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

Abstract

Provided in the present application are a polymer and a preparation method therefor, a positive electrode sheet, a secondary battery, and an electric device. The polymer comprises a structure as represented by formula I, wherein X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether chain segment, a polyester chain segment, hydrogen and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether chain segment or a polyester chain segment; and R2 comprises an organic chain segment. The polymer provided in the present application can effectively improve the maximum solid content of a positive electrode slurry, shorten the filtering time, improve the production efficiency and quality of the electrode sheet, and also improve the flexibility of the electrode sheet.

Description

Polymer, preparation method thereof, positive electrode sheet, secondary battery, and electrical device

[0001] Cross-references

[0002] This application refers to Chinese Patent Application No. 202310961340.X filed on August 1, 2023, entitled “Polymer, Preparation Method Thereof, Positive Electrode Sheet, Secondary Battery, and Electrical Device” and Chinese Patent Application No. 202311098921.1 filed on August 29, 2023, entitled “Polymer, Preparation Method Thereof, Positive Electrode Sheet, Secondary Battery, and Electrical Device”, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a polymer, a preparation method thereof, a positive electrode sheet, a secondary battery, and an electrical device. Background Art

[0004] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0005] The electrodes in secondary batteries are often prepared by coating a slurry containing active materials on a current collector and then drying it. Increasing the solvent content and reducing the solid content of the slurry are effective means to optimize the slurry dispersion uniformity and improve the slurry coating quality. However, slurries with high solvent content require long drying times and high manufacturing costs. How to increase the slurry solid content while ensuring the slurry dispersion uniformity and thereby effectively increase the maximum solid content of the slurry is a technical problem that urgently needs to be solved in this field.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its object is to provide a dispersant that can increase the maximum solid content of the slurry.

[0008] The first aspect of the present application provides a polymer comprising a structure shown in Formula I,

[0009] Wherein X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment; and R2 comprises an organic segment.

[0010] The polymer can effectively increase the maximum solid content of the positive electrode slurry, shorten the filtration time, improve the production efficiency and quality of the electrode, and improve the flexibility of the electrode.

[0011] In any embodiment, the organic segment of R2 comprises at least one of an amide group, an amino group, and an aromatic group.

[0012] The nitrogen-containing groups or aromatic groups in the polymer help to improve the anchoring effect between the polymer and the positive electrode active material, making the polymer particularly suitable for carbon-coated positive electrode active materials, further improving the versatility of the polymer as a dispersant, and by increasing the anchoring sites of the dispersant, more effectively exerting the dispersing effect of the polymer, thereby further increasing the maximum solid content of the slurry, improving the quality of electrode molding, and reducing costs and increasing efficiency.

[0013] In any embodiment, the organic segment of R2 further includes C 2-12 Hydrocarbon group.

[0014] The polymer contains C 2-12 The hydrocarbon group helps to further improve the anchoring effect between the polymer and the carbon-modified positive electrode active material. The hydrocarbon group can effectively anchor to the carbon on the positive electrode active material, increase the dispersion of the anchoring sites of the polymer on the positive electrode active material, thereby further improving the application range of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the quality of the electrode forming while reducing costs and increasing efficiency.

[0015] In any embodiment, R2 comprises the structure shown in Formula II

[0016] Among them, R4 and R5 are random copolymers, and R4 includes C 2-12 Hydrocarbylene, C 3-13 At least one of the amide groups, R5 includes At least one of;

[0017] Wherein, q1, q2, q3, q4 are each independently any integer between 0 and 4, R6 a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

[0018] The organic chain segments of the above structure can more effectively play an anchoring role through the copolymerization of nitrogen-containing groups and hydrocarbon groups, enhance the dispersion effect of the polymer, and effectively increase the solid content of the slurry.

[0019] In any embodiment, R2 comprises the structure shown in Formula III

[0020] Among them, R6 includes C 2-12 Alkylene, R7 includes At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

[0021] The organic chain segments of the above structure can more effectively play an anchoring role through the alternating copolymerization of nitrogen-containing groups and hydrocarbon groups, enhance the dispersion effect of the polymer, and effectively increase the solid content of the slurry.

[0022] In any embodiment, the terminal group of R2 comprises at least one of -C(O)-NH2 and -CH2-NH2.

[0023] Polymers whose end groups contain -C(O)-NH2 and -CH2-NH2 can more effectively exert their dispersing effect, increase the maximum solid content of the slurry, and thereby improve the molding quality and efficiency of the pole pieces.

[0024] In any embodiment, at least one of R1 and R3 comprises a polyether segment. Alternatively, both R1 and R3 comprise a polyether segment.

[0025] In any embodiment, at least one of R1 and R3 comprises a polyether segment represented by formula IV

[0026] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50.

[0027] The polyether segment with the above structure has suitable steric hindrance and low glass transition temperature, which can more effectively reduce the order and glass transition temperature of the binder crystallization in the positive electrode slurry, thereby reducing the crystallinity of the binder and improving the flexibility of the electrode. Through the effects of dispersion and softening, the uniformity and flexibility of the electrode are improved, thereby improving the safety performance and ultimate compaction density of the battery, increasing the positive electrode active material loading of the battery, and helping to further improve the energy density of the battery.

[0028] In any embodiment, the end groups of the polyether segments include aromatic groups.

[0029] The aromatic group has excellent compatibility with the carbon layer on the surface of the positive electrode active material, which helps to further improve the anchoring effect between the polymer and the carbon-modified positive electrode active material. With the help of the aromatic group and the carbon on the positive electrode active material, it can effectively anchor and increase the dispersion of the anchoring sites of the polymer on the positive electrode active material, thereby further improving the application range of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the quality of the electrode molding, and reducing costs and increasing efficiency.

[0030] In any embodiment, X comprises a phosphate group.

[0031] Phosphate polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode; and phosphate polymers have better stability, and can effectively improve the battery's cycle capacity retention rate on the basis of improving the slurry's dispersibility.

[0032] In any embodiment, the polymer comprises at least one of the polymers represented by the following formula:

[0033] Wherein, at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV

[0034] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤15, 4≤n1≤15, R6 and R4 each independently include C 4-8 Alkylene, C 4-8 At least one alkenylene group.

[0035] In any embodiment, the polymer is represented by the following formula:

[0036] Wherein, R2 comprises at least one of hydrogen, aryl, substituted or unsubstituted alkyl, and an organic segment containing an amino group or an amide group,

[0037] At least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV

[0038] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50, and the terminal group of the polyether segment includes phenyl.

[0039] In any embodiment, the weight average molecular weight of the polymer is 1,000-10,000, optionally 2,000-5,000.

[0040] Polymers with a weight-average molecular weight within the above range can not only exhibit excellent dispersibility, further increasing the solid content of the slurry, but also provide the slurry with excellent flow properties, reducing coating time and improving coating uniformity and speed. Polymers with a weight-average molecular weight of 2000-5000 can more effectively disperse, increase the maximum solid content of the slurry, and shorten filtration time.

[0041] A second aspect of the present application provides a method for preparing a polymer, the preparation method comprising:

[0042] The compound represented by formula VI is reacted with R3OH, R1OH, water, and a polymerizable monomer containing an unsaturated bond to prepare a polymer having a structure represented by formula I.

[0043] Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all include halogen; R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment or a polyester segment; and R2 includes an organic segment.

[0044] In any embodiment, the preparation method comprises the following steps:

[0045] The compound represented by formula VI is reacted with R3OH, R1OH and water to prepare the intermediate product represented by formula VII.

[0046] The intermediate product is subjected to a second reaction with a polymerization monomer comprising at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer.

[0047] In any embodiment, the second reaction specifically comprises the following steps:

[0048] The intermediate product undergoes an addition reaction with at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and then undergoes a substitution reaction with a halogen-substituted organic alcohol;

[0049] The polymer is prepared by cycling the addition reaction and substitution reaction in sequence for multiple times;

[0050] Wherein, R2 comprises the structure shown in formula III

[0051] Among them, R6 includes C 2-12 Hydrocarbyl, R7 includes At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

[0052] In any embodiment, the preparation method further comprises the following steps:

[0053] The intermediate product is reacted with (i) at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond and a cyclic amide monomer to prepare the polymer, wherein R2 comprises the structure shown in Formula II

[0054] Among them, R4 and R5 are random copolymers, and R4 includes C 2-12 Hydrocarbon, C 3-13 At least one of the amide groups, R5 includes At least one of;

[0055] Wherein, q1, q2, q3, q4 are each independently any integer between 0 and 4, R6a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

[0056] Another aspect of the present application provides a method for preparing a polymer, comprising: reacting a compound represented by Formula VI with a raw material including R3OH and R1OH to prepare a polymer having a structure represented by Formula I,

[0057] Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all include halogen; R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment, and the end group of at least one of the polyether segments includes an aromatic group; R2 includes an organic segment.

[0058] A third aspect of the present application provides a polymer or a polymer prepared by the preparation method of any embodiment as a dispersant.

[0059] A fourth aspect of the present application provides a positive electrode slurry, comprising a dispersant, wherein the dispersant comprises the polymer according to the first aspect of claim 1 or the polymer prepared by the preparation method according to the second aspect.

[0060] The positive electrode slurry has a high solid content, which helps to improve the forming efficiency and forming quality of the positive electrode film layer, and enhance the electrochemical performance and processing efficiency of the battery.

