Polymer, method of preparation, dispersant, positive electrode slurry, positive electrode sheet, secondary battery, and power using device

Abstract

The application provides a polymer, a preparation method, a dispersant, a positive electrode slurry, a positive electrode sheet, a secondary battery and an electric device. The polymer comprises a structure shown in Formula I, wherein G1 comprises C 1‑20 an alkyl group or a structure shown in Formula II, wherein A comprises a non-polar group, m1 is an integer between 3 and 60, n1 is an integer between 0 and 60, R1 comprises hydrogen or C 1‑3 an alkyl group, and R2 comprises C 1‑12 an alkylene group or a structure shown in Formula III, wherein m2 is an integer between 3 and 60, n2 is an integer between 0 and 60, and R3 comprises at least one of a carboxyl group, an ester group, a sulfonic acid group, a sulfonate group, a phosphoric acid group and a phosphate group.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more particularly to a polymer, a preparation method, a dispersant, a positive electrode slurry, a positive electrode sheet, a secondary battery, and an electrical device. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] The positive electrode, as a major component of a secondary battery, directly affects its application performance. A positive electrode typically consists of a current collector, positive active material, conductive agent, and binder. However, the positive active material is generally a nanoscale material with a large specific surface area, resulting in higher surface activity. During the homogenization process of the positive electrode slurry, agglomeration easily occurs, forming large agglomerates that affect the electrode coating effect, leading to low conductivity of the prepared electrode and directly impacting the battery's electrochemical performance. Current technologies generally add dispersants to improve slurry dispersibility. However, existing dispersants are not suitable for slurry systems containing positive active materials with different graphitization degrees produced using different processes. The poor versatility of existing dispersants hinders cost reduction. Therefore, it is necessary to develop a new dispersant suitable for slurry systems containing positive active materials produced using different processes. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a polymer, which, when used as a dispersant, can be adapted to positive electrode active materials with different degrees of graphitization, improve the dispersibility of slurry systems containing positive electrode active materials with different degrees of graphitization, effectively increase the solid content of the slurry, slow down the gelation phenomenon of the slurry, reduce the film resistance of the electrode, improve the flexibility of the electrode, and improve the first coulombic efficiency and high-temperature cycle performance of the battery.

[0005] The first aspect of this application provides a polymer comprising the structure shown in Formula I.

[0006]

[0007] Where G1 contains C 1-20 Alkyl groups or structures represented by Formula II,

[0008]

[0009] Where A contains nonpolar groups, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60.

[0010] R1 contains hydrogen or C.1-3 Alkyl, R2 contains C 1-12 Alkylene or the structure shown in Formula III,

[0011]

[0012] Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60.

[0013] R3 contains at least one of the following groups: carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphate group, and phosphate ester group.

[0014] The polymer has a C-terminal group at one end. 1-20 The polymer contains either an alkyl or A group, both of which are nonpolar and exhibit lipophilic properties. The terminal R3 group at the other end contains at least one of a carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester group, which is a polar group and exhibits hydrophilic properties. When this polymer is added to a slurry system, the carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester group at one end acts as an anchoring point and adsorbs onto the surface of solid particles. The nonpolar group at the other end is suspended in the slurry, forming a steric barrier. When solid particles approach each other, this steric barrier generates a strong repulsive force, preventing particle aggregation and forming a uniformly dispersed and stable slurry. Simultaneously, the amide group in the polymer is a polar group, which can generate strong intermolecular inductive forces, further enhancing the polymer's dispersing effect. Furthermore, the polymer backbone contains fewer branches and relatively fixed bond angles, exhibiting a linear structure in the slurry system. The chain segments are fully extended in the slurry system, and entanglement between them is not easily formed. The resulting steric hindrance effectively isolates the solid particles, further improving the dispersion effect.

[0015] In addition, the polymer contains amide groups. Due to the p-π conjugation effect, the lone pair charge of the nitrogen atom adjacent to the carbonyl carbon will be delocalized to the CN single bond, thereby increasing the charge density of the CN single bond. At the same time, as a carboxylic acid-derived group, the amide group will produce enol tautomerism under acidic or alkaline conditions, and the C on the carbonyl group will generate a transient double bond. Therefore, the entire polymer chain contains some double bond properties. The polymer chain is more linear, which will reduce the sliding resistance between the positive electrode active materials during cold pressing, thereby increasing the flexibility of the electrode and improving its toughness.

[0016] In summary, compared to existing dispersants, the polymer dispersant of this application has broad versatility and is suitable for slurry systems containing positive electrode active materials with different degrees of graphitization. Compared to existing dispersants, this application improves the dispersing ability of the polymer through the combined action of the terminal R3 group, amide group, and polymer backbone segments, thereby enhancing the applicability of the polymer dispersant to positive electrode active materials with different degrees of graphitization, which helps to reduce preparation costs and improve production efficiency.

[0017] In any embodiment, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4.

[0018]

[0019]

[0020] Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 each independently contain hydrogen and C. 1-12 Alkyl, C 1-12 At least one of alkyl alcohols and *-NH-R9-OH, wherein R6, R7, and R8 each independently contain hydrogen and C. 1-12 Alkyl, C 1-12 Alkyl alcohols, *-NH-R 10 -OH、 At least one of them, wherein R9, R 10 Each independently contains C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

[0021] In any embodiment, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4.

[0022]

[0023]

[0024] Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 each independently contain hydrogen and C. 1-12 At least one of alkyl alcohols and *-NH-R9-OH, where R8 contains hydrogen and C 1-12 Alkyl alcohols, *-NH-R 10 -OH、 At least one of them, wherein R9, R 10 Each independently contains C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

[0025] In any embodiment, R1 comprises hydrogen.

[0026] R1 contains hydrogen, which can form hydrogen bonds with oxygen atoms on the surface of the positive electrode active material, further increasing the dispersion effect of the polymer on the slurry, increasing the solid content of the slurry, slowing down the gelation phenomenon of the slurry, improving the flexibility of the electrode, reducing the film resistance of the electrode, and improving the initial coulombic efficiency and high-temperature storage performance of the battery.

[0027] In any implementation, G1 includes the structure shown in Formula II, and R2 includes the structure shown in Formula III, wherein n1 or n2 is 0, and m1 and m2 are each independently an integer between 3 and 60.

[0028] The polymer contains polyethylene oxide segments or polyethylene oxide-propylene oxide segments, which can improve the polymer's flexibility, reduce the slip resistance between particles during the cold pressing process of the electrode, improve the electrode's flexibility, and enhance the battery's initial coulombic efficiency and high-temperature storage performance.

[0029] In any implementation, G1 includes the structure shown in Formula II, and R2 includes the structure shown in Formula III, wherein n1 and n2 are each independently an integer between 1 and 60, and m1 and m2 are each independently an integer between 3 and 30.

[0030] The polymer contains polyethylene oxide-propylene oxide segments, which can further improve the polymer's flexibility, reduce the slip resistance between particles during the cold pressing process of the electrode, improve the electrode's flexibility, reduce the electrode's film resistance, and improve the battery's initial coulombic efficiency and high-temperature storage performance.

[0031] In any implementation, A includes C. 3-30 Alkyl, C 6-30 At least one of the aromatic groups.

[0032] In any embodiment, the weight-average molecular weight of the polymer is 500 g / mol to 20000 g / mol.

[0033] In any embodiment, the glass transition temperature of the polymer is 50°C-180°C.

[0034] In any embodiment, the polymer has a melting point of 90°C-220°C at 1 standard atmosphere.

[0035] In any embodiment, the polymer has a hydrophilic-lipophilic balance value of 6-16.

[0036] In any embodiment, the hydrophilic-lipophilic balance value of the polymer is 10-12.

[0037] A second aspect of this application provides a method for preparing a polymer, the polymer comprising the structure shown in Formula I.

[0038]

[0039] Where G1 contains C 1-20 Alkyl groups or structures represented by Formula II,

[0040]

[0041] Where A contains nonpolar groups, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60;

[0042] R1 contains hydrogen or C. 1-3 Alkyl, R2 contains C 1-12 Alkylene or the structure shown in Formula III,

[0043]

[0044] Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60.

