene group, 2-methyl-1,5-pentylene group, 3-methyl-1,5-pentylene group, 2,3-dimethyl-1,4-butylene group, 1,7-heptylene group, 2-methyl-1,6-hexylene group, 3-methyl-1,6-hexylene group, and 2-ethyl-1 ,5-pentylene group, 3-ethyl group-1, ,5-pentylene group, 2,3-dimethyl-1, ,5-pentylene group, 2,4-dimethyl-1, ,5-pentylene group, 1,8-octylene group, 2-methyl-1, ,7-heptylene group, 3-methyl-1, ,7-heptylene group, 4-methyl-1, ,7-heptylene group, 2-ethyl group-1, 6-hexylene group, 3-ethyl group-1, ,6-hexylene group, 2,3-dimethyl-1, ,6-hexylene group, 2,4-dimethyl-1, ,6-hexylene group, 1,9-nonylene group, 2-methyl-1, ,8-octylene group, 3-methyl-1, ,8-octylene group, 4-methyl-1, ,8-octylene group, 2-ethyl group-1 This includes, but is not limited to, ,7-heptylene group, 3-ethyl group-1, ,7-heptylene group, 1,10-decylene group, 2-methyl-1, ,9-nonylene group, 3-methyl-1, ,9-nonylene group, 4-methyl-1, ,9-nonylene group, 5-methyl-1, ,9-nonylene group, 1,11-undecylene group, 2-methyl-1, ,10-decylene group, 3-methyl-1, ,10-decylene group, 5-methyl-1, ,10-decylene group, 1,12-dodecylene group.

[0085] C 2-12 An alkenylene group is a divalent hydrocarbon group containing at least one double bond. For example, C 2-12Alkenylene groups include, for example, vinylene group, propenylene group, 1-methylvinylene group, 1-butenylene group, 2-butenylene group, 1-methylpropenylene group, 2-methylpropenylene group, 1-pentenylene group, 2-pentenylene group, 1-methyl-1-butenylene group, 1-methyl-2-butenylene group, 1-hexenylene group, 2-hexenylene group, 3-hexenylene group, 1-methyl-1-pentenylene group, 1-methyl-2-pentenylene group, 1-methyl-3-pentenylene group, 1,4-dimethyl-1-butenylene group, 1 It contains a 4-dimethyl-2-butenylene group, a 1-heptenylene group, a 2-heptenylene group, a 3-heptenylene group, a 1-octenylene group, a 2-octenylene group, and a 3-octenylene group.

[0086] In some embodiments, C 3-13 The amide group is [ka] It includes x, and x is between 2 and 12, selectively between 2 and 5.

[0087] In some embodiments, x is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0088] In this specification, C 1-4 The alkyl group includes at least one of the following: a methyl group, an ethyl group, a propyl group, an isopropyl group, a 2-methyl-1-propyl group, or a 2-methyl-2-propyl group.

[0089] In some embodiments, s is one of 1, 2, 3, 4, 5, or 6.

[0090] In some embodiments, t is one of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0091] In some embodiments, q1, q2, q3, and q4 are each independently selected from 0, 1, 2, 3, or 4.

[0092] The organic segment with the above structure contains a nitrogen-containing group and a hydrocarbylene group, which allows it to exert an anchoring effect more effectively, improve the dispersion of the polymer, and effectively increase the solid content of the slurry.

[0093] In some embodiments, R2 includes the structure shown in formula III, [ka] In the formula, R6 is C 2-12 It contains a hydrocarbylene group, and R7 is [ka] It contains at least one of the following, and q5 and q6 each independently contain any integer from 0 to 4, and 1 ≤ n ≤ 6.

[0094] In some embodiments, q5 and q6 each independently include 0, 1, 2, 3, or 4.

[0095] In some embodiments, n is one of 1, 2, 3, 4, 5, or 6.

[0096] The organic segment with the above structure, through the alternating arrangement of nitrogen-containing groups and hydrocarbylene groups, exhibits a more effective anchoring effect, improves the dispersion of the polymer, and effectively increases the solid content of the slurry.

[0097] In some embodiments, the terminal group of R2 includes at least one of -C(O)-NH2 and -CH2-NH2.

[0098] Polymers containing terminal groups -C(O)-NH2 and -CH2-NH2 can exhibit more effective dispersion, increase the maximum solid content of the slurry, and further improve the molding quality and efficiency of electrode sheets.

[0099] In some embodiments, at least one of R1 and R3 contains a polyether segment. In some embodiments, both R1 and R3 contain a polyether segment. Polymers containing polyether segments are characterized by infrared absorption spectroscopy, where the absorption peak of the ether bond is 1250–1100 cm⁻¹. -1 It can be observed that it is located within a specific wavelength range.

[0100] In some embodiments, R2 includes at least one of H and an aryl group.

[0101] In some embodiments, one of R1 and R3 includes a polyether segment, and the other includes C 1-4 Contains alkyl groups.

[0102] In some embodiments, both R1 and R3 include a polyether segment.

[0103] Both R1 and R3 contain polyether segments, which means that at least one of R1 and R3 contains a polyether segment and the other contains C 1-4 Compared to containing alkyl groups, polymers further optimize the filterability of the slurry and further improve the flexibility of the electrode sheet.

[0104] In some embodiments, at least one of R1 and R3 includes a polyether segment represented by formula IV, [ka] In the formula, EO represents -CH2-CH2-O- and PO represents -CH(CH3)-CH2-O-, and 4≦m1≦50 and 4≦n1≦50.

[0105] In some embodiments, the polyether segment is a block copolymer segment. In some embodiments, the polyether segment is a random copolymer segment.

[0106] In some embodiments, m1 and n1 may be any number independently selected from 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, or any two of them.

[0107] The polyether segment having the above structure possesses appropriate steric hindrance and a low glass transition temperature, which more effectively reduces the order and glass transition temperature of the binder crystals in the positive electrode slurry, thereby lowering the crystallinity of the binder and improving the flexibility of the electrode sheet. Through dispersion and flexibility, it improves the uniformity and flexibility of the electrode sheet, thereby improving the safety and critical pressure density of the battery, increasing the load of the positive electrode active material in the battery, and contributing to a further improvement in the energy density of the battery.

[0108] In some embodiments, the terminal groups of the polyether segment include aryl groups.

[0109] The aryl groups and the carbon layer on the surface of the cathode active material exhibit excellent compatibility, further improving the anchoring and fixation of the polymer and the carbon-modified cathode active material. The effective anchoring and fixation of the aryl groups and carbon on the cathode active material increases the dispersibility of the anchoring sites of the polymer on the cathode active material, thereby further improving the applicability of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the molding quality of the electrode sheet, reducing costs, and improving effectiveness.

[0110] In some embodiments, X includes a phosphate group.

[0111] Phosphate polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode sheet. Furthermore, phosphate polymers possess higher stability and, in addition to improving slurry dispersibility, can effectively improve the battery's cycle capacity retention rate.

[0112] In some embodiments, the polymer comprises at least one polymer represented by the following formula: [ka] In the formula, at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV, [ka] In the formula, EO represents -CH2-CH2-O- and PO represents -CH(CH3)-CH2-O-, and 4≦m1≦15 and 4≦n1≦15.

[0113] In some embodiments, R6 and R4 are independently C 4-8 Alkylene group, C 4-8 It contains at least one of the alkenylene groups.

[0114] In some embodiments, R6 and R4 are independently [ka] It includes at least one of the bases.

[0115] In some embodiments, the terminal groups of the polyether segment include phenyl groups.

[0116] In some embodiments, the polymer is represented by the following formula: [ka] In the formula, R2 comprises at least one of hydrogen, an aryl group, a substituted or unsubstituted alkyl group, an amino group, or an amide group in an organic segment, and at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV. [ka] In the formula, EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≦m1≦50, 4≦n1≦50, and the terminal group of the polyether segment contains a phenyl group.

[0117] In some embodiments, the weight-average molecular weight of the polymer is 1000 to 10000. In some embodiments, the weight-average molecular weight of the polymer is 2000 to 5000.

[0118] Weight-average molecular weight has a known meaning in this art and can be tested by methods known in this art. For example, weight-average molecular weight can be tested by gel chromatography.

[0119] In some embodiments, the weight-average molecular weight of the polymer is 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, or any number in between.

[0120] Polymers with a weight-average molecular weight within the above range exhibit excellent dispersibility, can further increase the solid content of the slurry, and can also provide the slurry with excellent flowability, reduce coating time, and improve coating uniformity and speed. A weight-average molecular weight of 2000-5000 allows for more effective dispersion, increases the maximum solid content of the slurry, and shortens filtration time.

[0121] A second aspect of this application provides a method for preparing a polymer. The preparation method is as follows: The process includes the step of reacting a compound represented by formula VI with a polymerization monomer containing R3OH, R1OH, water, and an unsaturated bond to prepare a polymer having the structure represented by formula I. [ka] In the formula, X comprises a phosphate group or a phosphite group, X1, X2, and X3 each comprises a halogen, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, or a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment.

[0122] In this specification, halogens include at least one of fluorine, chlorine, bromine, and iodine.