[0061] In any embodiment, the positive electrode slurry includes a positive electrode active material, and the positive electrode active material includes at least one of lithium phosphate and its carbon-modified material; optionally, the positive electrode active material includes at least one of lithium iron phosphate and its doping material, lithium manganese iron phosphate and its doping material, lithium iron phosphate and its doping material carbon-coated material, and lithium manganese iron phosphate and its doping material carbon-coated material.

[0062] The polymer is negatively charged, further strengthening its mutual anchoring with the weakly acidic lithium-containing phosphate through electrostatic interactions, thereby improving the polymer's dispersion of the lithium-containing phosphate. Furthermore, lithium-containing phosphates have poor conductivity. Therefore, in the preparation of positive electrode active materials, a carbon layer coated with organic materials such as sintered glucose and sucrose is often used to improve their conductivity. This polymer also has groups that anchor to the carbon coating, providing excellent dispersion for carbon-modified lithium-containing phosphates, further improving the dispersibility of the slurry and thereby increasing the maximum solids content of the slurry.

[0063] In any embodiment, the positive electrode active material includes a core and a carbon coating layer, wherein the carbon coating layer covers at least a portion of the surface of the core, wherein the carbon coating layer has a sp2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not less than 0.2, and may be not less than 0.5, and may be not less than 0.8.

[0064] The formation of a carbon coating layer on the surface of the core can improve the conductivity of the positive electrode active material. 2 When the molar ratio of hybridized carbon atoms to sp3 hybridized carbon atoms is not less than 0.5, the structure of the carbon coating layer of the positive electrode active material is highly ordered, and the pore structure of the carbon coating layer has a high density and a small pore size distribution range. During the production process of the battery, it is difficult for external moisture to enter the pores of the carbon coating layer, thereby effectively reducing the water absorption and water storage properties of the positive electrode active material, achieving improved battery safety and cycle performance, effectively saving energy consumption in the drying process, and significantly reducing production costs.

[0065] But sp 2 Hybridized carbon atoms with sp 3 A carbon coating with a molar ratio of hybridized carbon atoms of no less than 0.5 has a high degree of graphitization, which makes the positive electrode active material prone to agglomeration and difficult to effectively disperse during the slurrying process. The dispersant provided in the embodiments of the present application and the highly graphitized carbon coating have abundant anchoring groups and are particularly suitable for dispersing positive electrode active materials with highly graphitized coatings. The combination of the two can simultaneously improve the performance and processing properties of the battery.

[0066] In any embodiment, the thickness of the carbon coating layer is no greater than 15 nm; alternatively, the thickness of the carbon coating layer is no greater than 10 nm, and alternatively, the thickness of the carbon coating layer is 4 nm to 8 nm. The carbon coating layer within the above thickness range can form a relatively thin carbon coating layer on the surface of the core, thereby effectively improving the conductivity of the positive electrode active material and improving the compaction performance when using the positive electrode active material to prepare a battery electrode sheet.

[0067] In any embodiment, based on the total mass of the dry material of the positive electrode slurry, the mass content of the polymer is 0.1%-2.0%, and optionally 0.2%-1.0%.

[0068] The polymer within the above range can not only play an effective dispersing role, but also take into account the volume energy density of the battery, and will not have a serious negative impact on the electrochemical performance of the battery.

[0069] In any embodiment, the positive electrode slurry includes a binder, and the binder includes a vinylidene fluoride polymer with a weight average molecular weight of not less than 300,000. Optionally, the weight average molecular weight of the binder is 700,000-9,000,000.

[0070] Vinylidene fluoride polymers with a weight-average molecular weight in this range have excellent bonding properties and electrochemical stability. The use of vinylidene fluoride polymers with a weight-average molecular weight of 700,000-9 million can further reduce the amount of vinylidene fluoride used, reduce the rigidity of the positive electrode film layer, and increase the flexibility of the electrode, thereby increasing the battery's ultimate compaction density and helping to improve the battery's energy density.

[0071] In any embodiment, the maximum solid content of the positive electrode slurry is not less than 60%, and can be optionally 60%-80%.

[0072] The fifth aspect of the present application provides a positive electrode plate, which includes a positive electrode film layer, which is prepared by the positive electrode slurry of any embodiment or the positive electrode film layer includes a dispersant, and the dispersant includes the polymer of the first aspect or the polymer prepared by the preparation method of the second aspect.

[0073] In any embodiment, the positive electrode sheet has a compaction density of 2.6 g / cm 3 The number of times that it can be folded is not less than 2 times, and can be selected as 3-6 times.

[0074] The polymer can not only effectively increase the solid content of the slurry, but also act as a softener, thereby increasing the flexibility of the positive electrode and further improving the safety and electrochemical performance of the battery.

[0075] In any embodiment, the surface density of the positive electrode sheet is not less than 300 mg / 1540.25 cm 2 , optional 300mg / 1540.25cm 2 -600mg / 1540.25cm 2 .

[0076] Polymers can effectively increase the maximum solid content of the slurry, increasing the coating speed by more than 30%. They are particularly suitable for high-speed coating and thick coating molding methods. They can effectively solve the problem of easy cracking of the electrode during thick coating, and help to prepare positive electrode sheets with high flexibility and no cracks after winding molding.

[0077] In any embodiment, the positive electrode film layer includes a dispersant, and the dispersant includes a structure shown in Formula I,

[0078] Wherein X includes a phosphate group or a phosphite group, R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment or a polyester segment, and R2 includes an organic segment; optionally, the organic segment of R2 includes at least one of an amide group and an amino group, and optionally, the end group of the polyether segment includes an aromatic group; the positive electrode active material includes at least one of lithium iron phosphate and its doping materials, lithium manganese iron phosphate and its doping materials, a carbon-coated material of lithium iron phosphate and its doping materials, and a carbon-coated material of lithium manganese iron phosphate and its doping materials; optionally, the positive electrode active material includes at least one of lithium manganese iron phosphate and its doping materials, and a carbon-coated material of lithium manganese iron phosphate and its doping materials; based on the total mass of the positive electrode film layer, the mass content of the dispersant is 0.1%-2.0%, and optionally 0.2%-1.0%.

[0079] The positive electrode film layer has good dispersibility and processability, which is beneficial to improving manufacturing efficiency and battery performance.

[0080] A sixth aspect of the present application provides a secondary battery comprising the positive electrode sheet of the fifth aspect.

[0081] A seventh aspect of the present application provides an electrical device comprising the secondary battery of the sixth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] FIG1 is a schematic diagram of a polymer dispersion mechanism according to one embodiment of the present application;

[0083] FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0084] FIG3 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG2 ;

[0085] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application;

[0086] FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0087] FIG6 is an exploded view of the battery pack shown in FIG5 according to an embodiment of the present application;

[0088] FIG. 7 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0089] Explanation of the reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate; 6 polymer; 61 anchoring group; 62 flexible segment; 7 positive electrode active material. DETAILED DESCRIPTION

[0090] Below, the embodiments of the polymer, preparation method thereof, positive electrode sheet, secondary battery, and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0091] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0092] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0093] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0094] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0095] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0096] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0097] To improve the battery's kinetic and electrochemical performance, the synthesis of positive electrode active materials tends to be nano-sized and more densely coated with carbon. This results in a larger specific surface area for the positive electrode active materials, requiring more solvent for effective dispersion during the slurry mixing process, thereby reducing the slurry's solid content. Low-solids slurries require extended drying times during the electrode coating and drying process, resulting in low production efficiency and high energy consumption. Furthermore, the long heating and drying process of low-solids slurries can lead to problems such as electrode warping, cracking, and binder floating, which deteriorate the electrode quality.

[0098] Based on this, the first aspect of the present application provides a polymer comprising the structure shown in Formula I,

[0099] Wherein X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment; and R2 comprises an organic segment.

[0100] In this context, polymers include, on the one hand, aggregates of chemically uniform macromolecules prepared by polymerization reactions but differing in degree of polymerization, molar mass and chain length; on the other hand, they also include derivatives of such aggregates of macromolecules formed by polymerization reactions, i.e. polymers that can be obtained by reactions of functional groups in the above-mentioned macromolecules, such as addition or substitution, and which may be chemically uniform or chemically heterogeneous.

[0101] In some embodiments, the polymer comprises a phosphate polymer. The structure of the phosphate polymer is shown in Formula V:

[0102] In some embodiments, the polymer comprises a phosphite polymer. The structural formula of the phosphite polymer is shown in V':

[0103] Herein, the polyether segment refers to a polymer segment containing an ether bond (-COC-) in its structural unit.

[0104] Herein, the polyester segment refers to a polymer segment containing an ester group (-COO-) in its structural unit.

[0105] As used herein, a hydrocarbon group refers to a group containing carbon and hydrogen atoms, including but not limited to an alkyl group, an alkenyl group, and an alkynyl group.

[0106] In this article, the organic segment can be either a polymerized repeating structural unit or an organic group formed by a small molecule monomer. The dispersion mechanism of the polymer provided in the embodiment of the present application is shown in Figure 1. Polymer 6 includes an anchoring group 61 and a flexible segment 62. The anchoring group 61 at one end of the polymer 6 acts on the surface of the positive electrode active material 7, and the purpose of dispersion is achieved through the steric hindrance effect of the flexible segment 62. The phosphate group or phosphite group in the polymer 6 can be effectively anchored to the surface of the positive electrode active material 7 through intermolecular forces or electrostatic effects, playing the role of the anchoring group 61. With the help of the anchoring effect of the anchoring group on the surface of the positive electrode active material, the steric hindrance effect of the flexible segment 62 such as the polyether segment and the polyester segment can be effectively exerted on the surface of the positive electrode active material particles, playing the role of blocking the agglomeration of the positive electrode active material 7, thereby increasing the amount of positive electrode active material 7 that can be effectively dispersed in a unit volume of solvent, slowing down the gelation and agglomeration of the slurry during the homogenization process, reducing the slurry viscosity, significantly improving the effective solid content of the slurry, reducing the filtration time of the slurry, and improving the forming efficiency and quality of the electrode. The polymer provided in the embodiments of the present application can make the slurry suitable for thick coating processes, which helps to improve the energy density of the battery.