[0045] R3 contains at least one of the following groups: carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphate group, and phosphate ester group.

[0046] The preparation method of this application can obtain a nonpolar group containing a carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphoric acid group, or phosphate ester group at one end and an alkyl group or A group at the other end, and the main chain contains an amide group. Using this polymer as a dispersant, it can be applied to positive electrode active materials with different degrees of graphitization, improve the dispersibility of slurry systems containing positive electrode active materials with different degrees of graphitization, increase the solid content of the slurry, mitigate the gelation phenomenon of the slurry, reduce the film resistance of the electrode, improve the flexibility of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0047] In any embodiment, the preparation method specifically includes:

[0048] Reacting the acid represented by Formula IV with the amine represented by Formula V yields a polymer containing the structure shown in Formula I.

[0049]

[0050] In some embodiments, a catalyst, an acid of formula IV, and an amine of formula V are reacted to obtain a polymer containing the structure shown in formula I.

[0051] In some embodiments, the catalyst comprises 5% by mass of dilute sulfuric acid.

[0052] This application utilizes a one-step amidation reaction between carboxyl and amino groups to prepare polymers, which is a simple preparation method and improves production efficiency.

[0053] A third aspect of this application provides a dispersant comprising the polymer of the first aspect or a polymer prepared by the preparation method of the second aspect.

[0054] A fourth aspect of this application provides the application of the polymer of the first aspect in a secondary battery.

[0055] A fifth aspect of this application provides a positive electrode slurry comprising a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant comprises the polymer of the first aspect.

[0056] This positive electrode slurry has excellent dispersibility and high solid content, and can be used to prepare high-performance electrodes.

[0057] In any embodiment, the positive electrode active material includes lithium iron phosphate with a carbon coating on its surface.

[0058] In any embodiment, the degree of graphitization of lithium iron phosphate with a carbon coating on the surface is 10%-30%.

[0059] The polymer dispersant of this application is applicable to slurry systems using lithium iron phosphate with different degrees of graphitization as the positive electrode active material. It has universality and helps to reduce preparation costs and improve production efficiency.

[0060] In any embodiment, the mass fraction of the dispersant is 0.01%-3%, based on the total mass of solid matter in the positive electrode slurry.

[0061] When the mass fraction of the dispersant is within a suitable range, the slurry has a high solid content, the electrode has excellent flexibility, and the battery has excellent initial coulombic efficiency and high-temperature storage performance.

[0062] In any embodiment, the mass fraction of the dispersant is 0.03%-2%, based on the total mass of solid matter in the positive electrode slurry.

[0063] When the mass fraction of the dispersant is within a suitable range, the flexibility of the electrode can be further improved, thus enhancing its performance.

[0064] A sixth aspect of this application provides an improved positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, said positive electrode film layer being prepared from the positive electrode slurry of the fifth aspect.

[0065] The positive electrode of this application has excellent flexibility and low film resistance, and the electrode has excellent performance in use.

[0066] A seventh aspect of this application provides a secondary battery, including a separator, a negative electrode, an electrolyte, and a positive electrode as described in the sixth aspect.

[0067] An eighth aspect of this application provides an electrical device including a secondary battery as described in the seventh aspect. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0069] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0070] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0071] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0072] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0073] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0074] Explanation of reference numerals in the attached figures:

[0075] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0076] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0077] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0079] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0080] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0081] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0082] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0083] The cathode slurry is primarily a solid-liquid phase mixture composed of the cathode active material, conductive agent, binder, and solvent. In existing technologies, dispersants are often added to improve the slurry's dispersibility. However, existing dispersants are typically only suitable for slurry systems with fixed components, lacking versatility. When the properties of the components in the slurry change, the dispersant often needs to be adjusted. For example, lithium iron phosphate produced under different process conditions in existing technologies has varying degrees of carbon coating and graphitization. Often, a single dispersant cannot be applied to lithium iron phosphate with different degrees of graphitization. Using existing dispersants in slurry systems with lithium iron phosphate using different degrees of graphitization as the cathode active material results in less than ideal dispersion, failing to meet the performance requirements of the electrode and battery.

[0084] [Dispersant]

[0085] Based on this, this application provides a polymer comprising the structure shown in Formula I.

[0086]

[0087] Where G1 contains C 1-20 Alkyl groups or structures represented by Formula II,

[0088]

[0089] Where A contains nonpolar groups, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60.

[0090] R1 contains hydrogen or C. 1-3 Alkyl, R2 contains C 1-12 Alkylene or the structure shown in Formula III,

[0091]

[0092] Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60.

[0093] R3 contains at least one of the following groups: carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphate group, and phosphate ester group.

[0094] In this document, the term "polymer" includes, on the one hand, an aggregate of chemically homogeneous macromolecules prepared by polymerization reactions, but differing in degree of polymerization, molar mass, and chain length. On the other hand, the term also includes derivatives of such aggregates of macromolecules formed by polymerization reactions, i.e., compounds that can be obtained through reactions of the functional groups in the aforementioned macromolecules, such as addition or substitution, and which may be chemically homogeneous or chemically heterogeneous.

[0095] In this article, the term "carboxyl group" refers to -COOH.

[0096] In this article, the term "ester group" refers to R 12 It is a non-hydrogen group.

[0097] In this paper, the term "sulfonic acid group" refers to -SO3H.

[0098] In this article, the term "sulfonate group" refers to R 13 It is a non-hydrogen group.

[0099] In this article, the term "phosphate group" refers to

[0100] In this article, the term "phosphate group" refers to R 14 It is a non-hydrogen group.

[0101] In this article, the term "amide group" refers to R 15 R 16 Each can be a hydrogen or non-hydrogen group independently.

[0102] In this article, the term "amino" refers to R 17 R 18 Each can be a hydrogen or non-hydrogen group independently.

[0103] In this document, the term "nonpolar group" refers to a group whose positive and negative charge centers coincide, including but not limited to alkyl and aromatic groups.

[0104] In this paper, the term "alkyl" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, and the group is not unsaturated.

[0105] In this paper, the term "aromatic group" refers to an aromatic ring system in which at least one ring is an aromatic group.

[0106] In some implementations, A includes C. 3-30 Alkyl or C 6-30 Aromatic group.

[0107] In this article, the term "C"3-30 "Alkyl" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, without any unsaturation, having 6 to 30 carbon atoms, and attached to the rest of the molecule by single bonds. The term "C" is also used in this context. 1-3 Alkyl", C 1-20 "alkyl" and "C" 1-12 The term "alkyl" should be interpreted accordingly.

[0108] In this article, the term "C" 6-30 "Aromatic group" refers to a monovalent functional group formed by removing a hydrogen atom from the ring of an aromatic hydrocarbon containing 6 to 30 carbon atoms, such as phenyl or naphthyl. Aromatic hydrocarbons refer to hydrocarbons having aromatic rings, and include monocyclic and polycyclic hydrocarbons, wherein the additional ring of a polycyclic hydrocarbon can be aromatic or non-aromatic.

[0109] In this article, the term "C" 1-12 "Alkylene" refers to a branched or straight-chain saturated aliphatic divalent hydrocarbon group with a specified number of carbon atoms. The group is not unsaturated, has 1 to 12 carbon atoms, and is attached to the rest of the molecule by single bonds.

[0110] In this paper, the structures shown in Equations II and III... Unit and The units can be arranged randomly or in segments.

[0111] In this paper, the term "dispersant" refers to a class of substances that prevent solid particles from aggregating in a solid-liquid dispersion system, thereby keeping the solid particles uniformly dispersed in the liquid phase for a relatively long time.

[0112] In some embodiments, the dispersion medium for the dispersant is an aqueous solvent, such as water. That is, the dispersant is dissolved in an aqueous solvent.

[0113] In some embodiments, the dispersion medium for the dispersant is an oily solvent. Examples of oily solvents include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate. That is, the dispersant is dissolved in an oily solvent.

[0114] In some embodiments, the dispersant serves as a positive electrode slurry dispersant. It is used to disperse the positive electrode active material, conductive agent, and binder to form the positive electrode slurry.