[0123] In some embodiments, in formula VI, phosphorus and oxygen are bonded via a double bond, and in formula I, X is a phosphate group.

[0124] In some embodiments, formula VI does not contain oxygen, and in formula I, X is a phosphite group.

[0125] In some embodiments, formula VI includes POCl3 or PCl3.

[0126] In some embodiments, the preparation method is The first step involves reacting the compound represented by formula VI with R3OH, R1OH, and water to prepare the intermediate product represented by formula VII. [ka] The process includes the step of reacting the intermediate product with a polymerization monomer containing at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer.

[0127] In some embodiments, the first reaction is, specifically, The reaction involves adding R3OH dropwise to the compound represented by formula VI under stirring conditions, maintaining the reaction temperature below 20°C, stirring for a certain period of time, then raising the temperature to 40-50°C and reacting for 6-7 hours, followed by the addition of water, and reacting at 50-60°C for 3-4 hours to obtain the first intermediate product represented by formula A. The molar ratio of R3OH added during the reaction to the compound represented by formula VI is 1.2-1.5, and R3 is C 1-4 Contains alkyl groups, [ka]

[0128] The above reaction conditions are advantageous for improving the purity of the product.

[0129] In some embodiments, the first reaction is The method further comprises reacting a polyether with a first intermediate product under conditions of 100°C to 120°C for 4 to 7 hours to obtain an intermediate product represented by formula VII, where R1 comprises a polyether segment.

[0130] In some embodiments, the second reaction is, specifically, The intermediate product is subjected to an addition reaction with at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond, and then further subjected to a substitution reaction with a halogen-substituted organic alcohol. The process involves preparing the polymer by repeating the above addition reaction and substitution reaction multiple times, R2 includes the structure shown in Equation III, [ka] In the formula, R6 is C 2-12 It contains a hydrocarbon group, and R7 is [ka] It contains at least one of the following, and q5 and q6 each independently contain any integer from 0 to 4, and 1 ≤ n ≤ 6.

[0131] An addition reaction is a reaction in which a π bond in a double bond is broken, and two single bonds are formed.

[0132] A substitution reaction is a chemical reaction in which one atom or group replaces another atom or group in an organic molecule.

[0133] In some embodiments, the preparation method is The process further comprises the step of a third reaction in which the intermediate product is reacted with (i) at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond or a cyclic amide monomer, thereby preparing the polymer, wherein R2 comprises the structure shown in formula II. [ka] In the formula, R4 and R5 copolymerize randomly, and R4 is C 2-12 hydrocarbon group, C 3-13 It contains at least one of the amide groups, and R5 is [ka] It includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R6 a R6 b is hydrogen, C 1-4 It contains at least one alkyl group, and satisfies 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10.

[0134] In some embodiments, the hydrocarbon monomer containing an unsaturated bond includes at least one of olefin monomers, alkyne monomers, and cyclic alkanes.

[0135] In some embodiments, a cyclic amide monomer refers to a cyclic monomer containing an amide bond.

[0136] In some embodiments, the third reaction specifically involves mixing the intermediate product with at least one of a hydrocarbon monomer or cyclic amide monomer containing an unsaturated bond and reacting them for a certain period of time, followed by the addition of at least one of an amide or amine containing an unsaturated bond to induce a copolymerization reaction.

[0137] In some embodiments, the preparation method is The method further includes the step of preparing a polymer having amide or amino groups as terminal groups by capping a polymer having hydroxyl groups as terminal groups with an unsaturated monomer containing an amide or amino group.

[0138] This application provides a method for preparing polymers. The preparation method is as follows: The process includes the step of reacting a compound represented by formula VI with a starting material containing R3OH and R1OH to prepare a polymer having the structure represented by formula I, [ka] In the formula, X comprises a phosphate group or a phosphite group, X1, X2, and X3 each comprise a halogen, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment, at least one terminal group of the polyether segment comprises an aryl group, and R2 comprises an organic segment.

[0139] In some embodiments, the monomer represented by formula VI is reacted with R1OH and R3OH in an inert, alkaline environment, and then water or phenol is added and reacted to obtain a polymer.

[0140] In some embodiments, a polymer in which R2 contains a hydroxyl group is subsequently subjected to a second reaction with a polymerization monomer containing at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond to prepare a polymer in which R2 contains nitrogen.

[0141] In some embodiments, polymers prepared by any embodiment of this application and polymers prepared by any embodiment of this application are used as dispersants.

[0142] In some embodiments, polymers prepared according to any embodiment of this application and polymers prepared by the preparation method of any embodiment of this application are used as dispersants in electrode sheet slurries of secondary batteries.

[0143] In some embodiments, polymers prepared according to any embodiment of this application and polymers prepared by the preparation method of any embodiment of this application are used as dispersants in the positive electrode slurry of a secondary battery.

[0144] [Positive electrode slurry] A third aspect of this application provides a cathode slurry comprising a dispersant containing a polymer in any embodiment or a polymer prepared by the preparation method of any embodiment.

[0145] The positive electrode slurry has a high solid content, which improves the molding efficiency and quality of the positive electrode film layer, and helps to enhance the electrochemical expression and processing efficiency of the battery.

[0146] In some embodiments, the positive electrode slurry includes a positive electrode active material comprising at least one lithium-containing phosphate and a carbon-modified material thereof.

[0147] In some embodiments, the lithium-containing phosphate comprises at least one of lithium iron phosphate and its doping material, or lithium manganese iron phosphate and its doping material. In some embodiments, the doping material comprises doping material of any site and is selectively lithium site doping, phosphate site doping, manganese site doping, or iron site doping.

[0148] In some embodiments, the carbon-modified material includes at least one of a carbon-coated material and a carbon-doped material.

[0149] In some embodiments, the positive electrode active material includes at least one of lithium iron phosphate and its doping material, lithium iron manganese phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, and lithium iron manganese phosphate and its doping material.

[0150] The polymer exhibits electronegative properties and can further strengthen its mutual anchoring with lithium-containing phosphate, which exhibits weak acidity, through electrostatic action, thereby improving the dispersive effect of the polymer with respect to lithium-containing phosphate. Furthermore, since lithium-containing phosphate has poor conductivity, its conductivity is often improved during the preparation of the positive electrode active material by sintering organic materials such as glucose and sucrose and coating them with a carbon layer. The polymer simultaneously possesses groups that anchor and fix to the carbon coating layer, and also exhibits excellent dispersive properties with respect to carbon-modified lithium-containing phosphate, further improving the dispersibility of the slurry and increasing the maximum solid content of the slurry.

[0151] In some embodiments, the positive electrode active material comprises a core and a carbon coating layer, the carbon coating layer covering at least a portion of the surface of the core, and sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of the hybridized carbon atoms is 0.2 or greater. In some embodiments, sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of the hybridized carbon atoms is 0.5 or greater. In some embodiments, sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is 0.8 or higher.

[0152] In some embodiments, sp2 hybridized carbon atoms and sp2 carbon atoms in the carbon coating layer 3 The molar ratio of the hybridized carbon atoms is selectively a numerical range between 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or any two of these values.

[0153] The carbon structure and characteristics of the carbon coating layer can be measured by methods known in this art. For example, it can be measured by Raman spectroscopy. Specifically, the Raman spectrum of the positive electrode active material is measured first, and then peak splitting is performed on the energy spectrum of the Raman measurement to obtain the Ig / Id ratio (where Id is sp). 3 This is the peak intensity of hybridized carbon atoms, where Ig is sp 2 This is the peak intensity of the hybridized carbon atoms, and the ratio of these peak intensities is i.e., sp 2 Peak height and sp of hybridized carbon atoms 3 The ratio of the peak heights of the hybridized carbon atoms is obtained, and sp 2 Hybrid carbon and sp 3 Obtain the molar ratio of the mixed carbon. Determine the sp in the carbon coating layer of the positive electrode active material. 2 Hybrid carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is not particularly limited; for example, sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of hybridized carbon atoms may be 0.5 or higher, and in some examples, sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 The molar ratio of hybrid carbon atoms may be 0.8 or higher. sp in the carbon coating layer 2 Hybrid carbon atoms and sp 3 When the molar ratio of the mixed carbon atoms is within the above range, the carbon coating layer on the core surface has a high degree of graphitization, the structure of the carbon coating layer is denser, which not only reduces the water absorption of the carbon coating layer but also ensures good conductivity of the carbon coating layer and guarantees the passage of lithium ions, which is advantageous for improving the cycle performance and safety of the positive electrode active material.

[0154] In some embodiments, the core comprises a phosphate, and in some embodiments, the phosphate comprises at least one of lithium manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, and doping materials thereof.

[0155] By forming a carbon coating layer on the core surface, the conductivity of the positive electrode active material can be improved. In the carbon coating layer on the core surface, when the molar ratio of sp 2 hybrid carbon atoms to sp3 hybrid carbon atoms is 0.5 or more, the regularity of the carbon coating layer structure of the positive electrode active material is high, the pore structure of the carbon coating layer has high density and a small pore size distribution range. In the battery production process, it is difficult for external moisture to enter the pores of the carbon coating layer, thereby effectively reducing the water absorption and water storage performance of the positive electrode active material, realizing the improvement of the battery safety and cycle performance, effectively saving the energy consumption in the drying process, and significantly reducing the production cost.