[0107] At the same time, the flexible segments such as polyether segments and polyester segments in the polymer have suitable steric hindrance and low glass transition temperature, which can improve the flexibility of the electrode through the movement of the flexible segments, and simultaneously play a role of dispersion and softening.

[0108] In some embodiments, the organic segment of R2 comprises at least one of an amide group, an amino group, and an aromatic group.

[0109] In this context, an amide group refers to The group includes both primary amides and secondary and tertiary amides.

[0110] In this context, amino groups refer to The amino groups include primary amino groups, secondary amino groups and tertiary amino groups.

[0111] As used herein, "aryl" refers to an organic group derived from a monocyclic or polycyclic aromatic hydrocarbon by removing a hydrogen atom. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, and benzyl. An aryl group may be unsubstituted or substituted with one or more suitable substituents.

[0112] In addition, the aryl group can be monocyclic or polycyclic. In some embodiments, the aryl group contains at least 6, 7, 8, 9 or 10 carbon atoms. The polymer containing the amide group was characterized by infrared absorption spectroscopy, and the carbonyl group was observed at 1900 cm -1 ~1650cm -1 The absorption peak of the band and the amide group are located at 3500cm -1 ~3100cm -1 The band has a medium-intensity double-peak absorption peak.

[0113] The nitrogen-containing groups or aromatic groups in the polymer help to improve the anchoring effect between the polymer and the positive electrode active material, making the polymer particularly suitable for carbon-coated positive electrode active materials, further improving the versatility of the polymer as a dispersant, and more effectively exerting the dispersing effect of the polymer by increasing the anchoring sites of the dispersant, thereby further increasing the maximum solid content of the slurry, improving the quality of the electrode molding, and reducing costs and increasing efficiency.

[0114] In some embodiments, the organic segment of R2 further comprises C 2-12 Hydrocarbon group.

[0115] In this article, “C 2-12 "Hydrocarbyl" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with or without unsaturation, having from two to twelve carbon atoms, and attached to the remainder of the molecule by at least one single bond. 2-12 Examples of hydrocarbon groups include, but are not limited to: 2-12 Alkyl, C2-12 Alkylene, C 2-12 Alkenyl, C 2-12 Alkenylene. For example, ethylene, ethyl, n-propyl, 1-methylethyl (isopropyl), isopropylidene, 1,3-propylene, butyl, isobutyl, tert-butyl, 1,4-butylene, 1,3-butylene, 2-butylene, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, etc. The polymer contains C 2-12 The hydrocarbon group helps to further improve the anchoring effect between the polymer and the carbon-modified positive electrode active material. The hydrocarbon group can effectively anchor to the carbon on the positive electrode active material, increase the dispersion of the anchoring sites of the polymer on the positive electrode active material, thereby further improving the application range of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the quality of the electrode forming while reducing costs and increasing efficiency.

[0116] In some embodiments, R2 comprises a structure as shown in Formula II:

[0117] Among them, R4 and R5 are random copolymers, and R4 includes C 2-12 Hydrocarbylene, C 3-13 At least one of the amide groups, R5 includes At least one of;

[0118] Wherein, q1, q2, q3, q4 are each independently any integer between 0 and 4, R6 a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

[0119] C 2-12 Hydrocarbylene refers to a divalent hydrocarbon group having 2 to 12 carbon atoms; including C 2-12 Alkylene, C 2-12 As an example, C 2-12Alkylene includes, but is not limited to, 1,2-ethylene, 1,2-propylene, 1,3-propylene, 1,3-butylene, 1,4-butylene, 2-methyl-1,3-propylene, 1,1-dimethyl-1,2-ethylene, 1,4-pentylene, 1,5-pentylene, 2-methyl-1,4-butylene, 2,2-dimethyl-1,3-propylene, 1,6-hexylene, 2-methyl-1,5-pentylene 1,5-pentylene, 2,3-dimethyl-1,4-butylene, 1,7-heptylene, 2-methyl-1,6-hexylene, 3-methyl-1,6-hexylene, 2-ethyl-1,5-pentylene, 3-ethyl-1,5-pentylene, 2,3-dimethyl-1,5-pentylene, 2,4-dimethyl-1,5-pentylene, 1,8-octylene, 2-methyl-1,7-heptylene 1,7-heptylene, 2-ethyl-1,6-hexylene, 3-ethyl-1,6-hexylene, 2,3-dimethyl-1,6-hexylene, 2,4-dimethyl-1,6-hexylene, 1,9-nonylene, 2-methyl-1,8-octylene, 3-methyl-1,8-octylene, 4-methyl-1,8-octylene, 2-ethyl-1,7- Heptylene, 3-ethyl-1,7-heptylene, 1,10-decylene, 2-methyl-1,9-nonylene, 3-methyl-1,9-nonylene, 4-methyl-1,9-nonylene, 5-methyl-1,9-nonylene, 1,11-undecylene, 2-methyl-1,10-decylene, 3-methyl-1,10-decylene, 5-methyl-1,10-decylene, 1,12-dodecylene.

[0120] C 2-12 Alkenylene is a divalent hydrocarbon radical containing at least one double bond. 2- 12 Alkenylene groups include, for example, vinylene, propenylene, 1-methylvinylene, 1-butenylene, 2-butenylene, 1-methylpropenylene, 2-methylpropenylene, 1-pentenylene, 2-pentenylene, 1-methyl-1-butenylene, 1-methyl-2-butenylene, 1-hexenylene, 2-hexenylene, 3-hexenylene, 1-methyl-1-pentenylene, 1-methyl-2-pentenylene, 1-methyl-3-pentenylene, 1,4-dimethyl-1-butenylene, 1,4-dimethyl-2-butenylene, 1-heptenylene, 2-heptenylene, 3-heptenylene, 1-octenylene, 2-octenylene, 3-octenylene.

[0121] In some embodiments, C 3-13 Amide groups include the following groups:

[0122] Here, x is 2 to 12, and can be selected from 2 to 5.

[0123] In some embodiments, x is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0124] In this paper, C 1-4 The alkyl group includes at least one of a methyl group, an ethyl group, a propyl group, an isopropyl group, a 2-methyl-1-propyl group, and a 2-methyl-2-propyl group.

[0125] In some embodiments, s is any one of 1, 2, 3, 4, 5, and 6.

[0126] In some embodiments, t is any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0127] In some embodiments, q1, q2, q3, and q4 are each independently selected from 0, 1, 2, 3, or 4.

[0128] The organic chain segments of the above structure include nitrogen-containing groups and alkylene groups, which can more effectively play an anchoring role, enhance the dispersion effect of the polymer, and effectively increase the solid content of the slurry.

[0129] In some embodiments, R2 comprises the structure shown in Formula III

[0130] Among them, R6 includes C 2-12 Alkylene, R7 includes At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

[0131] In some embodiments, q5 and q6 each independently include 0, 1, 2, 3 or 4.

[0132] In some embodiments, n is any one of 1, 2, 3, 4, 5, and 6.

[0133] The organic chain segments of the above structure can more effectively play an anchoring role through the alternating arrangement of nitrogen-containing groups and alkylene groups, enhance the dispersion effect of the polymer, and effectively increase the solid content of the slurry.

[0134] In some embodiments, the terminal group of R2 comprises at least one of -C(O)-NH2, -CH2-NH2.

[0135] Polymers whose end groups contain -C(O)-NH2 and -CH2-NH2 can more effectively exert their dispersing effect, increase the maximum solid content of the slurry, and thereby improve the molding quality and efficiency of the pole pieces.

[0136] In some embodiments, at least one of R1 and R3 comprises a polyether segment. In some embodiments, both R1 and R3 comprise a polyether segment. The polymer comprising the polyether segment is characterized by infrared absorption spectroscopy, and an ether bond absorption peak can be observed at 1250-1100 cm -1 band.

[0137] In some embodiments, R2 includes at least one of H and aryl.

[0138] In some embodiments, one of R1 and R3 comprises a polyether segment and the other comprises C 1-4 alkyl.

[0139] In some embodiments, both R1 and R3 include polyether segments.

[0140] R1 and R3 both include polyether segments. Compared with R1 and R3, one of them includes polyether segments and the other includes C 1-4 Alkyl and polymer further optimize the filterability of the slurry and further improve the flexibility of the electrode.

[0141] In some embodiments, at least one of R1 and R3 comprises a polyether segment represented by Formula IV

[0142] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50.

[0143] In some embodiments, the polyether segment is a block copolymer segment. In some embodiments, the polyether segment is a random copolymer segment.

[0144] In some embodiments, m1 and n1 can be independently selected from 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50 or any number therebetween.

[0145] The polyether segment with the above structure has suitable steric hindrance and low glass transition temperature, which can more effectively reduce the order and glass transition temperature of the binder crystallization in the positive electrode slurry, thereby reducing the crystallinity of the binder and improving the flexibility of the electrode. Through the effects of dispersion and softening, the uniformity and flexibility of the electrode are improved, thereby improving the safety performance and ultimate compaction density of the battery, increasing the positive electrode active material loading of the battery, and helping to further improve the energy density of the battery.