[0115] In some embodiments, the dispersant serves as a negative electrode slurry dispersant. It is used to disperse the negative electrode active material, conductive agent, and binder to form the negative electrode slurry.

[0116] In some embodiments, R3 comprises a carboxyl group, a sulfonic acid group, or a phosphate group.

[0117] Carboxyl, sulfonic acid, or phosphate groups can ionize to generate negative ions, which mainly adsorb onto the surface of the positive electrode active material particles in the slurry system through electrostatic interaction, anchoring one end of the polymer to the surface of the positive electrode active material particles.

[0118] In some embodiments, R3 comprises an ester group, a sulfonate group, or a phosphate group.

[0119] Ester groups, sulfonate groups, or phosphate groups adsorb onto the surface of the positive electrode active material particles in the slurry system through intermolecular forces, anchoring one end of the polymer to the surface of the positive electrode active material particles.

[0120] The polymer has a C-terminal group at one end. 1-20 The alkyl or A group contains a nonpolar group, exhibiting lipophilic properties. The terminal group R3 at the other end contains at least one of carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester groups, exhibiting hydrophilic properties. When the polymer is added to the slurry system, the carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester groups at one end act as anchoring sites, adsorbing onto the surface of the positive electrode active material particles. The other end remains suspended in the slurry, forming a steric barrier. When particles approach each other, this steric barrier generates a strong repulsive force, preventing particle aggregation and forming a uniformly dispersed and stable slurry. The amide group in the polymer is a polar group, which can generate strong intermolecular inductive forces, forming strong intermolecular interactions with the particles, further improving the polymer's dispersing ability. In addition, the oxygen and nitrogen atoms in the amide group can form hydrogen bonds with the hydroxyl and / or carboxyl groups on the surface of the positive electrode active material, and simultaneously, the oxygen and nitrogen atoms can form coordination interactions with the positive electrode active material, jointly enhancing the dispersion effect of the polymer dispersant on the particles in the slurry system. The R2 and G1 structures in the polymer contain fewer branches, resulting in a linear main chain segment with relatively fixed bond angles. This leads to a linear structure in the slurry system, allowing the chain segments to fully extend and preventing entanglement. The resulting steric hindrance effectively isolates solid particles. Simultaneously, the full extension of the main chain segments allows the amide groups to interact effectively with different particles, further improving the dispersion effect. The polymer dispersant of this application can achieve multi-site adsorption on the surface of positive electrode active materials with different degrees of graphitization, making the adsorption effect more significant and enhancing the dispersion effect of the polymer dispersant on the slurry.

[0121] In addition, the polymer contains amide groups. Due to the p-π conjugation effect, the lone pair charge of the nitrogen atom adjacent to the carbonyl carbon will be delocalized to the CN single bond, thereby increasing the charge density of the CN single bond. At the same time, as a carboxylic acid-derived group, the amide group will produce enol tautomerism under acidic or alkaline conditions, and the C on the carbonyl group will generate a transient double bond. Therefore, the entire polymer chain contains some double bond properties. The polymer chain is more linear, which will reduce the sliding resistance between the positive electrode active materials during cold pressing, thereby increasing the flexibility of the electrode and improving its toughness.

[0122] In summary, the polymer of this application, acting as a dispersant, can improve the dispersibility of slurries containing positive electrode active materials with different degrees of graphitization through multi-site adsorption, increase the solid content of the slurry, slow down slurry gelation, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery. Simultaneously, it can also improve the flexibility of the electrode, providing a foundation for the subsequent preparation of thick-coated high-voltage dense electrode sheets.

[0123] Existing dispersants have poor compatibility and cannot be applied to the differences in positive electrode active materials under different process conditions in slurries. This application improves the dispersing ability of the polymer through the combined action of the terminal R3 group, amide group, and polymer backbone segments, thereby improving the applicability of the polymer dispersant to positive electrode active materials with different degrees of graphitization, enhancing the universality of the polymer dispersant, and contributing to the reduction of preparation costs and the improvement of production efficiency.

[0124] In some embodiments, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4.

[0125]

[0126] Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 each independently contain hydrogen and C. 1-12 Alkyl, C 1-12 At least one of alkyl alcohols and *-NH-R9-OH, wherein R6, R7, and R8 each independently contain hydrogen and C. 1-12 Alkyl, C 1-12 Alkyl alcohols, *-NH-R 10 -OH、 At least one of them, wherein R9, R 10 Each independently contains C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

[0127] In this article, the term "C" 1-12"Alkyl alcohol" refers to a monovalent atomic group in which an alkylene group is bonded to a hydroxyl group (-OH), and is characterized by "-C". n H 2n -OH" is represented by "n" (where n is a natural number from 1 to 12).

[0128] In some embodiments, the polymer comprises at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4.

[0129]

[0130] Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 each independently contain hydrogen and C. 1-12 At least one of alkyl alcohols and *-NH-R9-OH, where R8 contains hydrogen and C 1-12 Alkyl alcohols, *-NH-R 10 -OH、 At least one of them, wherein R9, R 10 Each independently contains C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

[0131] In some embodiments, R4 in the structure shown in Formula I-1 contains hydrogen.

[0132] R4 contains hydrogen, and the polymer can ionize to generate negative ions. These ions can be adsorbed onto the surface of the positive electrode active material particles in the slurry system through electrostatic interaction, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, mitigating the gelation phenomenon of the slurry, improving the flexibility of the electrode, and improving the performance of the slurry and the electrode. At the same time, it can also improve the battery's initial coulombic efficiency and high-temperature storage performance.

[0133] In some embodiments, R4 in the structure shown in Formula I-1 contains C 1-12 Alkyl alcohols or *-NH-R9-OH.

[0134] R4 contains C 1-12 Alkyl alcohols or *-NH-R9-OH, where the amino or hydroxyl groups can adsorb onto the positively charged active material particles in the slurry system, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, and improving the performance of the slurry.

[0135] In some embodiments, R5 in the structure shown in Formula I-2 contains hydrogen.

[0136] R5 contains hydrogen, and the polymer can ionize to generate negative ions. These ions can be adsorbed onto the surface of the positive electrode active material particles in the slurry system through electrostatic interaction, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, mitigating the gelation phenomenon of the slurry, improving the flexibility of the electrode, reducing the film resistance of the electrode, and improving the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0137] In some embodiments, R5 in the structure shown in Formula I-2 includes C 1-12 Alkyl alcohols or *-NH-R9-OH.

[0138] R5 includes C 1-12 Alkyl alcohols or *-NH-R9-OH, where the amino or hydroxyl groups can adsorb onto the positive electrode active material particles in the slurry system, enhance the dispersion effect of the polymer dispersant, increase the solid content of the slurry, slow down the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0139] In some embodiments, R6 or R7 in the structure shown in Formula I-3 contains hydrogen.

[0140] R6 or R7 contains hydrogen, and the polymer can ionize to generate negative ions. These ions can be adsorbed onto the surface of the positive electrode active material particles in the slurry system through electrostatic interaction, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, mitigating the gelation phenomenon of the slurry, improving the flexibility of the electrode sheet, and improving the initial coulombic efficiency and high-temperature storage performance of the battery.

[0141] In some embodiments, R6 or R7 in the structure shown in Formula I-3 contains C 1-12 Alkyl alcohols, *-NH-R 10 -OH or

[0142] R6 or R7 includes C 1-12 Alkyl alcohols, *-NH-R 10 -OH or The amino, hydroxyl, and ester groups can adsorb onto the positively charged active material particles in the slurry system, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, and improving the performance of the slurry.

[0143] In some embodiments, R8 in the structure shown in Formula I-4 contains hydrogen.

[0144] R8 contains hydrogen, and the polymer can ionize to generate negative ions. These ions can be adsorbed onto the surface of the positive electrode active material particles in the slurry system through electrostatic interaction, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, mitigating the gelation phenomenon of the slurry, improving the flexibility of the electrode sheet, and improving the battery's initial coulombic efficiency and high-temperature storage performance.