[0156] However, since the graphitization degree of the carbon coating layer with a molar ratio of sp 2 hybrid carbon atoms to sp 3 hybrid carbon atoms of 0.5 or more is high, the positive electrode active material is likely to aggregate and is difficult to disperse effectively during the slurry preparation process. The dispersant provided in the embodiments of the present application has abundant anchor groups for the carbon coating layer with a high graphitization degree, and is particularly suitable for dispersing the positive electrode active material with a high graphitization degree of the coating layer. The combination of the two can improve the battery use performance and processing performance simultaneously.

[0157] In some embodiments, the core is Li 1+x Mn 1-y A y P 1-z R zIt contains O4, where x is any numerical value within the range from -0.100 to 0.100, y is any numerical value within the range from 0.001 to 0.500, z is any numerical value within the range from 0.001 to 0.100, A contains one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R contains one or more elements selected from B (boron), S, Si, and N. The manganese site doping element A selected from the above elements reduces the lattice change rate of lithium manganese phosphate in the lithium desorption and insertion process of the material, improves the structural stability of the cathode active material, significantly reduces the elution of manganese, and helps reduce the oxygen activity on the particle surface. The phosphorus site doping element R selected from the above elements also helps to change the ease of change of the Mn - O bond length, thereby improving electron conduction, reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the rate performance of the secondary battery.

[0158] Unless otherwise specified, in the chemical formula of the above core, when two or more elements are included in a certain doping site, the above limitations on the numerical ranges of x, y, z, or m are not only limitations on the stoichiometric numbers of each element at the site, but also limitations on the sum of the stoichiometric numbers of each element at the site. For example, when the chemical formula is Li 1+x Mn 1-y AyP 1-z R z For a compound with O4, when A is two or more elements A1, A2... An, the stoichiometric numbers y1, y2... yn of each of A1, A2... An must all fall within the numerical range limited for y in this application, and the sum of y1, y2... yn must also fall within this numerical range. Similarly, when R is two or more elements, the limitation on the numerical range of the stoichiometric number of R in this application also has the above meaning.

[0159] According to some embodiments of this application, the type of the core is not particularly limited. For example, the core is Li 1+x C m Mn 1-y A y P 1-z Rz O 4-n D nIt may include, and the magnitude of x is influenced by the magnitudes of the valencies of A and R and the magnitudes of y and z to ensure that the entire system is electrically neutral. If the value of x is too small, the lithium content of the entire core system will decrease, affecting the capacity per gram of the material. More specifically, x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.500, z is any number in the range of 0.001 to 0.100, n is any number in the range of 0.001 to 0.1, and m is any number in the range of 0.9 to 1.1. For example, 1+x is selected from the range of 0.9 to 1.1, e.g., 0.97, 0.977, 0.984, 0.988, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 1.01, x is selected from the range of 0.001 to 0.1, e.g., 0.001, 0.005, and y is selected from the range of 0.001 to 0.5, e.g., 0.00 The values ​​are 1, 0.005, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.34, 0.345, 0.349, 0.35, and 0.4, z is selected from the range of 0.001 to 0.1, for example 0.001, 0.005, 0.08, and 0.1, n is selected from the range of 0.001 to 0.1, for example 0.001, 0.005, 0.08, and 0.1, and the positive electrode active material is electrically neutral. C contains one or more elements from Zn, Al, Na, K, Mg, Nb, Mo, and W; A contains one or more elements from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; R contains one or more elements from B (boron), S, Si, and N; and D contains one or more elements from S, F, Cl, and Br. By simultaneously doping specific elements in specific amounts at the Li, Mn, P, and O sites of the compound, significantly improved rate performance can be obtained, the elution of Mn and Mn site-doped elements can be significantly reduced, significantly improved cycle performance and / or high-temperature stability can be obtained, and the volume and pressure density per gram of the positive electrode active material can also be improved.

[0160] In some embodiments, the thickness of the carbon coating layer is 15 nm or less. In some embodiments, the thickness of the carbon coating layer is 10 nm or less. In some embodiments, the thickness of the carbon coating layer is 4 nm to 8 nm.

[0161] In some embodiments, the thickness of the carbon coating layer is selectively a numerical range of 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or any two of these.

[0162] The thickness of the carbon coating layer can be obtained by testing using the following method: A thin section approximately 100 nm thick is cut from the center of a single particle of the positive electrode active material using FIB (Fibrillation Isolation). Then, a transmission electron microscope (TEM) test is performed on the thin section to obtain the original image of the TEM test, which is saved in the original image format (xx.dm3). The original image obtained from the above TEM test is opened with Digital Micrograph software, and the carbon coating layer is identified based on the grid spacing and angle information, and the thickness of the carbon coating layer is measured. The thickness is measured at three locations for the selected particle, and the average value is obtained.

[0163] A carbon coating layer within the above thickness range can effectively improve the conductivity of the positive electrode active material by forming a thin carbon coating layer on the core surface, and can also improve the compaction performance when manufacturing the electrode sheet of a battery using the positive electrode active material.

[0164] In some embodiments, the positive electrode active material is The material is prepared by preparing a core and forming a carbon coating layer on at least a portion of the surface of the core, wherein the molar ratio of sp2 hybridized carbon atoms to sp3 hybridized carbon atoms in the carbon coating layer is 0.2 or higher, and selectively 0.5 or higher.

[0165] In some embodiments, forming a carbon coating layer on at least a part of the surface of the core includes obtaining a preliminarily coated cathode active material by forming a preliminary carbon coating layer on the core surface with a carbon source, and sintering the preliminarily coated cathode active material to form the carbon coating layer to obtain the cathode active material. The carbon source includes a first carbon source and a second carbon source.

[0166] In some embodiments, obtaining a preliminarily coated cathode active material by forming a preliminary carbon coating layer on the core surface, and the method for forming the preliminary carbon coating layer on the core surface is not particularly limited. For example, the carbon source and the core can be placed in the same reaction vessel, and the carbon source can be reacted on the core surface by hydrothermal treatment to form a carbon coating layer on the core surface. The carbon source and the core can also be placed in a ball milling device, such as a sand mill, and the carbon source can form a carbon coating layer on the core surface by mechanical mixing. In some embodiments, the carbon source includes a first carbon source and a second carbon source. The first carbon source includes at least one of polyvinyl alcohol, polyethylene glycol, and citric acid. The second carbon source includes at least one of starch, sucrose, and glucose. In some examples, the molecular weight of the first carbon source is 1000 or more. In some other embodiments, the molecular weight of the first carbon source may be 2000 - 5000. Thereby, a preliminary carbon coating layer with uniform distribution and consistent thickness can be formed on the core surface by ball milling treatment, which is helpful for forming a dense and uniform pore structure of the carbon coating layer after sintering treatment as well. In some embodiments, the second carbon source may include at least one of starch, sucrose, and glucose. In some examples, the second carbon source may be glucose.

[0167] In some embodiments, the preliminarily coated positive electrode active material is sintered under an inert gas atmosphere. In some embodiments, the preliminarily coated positive electrode active material is sintered to obtain a positive electrode active material. The sintering process should be carried out under an inert atmosphere to avoid the carbon source from undergoing an oxidation reaction and being unable to obtain a carbon coating layer with a high degree of graphitization. The type of inert gas is not particularly limited. For example, the inert gas may contain at least one of nitrogen and helium. The conditions of the sintering process are not particularly limited. For example, the temperature of the sintering process may be 650°C to 800°C, and the time of the sintering process may be 6h to 12h. Thereby, a carbon coating layer with a high degree of graphitization can be formed on the core surface. As the temperature of the sintering process increases, the degree of graphitization of carbon in the carbon coating layer also increases. By controlling the maximum sintering temperature of the sintering process, the degree of graphitization of the carbon coating layer can be effectively controlled, and the carbon coating layer has a dense pore structure and excellent conductivity.

[0168] In some embodiments, forming a carbon coating layer on at least a part of the surface of the core includes mixing the core with a first carbon source and obtaining a first coated positive electrode active material by a first sintering process, mixing the first coated positive electrode active material with a second carbon source, and obtaining the positive electrode active material by a second sintering process.

[0169] In some embodiments, the temperature of the first sintering process is 350°C to 800°C, and the time of the first sintering process is 6h to 12h. In some embodiments, the temperature of the second sintering process is 650°C to 850°C, and the time of the second sintering process is 6h to 24h.

[0170] In some embodiments, based on the total mass of the dry materials of the positive electrode slurry, the mass content of the polymer is 0.1% to 2.0%. In some embodiments, based on the total mass of the dry materials of the positive electrode slurry, the mass content of the polymer is 0.2% to 1.0%.

[0171] In some embodiments, the mass content of the polymer in the total mass of the dry material of the positive electrode slurry is selectively 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any value in between. Polymers within the above range can not only perform an effective dispersion effect but also maintain the volumetric energy density of the battery without seriously adversely affecting the electrochemical expression of the battery.

[0172] In some embodiments, the positive electrode slurry contains a binder comprising a vinylidene fluoride polymer with a weight-average molecular weight of 300,000 or more. In some embodiments, the weight-average molecular weight of the binder is between 700,000 and 9,000,000.