[0146] In some embodiments, the end groups of the polyether segments include aromatic groups.

[0147] The aromatic group has excellent compatibility with the carbon layer on the surface of the positive electrode active material, which helps to further improve the anchoring effect between the polymer and the carbon-modified positive electrode active material. With the help of the aromatic group and the carbon on the positive electrode active material, it can effectively anchor and increase the dispersion of the anchoring sites of the polymer on the positive electrode active material, thereby further improving the application range of the polymer dispersant, increasing the maximum solid content of the slurry, optimizing the quality of the electrode molding, and reducing costs and increasing efficiency.

[0148] In some embodiments, X comprises a phosphate group.

[0149] Phosphate polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode; and phosphate polymers have better stability, and can effectively improve the battery's cycle capacity retention rate on the basis of improving the slurry's dispersibility.

[0150] In some embodiments, the polymer comprises at least one of the following polymers:

[0151] Wherein, at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV

[0152] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤15, 4≤n1≤15.

[0153] In some embodiments, R6 and R4 each independently include C 4-8 Alkylene, C 4-8 At least one alkenylene group.

[0154] In some embodiments, R6 and R4 each independently include -(CH2)4-, -(CH2)5-, -(CH2)6-, -(CH2)7-, -(CH2)8-, At least one of the groups.

[0155] In some embodiments, the end groups of the polyether segments include phenyl groups.

[0156] In some embodiments, the polymer is represented by the following formula:

[0157] Wherein, R2 comprises at least one of hydrogen, aryl, substituted or unsubstituted alkyl, and an organic segment containing an amino group or an amide group; at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV;

[0158] Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50, and the terminal group of the polyether segment includes phenyl.

[0159] In some embodiments, the weight average molecular weight of the polymer is 1000 to 10000. In some embodiments, the weight average molecular weight of the polymer is 2000 to 5000.

[0160] The weight average molecular weight has a meaning well known in the art and can be measured by methods well known in the art. For example, the weight average molecular weight can be measured by gel chromatography.

[0161] In some embodiments, the polymer has a weight average molecular weight of 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, or any number therebetween.

[0162] Polymers with a weight-average molecular weight within the above range can not only exhibit excellent dispersibility, further increasing the solid content of the slurry, but also provide the slurry with excellent flow properties, reducing coating time and improving coating uniformity and speed. Polymers with a weight-average molecular weight of 2000-5000 can more effectively disperse, increase the maximum solid content of the slurry, and shorten filtration time.

[0163] A second aspect of the present application provides a method for preparing a polymer, the method comprising the following steps:

[0164] The compound represented by formula VI is reacted with R3OH, R1OH, water, and a polymerizable monomer containing an unsaturated bond to prepare a polymer having a structure represented by formula I.

[0165] Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all include halogen; R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment or a polyester segment; and R2 includes an organic segment.

[0166] Herein, the halogen includes at least one of fluorine, chlorine, bromine and iodine.

[0167] In some embodiments, phosphorus and oxygen in Formula VI are connected via a double bond, and X in Formula I is a phosphate group.

[0168] In some embodiments, Formula VI does not include oxygen, and X in Formula I is a phosphite group.

[0169] In some embodiments, Formula VI comprises POCl 3 or PCl 3 .

[0170] In some embodiments, the preparation method comprises the following steps:

[0171] The compound represented by formula VI is reacted with R3OH, R1OH and water to prepare the intermediate product represented by formula VII.

[0172] The intermediate product is subjected to a second reaction with a polymerization monomer comprising at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer.

[0173] In some embodiments, the first reaction specifically comprises:

[0174] Add R3OH dropwise to the compound represented by Formula VI under stirring, keep the reaction temperature below 20°C, stir for a period of time, heat to 40-50°C, react for 6-7 hours, add water, and react at 50-60°C for 3-4 hours to obtain the first intermediate product represented by Formula A. The molar ratio of R3OH added during the reaction to the compound represented by Formula VI is 1.2-1.5, wherein R3 includes C 1-4 alkyl,

[0175] The above reaction conditions are conducive to improving the purity of the product.

[0176] In some embodiments, the first reaction further comprises:

[0177] The polyether and the first intermediate product are reacted at 100° C.-120° C. for 4 h-7 h to generate an intermediate product represented by formula VII, wherein R1 comprises a polyether segment.

[0178] In some embodiments, the second reaction specifically comprises the following steps:

[0179] The intermediate product undergoes an addition reaction with at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and then undergoes a substitution reaction with a halogen-substituted organic alcohol;

[0180] The polymer is prepared by cycling the addition reaction and substitution reaction multiple times;

[0181] Wherein, R2 comprises the structure shown in formula III

[0182] Among them, R6 includes C 2-12 Hydrocarbyl, R7 includes At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

[0183] An addition reaction is a reaction in which the π bond in a double bond is broken to form two single bonds.

[0184] Substitution reaction refers to a type of chemical reaction in which an atom or group replaces a certain atom or group in an organic molecule and takes its place.

[0185] In some embodiments, the preparation method further comprises the following steps:

[0186] The intermediate product is reacted with (i) at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond and a cyclic amide monomer to prepare the polymer, wherein R2 comprises the structure shown in Formula II

[0187] Among them, R4 and R5 are random copolymers, and R4 includes C 2-12 Hydrocarbon, C 3-13 At least one of the amide groups, R5 includes At least one of;

[0188] Wherein, q1, q2, q3, q4 are each independently any integer between 0 and 4, R6 a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

[0189] In some embodiments, the hydrocarbon monomer containing an unsaturated bond comprises at least one of an olefin monomer, an alkyne monomer, and a cyclic alkane.

[0190] In some embodiments, a cyclic amide monomer refers to a cyclic monomer that includes an amide bond.

[0191] In some embodiments, the third reaction specifically includes mixing the intermediate product with at least one of a hydrocarbon monomer containing an unsaturated bond and a cyclic amide monomer to react for a period of time, and then adding at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to cause a copolymerization reaction.

[0192] In some embodiments, the preparation method further comprises the following steps:

[0193] The polymer having a terminal group of hydroxyl group is subjected to a capping reaction with an unsaturated monomer containing an amide group or an amino group to prepare a polymer having a terminal group containing an amide group or an amino group.

[0194] The present application provides a method for preparing a polymer, the preparation method comprising:

[0195] The compound represented by formula VI is reacted with raw materials including R3OH and R1OH to prepare a polymer having a structure represented by formula I.

[0196] Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all include halogen; R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment, and the end group of at least one of the polyether segments includes an aromatic group; R2 includes an organic segment.

[0197] In some embodiments, the monomer represented by formula VI is reacted with R1OH and R3OH in an inert, alkaline environment, and then water or phenol is added to react to obtain a polymer.

[0198] In some embodiments, the polymer containing a hydroxyl group in R2 is further subjected to a second reaction with a polymerized monomer containing at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare a nitrogen-containing polymer in R2.

[0199] In some embodiments, the polymer according to any embodiment of the present application and the polymer prepared by the preparation method according to any embodiment of the present application are used as dispersants.

[0200] In some embodiments, the polymer according to any embodiment of the present application and the polymer prepared by the preparation method according to any embodiment of the present application are used as a dispersant in a secondary battery electrode slurry.

[0201] In some embodiments, the polymer according to any embodiment of the present application and the polymer prepared by the preparation method according to any embodiment of the present application are used as a dispersant in a positive electrode slurry of a secondary battery.

[0202] [Cathode slurry]

[0203] A third aspect of the present application provides a positive electrode slurry, which includes a dispersant. The dispersant includes a polymer in any embodiment or a polymer prepared by a preparation method in any embodiment.

[0204] The positive electrode slurry has a high solid content, which helps to improve the forming efficiency and forming quality of the positive electrode film layer, and enhance the electrochemical performance and processing efficiency of the battery.

[0205] In some embodiments, the positive electrode slurry includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium-containing phosphate and a carbon-modified material thereof.

[0206] In some embodiments, the lithium-containing phosphate includes at least one of lithium iron phosphate and its doping materials, lithium manganese iron phosphate and its doping materials. In some embodiments, the doping material includes a doping material at any site, which can be lithium doping, phosphorus doping, manganese doping, or iron doping.

[0207] In some embodiments, the carbon-modified material includes at least one of a carbon-coated material and a carbon-doped material.

[0208] In some embodiments, the positive electrode active material includes at least one of lithium iron phosphate and its doping materials, lithium manganese iron phosphate and its doping materials, carbon coating materials of lithium iron phosphate and its doping materials, and carbon coating materials of lithium manganese iron phosphate and its doping materials.

[0209] The polymer is negatively charged, further strengthening its mutual anchoring with the weakly acidic lithium-containing phosphate through electrostatic interactions, thereby improving the polymer's dispersion of the lithium-containing phosphate. Furthermore, lithium-containing phosphates have poor conductivity. Therefore, in the preparation of positive electrode active materials, a carbon layer coated with organic materials such as sintered glucose and sucrose is often used to improve their conductivity. This polymer also has groups that anchor to the carbon coating, providing excellent dispersion for carbon-modified lithium-containing phosphates, further improving the dispersibility of the slurry and thereby increasing the maximum solids content of the slurry.

[0210] In some embodiments, the positive electrode active material includes a core and a carbon coating layer, wherein the carbon coating layer covers at least a portion of the surface of the core, wherein the carbon coating layer has a sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not less than 0.2. In some embodiments, the sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not less than not less than 0.5. In some embodiments, the sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not less than not less than 0.8.