[0145] In some embodiments, R8 in the structure shown in Formula I-4 includes C 1-12 Alkyl alcohols, *-NH-R 10 -OH or

[0146] R8 includes C 1-12 Alkyl alcohols, *-NH-R 10 -OH or The amino, hydroxyl, and ester groups can adsorb onto the positively charged active material particles in the slurry system, enhancing the dispersion effect of the polymer dispersant, increasing the solid content of the slurry, and improving the performance of the slurry.

[0147] In some embodiments, the polymer comprises the structure shown in Formula I-4.

[0148] Compared to the structure shown in Formula I-3, which contains only one amide group, the structure shown in Formula I-4 contains two amide groups and has a longer main chain segment, which can enhance the dispersion effect of the polymer dispersant, resulting in a high solid content in the slurry, improving the battery's initial coulombic efficiency and high-temperature cycle performance, and enhancing the battery's electrochemical performance.

[0149] In some embodiments, R1 contains hydrogen.

[0150] R1 contains hydrogen, which can form hydrogen bonds with oxygen atoms on the surface of the positive electrode active material. This can further improve the dispersibility of the slurry, increase the solid content of the slurry, slow down the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature storage performance of the battery.

[0151] In some embodiments, G1 includes the structure shown in Formula II; R2 includes the structure shown in Formula III, wherein n1 or n2 is 0, and m1 and m2 are each independently an integer between 3 and 60.

[0152] In some implementations, G1 includes the structure shown in Formula II, where n1 is 0 and m1 is an integer between 3 and 60.

[0153] In some implementations, R2 includes the structure shown in Formula III, where n2 is 0 and m2 is an integer between 3 and 60.

[0154] In this paper, the term "polyoxyethylene segment" refers to a polymer segment containing -CH2-CH2-O- structural units.

[0155] In this paper, the term "polyoxyethylene-propylene oxide segment" refers to a polymer segment containing -CH2-CH2-O- and -CH(CH3)-CH2-O- structural units.

[0156] The polymer contains polyethylene oxide segments or polyethylene oxide-propylene oxide segments, which can improve the flexibility of the polymer, reduce the sliding resistance between particles during the cold pressing process of the electrode, improve the flexibility of the electrode, and improve the performance of the electrode.

[0157] In some embodiments, G1 includes the structure shown in Formula II, and R2 includes the structure shown in Formula III, wherein n1 and n2 are each independently an integer between 1 and 60, and m1 and m2 are each independently an integer between 3 and 30.

[0158] In some embodiments, G1 includes the structure shown in Formula II, where n1 is an integer between 1 and 60, and m1 is an integer between 3 and 30.

[0159] In some embodiments, R2 includes the structure shown in Formula III, where n2 is an integer between 1 and 60, and m2 is an integer between 3 and 30.

[0160] The polymer contains polyethylene oxide-propylene oxide segments, which can further improve the polymer's flexibility, reduce the slip resistance between particles during the cold pressing process of the electrode, improve the electrode's flexibility, improve the electrode's performance, and enhance the battery's high-temperature storage performance.

[0161] In some implementations, the mass percentage of R3 in the polymer is 0.5%-20% based on the mass of the polymer.

[0162] In some implementations, the total mass percentage of G1 and R2 in the polymer is 20%-80% based on the polymer mass.

[0163] In some implementations, based on a polymer mass meter, the polymer contains... The mass percentage ranges from 0.5% to 50%.

[0164] By controlling the mass percentages of R3 groups, main chain segments G1 and R2, and amide groups within a suitable range, the R3 groups, G1 and R2, and amide groups can fully exert their respective advantages and work together to give the polymer excellent dispersibility and improve the dispersibility of the slurry.

[0165] In some embodiments, the weight-average molecular weight of the polymer is 500 g / mol to 20000 g / mol.

[0166] In some embodiments, the weight-average molecular weight of the polymer can be selected from any value or a range of any two of the following: 500 g / mol, 600 g / mol, 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, 6000 g / mol, 6500 g / mol, 7000 g / mol, 7500 g / mol, 8000 g / mol, 8500 g / mol, 9000 g / mol, 9500 g / mol, 10000 g / mol, 15000 g / mol, and 20000 g / mol.

[0167] In some embodiments, the weight-average molecular weight of the polymer is 2000 g / mol to 5000 g / mol.

[0168] In some embodiments, the weight-average molecular weight of the polymer can be selected as any value or a range of any two of the following: 2000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, and 5000 g / mol.

[0169] In this paper, the term "weight-average molecular weight" refers to the sum of the products of the weight fraction of molecules of different molecular weights in a polymer and their corresponding molecular weights.

[0170] In this application, the weight-average molecular weight of the polymer can be determined using methods known in the art, such as gel permeation chromatography (GPC), specifically a Waters 2695 Isocratic HPLC gel permeation chromatograph (differential refractive index detector 2141). In some embodiments, the test method uses a 3.0% polystyrene solution sample as a reference, selecting a matched chromatographic column (oil-based: Styragel HT5DMF7.8*300mm + Styragel HT4). A 3.0% fluorinated polymer solution is prepared using purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. During testing, tetrahydrofuran is first drawn into a syringe for rinsing, repeated several times. Then, 5 ml of the test solution is drawn, air is expelled from the syringe, and the needle tip is dried. Finally, the sample solution is slowly injected into the injection port. After the reading stabilizes, the data is acquired, and the weight-average molecular weight is read.

[0171] If the weight-average molecular weight of the polymer is too high, the polymer will be difficult to dissolve and will not be able to act as a dispersant. If the weight-average molecular weight of the polymer is too low, it will not be able to effectively disperse the polymer, which will hinder the formation of the conductive network, leading to an increase in the film resistance of the electrode and a decrease in the battery's initial coulombic efficiency and high-temperature storage performance.

[0172] In some embodiments, the glass transition temperature of the polymer is 50°C-180°C.

[0173] In some embodiments, the glass transition temperature of the polymer is any value or a range of any two of the following: 50°C, 60°C, 90°C, 100°C, 120°C, 140°C, 150°C, and 180°C.

[0174] In this paper, the term "glass transition temperature" refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from a glassy state to a rubbery state or vice versa. It is the lowest temperature at which the macromolecular chain segments of an amorphous polymer can move freely.

[0175] In this paper, the term "glassy state" refers to the state of an amorphous polymer where the deformation under external force is very small, directly proportional to the magnitude of the force, and the deformation immediately recovers after the force is removed. In the glassy state, the energy of molecular motion is very low, insufficient to overcome the rotational barriers within the main chain, and insufficient to excite chain segment motion; the chain segments are in a frozen state. For example, when subjected to external force, because chain segment motion is frozen, only minor changes in the bond lengths and bond angles of the main chain occur. Therefore, macroscopically, the deformation of the polymer under force is very small.

[0176] In this paper, the term "highly elastic state" refers to the large deformation that an amorphous polymer undergoes under a small external force. In the highly elastic state, when an amorphous polymer is subjected to external force, the molecular chains adapt to the force through internal rotation of single bonds and conformational changes in chain segments. For example, under tensile force, the molecular chains can change from a coiled state to an extended state, thus exhibiting large deformation on a macroscopic scale. Once the external force is removed, the molecular chains return to their original coiled state through internal rotation of single bonds and chain segment movement, macroscopically exhibiting elastic recoil.

[0177] In this application, the glass transition temperature of the polymer can be tested using methods known in the art, such as a differential scanning calorimeter (Q1000 model) from TA Instruments. A 6-9g polymer sample is heated from room temperature to 200℃ at a heating rate of 10℃ / min. The resulting differential scanning calorimetry curve is analyzed to obtain the glass transition temperature of the polymer, expressed in °C.

[0178] In some embodiments, the polymer has a melting point of 90°C-220°C at 1 standard atmosphere.

[0179] In some embodiments, the melting point of the polymer at 1 standard atmosphere is any value or a range of any two of the following: 90°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, and 220°C.

[0180] In this article, the term "1 standard atmosphere" refers to the air pressure at sea level under standard atmospheric conditions, which is 101.325 kPa and is a unit of pressure, denoted as atm.