[0173] In some embodiments, the vinylidene fluoride polymer is a vinylidene fluoride homopolymer.

[0174] In some embodiments, the vinylidene fluoride polymer is a vinylidene fluoride copolymer.

[0175] The weight-average molecular weight has a known meaning in this art and can be tested by any known method. In some embodiments, the weight-average molecular weight of the binder is characterized by gel chromatography.

[0176] In some embodiments, the weight-average molecular weight of the binder is selectively 700,000, 1,000,000, 2,000,000, 3,000,000, 4,000,000, 5,000,000, 6,000,000, 7,000,000, 8,000,000, 9,000,000, or any number in between.

[0177] Vinylidene fluoride polymers with a weight-average molecular weight in this range possess excellent binding properties and electrochemical stability. By using vinylidene fluoride polymers with a weight-average molecular weight of 700,000 to 9,000,000, the amount of vinylidene fluoride used can be further reduced, decreasing the rigidity of the positive electrode film layer, improving the flexibility of the electrode sheet, and further increasing the critical pressure density of the battery, thus contributing to an improvement in the battery's energy density.

[0178] In some embodiments, the maximum solid content of the positive electrode slurry is 60% or more. In some embodiments, the maximum solid content of the positive electrode slurry is 60% to 80%.

[0179] The maximum solid content of a positive electrode slurry refers to the maximum solid content of a slurry that satisfies the following conditions: the shipping viscosity is 4000 to 35000 MPa.s, and no gel phenomenon occurs after the slurry has been left to stand for 24 hours. For the actual test method of the solid content of the positive electrode slurry, take a slurry with a weight denoted as m0, place it in a weight loss rate test apparatus, evaporate the solvent until the slurry's weight loss rate is less than 0.3%, and denot the remaining weight as m1. The solid content = m1 / m0 * 100%.

[0180] In some embodiments, the maximum solid content of the positive electrode slurry is selectively 60%, 65%, 70%, 75%, 80%, or any number in between.

[0181] By adding a polymer to the positive electrode slurry, the solid content and flexibility of the slurry are effectively improved, thereby improving the flexibility and molding efficiency of the electrode sheet.

[0182] [Positive electrode sheet] This application further provides a positive electrode sheet, the positive electrode sheet comprising a positive electrode film layer, the positive electrode film layer being prepared from a positive electrode slurry of any embodiment, or the positive electrode film layer comprising a dispersant, the dispersant comprising a polymer of any embodiment or a polymer prepared by a preparation method of any embodiment.

[0183] In some embodiments, the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0184] In some embodiments, a metal foil or a composite current collector can be used as the positive electrode current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0185] In some embodiments, the pressure density of the positive electrode sheet is 2.6 g / cm³. 3 In this case, the number of folds is two or more. In some embodiments, the pressure density of the positive electrode sheet is 2.6 g / cm³. 3 In that case, the number of times it needs to be folded in half is 3 to 6 times.

[0186] The pressure density of the positive electrode sheet is 2.6 g / cm³. 3 The number of folds in this case can be used to characterize the flexibility of the electrode sheet and can be measured by any known method. For example, a defect-free sheet with a pressure density of 2.6 g / cm³. 3 Take a positive electrode sheet and cut it lengthwise into samples measuring 25cm x 4cm, with a sample count of ≥ 4 pieces. First, fold each sample in half lengthwise (25cm direction), then place the sample on a test bench and roll-press it once with a 2kg cylindrical press roll. If light passes through, the number of light transmissions for brittleness is 1. If light does not pass through, repeat the process of folding in half in the opposite direction and roll-pressing. Observe the folds with light to see if light passes through or if the sample breaks, record the actual number of folds, perform the test 4 times, and use the average value as the test result.

[0187] In some embodiments, when the tap density of the positive electrode sheet is 2.6 g / cm 3 the number of double folds is selectively 2, 3, 4, 5 or 6 times.

[0188] The polymer can not only effectively increase the solid content of the slurry, but also act as a flexibilizer to improve the flexibility of the positive electrode sheet and further improve the safety and electrochemical performance of the battery.

[0189] In some embodiments, the areal density of the positive electrode sheet is 300 mg / 1540.25 cm 2 or more. In some embodiments, the areal density of the positive electrode sheet is 300 mg / 1540.25 cm 2 ~600 mg / 1540.25 cm 2 is.

[0190] In some embodiments, the areal density of the positive electrode sheet is 300 mg / 1540.25 cm 2 , 400 mg / 1540.25 cm 2 450 mg / 1540.25 cm 2 500 mg / 1540.25 cm 2 600 mg / 1540.25 cm 2 or any numerical value therebetween. The areal density of the electrode sheet has a known meaning and can be measured by any known method.

[0191] In some embodiments, the positive electrode sheet contains lithium iron phosphate, and the areal density of the positive electrode sheet is 360 mg / 1540.25 cm 2 or more. In some embodiments, the areal density of the positive electrode sheet is 360 mg / 1540.25 cm 2 ~600 mg / 1540.25 cm 2 is.

[0192] In some embodiments, the positive electrode sheet contains lithium manganese iron phosphate, and the areal density of the positive electrode sheet is 300 mg / 1540.25 cm ; 2That concludes the explanation. In some embodiments, the surface density of the positive electrode sheet is 300 mg / 1540.25 cm². 2 ~600 mg / 1540.25 cm 2 That is the case.

[0193] The polymer can effectively increase the maximum solid content of the slurry, thereby accelerating the coating speed by more than 30%, making it particularly suitable for high-speed coating and thick coating molding methods. It effectively solves the problem of electrode sheets being prone to cracking during the thick coating process, and its high flexibility helps in the production of crack-free positive electrode sheets after winding molding.

[0194] In some embodiments, the positive electrode film layer comprises a dispersant, and the dispersant comprises a structure represented by formula I. [ka] In the formula, X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, or a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, R2 comprises an organic segment, selectively comprising at least one of an amide group or an amino group in the organic segment of R2, selectively comprising an aryl group as the terminal group of the polyether segment, the positive electrode active material comprises at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, selectively comprising at least one of lithium manganese iron phosphate and its doping material, and the mass content of the dispersant in the total mass of the positive electrode film layer is 0.1% to 2.0%, selectively 0.2% to 1.0%.

[0195] The positive electrode film layer has good dispersibility and processability, which is advantageous for simultaneously improving manufacturing efficiency and battery performance. In some embodiments, the positive electrode film layer further selectively comprises a conductive agent. For 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.

[0196] In some embodiments, the positive electrode sheet can be manufactured as follows: Components for manufacturing the above-mentioned positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and a dispersant, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, the positive electrode slurry is applied to a positive electrode current collector, and the positive electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0197] [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, the negative electrode film layer containing a negative electrode active material.

[0198] For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0199] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0200] In some embodiments, known negative electrode active materials for batteries in the art can be used as the negative electrode active material. 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 elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxygen compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0201] In some embodiments, the negative electrode film layer selectively further comprises a binder. The binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide group (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0202] In some embodiments, the negative electrode film layer further selectively comprises a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0203] In some embodiments, the negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0204] In some embodiments, the negative electrode sheet can be manufactured as follows: Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is applied to a negative electrode current collector; and the negative electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0205] [Electrolyte] The electrolyte plays a role in conducting 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-like, or all-solid.

[0206] In some embodiments, the electrolyte is an electrolyte solution, which comprises an electrolyte salt and a solvent.

[0207] 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.

[0208] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethylmethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl 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, ethylmethyl sulfone, and diethyl sulfone.

[0209] In some embodiments, the electrolyte selectively further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may further include additives that can improve certain aspects of the battery's performance, such as additives that can improve the battery's overcharge performance or additives that can improve the battery's high-temperature or low-temperature performance.

[0210] [Separator] In some embodiments, the secondary battery further includes a separator. In this application, the type of separator is not particularly limited, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0211] In some embodiments, the material of the separator may be at least one 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. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0212] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be assembled into an electrode assembly by a winding process or a lamination process.

[0213] In some embodiments, the secondary battery may include an casing. This casing can be used to enclose the electrode assembly and electrolyte.

[0214] In some embodiments, the casing of the secondary battery may be a rigid case, such as a hard plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft pack, such as a bag-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0215] [Secondary battery] Another aspect of this application provides a secondary battery including a positive electrode sheet of any embodiment.

[0216] In this application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 2 shows a rectangular secondary battery 5 as an example. The secondary battery may be a sodium-ion battery, a magnesium-ion battery, or a potassium-ion battery.

[0217] In some embodiments, referring to Figure 3, the casing 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 and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening and seal the housing cavity. The positive electrode sheet, negative electrode sheet and separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and a person skilled in the art can select one according to specific practical requirements.

[0218] [Battery Module] In some embodiments, the secondary battery may be assembled as a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0219] Figure 4 shows an example of a battery module 4. Referring to Figure 4, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by fastening members.

[0220] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0221] [Battery pack] In some embodiments, the battery modules may be assembled as a battery pack, and the number of battery modules included in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0222] Figures 5 and 6 show an example of a battery pack 1. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided within the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged within the battery box in any manner.