[0211] In some embodiments, the sp2 hybridized carbon atoms in the carbon coating layer are sp 3 The molar ratio of hybridized carbon atoms can be selected as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any range therebetween.

[0212] The carbon structure and characteristics of the carbon coating layer can be determined by methods known in the art. For example, Raman spectroscopy can be used to determine the carbon structure and characteristics of the carbon coating layer. Specifically, the Raman spectrum of the positive electrode active material is first measured, and the energy spectrum of the Raman test is separated to obtain the Ig / Id (where Id is sp 3 Peak intensity of hybridized carbon atoms, Ig is sp 2 The peak intensity of the hybridized carbon atom is the ratio of the peak intensity to the sp 2 The peak height of hybridized carbon atoms is related to the sp 3 hybridized carbon atoms), thereby obtaining sp 2 Hybridized carbon and sp 3 The molar ratio of hybrid carbon. sp in the carbon coating layer of the positive electrode active material2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not particularly limited. For example, the sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms may be not less than 0.5. In some embodiments, the sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms may be not less than 0.8. 2 Hybridized carbon atoms with sp 3 When the molar ratio of hybridized carbon atoms is within the above range, the carbon coating on the surface of the inner core has a higher degree of graphitization and a denser structure, which can not only reduce the water absorption of the carbon coating, but also enable the carbon coating to achieve good conductivity, thereby ensuring the passage of lithium ions and being beneficial to improving the cycle performance and safety performance of the positive electrode active material.

[0213] In some embodiments, the core comprises phosphate; in some embodiments, the phosphate comprises at least one of lithium manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, and doped materials thereof.

[0214] The formation of a carbon coating layer on the surface of the core can improve the conductivity of the positive electrode active material. 2 Hybridized carbon atoms with sp 3 When the molar ratio of hybridized carbon atoms is not less than 0.5, the orderliness of the structure of the carbon coating layer of the positive electrode active material is high, the pore structure of the carbon coating layer has high density and a small pore size distribution range, and during the production process of the battery, it is difficult for external moisture to enter the pores of the carbon coating layer, thereby effectively reducing the water absorption and water storage properties of the positive electrode active material, achieving improved battery safety and cycle performance, effectively saving energy consumption in the drying process, and significantly reducing production costs.

[0215] But sp 2 Hybridized carbon atoms with sp 3 A carbon coating with a molar ratio of hybridized carbon atoms of no less than 0.5 has a high degree of graphitization, which makes the positive electrode active material prone to agglomeration and difficult to effectively disperse during the slurrying process. The dispersant provided in the embodiments of the present application and the highly graphitized carbon coating have abundant anchoring groups and are particularly suitable for dispersing positive electrode active materials with highly graphitized coatings. The combination of the two can simultaneously improve the performance and processing properties of the battery.

[0216] In some embodiments, the core comprises Li 1+x Mn 1-y A y P 1-z R zO4, x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, A includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R includes one or more elements selected from B (boron), S, Si and N. The manganese-site doping element A selected from the above elements helps to reduce the lattice change rate of the lithium manganese phosphate during the lithium insertion and extraction process of the material, improves the structural stability of the positive electrode active material, greatly reduces the dissolution of manganese and reduces the oxygen activity on the particle surface; the phosphorus-site doping element R selected from the above elements also helps to change the difficulty of the Mn-O bond length change, thereby improving electronic conductivity and reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the rate performance of the secondary battery.

[0217] Unless otherwise specified, in the chemical formula of the above core, when a doping site has two or more elements, the above numerical ranges for x, y, z or m are not only limited to the stoichiometric number of each element as the site, but also to the sum of the stoichiometric numbers of the elements as the site. For example, when the chemical formula is Li 1+x Mn 1-y AyP 1-z R z For compounds of O4, when A is two or more elements A1, A2, ...An, the stoichiometric numbers y1, y2, ...yn of A1, A2, ...An must each fall within the numerical range specified for y in this application, and the sum of y1, y2, ...yn must also fall within this numerical range. Similarly, for the case where R is two or more elements, the numerical range of the stoichiometric number of R specified in this application also has the above meaning.

[0218] According to some embodiments of the present application, the type of the core is not particularly limited. For example, the core may include Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D n, the size of x is affected by the valence of A and R and the sizes of y and z to ensure that the entire system is electrically neutral. If the value of x is too small, the lithium content of the entire core system will be reduced, affecting the gram capacity of the material. More specifically, x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, n is any value in the range of 0.001 to 0.1, and m is any value in the range of 0.9 to 1.1. For example, 1+x is selected from the range of 0.9 to 1.1, for example, 0.97, 0.977, 0.984, 0.988, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 1.01, x is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005, y is selected from the range of 0.001 to 0.5, for example, 0.001 , 0.005, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.34, 0.345, 0.349, 0.35, 0.4, z is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005, 0.08, 0.1, n is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005, 0.08, 0.1, and the positive electrode active material is electrically neutral. C includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo, and W; A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; R includes one or more elements selected from the group consisting of B (boron), S, Si, and N; and D includes one or more elements selected from the group consisting of S, F, Cl, and Br. By simultaneously doping specific elements in specific amounts at the Li, Mn, P, and O positions of the compound, significantly improved rate performance can be achieved, while significantly reducing the dissolution of Mn and the doping element at the Mn position, thereby achieving significantly improved cycle performance and / or high-temperature stability, and increasing the gram capacity and compaction density of the positive electrode active material.

[0219] In some embodiments, the thickness of the carbon coating layer is no greater than 15 nm. In some embodiments, the thickness of the carbon coating layer is no greater than 10 nm. In some embodiments, the thickness of the carbon coating layer is 4 nm to 8 nm.

[0220] In some embodiments, the thickness of the carbon coating layer may be 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or any range therebetween.

[0221] The thickness of the carbon coating can be measured as follows: a thin slice of approximately 100 nm thick is cut from the center of a single particle of the positive electrode active material using FIB. The slice is then subjected to transmission electron microscopy (TEM) testing to obtain the original TEM test image and save the original image format (xx.dm3). The original TEM test image obtained above is opened in Digital Micrograph software. The carbon coating is identified based on the lattice spacing and angle information, and the thickness of the carbon coating is measured. The thickness of the selected particle is measured at three locations and the average value is taken.

[0222] The carbon coating layer within the above thickness range can form a thin carbon coating layer on the surface of the core, which can effectively improve the conductivity of the positive electrode active material and improve the compaction performance when using the positive electrode active material to prepare battery pole pieces.

[0223] In some embodiments, the positive electrode active material is prepared by the following method:

[0224] Providing an inner core; forming a carbon coating layer on at least a portion of the surface of the inner core, wherein the molar ratio of sp2 hybridized carbon atoms to sp3 hybridized carbon atoms in the carbon coating layer is not less than 0.2, and optionally not less than 0.5.

[0225] In some embodiments, forming a carbon coating layer on at least a portion of the surface of the inner core includes: forming a pre-carbon coating layer on the inner core surface through a carbon source to obtain a pre-coated positive electrode active material; sintering the pre-coated positive electrode active material to form the carbon coating layer to obtain the positive electrode active material, and the carbon source includes a first carbon source and a second carbon source.

[0226] In some embodiments, a pre-carbon coating is formed on the surface of the inner core to obtain a pre-coated positive electrode active material. The method for forming the pre-carbon coating on the inner core surface is not particularly limited. For example, the carbon source and the inner core can be placed in the same reaction vessel and subjected to hydrothermal treatment to cause the carbon source to react on the inner core surface, thereby forming a carbon coating on the inner core surface. Alternatively, the carbon source and the inner core can be placed in a ball milling apparatus, such as a sand mill, and mechanically mixed to form a carbon coating on the inner core surface. In some embodiments, the carbon source includes a first carbon source and a second carbon source, wherein the first carbon source includes at least one of polyvinyl alcohol, polyethylene glycol, and citric acid; and the second carbon source includes at least one of starch, sucrose, and glucose. In some embodiments, the molecular weight of the first carbon source is not less than 1000; in other embodiments, the molecular weight of the first carbon source can range from 2000 to 5000. Thus, the ball milling process can form a uniformly distributed pre-carbon coating with a relatively uniform thickness on the inner core surface, thereby facilitating the formation of a dense and uniform pore structure of the carbon coating layer after sintering. In some embodiments, the second carbon source can include at least one of starch, sucrose, and glucose. In some embodiments, the second carbon source can be glucose.

[0227] In some embodiments, the pre-coated positive electrode active material is sintered under an inert gas atmosphere. In some embodiments, the pre-coated positive electrode active material is sintered to obtain the positive electrode active material. The sintering treatment should be carried out under an inert atmosphere to avoid oxidation reaction of the carbon source and thus fail to obtain a carbon coating layer with a high degree of graphitization. The type of inert gas is not particularly limited. For example, the inert gas may include at least one of nitrogen and helium. The conditions for the sintering treatment are not particularly limited. For example, the temperature of the sintering treatment may be 650°C-800°C, and the sintering treatment time may be 6h-12h. Thus, a carbon coating layer with a high degree of graphitization can be formed on the surface of the inner core. As the temperature of the sintering treatment increases, the degree of graphitization of the carbon in the carbon coating layer also increases. By controlling the highest sintering treatment of the sintering treatment, the degree of graphitization of the carbon coating layer can be effectively controlled, and the carbon coating layer has a dense pore structure and better conductivity.