[0181] In this application, the melting point of the polymer at 1 standard atmosphere can be tested using methods known in the art, such as a precision microscopic melting point apparatus (X-5 type). At 1 standard atmosphere, 0.01 mg of uniformly ground sample is placed on a glass slide, covered with another glass slide, and gently pressed down, then placed in the center of the hot stage. After covering with a heat shield, the microscope focus is adjusted until the sample can be clearly observed. The temperature knob is then adjusted to rapidly heat the polymer until it exhibits slight melting, and then the heating rate is slowly adjusted until the sample is completely melted. The temperature of complete melting is recorded as the melting point of the polymer, in °C.

[0182] In some implementations, the polymer has a hydrophilic-lipophilic balance value of 6-16.

[0183] In some embodiments, the hydrophilic-lipophilic balance value of the polymer can be selected as any value from 6, 8, 10, 12, 14, 16 or a range of any two of these values.

[0184] In this paper, the term "hydrophilic-lipophilic balance value" is used to characterize the overall tendency of a polymer to be hydrophilic and lipophilic. The larger the hydrophilic-lipophilic balance value, the better the hydrophilicity of the polymer; conversely, the smaller the hydrophilic-lipophilic balance value, the worse the hydrophilicity and the better the lipophilicity.

[0185] In this paper, the hydrophilic-lipophilic balance (HLB) value of polymers can be tested using methods known in the art, such as the emulsification method. The principle is that when a polymer emulsifies an oily medium, the resulting emulsion exhibits the best stability when the polymer's HLB value matches the required HLB value of the oil phase medium. The ideal HLB value can be obtained by mixing standard samples with known HLB values ​​in a specific ratio. The polymer is then emulsified into the prepared oil phase and allowed to stand for 24 hours. The HLB value required for the oil phase in the sample exhibiting the best stability is the HLB value of the polymer.

[0186] In some embodiments, the polymer has a hydrophilic-lipophilic balance value of 10-12.

[0187] In some embodiments, the hydrophilic-lipophilic balance value of the polymer can be selected as any value among 10, 11, and 12, or a range consisting of any two of these values.

[0188] One embodiment of this application provides a method for preparing a polymer, the polymer comprising the structure shown in Formula I.

[0189]

[0190] G1 contains C 1-20 Alkyl groups or structures represented by Formula II,

[0191]

[0192] Where A contains nonpolar groups, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60.

[0193] R1 contains hydrogen or C. 1-3 Alkyl, R2 contains C 1-12 Alkylene or the structure shown in Formula III,

[0194]

[0195] Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60.

[0196] R3 contains at least one of the following groups: carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphate group, and phosphate ester group.

[0197] The preparation method yields a polymer containing a polar group (carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester) at one end and a nonpolar group (alkyl or A) at the other end, with an amide group in the main chain. Using this polymer as a dispersant, it is suitable for positive electrode active materials with different degrees of graphitization. It can improve the dispersibility of slurry systems containing positive electrode active materials with different degrees of graphitization, increase the solid content of the slurry, mitigate gelation, reduce the film resistance of the electrode, improve the flexibility of the electrode, and enhance the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0198] In some embodiments, the preparation method specifically includes:

[0199] Reacting the acid represented by Formula IV with the amine represented by Formula V yields a polymer containing the structure shown in Formula I.

[0200]

[0201] This application utilizes a one-step reaction between carboxyl and amino groups to prepare polymers, which is simple and improves production efficiency.

[0202] In some embodiments, the acid represented by Formula IV contains

[0203]

[0204] Where A contains C 3-30 Alkyl, C 6-30 At least one of the aromatic groups, B contains C 1-20 alkyl.

[0205] In some embodiments, the amine represented by Formula V contains

[0206]

[0207] This application utilizes a one-step reaction between carboxyl and amino groups to prepare polymers, which is simple and improves production efficiency.

[0208] In some embodiments, a dispersant is provided, the dispersant comprising the polymer of any embodiment or a polymer prepared by any preparation method of any embodiment.

[0209] In some embodiments, the use of the polymer in a secondary battery according to any embodiment is provided.

[0210] [Positive electrode slurry]

[0211] In some embodiments, a positive electrode slurry is provided, comprising a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant comprises a polymer as described in any of the embodiments.

[0212] This positive electrode slurry has excellent dispersibility and high solid content, which is beneficial for preparing high-performance electrodes.

[0213] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0214] In some embodiments, the positive electrode slurry includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0215] In some embodiments, the positive electrode active material includes lithium iron phosphate with a carbon coating on its surface.

[0216] On the one hand, the polymer backbone contains amide groups, and the oxygen and nitrogen atoms on the amide groups can coordinate with the iron atoms in lithium iron phosphate. On the other hand, the oxygen and nitrogen atoms on the amide groups can form hydrogen bonds with the carboxyl or hydroxyl groups in the carbon coating layer. The two work together to improve the polymer's ability to disperse slurry, so that the polymer dispersant has excellent dispersion ability for slurry systems with lithium iron phosphate with a carbon coating layer on the surface as the positive electrode active material.

[0217] In some embodiments, the degree of graphitization of lithium iron phosphate with a carbon coating on the surface is 10%-30%.

[0218] In some embodiments, the degree of graphitization of the lithium iron phosphate with a carbon coating on its surface can be selected as any value from 10%, 15%, 20%, 25%, 30%, or a range of any two of these values.

[0219] In this application, the term "graphitization degree" refers to the degree of graphitization of the carbon component, reflecting the integrity of the graphite crystal structure in carbon-coated lithium iron phosphate, especially in the carbon coating layer, that is, the regularity of the arrangement of carbon atoms in the graphite structure.

[0220] In this paper, the graphitization degree of lithium iron phosphate can be measured using methods known in the art, such as Raman spectroscopy. Specifically, the graphitization degree was characterized using a HORIBA Jobin Yvon high-resolution Raman spectrometer (LabRAM HR Evlution), France. After background subtraction, the following Gaussian function was used for fitting. Raman spectrum test conditions: wavelength 532 nm, scanning range 200-4000 cm⁻¹. -1 Accumulate twice, measuring 10 points for each sample, and use the average value to fit the result:

[0221]

[0222] In the above formula, G represents the degree of graphitization, and Ai, Vi, and wi represent the peak intensity, peak position, and peak width, respectively.

[0223] In existing technologies, carbon coating is applied to the surface of the positive electrode active material to improve the electronic and ionic conductivity of lithium iron phosphate (LFP). However, the existing LFP coating processes on the market vary widely, with varying degrees of carbon coating and different graphitization levels of LFP. Existing dispersants are not suitable for slurries using LFP with different degrees of graphitization as the positive electrode active material. The polymer dispersant of this application, however, is universally applicable, improving the dispersibility of slurries using LFP with different degrees of graphitization as the positive electrode active material, increasing the solid content of the slurry, mitigating gelation, reducing film resistance of the electrode, improving electrode flexibility, and enhancing the battery's initial coulombic efficiency and high-temperature cycle performance. This polymer dispersant is universally applicable to positive electrode slurries containing LFP produced by different processes and with different degrees of graphitization, contributing to reduced manufacturing costs and increased production efficiency.

[0224] In some embodiments, the dispersant has a mass fraction of 0.01%-3%, based on the total mass of solids in the positive electrode slurry.

[0225] In some embodiments, based on the total mass of solid matter in the positive electrode slurry, the mass fraction of the dispersant can be selected as any value or a range of any two of the following: 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%.

[0226] When the mass fraction of the dispersant is within a suitable range, the slurry has a high solid content, the electrode has excellent flexibility, and the battery has excellent initial coulombic efficiency and high-temperature storage performance.

[0227] In some embodiments, the dispersant has a mass fraction of 0.03%-2%, based on the total mass of solids in the positive electrode slurry.

[0228] In some embodiments, based on the total mass of solid matter in the positive electrode slurry, the mass fraction of the dispersant can be selected as any value or a range of any two of 0.03%, 0.1%, 0.5%, 1%, 1.5%, 2%.

[0229] When the mass fraction of the dispersant is within a suitable range, the flexibility of the electrode can be further improved, thus enhancing its performance.

[0230] [Positive electrode plate]

[0231] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer being prepared from the positive electrode slurry in any embodiment.