[0223] [Electrical equipment] In one embodiment of this application, an electrical device is provided that includes at least one of a secondary battery of any embodiment, a battery module of any embodiment, or a battery pack of any embodiment.

[0224] The electrical device includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device includes, 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 and satellites, energy storage systems, etc.

[0225] The aforementioned electrical device can be selected as a secondary battery, battery module, or battery pack, depending on its intended use.

[0226] Figure 7 shows an example of an electrical device. This electrical device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the requirements for high power output and high energy density of secondary batteries, this electrical device may use a battery pack or battery module.

[0227] Other examples of devices may include mobile phones, tablet computers, and laptop computers. These devices are typically required to be lightweight and thin, and may use rechargeable batteries as a power source.

[0228] Examples Examples of the present application are described below. The examples described below are illustrative and are for interpretive purposes only, and should not be understood as limiting this application. Unless otherwise specified in the examples, specific techniques or conditions are followed in accordance with the techniques or conditions described in the literature in the art or in the specifications of the products. Unless otherwise specified, the reagents or equipment used are common products available commercially.

[0229] Example 1 1) Preparation of dispersant: Preparation of the first intermediate product POCl3 was added to a four-necked flask equipped with a thermometer, stirrer, and hydrogen chloride gas collector. R3OH was added dropwise while stirring, and the reaction temperature was maintained below 20°C. After stirring for 20 minutes, the temperature was raised to 40-50°C, where n(POCl3):n(R3-OH) was 1.2-1.5. After reacting for 6-7 hours, a fixed amount of distilled water was added dropwise to the system, and the reaction was carried out at 55°C for 3.5 hours to prepare the first intermediate product. A yield of ≥95% of the first intermediate product can be achieved by controlling the reaction parameters, where R3 is -CH2CH3.

[0230] [ka]

[0231] Preparation of the second intermediate product: 1,2-propanediol (ethylene oxide, propylene oxide monomer, 0.4% of the total mass of the first intermediate product) and concentrated sulfuric acid (0.3% of the total mass) solids are weighed and placed in the reaction vessel, the lid of the reaction vessel is closed and the fixing bolts are tightened with a wrench. The reaction vessel is evacuated and replaced three times with high-purity nitrogen gas, and ethylene oxide and propylene oxide are added sequentially with a molar ratio of n2:m2. A block polymerization reaction is carried out, and the pressure is maintained at 0.3±0.05 MPa and the temperature at 115±5°C during the reaction process. After 5 hours of reaction, the first intermediate product is added and the reaction is carried out for 5 hours under conditions of 115±5°C to produce the second intermediate product. A schematic diagram of the reaction process is shown below, where A1 is [ka] So, n2 is 25, m2 is 25, and R3 is -CH2CH3.

[0232] [ka]

[0233] Polymer preparation: The second intermediate product was added to acrylamide at room temperature for 12 hours, and then HO(CH2)4Cl was added and the mixture was substituted for 6 hours under alkaline conditions at room temperature. The addition and substitution reactions were then repeated once to prepare the product represented by formula X in the following figure, where R6 is -(CH2)4- and n is 2. The weight-average molecular weight of the polymer is 3109.

[0234] [ka]

[0235] 2) Preparation of the positive electrode slurry: Carbon-coated lithium iron phosphate (LFP@C), the positive electrode active material, carbon black (SP), the conductive agent, polyvinylidene fluoride (PVDF), the binder, and the dispersant (the polymer mentioned above) were added to N-methylpyrrolidone (NMP) in a mass ratio of 96.5:2:1:0.5. The mass fraction of the dispersant was 0.5% of the dry material in the slurry, and the weight-average molecular weight of PVDF was 700,000. The sp in the carbon coating layer of lithium iron phosphate... 2 Hybrid carbon atoms and sp 3 The molar ratio of the hybridized carbon atoms is 0.271.

[0236] 3) Manufacturing of positive electrode sheets: The positive electrode slurry is uniformly applied to two surfaces of an aluminum foil positive electrode current collector, then dried to obtain a film layer, followed by cold pressing and cutting to obtain a positive electrode sheet. The surface density of the positive electrode sheet is 450 mg / 1540.25 mm². 2 That is the case.

[0237] 4) Manufacturing of negative electrode sheets Artificial graphite, a negative electrode active material, carbon black, a conductive agent, styrene-butadiene rubber (SBR), a binder, and sodium carboxymethylcellulose (CMC), a thickener, were dissolved in deionized water, a solvent, in a weight ratio of 96:2:1:1. After uniform mixing, a negative electrode slurry was obtained. This negative electrode slurry was then uniformly applied multiple times to two surfaces of copper foil, which served as the negative electrode current collector. The negative electrode sheet was then obtained by oven drying, cold pressing, and cutting.

[0238] 5) Separator A polypropylene film is used as the separator.

[0239] 6) Preparation of the electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethylmethyl carbonate (EMC), which are organic solvents, were uniformly mixed in a volume ratio of 3 / 7. LiPF6 lithium salt was dissolved in the organic solvent to obtain a solution with a mass content of 12.5%, thus obtaining the electrolyte.

[0240] 7) Manufacturing of secondary batteries The positive electrode sheet, separator, and negative electrode sheet manufactured in Example 1 were stacked in this order so that the separator would separate the positive and negative electrode sheets, then wound up to obtain a bare cell, tabs were welded to the bare cell, the bare cell was placed in an aluminum case, baked at 80°C to remove water, and then immediately injected electrolyte and sealed to obtain an uncharged battery. The uncharged battery was subjected to processes such as standing, hot pressing, cold pressing, chemical conversion, molding, and capacity testing to obtain the lithium-ion battery product of Example 1.

[0241] Example 2 The preparation method is similar to that of Example 1, differing only in the type of dispersant used. The first two steps in the dispersant synthesis process are consistent with Example 1, and the nitrogen-containing monomer added in the third step is 3-amino-1-propene. The structural formula of the dispersant is as follows, where R1, R3, R6, and n are consistent with those in Example 1.

[0242] [ka]

[0243] Example 3 The preparation method is similar to that of Example 1, differing only in the type of dispersant used. The two steps preceding the dispersant synthesis process are consistent with Example 1, and the polymer preparation process in the third step is as follows.

[0244] Butadiene was added to the second intermediate product and reacted at 100°C for 0.5 hours. Then, acrylamide was added and reacted at 110°C in an alkaline environment for 6 hours to obtain the polymer. The schematic diagram of the reaction is shown in the figure below, where R1 and R3 are the same as in Example 1, s is 3, t is 3, and the structural units derived from butadiene and acrylamide are random copolymerized. [ka]

[0245] Example 4 The preparation method is similar to that of Example 1, differing only in the type of dispersant used. The two steps preceding the dispersant synthesis process are consistent with Example 1, and the polymer preparation process in the third step is as follows.

[0246] Butadiene was added to the second intermediate product and reacted at 100°C for 0.5 hours. Then, 3-amino-1-propene was added and reacted at 110°C in an alkaline environment for 6 hours to obtain the polymer. The schematic diagram of the reaction is shown in the figure below, where R1 and R3 are the same as in Example 1, s is 3, t is 3, and the structural units derived from butadiene and 3-amino-1-propene are random copolymerized. [ka]

[0247] Example 5 The preparation method is similar to that of Example 1, differing only in the type of dispersant used. The two steps preceding the dispersant synthesis process are consistent with Example 1, and the polymer preparation process is as follows.

[0248] Butadiene was added to the second intermediate product, and the reaction was carried out in an alkaline environment at 100°C for 6.5 hours to obtain a polymer. The schematic diagram of the reaction is shown in the figure below, where R1 and R3 are the same as in Example 1, and s+t is 6. [ka]

[0249] Example 6 The preparation method is similar to that of Example 1, but the dispersant is different. The dispersant was prepared by further reacting the product from Example 1 with 3-amino-1-propene to prepare a polymer with amino groups at the end. The structure is shown below, where R1, R3, R6, and n are the same as in Example 1. [ka]

[0250] Example 7 The preparation method is similar to that of Example 1, except that the product from Example 1 is further reacted with an acrylamide reaction to prepare a polymer whose terminal groups are amide groups. The structure is shown below, where R1, R3, R6, and n are the same as in Example 1.

[0251] [ka]

[0252] The preparation methods for Examples 8-15 are similar to those for Example 7. The difference is that in Examples 8-11, the weight-average molecular weight of the polymer is adjusted by adjusting the degree of polymerization of the polyether segment, while in Examples 12-15, the amount of dispersant added is adjusted to maintain a constant total mass of the positive electrode film layer, and the mass percentage content of the positive electrode active material is adjusted accordingly in response to changes in the mass content of the dispersant. The specific parameters are shown in Table 1.

[0253] The preparation method for Example 16 is similar to that of Example 3, and the organic monomer containing an unsaturated bond added during the polymer preparation process in the dispersant preparation process is [ka] Therefore, m=4, and the structural formula of the prepared dispersant is [ka] In the formula, R1, R3, s, and t are the same as in Example 3.

[0254] Example 17 Example 17 is basically the same as the preparation method of Example 7, but differs in that the monomers added in the preparation process of R1 are all ethylene oxides, and therefore the polyether segment is polyethylene oxide.