[0228] In some embodiments, forming a carbon coating layer on at least a portion of the surface of the inner core includes: mixing the inner core with a first carbon source and obtaining a first coated positive electrode active material through a first sintering treatment; mixing the first coated positive electrode active material with a second carbon source and obtaining the positive electrode active material through a second sintering treatment.

[0229] In some embodiments, the first sintering process is performed at a temperature of 350°C to 800°C for a time of 6 hours to 12 hours. In some embodiments, the second sintering process is performed at a temperature of 650°C to 850°C for a time of 6 hours to 24 hours.

[0230] In some embodiments, the mass content of the polymer is 0.1%-2.0% based on the total mass of the dry material of the positive electrode slurry. In some embodiments, the mass content of the polymer is 0.2%-1.0% based on the total mass of the dry material of the positive electrode slurry.

[0231] In some embodiments, based on the total mass of the dry material of the positive electrode slurry, the mass content of the polymer may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any value therebetween. The polymer within the above range can not only play an effective dispersion role, but also take into account the volume energy density of the battery, and will not have a serious negative impact on the electrochemical performance of the battery.

[0232] In some embodiments, the positive electrode slurry includes a binder, and the binder includes a vinylidene fluoride polymer having a weight average molecular weight of not less than 300,000. In some embodiments, the weight average molecular weight of the binder is 700,000-9,000,000.

[0233] In some embodiments, the vinylidene fluoride polymer is a vinylidene fluoride homopolymer.

[0234] In some embodiments, the vinylidene fluoride polymer is a vinylidene fluoride copolymer.

[0235] The weight average molecular weight has a well-known meaning in the art and can be measured by any well-known method. In some embodiments, the weight average molecular weight of the binder is characterized by gel chromatography.

[0236] In some embodiments, the weight average molecular weight of the binder can be selected to be 700,000, 1,000,000, 2,000,000, 3,000,000, 4,000,000, 5,000,000, 6,000,000, 7,000,000, 8,000,000, 9,000,000, or any value therebetween.

[0237] Vinylidene fluoride polymers with a weight-average molecular weight in this range have excellent bonding properties and electrochemical stability. The use of vinylidene fluoride polymers with a weight-average molecular weight of 700,000-9 million can further reduce the amount of vinylidene fluoride used, reduce the rigidity of the positive electrode film layer, and increase the flexibility of the electrode, thereby increasing the battery's ultimate compaction density and helping to improve the battery's energy density.

[0238] In some embodiments, the maximum solid content of the positive electrode slurry is not less than 60%. In some embodiments, the maximum solid content of the positive electrode slurry is 60%-80%.

[0239] The maximum solids content of the positive electrode slurry is defined as the maximum solids content required to maintain a shipping viscosity between 4,000 and 35,000 MPa.s and to avoid gelation after 24 hours of standing. The actual solids content of the positive electrode slurry is determined by taking the weight of the slurry, recorded as m0, and placing it in a weight loss tester. Evaporate the solvent until the weight loss is less than 0.3%, and record the remaining weight as m1. Solids content = m1 / m0 * 100%.

[0240] In some embodiments, the maximum solid content of the positive electrode slurry may be 60%, 65%, 70%, 75%, 80%, or any value therebetween.

[0241] By adding polymers to the positive electrode slurry, the solid content and flexibility of the slurry are effectively increased, and the flexibility and molding efficiency of the electrode are improved.

[0242] [Positive electrode]

[0243] The present application also provides a positive electrode plate, which includes a positive electrode film layer, which is prepared by the positive electrode slurry of any embodiment or the positive electrode film layer includes a dispersant, and the dispersant includes a polymer of any embodiment or a polymer prepared by the preparation method of any embodiment.

[0244] In some embodiments, the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0245] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0246] In some embodiments, the positive electrode sheet has a compaction density of 2.6 g / cm 3 In some embodiments, the positive electrode sheet has a compaction density of 2.6 g / cm 3 The number of times it can be folded is 3-6 times.

[0247] The compacted density of the positive electrode is 2.6g / cm 3 The number of times a pole piece can be folded in half can be used to characterize its flexibility and can be measured by any known method. As an example, a defect-free pole piece with a compaction density of 2.6 g / cm 3Cut the positive electrode sheet longitudinally into samples measuring 25cm x 4cm in length and width, with a sample size of ≥4 sheets. Pre-fold the sheet in half longitudinally (at 25cm), then place the sheet on the test platform and roll it once with a 2kg cylindrical roller. If light is translucent, the number of times the film is translucent is one. If not, repeat the folding and rolling in the opposite direction. Observe the fold against the light to see if it is translucent or fractured. Record the actual number of folds. Repeat the test four times and take the average as the test result.

[0248] In some embodiments, the positive electrode sheet has a compaction density of 2.6 g / cm 3 The number of folds that can be selected is 2, 3, 4, 5 or 6.

[0249] The polymer can not only effectively increase the solid content of the slurry, but also act as a softener, thereby increasing the flexibility of the positive electrode and further improving the safety and electrochemical performance of the battery.

[0250] In some embodiments, the surface density of the positive electrode sheet is not less than 300 mg / 1540.25 cm 2 In some embodiments, the surface density of the positive electrode sheet is 300 mg / 1540.25 cm 2 -600mg / 1540.25cm 2 .

[0251] In some embodiments, the surface density of the positive electrode sheet is 300 mg / 1540.25 cm 2 、400mg / 1540.25cm 2 、450mg / 1540.25cm 2 、500mg / 1540.25cm 2 、600mg / 1540.25cm 2 The areal density of a pole piece has a well-known meaning and can be measured by any well-known method.

[0252] In some embodiments, the positive electrode plate comprises lithium iron phosphate, and the surface density of the positive electrode plate is not less than 360 mg / 1540.25 cm 2 In some embodiments, the surface density of the positive electrode sheet is 360 mg / 1540.25 cm 2 -600mg / 1540.25cm 2 .

[0253] In some embodiments, the positive electrode plate comprises lithium manganese iron phosphate, and the surface density of the positive electrode plate is not less than 300 mg / 1540.25 cm 2 In some embodiments, the surface density of the positive electrode sheet is 300 mg / 1540.25 cm2 -600mg / 1540.25cm 2 .

[0254] Polymers can effectively increase the maximum solid content of the slurry, increasing the coating speed by more than 30%. They are particularly suitable for high-speed coating and thick coating molding methods. They can effectively solve the problem of easy cracking of the electrode during thick coating, and help to prepare positive electrode sheets with high flexibility and no cracks after winding molding.

[0255] In some embodiments, the positive electrode film layer includes a dispersant, and the dispersant includes a structure shown in Formula I,

[0256] Wherein X includes a phosphate group or a phosphite group, R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment or a polyester segment, and R2 includes an organic segment; optionally, the organic segment of R2 includes at least one of an amide group and an amino group; optionally, the end group of the polyether segment includes an aromatic group; the positive electrode active material includes at least one of lithium iron phosphate and its doping materials, lithium manganese iron phosphate and its doping materials, a carbon-coated material of lithium iron phosphate and its doping materials, and a carbon-coated material of lithium manganese iron phosphate and its doping materials; optionally, the positive electrode active material includes at least one of lithium manganese iron phosphate and its doping materials, and a carbon-coated material of lithium manganese iron phosphate and its doping materials; based on the total mass of the positive electrode film layer, the mass content of the dispersant is 0.1%-2.0%, and optionally 0.2%-1.0%.

[0257] The positive electrode film layer has good dispersibility and processability, which is conducive to the simultaneous improvement of manufacturing efficiency and battery performance. In some embodiments, the positive electrode film layer may also optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0258] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and the dispersant, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0259] [Negative electrode]

[0260] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0261] As an example, the negative electrode current collector has two surfaces opposite to each other in its 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.

[0262] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0263] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0264] In some embodiments, the negative electrode film layer may further 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).

[0265] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0266] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0267] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0268] [Electrolytes]

[0269] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0270] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0271] 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0272] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0273] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0274] [Isolation film]

[0275] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0276] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0277] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0278] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0279] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0280] [Secondary battery]

[0281] Another aspect of the present application provides a secondary battery, which includes the positive electrode sheet according to any embodiment.

[0282] The present application does not particularly limit the shape of the secondary battery; it can be cylindrical, square, or any other shape. For example, FIG2 shows a secondary battery 5 having a square structure as an example. The secondary battery can also be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.

[0283] In some embodiments, referring to Figure 3, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0284] [Battery Module]

[0285] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0286] Figure 4 shows an example battery module 4. Referring to Figure 4 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0287] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0288] [Battery Pack]

[0289] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0290] Figures 5 and 6 illustrate an example battery pack 1. Referring to Figures 5 and 6 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0291] [Electrical devices]

[0292] In one embodiment of the present application, an electric device is provided, comprising at least one of a secondary battery according to any embodiment, a battery module according to any embodiment, or a battery pack according to any embodiment.

[0293] 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, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0294] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0295] Figure 7 shows an example of an electric device. This device is 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, a battery pack or battery module can be used.

[0296] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0297] Example

[0298] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0299] Example 1

[0300] 1) Preparation of dispersant:

[0301] Preparation of the first intermediate product

[0302] POCl3 is added to a four-necked flask equipped with a thermometer, a stirrer, and a hydrogen chloride gas collection device. R3OH is added dropwise while stirring. The reaction temperature is maintained below 20°C. After stirring for 20 minutes, the temperature is raised to 40-50°C, where the ratio of n(POCl3):n(R3-OH) is 1.2-1.5. After reacting for 6-7 hours, a certain amount of distilled water is added dropwise to the system. The reaction is then continued at 55°C for 3.5 hours to produce a first intermediate product. By controlling the reaction parameters, a yield of ≥95% of the first intermediate product can be achieved, where R3 is -CH2CH3.