[0232] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0233] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0234] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder, dispersant and any other components, in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0235] [Negative electrode plate]

[0236] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0237] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0238] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0239] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0240] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0241] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0242] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0243] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0244] [Electrolytes]

[0245] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0246] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0247] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0248] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0249] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0250] [Isolation membrane]

[0251] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0252] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0253] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0254] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0255] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0256] [Rechargeable Battery]

[0257] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5. The secondary battery can also be a sodium-ion battery, a magnesium-ion battery, or a potassium-ion battery.

[0258] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0259] [Battery Module]

[0260] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0261] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0262] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0263] [Battery Pack]

[0264] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0265] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0266] [Electrical appliances]

[0267] In one embodiment of this application, an electrical device is provided, including at least one of a secondary battery, a battery module, or a battery pack according to any embodiment.

[0268] 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 can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0269] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0270] Figure 6This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0271] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0272] Example

[0273] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0274] I. Preparation Method

[0275] Example 1

[0276] 1) Preparation of polymer: Add acid and amine in a molar ratio of 1:1.1 to the reaction apparatus, raise the reaction temperature to 150°C, use 5% dilute sulfuric acid as catalyst, wherein the mass content of dilute sulfuric acid is 1%, and react for 6 to 10 hours based on the mass of added amine and acid. At the same time, use a water separator to remove the by-product water generated during the reaction. After the reaction is completed, return to room temperature to obtain polymer P-1.

[0277] The structural formula of the acid is:

[0278]

[0279] The structural formula of amine is

[0280]

[0281] The reaction process of polymer P-1 is shown below.

[0282]

[0283] 2) Preparation of positive electrode slurry

[0284] Lithium iron phosphate (LFP@C) with carbon coating as the positive electrode active material, acetylene black (SP) as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and dispersant (P-1) were added to N-methylpyrrolidone (NMP) and stirred to obtain a positive electrode slurry. The weight ratio of LFP@C, SP, and PVDF was 97:2:1. The mass fraction of the dispersant was 1.5% of the total mass of the positive electrode active material, conductive agent, binder, and dispersant. The theoretical solid content of the positive electrode slurry was 60%. After stirring, the viscosity of the slurry was tested and controlled to be less than 20,000 mPa·s. If the viscosity was too high, the minimum amount of NMP was added to bring the slurry viscosity below 20,000 mPa·s.

[0285] 3) Preparation of positive electrode sheet

[0286] The positive electrode slurry is uniformly coated on both surfaces of the aluminum foil positive electrode current collector and then dried to obtain a film layer; after cold pressing and slitting, the positive electrode sheet is obtained.

[0287] 4) Preparation of negative electrode sheet

[0288] Artificial graphite (anode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) are dissolved in deionized water at a weight ratio of 96:2:1:1 and mixed evenly to prepare a cathode slurry. The cathode slurry is then coated evenly on both surfaces of the cathode current collector copper foil multiple times. After drying, cold pressing, and slitting, the cathode sheet is obtained.

[0289] 5) Separating membrane

[0290] Polypropylene film is used as the separator.

[0291] 6) Preparation of electrolyte

[0292] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3 / 7. LiPF6 lithium salt was dissolved in the organic solvent to prepare a 12.5% ​​solution, thus obtaining the electrolyte.

[0293] 7) Preparation of secondary batteries

[0294] The positive electrode, separator, and negative electrode prepared in Example 1 are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed to obtain a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 1.

[0295] Example 2-12

[0296] The batteries in Examples 2-12 are prepared using a similar method to those in Example 1, but the type of amine is adjusted, thereby adjusting the polymer structure. Specific adjustment parameters are shown in Table 1.

[0297]

[0298]

[0299] In the polymer structures of Examples 1-12, G1 contains

[0300] R2 includes

[0301]

[0302] Examples 13-16

[0303] The batteries in Examples 13-16 are prepared using a similar method to those in Example 1, but the types of acid and amine are adjusted, thereby modifying the structure of G1 and R2 in the polymer. Specific adjustment parameters are shown in Table 2, and the corresponding G1 and R2 groups are shown in Table 3.

[0304] Table 2

[0305]

[0306] Table 3

[0307]

[0308] Examples 17-20

[0309] Compared to Example 1, the mass fraction of the polymer dispersant was adjusted, as detailed in the example table.

[0310] Examples 21-24

[0311] Compared to Example 1, the degree of graphitization of lithium iron phosphate was adjusted, as detailed in the example table.

[0312] Example 25

[0313] Compared to Example 1, the positive electrode active material was adjusted to carbon-coated LiNi. 0.6 Co 0.2 Mn 0.2 O2(NCM@C).

[0314] Example 26

[0315] Compared to Example 1, the structural formula of the amine was adjusted. The structural formula of the amine is shown below.

[0316]

[0317] Comparative Example

[0318] Comparative Examples 1-4

[0319] Compared to Example 1, the dispersant was replaced with polyvinylpyrrolidone (PVP) dispersant, and the degree of graphitization of lithium iron phosphate was adjusted.

[0320] Comparative Example 5

[0321] Compared to Example 1, the dispersant was replaced with polymeric dispersant D-1, whose structural formula is [insert structural formula here].

[0322] The specific preparation process is as follows:

[0323] With 1 mol of C 12 H 25 -OH was used as the initiator, and 0.5% KOH (by mass) was used as the catalyst. The system was evacuated and purged with nitrogen. The reaction apparatus was then heated to 130°C and evacuated again. 45 mol of ethylene oxide gas was then introduced to maintain the pressure inside the reaction apparatus below 0.3 MPa. The reaction was carried out at this pressure and temperature for 1 hour, and then cooled to obtain the first product. Then, 0.5% KOH (by mass) of the initiator was added again, the system was evacuated and purged with nitrogen, the reaction apparatus was then heated to 130°C and evacuated again, and then 25 mol of propylene oxide gas was introduced. The reaction was carried out for 1 hour, and then cooled to obtain the product. The product was further neutralized by acid washing, extracted three times with dichloromethane, dried, filtered, and rotary evaporated to obtain the intermediate product.

[0324] 1 mol of the intermediate product and 1.5 mol of the anchoring and capping agent Cl-C4H8-COOH were dissolved in 1000 mL of dichloromethane and subjected to a halogenation reaction at room temperature. After 6 h of reaction, 500 mL of deionized water was added to quench the reaction. The reaction mixture was extracted three times in dichloromethane, and the oil phase product was collected. The product was then dried with magnesium sulfate, separated by rotary evaporation, and finally separated by column chromatography to obtain polymer dispersant D-1.

[0325] Comparative Example 6

[0326] Compared to Example 1, the dispersant was replaced with polymeric dispersant D-2, and the preparation process was adjusted compared to Example 1. The structural formula of the amine is shown below.

[0327]

[0328] II. Performance Testing

[0329] 1. Characterization of polymers

[0330] 1) Weight-average molecular weight

[0331] A Waters 2695 Isocratic HPLC gel electrophoresis system (differential refractive index detector 2141) was used. A 3.0% polystyrene solution was used as a reference, and a matched column was selected (oil-based: Styragel HT5 DMF7.8*300mm + Styragel HT4). A 3.0% polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. For testing, tetrahydrofuran was first used to flush the syringe, repeated several times. Then, 5 ml of the experimental solution was drawn, air was expelled from the syringe, and the needle tip was dried. Finally, the sample solution was slowly injected into the injection port. Data was acquired after the reading stabilized.

[0332] 2) Glass transition temperature

[0333] The glass transition temperature was measured using a differential scanning calorimeter (Q1000 model) from TA Instruments. A 6-9 g polymer sample was taken and heated from room temperature to 200 °C at a rate of 10 °C / min. The resulting differential scanning calorimetry curve was analyzed to obtain the glass transition temperature of the polymer, expressed in °C.

[0334] 3) Melting point

[0335] The melting point was tested using a precision microscopic melting point apparatus (X-5 type). The test was conducted at standard atmospheric pressure. A 0.01 mg sample, uniformly ground, was placed on a glass slide, covered with another slide, and gently pressed down. The slide was then placed in the center of the hot stage. After covering with a heat shield, the microscope focus was adjusted until the sample could be clearly observed. The temperature knob was then adjusted to rapidly increase the temperature until the polymer showed slight melting. The heating rate was then slowly adjusted until the sample was completely melted. The temperature at which the sample completely melted was recorded as the melting point of the polymer, in °C.