[0255] Example 18 Example 18 is basically the same as the preparation method of Example 7, but differs in that the anchor group of the dispersant in Example 7 is a phosphite group, and the preparation method is basically the same as the preparation method of the dispersant in Example 7, but differs in that the first substance added in the preparation process is PCl3 instead of POCl3, and the structure of the dispersant is as shown below, where R1, R3, R6, and n are the same as in Example 1.

[0256] [ka]

[0257] Example 19 Example 19 is basically the same as the preparation method of Example 7, but differs in that the R3 group in Example 19 is the same as the R1 group, and both are polyether segments, n2 is 12 in both cases, and m2 is 13 in both cases.

[0258] The preparation process for the dispersant is basically the same as in Example 7, but differs in the preparation process for the second intermediate product, specifically as follows.

[0259] 1,2-propanediol (ethylene oxide, propylene oxide monomer, POCl3) and concentrated sulfuric acid (0.3% of total mass) solids are weighed and placed in a reaction vessel. The lid of the reaction vessel is closed and the fixing bolts are tightened with a wrench. The reaction vessel is evacuated and replaced three times with high-purity nitrogen gas. Ethylene oxide and propylene oxide are added sequentially in a molar ratio of n2:m2, and a block polymerization reaction is carried out. The pressure is maintained at 0.3±0.05 MPa and the temperature at 115±5°C during the reaction process. After 5 hours of reaction, POCl3, dichloromethane (DCM) and sodium hydroxide are added, and the reaction is carried out for 5 hours under a nitrogen atmosphere and at 115±5°C. Then water is added and the reaction is carried out at 50°C for 10 hours to produce the product. A schematic diagram of the reaction process is shown below, where A1 is [ka] So, n2 is 12 and m2 is 13.

[0260] [ka]

[0261] The product was continued to react in the same manner as in Example 7 to bond the R2 group and produce a phosphorus-containing polymer as a dispersant.

[0262] Example 20 Example 20 is basically the same as the preparation method of Example 7, but differs in that the weight-average molecular weight of the binder PVDF is 300,000, and the ratio of the positive electrode active material, carbon-coated lithium iron phosphate (LFP@C), the conductive agent, carbon black (SP), the binder, polyvinylidene fluoride (PVDF), and the dispersant is 96:2:1.5:0.5.

[0263] Example 21 In Example 21, the preparations made in Example 19 were used [ka] This is used as a dispersant without binding the R2 group.

[0264] Example 22 Example 22 is basically the same as the preparation method of Example 19, however, in the synthesis process of the polyether segment in the preparation of the dispersant, phenol was added first instead of 1,2-propanediol, the catalyst was potassium hydroxide, and A1 is [ka] The differences are that n2 is 12, m2 is 13, R6 is -(CH2)4-, and n is 2.

[0265] Specifically, the dispersants are as follows: [ka]

[0266] Example 23 In Example 23, the product prepared during the synthesis process of Example 22 was used directly as a dispersant, and its specific structural formula is as follows. [ka]

[0267] Example 24 Example 24 is basically the same as the preparation method of Example 23, but differs in that in the final step of the product preparation process, instead of adding water and performing hydrolysis, phenol is added and reacted at 50°C for 10 hours to produce the product, which is then used directly as a dispersant. The specific structural formula is as follows. [ka]

[0268] Example 25 Example 25 is basically the same as the preparation method of Example 7, but differs in that phenol was added first in the synthesis process of the polyether segment instead of 1,2-propanediol, and A1 in the product is a phenyl group.

[0269] Example 26 Example 26 is basically the same as the preparation method of Example 22, but differs in that the positive electrode active material is carbon-coated manganese iron lithium phosphate, and its preparation method is specifically as follows.

[0270] In step S1, 689.6 g of manganese carbonate, 455.27 g of ferrous carbonate, 4.65 g of cobalt sulfate, and 4.87 g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added, and the mixture was heated to 80°C and stirred thoroughly at a rotation speed of 500 rpm for 6 hours until uniformly mixed, until the reaction was complete and no more bubbles were produced, to obtain a manganese oxalate suspension co-doped with Fe, Co, and V. The suspension was then filtered, oven-dried at 120°C, and further sanded to obtain manganese oxalate particles co-doped with Fe, Co, V, and S with a particle size of 100 nm.

[0271] In step S2, 1793.1 g of manganese oxalate, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in step S1 were taken and added to 20 L of deionized water, stirred thoroughly, and mixed uniformly at 80°C for 10 hours to obtain a slurry. The slurry was transferred to a spray dryer and spray-dried to obtain a powder material. The powder material was sintered in a roller hearth kiln at 700°C for 4 hours in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain the core Li of the positive electrode active material. 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4 was obtained.

[0272] In step S3, PEG-3000 was selected as the first carbon source, and 58.2 g of PEG-1000 was dissolved in 500 g of deionized water. The mixture was then stirred to ensure complete dissolution and obtain an aqueous solution. 1571.9 g of the core material was added to the solution and stirred together for 6 hours until uniformly mixed. After spray drying, a first sintering treatment was performed at a temperature of 600°C for 9 hours. The first sintering treatment was then performed to obtain the first coated positive electrode active material.

[0273] In step S4, glucose was selected as the second carbon source, and 37.3 g of glucose was dissolved in 500 g of deionized water. The mixture was then stirred to ensure complete dissolution and obtain an aqueous glucose solution. 1603.3 g of the first coated positive electrode active material obtained in step S3 was added to the glucose solution and stirred together for 6 hours until uniformly mixed. After spray drying, a second sintering treatment was performed at a temperature of 750°C for 20 hours, thereby obtaining the positive electrode active material through the second sintering treatment.

[0274] Examples 27, 28 Examples 27 and 28 are basically the same as the preparation method of Example 26, but differ in the preparation method of the positive electrode active material. The specific difference parameters are as follows.

[0275] In Example 27, the first carbon source was PEG-10000, the first sintering temperature was 500°C, and the first sintering treatment time was 5 hours. The second carbon source was glucose, the second sintering temperature was 550°C, and the second sintering treatment time was 20 hours.

[0276] In Example 28, the first carbon source was PEG-2000, the first sintering temperature was 660°C, and the first sintering treatment time was 9 hours. The second carbon source was sucrose, the second sintering temperature was 750°C, and the second sintering treatment time was 6 hours.

[0277] Comparative Example Comparative Examples 1 and 2 The preparation method for Comparative Example 1 is basically the same as that for Example 1, but differs in that a dispersant is not added. The preparation method for Comparative Example 2 is basically the same as that for Example 1, but the dispersant is different. [ka] They differ in that respect, In the equation, a is 3 and b is 3.

[0278] Comparative Example 3 Comparative Example 3 is basically the same as the preparation method of Example 26, but differs in that the dispersant used in Comparative Example 3 is the same as that used in Comparative Example 2.

[0279] Comparative Example 4 Comparative Example 4 is basically the same as the preparation method of Example 27, but differs in that the dispersant used in Comparative Example 4 is the same as that used in Comparative Example 2.

[0280] Comparative Example 5 Comparative Example 5 is basically the same as the preparation method of Example 28, but differs in that the dispersant used in Comparative Example 5 is the same as that used in Comparative Example 2.

[0281] 2. Performance Test 1. Characterization of polymers 1) Weight average molecular weight A Waters 2695 isocratic HPLC-type gel chromatograph (differential refractive index detector 2141) was used. A polystyrene solution sample with a mass fraction of 3.0% was used as a reference, and a suitable chromatography column (oil-based: Styragel HT5 DMF 7.8*300 mm + Styragel HT4) was selected. A 3.0% polymer solution was prepared in purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day to prepare for use. During the test, tetrahydrofuran was first drawn into the syringe, washed, and repeated several times. Next, 5 ml of the experimental solution was drawn into the syringe, the air in the syringe was removed, and the tip of the needle was wiped dry. Finally, the sample solution was gradually injected into the inlet. Once the reading stabilized, data was obtained.

[0282] 2, positive electrode active material 1) Measurement of the hybridization morphology of carbon atoms in the carbon coating layer: Measurement of the hybridization of carbon atoms in the carbon coating layer: This test was performed using Raman spectroscopy. By performing peak splitting on the energy spectrum of the Raman test, I g / I d Having obtained, here, I d is sp 3 This is the peak intensity of carbon in the morphology, I g is sp 2 This represents the peak intensity of carbon in the morphology, which was used to confirm the molar ratio of the two.

[0283] 2) Thickness test of the carbon coating layer For the carbon coating layer thickness test, a thin section approximately 100 nm thick was cut from the center of a single particle of the positive electrode active material prepared by FIB. Then, a TEM test was performed on the thin section to obtain the original image of the TEM test, which was saved in the original image format (xx.dm3). The original image obtained from the TEM test was opened with Digital Micrograph software, and the carbon coating layer was identified based on the grid spacing and angle information, and the thickness of the carbon coating layer was measured. The thickness was measured at three locations for the selected particle, and the average value was obtained.