[0303] Preparation of the second intermediate product:

[0304] Weigh 1,2-propylene glycol (0.4% of the total mass of ethylene oxide, propylene oxide monomer, and the first intermediate product) and concentrated sulfuric acid (0.3% of the total mass) into the reactor, close the reactor cover, and tighten the fixing bolts with a wrench. Evacuate the reactor and replace it with high-purity nitrogen three times. Add ethylene oxide and propylene oxide in sequence with a molar ratio of n2:m2 to carry out block polymerization. The pressure during the reaction process is maintained at 0.3±0.05MPa and the temperature is maintained at 115±5℃. After 5 hours of reaction, add the first intermediate product and react at 115±5℃ for 5 hours to generate the second intermediate product. The reaction process diagram is shown below, where A1 is n2 is 25, m2 is 25, and R3 is -CH2CH3.

[0305] Preparation of polymer:

[0306] The second intermediate product was subjected to an addition reaction with acrylamide at room temperature for 12 hours, followed by the addition of HO(CH2)4Cl and a substitution reaction under alkaline conditions at room temperature for 6 hours. The addition and substitution reactions were then repeated once to prepare the product represented by formula X in the figure below, where R6 is -(CH2)4- and n is 2. The weight-average molecular weight of the polymer was 3109.

[0307] 2) Preparation of positive electrode slurry:

[0308] The positive electrode active material carbon-coated lithium iron phosphate (LFP@C), conductive agent carbon black (SP), binder polyvinylidene fluoride (PVDF), and dispersant (the above polymer) are added to N-methylpyrrolidone (NMP) at a mass ratio of 96.5:2:1:0.5. The mass fraction of the dispersant is 0.5% of the dry material in the slurry. The weight average molecular weight of PVDF is 700,000. 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is 0.271.

[0309] 3) Preparation of positive electrode sheet:

[0310] The positive electrode slurry is evenly coated on both surfaces of the aluminum foil positive electrode current collector and then dried to obtain a film layer; after that, it is cold pressed and cut to obtain a positive electrode sheet. The surface density of the positive electrode sheet is 450mg / 1540.25mm 2 .

[0311] 4) Preparation of negative electrode sheet

[0312] The negative electrode active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in solvent deionized water in a weight ratio of 96:2:1:1, mixed evenly and prepared into a negative electrode slurry; the negative electrode slurry is evenly coated on the two surfaces of the negative electrode current collector copper foil multiple times, and the negative electrode sheets are obtained after drying, cold pressing and slitting.

[0313] 5) Isolation film

[0314] Polypropylene film is used as the isolation film.

[0315] 6) Preparation of electrolyte

[0316] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3 / 7, and LiPF6 lithium salt was dissolved in the organic solvent to prepare a solution with a mass content of 12.5% ​​to obtain an electrolyte.

[0317] 7) Preparation of secondary batteries

[0318] The positive electrode sheet, separator, and negative electrode sheet prepared in Example 1 were stacked in order, with the separator positioned between the positive and negative electrode sheets to provide isolation. The cells were then wound to obtain a bare cell. The tabs were welded to the bare cell and placed in an aluminum shell. The cells were then baked at 80°C to remove moisture. The electrolyte was then injected and sealed to obtain an uncharged battery. The uncharged battery then underwent a series of steps, including resting, hot and cold pressing, formation, shaping, and capacity testing, to obtain the lithium-ion battery product of Example 1.

[0319] Example 2

[0320] The preparation method is similar to that of Example 1, except that the type of dispersant is changed. The first two steps of the dispersant synthesis process are consistent with those of Example 1. The nitrogen-containing monomer added in the third step is 3-amino-1-propylene. The dispersant structural formula is as follows, wherein R1, R3, R6, and n are consistent with those of Example 1.

[0321] Example 3

[0322] The preparation method is similar to that of Example 1, except that the type of dispersant is changed. The first two steps of the dispersant synthesis process are consistent with those of Example 1. The preparation process of the third step polymer is as follows:

[0323] Butadiene was added to the second intermediate product and reacted at 100° C. for 0.5 h, and then acrylamide was added. The reaction was carried out in an alkaline environment at 110° C. for 6 h to obtain a polymer. The reaction schematic is shown in the figure below, wherein R1 and R3 are consistent with those in Example 1, s is 3, t is 3, and the structural units derived from butadiene and the structural units derived from acrylamide are random copolymers.

[0324] Example 4

[0325] The preparation method is similar to that of Example 1, except that the type of dispersant is changed. The first two steps of the dispersant synthesis process are consistent with those of Example 1. The preparation process of the third step polymer is as follows:

[0326] Butadiene was added to the second intermediate product and reacted at 100° C. for 0.5 h, and then 3-amino-1-propylene was added. The reaction was continued in an alkaline environment at 110° C. for 6 h to obtain a polymer. The reaction schematic is shown in the figure below, wherein R1 and R3 are consistent with those in Example 1, s is 3, t is 3, and the structural unit derived from butadiene and the structural unit derived from 3-amino-1-propylene are random copolymers.

[0327] Example 5

[0328] The preparation method is similar to that of Example 1, except that the type of dispersant is changed. The first two steps of the dispersant synthesis process remain the same as in Example 1. The preparation process of the polymer is as follows:

[0329] Butadiene was added to the second intermediate product and reacted at 100° C. for 6.5 h in an alkaline environment to obtain a polymer. The reaction schematic is shown in the figure below, wherein R1 and R3 are consistent with those in Example 1, s+t is 6,

[0330] Example 6

[0331] The preparation method is similar to that of Example 1, except that the dispersant is different. The preparation method of the dispersant is to further react the product of Example 1 with 3-amino-1-propylene to prepare a polymer with an amino terminal group. The structure is shown below, wherein R1, R3, R6, and n are consistent with those in Example 1.

[0332] Example 7

[0333] The preparation method is similar to that of Example 1, except that the product of Example 1 is further reacted with acrylamide to prepare a polymer with an amide terminal group. The structure is shown below, wherein R1, R3, R6, and n remain the same as in Example 1.

[0334] The preparation methods of Examples 8-15 are similar to those of Example 7, except that in Examples 8-11, the weight average molecular weight of the polymer is regulated by adjusting the degree of polymerization of the polyether segment, and in Examples 12-15, the amount of dispersant added is adjusted to keep the total mass of the positive electrode film layer unchanged. As the mass content of the dispersant changes, the mass percentage of the positive electrode active material is adjusted accordingly. For specific parameters, see Table 1.

[0335] The preparation method of Example 16 is similar to that of Example 3. The organic monomer containing unsaturated bonds added during the preparation of the dispersant and the preparation of the polymer is The structural formula of the dispersant prepared with m=4 is as follows:

[0336] Wherein R1, R3, s, and t are consistent with those in Example 3.

[0337] Example 17

[0338] The preparation method of Example 17 is basically the same as that of Example 7, except that the monomers added during the preparation of R1 are all ethylene oxide, so the polyether segment is polyethylene oxide.

[0339] Example 18

[0340] The preparation method of Example 18 is basically the same as that of Example 7, except that the anchoring group of the dispersant in Example 7 is a phosphite group. The preparation method is basically the same as that of the dispersant in Example 7, except that PCl3 is initially input during the preparation process instead of POCl3. The dispersant structure is shown below, wherein R1, R3, R6, and n remain the same as in Example 1.

[0341] Example 19

[0342] The preparation method of Example 19 is basically the same as that of Example 7, except that the R3 group in Example 19 is the same as the R1 group, both are polyether segments, wherein n2 is 12 and m2 is 13.

[0343] The preparation process of the dispersant is basically the same as that of Example 7, except that the preparation process of the second intermediate product is different, as follows:

[0344] Weigh 1,2-propylene glycol (0.4% of the total mass of ethylene oxide, propylene oxide monomer, and POCl3) and concentrated sulfuric acid (0.3% of the total mass) solids into the reactor, close the reactor cover, and tighten the fixing bolts with a wrench. The reactor was vacuumed and replaced with high-purity nitrogen three times. Ethylene oxide and propylene oxide were added in sequence with a molar ratio of n2:m2 to carry out block polymerization. The pressure during the reaction was maintained at 0.3±0.05MPa and the temperature was maintained at 115±5℃. After reacting for 5h, POCl3, dichloromethane (DCM) and sodium hydroxide were added. The reaction was carried out at 115±5℃ under a nitrogen atmosphere for 5h. After that, water was added and the reaction was carried out at 50℃ for 10h to generate the product. The reaction process diagram is shown below, where A1 is n2 is 12 and m2 is 13.

[0345] The product was further reacted in the same manner as in Example 7 to join the R2 group to form a phosphorus-containing polymer, which was used as a dispersant.

[0346] Example 20

[0347] The preparation method of Example 20 is basically the same as that of Example 7, except that the weight average molecular weight of the binder PVDF is 300,000; the ratio of the positive electrode active material carbon-coated lithium iron phosphate (LFP@C), the conductive agent carbon black (SP), the binder polyvinylidene fluoride (PVDF), and the dispersant is 96:2:1.5:0.5.

[0348] Example 21

[0349] In Example 21, the It acts as a dispersant directly without joining the R2 group.