[0336] 4) Hydrophilic-lipophilic balance (HLB) value

[0337] The emulsification method is used for determination. The principle is that when a polymer emulsifies an oily medium, the resulting emulsion exhibits the best stability when the polymer's HLB value matches the required HLB value of the oil phase. The ideal HLB value can be obtained by mixing standard samples with known HLB values ​​in a specific ratio. This polymer is then used to emulsify the prepared oil phase and allowed to stand for 24 hours. The HLB value required for the oil phase in the sample exhibiting the best stability is the HLB value of the polymer.

[0338] 2. Positive electrode active material

[0339] 1) Degree of graphitization

[0340] The degree of graphitization was characterized using a HORIBA Jobin Yvon high-resolution Raman spectrometer (LabRAM HR Evlution, France). After background subtraction, the spectra were fitted using the following Gaussian function. Raman spectroscopy test conditions: wavelength 532 nm, scanning range 200-4000 cm⁻¹. -1 Accumulate twice, measuring 10 points for each sample, and use the average value to fit the result:

[0341]

[0342] In the above formula, G represents the degree of graphitization, and Ai, Vi, and wi represent the peak intensity, peak position, and peak width, respectively.

[0343] 3. Positive electrode slurry

[0344] 1) Solid content

[0345] Weigh the copper foil in the weight loss rate measuring instrument and record the weight as M0, then zero the instrument.

[0346] Take a small amount of positive electrode slurry, coat it onto copper foil, and then weigh it in a moisture analyzer. Record the weight as M1.

[0347] Close the equipment and begin drying;

[0348] After completion, record the weighing data as M2, and calculate the solid content as (M2-M0) / (M1-M0).

[0349] 2) Slurry stability test

[0350] After re-stirring the slurry for 30 minutes, take a certain amount of slurry and pour it into the sample bottle of the stability tester. After placing the sample bottle, close the test tower lid and open the test tower lid. The test interface will start to show the scanning curve, and the sample stability test will begin. The test will continue for more than 72 hours to complete the test.

[0351] 4. Positive electrode sheet

[0352] 1) Brittleness test

[0353] Take a defect-free positive electrode sheet and cut it longitudinally into samples with a length and width of 20cm x 2.5cm. The sample size should be ≥8 pieces. First, pre-fold the sample in half. Then, place the sheet on the testing platform and roll it once with a 2kg cylindrical roller. If light is transmitted, the brittle light transmission test counts as one cycle. If light is not transmitted, repeat the reverse folding and rolling test. Observe the crease against the light to check for light transmission or breakage. Record the actual number of folds and take the average as the test result.

[0354] 2) Diaphragm resistance

[0355] Cut the dried positive electrode slurry (film layer) into small round pieces with a diameter of 3mm from the left, center, and right sides of the positive electrode sheet. Turn on the power of the Yuaneng Technology electrode resistance meter, place the probe at the appropriate position on the meter, and click the "Start" button. Wait for the reading to stabilize and then take the reading. Test two positions for each small round piece, and finally calculate the average of the six measurements, which is the resistance of the electrode film layer.

[0356] 5. Secondary batteries

[0357] 1) First Coulomb efficiency

[0358] At 25°C, the batteries of the above embodiments and comparative examples were charged at a constant current rate of 0.1C to a voltage of 4.3V. The charging capacity at this time was recorded as the first charge capacity of the secondary battery. After resting for 5 minutes, the batteries were discharged at a constant current rate of 0.1C to a voltage of 2.0V and then rested for 5 minutes. This is one charge-discharge cycle. The discharge capacity of this cycle was recorded as the first discharge capacity of the secondary battery, which is the initial capacity of the secondary battery.

[0359] The first-cycle coulombic efficiency (%) of a secondary battery = first-cycle discharge capacity / first-cycle charge capacity × 100%.

[0360] 2) Capacity retention rate during 45℃ cycling

[0361] At 45°C, the batteries in the examples and comparative examples were charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to rest for 10 minutes, and then discharged to 2.5V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle was recorded. The battery capacity retention rate after each cycle is then:

[0362] Pn = C n / C0×100%

[0363] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=100. The battery capacity retention rate data corresponding to Example 1 in Table 5 is the data measured after 300 cycles under the above test conditions, i.e., the value of P300.

[0364] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0365] Table 4. Parameters and Performance Test Results of the Examples

[0366]

[0367]

[0368] Table 5. Parameters and Performance Test Results of the Examples

[0369]

[0370]

[0371] Based on the above results, it can be concluded that the polymers in Examples 1-26 contain... G1 includes

[0372] R1 contains hydrogen or methyl, R2 contains R3 contains any one of the following groups: carboxyl, ester, sulfonic acid, sulfonate, phosphate, or phosphate ester.

[0373] As can be seen from the comparison of Examples 1-16, 21-24, and 26 with Comparative Examples 1-4, compared with traditional PVP dispersants, the polymer dispersant of this application has broad versatility. It can improve the dispersibility of slurries using lithium iron phosphate with different degrees of graphitization as the positive electrode active material, increase the solid content of the slurry, mitigate the gelation phenomenon of the slurry, reduce the film resistance of the electrode, improve the flexibility of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery. This polymer dispersant is universally applicable to positive electrode slurries containing lithium iron phosphate with different degrees of graphitization produced by different processes, which helps to reduce preparation costs and improve production efficiency.

[0374] A comparison of Example 1 and Comparative Example 5 shows that the amide groups in the polymer dispersant of this application can effectively increase the solid content of the slurry, alleviate the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery. A comparison of Examples 1-12 and Comparative Example 6 shows that the R3 groups in the polymer dispersant of this application, containing carboxyl, ester, sulfonic acid, sulfonate, phosphoric acid, or phosphate ester groups, can effectively increase the solid content of the slurry, alleviate the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0375] As can be seen from the comparison between Examples 1, 9-10 and Example 5, compared with R3 groups containing -C4H8-COO-C3H7, polymer dispersants containing R3 groups containing -C4H8-COOH, -C4H8-COO-C3H6-OH or -C4H8-COO-NH-C3H6-OH can further improve the dispersibility of the slurry, increase the solid content of the slurry, and improve the performance of the slurry. A comparison of Examples 1 with Examples 5 and 9-10 shows that, compared to R3 groups containing -C4H8-COO-C3H7, -C4H8-COO-C3H6-OH, or -C4H8-COO-NH-C3H6-OH, the polymer dispersant containing the -C4H8-COOH R3 group can further improve the dispersion effect of the slurry, increase the solid content of the slurry, mitigate the gelation phenomenon of the slurry, improve the flexibility of the electrode, and improve the performance of both the slurry and the electrode. It can also improve the initial coulombic efficiency and high-temperature storage performance of the battery. A comparison of Examples 2 with Examples 6 shows that, compared to R3 groups containing -C4H8-SO3-C3H7, the polymer dispersant containing the -C4H8-SO3H R3 group can further improve the dispersion effect of the slurry, increase the solid content of the slurry, mitigate the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature cycling performance of the battery. A comparison of Examples 4, 11-12, and Example 8 shows that, compared to polymer dispersants containing...

[0376] Polymer dispersants contain

[0377] This can further improve the dispersibility of the slurry, increase its solid content, and enhance its performance. A comparison of Example 4 with Examples 8 and 11-12 shows that, compared to polymer dispersants containing...

[0378]

[0379] Polymer dispersants contain This can further increase the solid content of the slurry, slow down the gelation phenomenon, improve the flexibility of the electrode, and enhance the initial coulombic efficiency and high-temperature storage performance of the battery. A comparison between Example 3 and Example 7 shows that, compared to polymers containing...

[0380] Polymer dispersants contain This can further increase the solid content of the slurry, slow down the gelation phenomenon, improve the flexibility of the electrode, and enhance the initial coulombic efficiency and high-temperature cycle performance of the battery. A comparison between Example 8 and Example 7 shows that, compared to polymers containing...