[0284] 3. Positive electrode slurry 1) Maximum solid content of slurry The maximum solid content of a positive electrode slurry refers to the maximum solid content of a slurry that satisfies the condition that no gel phenomenon occurs after the slurry is left to stand for 24 hours, given a shipping viscosity of 4000 to 35000 MPa.s. For the test method of the slurry's solid content, a slurry weight labeled m0 was taken, placed in a weight loss rate test apparatus, and the solvent was evaporated until the slurry's weight loss rate was less than 0.3%. The remaining weight was labeled m1, and the solid content was calculated as m1 / m0 * 100%.

[0285] 2) Filtration time Area 30×30cm 2 A 200-mesh filter was folded into a funnel shape, two beakers were taken, one was placed on a table, and the other was filled with 500 ml of slurry. The slurry was poured into the filter funnel, and the filtration time for dropping 300 ml of slurry was recorded.

[0286] 4. Positive electrode sheet 1) Brittleness test of electrode sheets It is free of defects and has a pressure density of 2.6 g / cm³. 3A positive electrode sheet was taken and cut along the longitudinal direction into samples measuring 25cm x 4cm in length x width, with a sample count of ≥ 4 pieces. First, each sample was folded in half lengthwise (25cm direction), then placed on a test bench and roll-pressed once with a 2kg cylindrical press roll. If light was transmitted, the number of light transmission cycles for brittleness was 1. If light was not transmitted, the process was repeated, folding in half in the opposite direction and roll-pressing. The folds were observed with light to see if light was transmitted or if the sample broke, the actual number of folds was recorded, and the average value was used as the test result.

[0287] 5, secondary battery 1) Maximum volumetric energy density The maximum volumetric energy density refers to the volumetric energy density of a battery measured when the positive electrode sheet is at its critical pressure density. The critical pressure density is defined as the smaller of the corresponding pressure densities when the elongation rate of the electrode sheet is 6‰ or when the number of flexible folds of the electrode sheet is 2.

[0288] The method for measuring the discharge energy of a battery cell is as follows: The battery cells were left standing at 25°C for 2 hours to ensure their temperature remained at 25°C. At 25°C, the battery cells were charged at 0.33C until they reached the charge cutoff voltage. Then, constant voltage charging was continued at the same cutoff voltage until the current reached 0.05C and charging was stopped (where C represents the rated capacity of the battery cell). After leaving the battery cells standing at 25°C for 1 hour, they were discharged at 25°C at 0.33C until they reached the discharge cutoff voltage. The total discharge capacity C0 released by the battery cells was recorded, and the total discharge energy was E0.

[0289] The method for measuring the volume of a battery cell is as follows: The length, width, and height of the battery cell were measured, and the volume value M0 of the battery cell was calculated.

[0290] The formula for calculating the energy density of a battery is as follows: Battery energy density = Battery cell discharge energy E0 / Battery cell volume M0.

[0291] 2) Cycle capacity retention rate when 40 cycles are performed at 25°C The voltage calibration method is as follows: The battery cell was left standing at 25°C for 2 hours to ensure its temperature remained at 25°C. At 25°C, the battery cell was charged to 4.25V with 0.33C0, and then left standing for 1 hour after constant voltage charging until the current reached 0.05C0 at 4.25V. At 25°C, it was discharged at 0.33C0 with a current of 0.95C0, and the voltage V1 at this time was recorded. After standing for 5 minutes, it was discharged to 2.0V at 25°C with 0.33C0. After standing for 5 minutes, the battery cell was charged at 25°C at 0.33C0 with a current of 0.97C0, and the voltage V2 at this time was recorded.

[0292] The cycle test flow is as follows: The battery cell was left standing at 25°C for 2 hours to ensure that the battery cell temperature remained at 25°C. At 25°C, the battery cell was charged to voltage V2 with 0.33C0 and then left standing for 0.5 hours. At 25°C, the battery cell was discharged to voltage V1 with 0.33C0, and the capacity at this time was recorded as Cn. After leaving it standing for 0.5 hours, the above steps were repeated until the number of cycles n reached 40 cls.

[0293] After 40 cycles using the above steps, the Cn / C0 ratio was recorded as the cycle capacity retention rate and used as an indicator to evaluate the battery's cycle performance.

[0294] 3) Full cell cycle count test: Under a constant temperature environment of 45°C, a full cell was charged to 4.3V at 1C from 2.5V to 4.3V, and then regulated to constant voltage charging at 4.3V until the current was 0.05mA or less. After standing for 5 minutes, it was discharged to 2.5V at 1C, and the discharge capacity at this time was recorded as D0. The above charge-discharge cycle was repeated until the discharge capacity decreased to 80% of D0. The number of battery cycles at this time was recorded.

[0295] III. Analysis of the test results of each example and comparative example. [Table 1]

[0296] As can be seen from the comparison between the examples and comparative examples, all of the examples contain the polymer dispersant shown in formula I, which effectively increases the maximum solid content of the slurry, shortens the filtration time, improves the production efficiency and quality of the electrode sheets, and improves the flexibility of the electrode sheets.

[0297] As can be seen from the comparison between Examples 1-4 and Example 5, the inclusion of at least one of an amide group or an amino group in the R2 organic segment can further increase the maximum solid content of the slurry.

[0298] As can be seen from the comparison between Examples 6 and 7 and Example 1, the presence of at least one of -C(O)-NH2 and -CH2-NH2 as the terminal group of R2 allows for a more effective dispersal of the polymer compared to other terminal groups, thereby increasing the maximum solid content of the slurry.

[0299] As can be seen from the comparison between Example 7 and Example 17, by including a poly(ethylene oxide-propylene oxide) polyether segment in at least one of R1 and R3, the dispersion and flexibility effects are more effectively exerted compared to polyethylene oxide polyether segments, further improving the maximum solid content of the slurry and the flexibility of the electrode sheet.

[0300] As can be seen from the comparison between Example 19 and Example 7, having both R1 and R3 be polyether segments further shortens the slurry filtration time and improves the flexibility of the electrode sheet compared to having only one of them be a polyether segment.

[0301] As can be seen from the comparison of Examples 7 to 11, having a weight-average molecular weight of 2000 to 5000 of the polymer further enhances the dispersion effect, increases the maximum solid content of the slurry, and shortens the filtration time.

[0302] [Table 2]

[0303] As can be seen from the comparison between Example 22 and Example 19, Example 25 and Example 7, and Example 23 and Example 21, the inclusion of a phenyl group at the end of the polyether segment can further improve the dispersibility of the slurry.

[0304] [Table 3]

[0305] As can be seen from Examples 12 to 15, the polymer mass content in the total mass of the dry material of the positive electrode slurry is 0.1% to 2.0%, and the slurry has a high maximum solids content, a low filtration time, and high flexibility. When the polymer mass content in the total mass of the dry material of the positive electrode slurry is 0.2% to 1.0%, it is possible to further balance the processing performance of the electrode sheet and the energy density of the battery.

[0306] [Table 4]

[0307] As can be seen from the comparison between Example 7 and Example 20, by including a polyvinylidene fluoride polymer with a weight-average molecular weight of 700,000 or more as a binder in the positive electrode slurry, the amount of binder used can be further reduced and the flexibility of the electrode sheet can be improved.

[0308] [Table 5]

[0309] As can be seen from the comparison between Example 7 and Example 18, phosphate-based polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode sheet compared to phosphite-based polymers. Furthermore, phosphate-based polymers have higher stability and can effectively improve the battery's cycle capacity retention rate in addition to improving slurry dispersibility.

[0310] [Table 6]

[0311] As can be seen from the comparison between Examples 26-28 and Comparative Examples 3-5, the polymers provided in the examples of this application can more effectively improve the dispersibility of positive electrode active materials with a high degree of order in the carbon coating layer, and by matching the dispersant with the surface coating layer of the positive electrode active material, the processability, cycle stability, and capacity per gram of the battery can be simultaneously improved.

[0312] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and all embodiments having substantially the same technical idea and achieving the same function and effect within the scope of the technical solution of this application are included in the technical scope of this application. Furthermore, other forms that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included in the scope of this application, without departing from the gist of this application. [Explanation of symbols]

[0313] 1 Battery pack 2. Top box 3. Lower box 4 Battery Modules 5 Secondary battery 51 cases 52 Electrode assembly 53 Lid plate 6 Polymers 61 Anchor base 62 Soft Segments 7 Positive active material

Claims

1. A polymer comprising the structure shown by formula I, 【Chemistry 1】 In the formula, X includes a phosphate group or a phosphite group, and R １ , R ３ Each independently comprises at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and R １ , R ３ At least one of them includes a polyether segment or a polyester segment, R ２ This is a polymer containing organic segments.

2. R ２ The polymer according to claim 1, wherein the organic segment contains at least one of an amide group, an amino group, and an aryl group.

3. R ２ The organic segment contains C ２－１２ The polymer according to claim 1 or 2, further comprising a hydrocarbon group.

4. R ２ comprises the structure represented by Formula II, 【Chemistry 2】 In the formula, R ４ and R ５ They copolymerize randomly, R ４ is C ２－１２ Hydrocarbylene group, C ３－１３ It contains at least one of the amide groups, R ５ teeth 【Transformation 3】 Includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R ６ ａ , R ６ ｂ is hydrogen, C １－４ The polymer according to any one of claims 1 to 3, comprising at least one alkyl group, wherein 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10.