[0381] Polymer dispersants contain This can improve the initial coulombic efficiency and high-temperature cycling performance of the battery, and enhance its electrochemical performance. A comparison of Example 4 and Example 3 shows that, compared to the polymer containing... Polymer dispersants contain It can further increase the solid content of the slurry, improve the flexibility of the electrode, and enhance the initial coulombic efficiency and high-temperature storage performance of the battery.

[0382] As can be seen from the comparison between Example 1 and Example 26, compared with R1 containing methyl, R1 containing hydrogen can further improve the dispersibility of the slurry, increase the solid content of the slurry, slow down the gelation phenomenon of the slurry, improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the initial coulombic efficiency and high-temperature storage performance of the battery.

[0383] A comparison of Examples 1, 13 and 14, and a comparison of Examples 1, 16 and 15, show that G1 includes... R2 includes This can increase the solid content of the slurry, slow down the gelation phenomenon, improve the flexibility of the electrode, and enhance the initial coulombic efficiency and high-temperature storage performance of the battery. A comparison of Example 1 and Examples 13-16 shows that G1 contains... R2 includes It can further increase the solid content of the slurry, slow down the gelation of the slurry, improve the flexibility of the electrode, and improve the first coulombic efficiency and high-temperature storage performance of the battery.

[0384] The positive electrode slurry of Examples 1-26 comprises a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant is a polymer of this application, and the positive electrode active material includes lithium iron phosphate without a carbon coating, lithium iron phosphate with a carbon coating, or lithium nickel cobalt manganese with a carbon coating.

[0385] As can be seen from the comparison between Example 1 and Example 25, compared with lithium nickel cobalt manganese with a carbon coating on the surface as the positive electrode active material, the polymer dispersant of this application is more suitable for lithium iron phosphate with a carbon coating on the surface. It can further increase the solid content of the slurry of lithium iron phosphate with a carbon coating on the surface, improve the flexibility of the electrode, and improve the performance of the electrode and the slurry.

[0386] As can be seen from Examples 1 and 22-24, the polymer dispersant of this application has universality and is suitable for slurry systems using lithium iron phosphate with a graphitization degree of 10%-30% as the positive electrode active material. A comparison of Examples 1 and 22-24 with Example 21 shows that using lithium iron phosphate with a graphitization degree of 10%-30% can further improve the flexibility of the electrode, reduce the film resistance of the electrode, and improve the performance of the electrode.

[0387] As can be seen from Examples 1 and 17-20, based on the total mass of solid matter in the positive electrode slurry, a polymer dispersant mass fraction of 0.01%-3% results in a slurry with high solid content, excellent electrode flexibility, and superior initial coulombic efficiency and high-temperature storage performance of the battery. Comparing Examples 1 and 18-19 with Examples 17 and 20, a polymer dispersant mass fraction of 0.03%-2% based on the total mass of solid matter in the positive electrode slurry can further improve the electrode flexibility and enhance its performance.

[0388] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A polymer, characterized in that, The polymer is selected from at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4. Formula I-1 Formula I-2 Formula I-3 Formula I-4 Where G1 is C 1-20 Alkyl groups or structures represented by Formula II, Formula II Where A is a nonpolar group, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60; R1 is hydrogen or C. 1-3 alkyl; R2 is the structure shown in Equation III. Formula III Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60; Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 are each independently selected from hydrogen and C. 1-12 Alkyl, C 1-12 Alkyl alcohols At least one of them, R6, R7, and R8 are each independently selected from hydrogen, C 1-12 Alkyl, C 1-12 Alkyl alcohols , At least one of them, wherein R9, R 10 Each is independently selected from C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

2. The polymer according to claim 1, characterized in that, The polymer is selected from at least one of the structures shown in Formula I-1, Formula I-2, and Formula I-4. Formula I-1 Formula I-2 Formula I-4 Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 are each independently selected from hydrogen and C. 1-12 Alkyl alcohols R8 is selected from at least one of the following, wherein R8 is selected from hydrogen, C 1-12 Alkyl alcohols , At least one of them, wherein R9, R 10 Each is independently selected from C 1-12 Alkylene, R 11 Selected from C 1-12 Alkyl or C 6-30 Aromatic group.

3. The polymer according to claim 1, characterized in that, R1 is hydrogen.

4. The polymer according to claim 1, characterized in that, G1 is the structure shown in Formula II; R2 is the structure shown in Formula III. Where n1 or n2 is 0, and m1 and m2 are each an integer between 3 and 60.

5. The polymer according to any one of claims 1 to 3, characterized in that, G1 is the structure shown in Formula II; R2 is the structure shown in Formula III. Where n1 and n2 are each independent integers between 1 and 60, and m1 and m2 are each independent integers between 3 and 30.

6. The polymer according to any one of claims 1 to 4, characterized in that, A is selected from C. 3-30 Alkyl, C 6-30 At least one of the aromatic groups.

7. The polymer according to any one of claims 1 to 4, characterized in that, The weight-average molecular weight of the polymer is 500 g / mol to 20000 g / mol.

8. The polymer according to any one of claims 1 to 4, characterized in that, The glass transition temperature of the polymer is 50℃-180℃.

9. The polymer according to any one of claims 1 to 4, characterized in that, The polymer has a melting point of 90°C-220°C at 1 standard atmosphere.

10. The polymer according to any one of claims 1 to 4, characterized in that, The polymer has a hydrophilic-lipophilic balance value of 6-16.

11. A method for preparing a polymer, characterized in that, The preparation method includes: The acid represented by formula IV is reacted with the amine represented by formula V to obtain a polymer. Formula IV Formula V; R3 contains at least one of the following groups: carboxyl group, ester group, sulfonic acid group, sulfonate group, phosphoric acid group, and phosphate ester group; The polymer is selected from at least one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4. Formula I-1 Formula I-2 Formula I-3 Formula I-4 Where G1 contains C 1-20 Alkyl groups or structures represented by Formula II, Formula II Where A is a nonpolar group, m1 is an integer between 3 and 60, and n1 is an integer between 0 and 60; R1 is hydrogen or C. 1-3 alkyl; R2 is the structure shown in Equation III. Formula III Where m2 is an integer between 3 and 60, and n2 is an integer between 0 and 60; Where a1 and a2 are each independent integers between 2 and 12, and R4 and R5 are each independently selected from hydrogen and C. 1-12 Alkyl, C 1-12 Alkyl alcohols At least one of them, R6, R7, and R8 are each independently selected from hydrogen, C 1-12 Alkyl, C 1-12 Alkyl alcohols , At least one of them, wherein R9, R 10 Each is independently selected from C 1-12 Alkylene, R 11 Includes C 1-12 Alkyl or C 6-30 Aromatic group.

12. A dispersant, characterized in that, The dispersant comprises the polymer according to any one of claims 1 to 10 or the polymer prepared by the preparation method according to claim 11.

13. The use of the polymer according to any one of claims 1 to 10 in a secondary battery.

14. A positive electrode slurry, characterized in that, It includes a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant comprises the polymer according to any one of claims 1 to 10.

15. The positive electrode slurry according to claim 14, characterized in that, The positive electrode active material includes lithium iron phosphate with a carbon coating on its surface.

16. The positive electrode slurry according to claim 15, characterized in that, The degree of graphitization of the lithium iron phosphate with a carbon coating on its surface is 10%-30%.

17. The positive electrode slurry according to claim 14, characterized in that, Based on the total mass of solids in the positive electrode slurry, the mass fraction of the dispersant is 0.01%-3%.

18. The positive electrode slurry according to claim 14, characterized in that, Based on the total mass of solid matter in the positive electrode slurry, the mass fraction of the dispersant is 0.03%-2%.

19. A positive electrode sheet, comprising a positive current collector and a positive electrode membrane disposed on the positive current collector, characterized in that, The positive electrode membrane is prepared from the positive electrode slurry according to any one of claims 14 to 18.

20. A secondary battery, characterized in that, It includes a separator, a negative electrode, an electrolyte, and the positive electrode as described in claim 19.

21. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 20.

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