5. R ２ It includes the structure shown by formula III, 【Chemistry 4】 In the formula, R ６ is C ２－１２ Contains a hydrocarbylene group, R ７ teeth 【Transformation 5】 The polymer according to any one of claims 1 to 4, comprising at least one of the above, wherein q5 and q6 each independently comprise any integer from 0 to 4, and 1 ≤ n ≤ 6.

6. R ２ The terminal group is -C(O)-NH ２ ien-CH ２ -NH ２ A polymer according to any one of claims 1 to 5, comprising at least one of the above.

7. R １ , R ３ At least one of them comprises a polyether segment, selectively R １ and R ３ The polymer according to any one of claims 1 to 6, wherein both contain polyether segments.

8. R １ , R ３ At least one of them comprises a polyether segment represented by formula IV, 【Transformation 6】 In the formula, EO is -CH ２ -CH ２ -O- represents -CH(CH ３ ) - CH ２ The polymer according to any one of claims 1 to 7, wherein it represents -O-, 4 ≤ m1 ≤ 50, and 4 ≤ n1 ≤ 50.

9. The polymer according to any one of claims 1 to 8, wherein the terminal group of the polyether segment contains an aryl group.

10. The polymer according to any one of claims 1 to 9, wherein X comprises a phosphate group.

11. The aforementioned polymer is the polymer represented by the following formula, 【Transformation 7】 Includes at least one of the following: In the formula, R １ , R ３ At least one of the components comprises a block copolymer polyether segment represented by formula IV, 【Transformation 8】 In the formula, EO is -CH ２ -CH ２ -O- represents -CH(CH ３ ) -CH ２ -O- represents 4 ≤ m1 ≤ 50, and 4 ≤ n1 ≤ 50, R ６ , R ４ Each is independently C ４－８ Alkylene group, C ４－８ The polymer according to any one of claims 1 to 10, comprising at least one of the alkenylene groups.

12. The polymer according to claim 11, wherein the terminal group of the polyether segment contains an aryl group.

13. The polymer is as shown by the following formula: 【Chemistry 9】 In the formula, R ２ It comprises at least one of the following organic segments: hydrogen, an aryl group, a substituted or unsubstituted alkyl group, an amino group, or an amide group. R １ , R ３ At least one of the components comprises a block copolymer polyether segment represented by formula IV, 【Chemistry 10】 In the formula, EO is -CH ２ -CH ２ -O- represents -CH(CH ３ ) - CH ２ The polymer according to any one of claims 1 to 10, wherein it represents -O-, 4 ≤ m1 ≤ 50, 4 ≤ n1 ≤ 50, and the terminal group of the polyether segment contains a phenyl group.

14. The polymer according to any one of claims 1 to 13, wherein the weight-average molecular weight of the polymer is 1,000 to 10,000, and selectively 2,000 to 5,000.

15. The compound represented by formula VI, R ３ OH, R １ A method for preparing a polymer, comprising the step of reacting an OH group, water, and an unsaturated bond with a polymerization monomer to prepare a polymer having a structure represented by formula I, 【Chemistry 11】 In the formula, X includes a phosphate group or a phosphite group, X １ , X ２ , X ３ All of them contain halogens, R １ , R ３ Each independently comprises at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and R １ , R ３ At least one of them includes a polyether segment or a polyester segment, R ２ It includes organic segments, Method for preparing polymers.

16. The compound represented by formula VI is R ３ OH, R １ The first step involves reacting OH with water to prepare an intermediate product shown in formula VII, 【Chemistry 12】 The process includes a step of reacting the aforementioned intermediate product with a polymerization monomer containing at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer. The preparation method according to claim 15.

17. The aforementioned second reaction is, specifically, The intermediate product is subjected to an addition reaction with at least one of an amide containing an unsaturated bond or an amine containing an unsaturated bond, and then further subjected to a substitution reaction with a halogen-substituted organic alcohol. The process includes preparing the polymer by sequentially repeating the above addition reaction and substitution reaction multiple times, R ２ It includes the structure shown by formula III, 【Chemistry 13】 In the formula, R ６ is C ２－１２ Contains a hydrocarbon group, R ７ teeth 【Chemistry 14】 The preparation method according to claim 16, comprising at least one of the above, wherein q5 and q6 each independently comprise any integer from 0 to 4, and 1 ≤ n ≤ 6.

18. The process further includes a third reaction of the intermediate product with (i) at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond and a cyclic amide monomer, to prepare the polymer, R ２ It includes the structure shown in formula II, 【Chemistry 15】 In the formula, R ４ and R ５ They copolymerize randomly, R ４ is C ２－１２ hydrocarbon group, C ３－１３ It contains at least one of the amide groups, R ５ teeth 【Chemistry 16】 Includes at least one of the following: q1, q2, q3, and q4 each independently contain any integer from 0 to 4, and R ６ ａ , R ６ ｂ is hydrogen, C １－４ It contains at least one alkyl group, and 1 ≤ s ≤ 6 and 1 ≤ t ≤ 10. The preparation method according to claim 16.

19. The compound represented by formula VI, R ３ OH, R １ A method for preparing a polymer, comprising the step of reacting it with a raw material containing OH to prepare a polymer having a structure represented by formula I, 【Chemistry 17】 wherein X contains a phosphate group or a phosphite group, and X １ , X ２ , X ３ all contain halogen, R １ , R ３ each independently contains at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R １ )]], R ３ contains a polyether segment, at least one end group of the polyether segment contains an aryl group, and R ２ contains an organic segment Method for preparing polymers.

20. Use as a dispersant for a polymer according to any one of claims 1 to 14, or a polymer prepared by the preparation method according to any one of claims 15 to 19.

21. A cathode slurry comprising a dispersant containing the polymer according to any one of claims 1 to 14, or the polymer prepared by the preparation method according to any one of claims 15 to 19.

22. The positive electrode slurry according to claim 21, wherein the positive electrode slurry contains a positive electrode active material, the positive electrode active material comprises at least one of a lithium-containing phosphate and a carbon-modified material thereof, and selectively, the positive electrode active material comprises at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, and lithium manganese iron phosphate and its doping material.

23. The positive electrode active material comprises a core and a carbon coating layer, the carbon coating layer covers at least a portion of the surface of the core, and sp in the carbon coating layer ２ Hybrid carbon atoms and sp ３ The positive electrode slurry according to claim 21 or 22, wherein the molar ratio of the hybridized carbon atoms is 0.2 or more, selectively 0.5 or more, and selectively 0.8 or more.

24. The positive electrode slurry according to claim 23, wherein the thickness of the carbon coating layer is 15 nm or less, selectively 10 nm or less, and selectively 4 nm to 8 nm.

25. The positive electrode slurry according to any one of claims 21 to 24, wherein the mass content of the polymer in the total mass of the dried material of the positive electrode slurry is 0.1% to 2.0%, selectively 0.2% to 1.0%.

26. The positive electrode slurry according to any one of claims 21 to 25, wherein the positive electrode slurry comprises a binder, the binder comprises a vinylidene fluoride polymer having a weight-average molecular weight of 300,000 or more, and selectively, the weight-average molecular weight of the binder is between 700,000 and 9,000,000.

27. The positive electrode slurry according to any one of claims 21 to 26, wherein the maximum solid content of the positive electrode slurry is 60% or more, and selectively 60% to 80%.

28. A positive electrode sheet comprising a positive electrode film layer, wherein the positive electrode film layer is prepared using a positive electrode slurry according to any one of claims 21 to 27, or the positive electrode film layer contains a dispersant, the dispersant comprising a polymer according to any one of claims 1 to 14, or a polymer prepared by the preparation method according to any one of claims 15 to 19.

29. The pressure density of the positive electrode sheet is 2.6 g / cm³. ３ The positive electrode sheet according to claim 28, wherein the number of times it is folded in half is two or more, selectively three to six times.

30. The areal density of the positive electrode sheet is 300 mg / 1540.25 cm ２ or more, selectively 300 mg / 1540.25 cm ２ to 600 mg / 1540.25 cm ２ The positive electrode sheet according to claim

31. The positive electrode film layer contains a dispersant, and the dispersant contains a structure represented by formula I. [Chemistry 18] In the formula, X includes a phosphate group or a phosphite group, and R １ , R ３ Each independently comprises at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and R １ , R ３ At least one of them includes a polyether segment or a polyester segment, R ２ It contains organic segments, selectively, R ２ The organic segment contains at least one of an amide group and an amino group, and selectively, the terminal group of the polyether segment contains an aryl group. The positive electrode active material comprises at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, a carbon coating material for lithium iron phosphate and its doping material, and selectively, the positive electrode active material comprises at least one of lithium manganese iron phosphate and its doping material, and a carbon coating material for lithium manganese iron phosphate and its doping material. The positive electrode sheet according to any one of claims 28 to 30, wherein the mass content of the dispersant in the total mass of the positive electrode film layer is 0.1% to 2.0%, and selectively 0.2% to 1.0%.

32. A secondary battery comprising a positive electrode sheet according to any one of claims 28 to 31.

33. An electrical device comprising a secondary battery as described in claim 32.

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