[0350] Example 22

[0351] The preparation method of Example 22 is basically the same as that of Example 19, except that the initial input in the synthesis process of the dispersant polyether segment is not 1,2-propylene glycol, but phenol, and the catalyst is potassium hydroxide, wherein A1 is n2 is 12, m2 is 13, R6 is -(CH2)4-, and n is 2.

[0352] Specifically, the dispersant is:

[0353] Example 23

[0354] In Example 23, the product prepared during the synthesis process of Example 22 was directly used as a dispersant. The specific structural formula is as follows:

[0355] Example 24

[0356] The preparation method of Example 24 is basically the same as that of Example 23, except that water is not added for hydrolysis in the last step of the preparation process of the product. Instead, phenol is added and reacted at 50°C for 10 hours to generate the product, which is directly used as a dispersant. The specific structural formula is

[0357] Example 25

[0358] The preparation method of Example 25 is basically the same as that of Example 7, except that phenol is not initially input into the synthesis of the polyether segment, and A1 in the product is a phenyl group.

[0359] Example 26

[0360] The preparation method of Example 26 is basically the same as that of Example 22, except that the positive electrode active material is carbon-coated lithium manganese iron phosphate. The specific preparation method is as follows:

[0361] Step S1: 689.6g of manganese carbonate, 455.27g of ferrous carbonate, 4.65g of cobalt sulfate, and 4.87g of vanadium dichloride were added to a mixer and thoroughly mixed for 6 hours. The resulting mixture was then transferred to a reactor, and 5L of deionized water and 1260.6g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred at 500 rpm for 6 hours, mixing until the reaction terminated and no bubbles were generated, thereby obtaining a Fe, Co, and V co-doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and sand-milled to obtain Fe, Co, V, and S co-doped manganese oxalate particles with a particle size of 100nm.

[0362] Step S2: Take 1793.1g of manganese oxalate prepared in step S1, 368.3g of lithium carbonate, 1146.6g of ammonium dihydrogen phosphate and 4.9g of dilute sulfuric acid, add them to 20L of deionized water, stir them thoroughly, and mix them evenly at 80°C for 10h to obtain a slurry. The slurry is transferred to a spray drying equipment for spray drying and granulation to obtain a powder. In a protective atmosphere (90% nitrogen and 10% hydrogen), the powder is sintered in a roller kiln at 700°C for 4h to obtain the core Li of the positive electrode active material. 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4.

[0363] Step S3: PEG-3000 was selected as the first carbon source. 58.2 g of PEG-1000 was dissolved in 500 g of deionized water, and then stirred and dissolved thoroughly to obtain an aqueous solution. 1571.9 g of the core material was added to the solution, and stirred and mixed for 6 hours until uniformly mixed. After spray drying, a first sintering treatment was performed at a temperature of 600°C and a sintering time of 9 hours, thereby obtaining a first coated positive electrode active material.

[0364] Step S4: Glucose was selected as the second carbon source. 37.3 g of glucose was dissolved in 500 g of deionized water, followed by stirring and dissolution to obtain a glucose aqueous solution. 1603.3 g of the first coated positive electrode active material obtained in step S3 was added to the glucose solution and stirred for 6 hours until uniformly mixed. After spray drying, a second sintering treatment was performed at a temperature of 750°C and for 20 hours, thereby obtaining the positive electrode active material.

[0365] Examples 27-28

[0366] The preparation methods of Examples 27 and 28 are basically the same as those of Example 26, except that the preparation methods of the positive electrode active materials are different. The specific parameters of the differences are:

[0367] In Example 27, the first carbon source is PEG-10000, the first sintering temperature is 500° C., and the first sintering treatment time is 5 h. The second carbon source is glucose, the second sintering temperature is 550° C., and the second sintering treatment time is 20 h.

[0368] In Example 28, the first carbon source is PEG-2000, the first sintering temperature is 660° C., and the first sintering treatment time is 9 h. The second carbon source is sucrose, the second sintering temperature is 750° C., and the second sintering treatment time is 6 h.

[0369] Comparative Example

[0370] Comparative Example 1-2

[0371] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that no dispersant is added.

[0372] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the dispersant is

[0373] Where a is 3 and b is 3.

[0374] Comparative Example 3

[0375] The preparation methods of Comparative Example 3 and Example 26 are basically the same, except that the dispersant in Comparative Example 3 is the same as that in Comparative Example 2.

[0376] Comparative Example 4

[0377] The preparation methods of Comparative Example 4 and Example 27 are basically the same, except that the dispersant in Comparative Example 4 is the same as that in Comparative Example 2.

[0378] Comparative Example 5

[0379] The preparation methods of Comparative Example 5 and Example 28 are basically the same, except that the dispersant in Comparative Example 5 is the same as that in Comparative Example 2.

[0380] 2. Performance Testing

[0381] 1. Characterization of polymers

[0382] 1) Weight average molecular weight

[0383] A Waters 2695 Isocratic HPLC gel chromatography instrument (differential refractive index detector 2141) was used. A 3.0% polystyrene solution sample was used as a reference, and a matching chromatographic 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. The prepared solution was allowed to stand for one day before use. During testing, tetrahydrofuran was first drawn into a syringe and rinsed several times. Then, 5 ml of the experimental solution was drawn, the air in the syringe was expelled, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the injection port. Data was acquired after the reading stabilized.

[0384] 2. Positive electrode active material

[0385] 1) Determination of the hybrid morphology of carbon atoms in the carbon coating layer:

[0386] Determination of hybrid morphology of carbon atoms in carbon coating layer: This test is carried out by Raman spectroscopy. By separating the energy spectrum of Raman test, I g / I d , where I d For sp 3 Peak intensity of carbon form, I g For sp 2 The peak intensity of the carbon morphology was measured to confirm the molar ratio of the two.

[0387] 2) Carbon coating thickness test

[0388] The thickness of the carbon coating layer was measured by cutting a thin slice approximately 100 nm thick from the center of a single particle of the positive electrode active material prepared above using FIB. The slice was then subjected to TEM analysis to obtain a raw TEM image, which was saved in the original image format (xx.dm3). The raw TEM image obtained from the above TEM test was opened in Digital Micrograph software. The carbon coating layer was identified based on the lattice spacing and angle information, and the thickness of the carbon coating layer was measured. The thickness of the selected particle was measured at three locations and the average was taken.

[0389] 3. Cathode slurry

[0390] 1) Maximum solid content of slurry

[0391] The maximum solid content of the positive electrode slurry refers to the maximum solid content of the slurry that meets the shipping viscosity between 4000 and 35000 mPa.s and does not gel after the slurry is left to stand for 24 hours. The slurry solid content test method is: take the slurry weight as m0, place it in the weight loss rate test instrument; evaporate the solvent of the slurry until the weight loss rate is less than 0.3%, and record the remaining weight as m1; solid content = m1 / m 0* 100%.

[0392] 2) Filtering time

[0393] Take an area of ​​30×30cm 2 Fold the 200-mesh filter into a funnel shape; take two beakers, place one on the table, and fill the other with 500 ml of slurry and pour it into the filter funnel, and record the filtration time of 300 ml of dripping slurry.

[0394] 4. Positive electrode

[0395] 1) Pole brittleness test

[0396] Take a defect-free, compacted density of 2.6g / cm 3Cut the positive electrode sheet longitudinally into samples measuring 25cm x 4cm in length and width, with a sample size of ≥4 sheets. Pre-fold the sheet in half longitudinally (25cm apart), then place the sheet on the test platform and roll it once with a 2kg cylindrical roller. If light is translucent, the number of times the film is brittle and translucent is one. If light is not translucent, repeat the folding and rolling in the opposite direction. Observe the crease against the light to see if it is translucent or broken. Record the actual number of folds and take the average as the test result.

[0397] 5. Secondary batteries

[0398] 1) Maximum volume energy density

[0399] The maximum volumetric energy density refers to the battery volumetric energy density measured when the positive electrode is at its ultimate compaction density. The ultimate compaction density is defined as the smaller of the compaction density corresponding to a pole piece elongation of 6‰ or two flexible folds.

[0400] The discharge energy measurement method of a battery cell is as follows:

[0401] Allow the battery cell to rest at 25°C for 2 hours, ensuring the cell temperature is 25°C. Charge the battery cell at 0.33C at 25°C to the charge cutoff voltage, then continue constant voltage charging at the charge cutoff voltage until the current reaches 0.05C, at which point the charge is cutoff (where C represents the rated capacity of the battery cell). Allow the battery cell to rest at 25°C for 1 hour, then discharge it at 0.33C at 25°C to the discharge cutoff voltage. Record the total discharge capacity (C0) and total discharge energy (E0) of the battery cell.

[0402] The battery cell volume measurement method is as follows:

[0403] Measure the length, width and height of the battery cell to calculate the volume value M0 of the battery cell.

[0404] The formula for calculating battery energy density is as follows:

[0405] Battery energy density = battery cell discharge energy E0 / battery cell volume M0.

[0406] 2) Cycle capacity retention rate after 40 cycles at 25°C

[0407] The voltage calibration method is as follows:

[0408] Allow the battery cell to rest at 25°C for 2 hours, ensuring the cell temperature is 25°C. Charge the battery cell to 4.25V at 0.33°C. Constant-voltage charge at 4.25V to a current of 0.05°C, then allow to rest for 1 hour. Discharge the battery cell at 0.33°C for 0.95°C at 25°C, recording the voltage V1 at this point. After 5 minutes of rest, discharge the battery cell at 0.33°C to 2.0V at 25°C. After 5 minutes of rest, charge the battery cell at 0.33°C for 0.97°C at 25°C, recording the voltage V2 at this point.

[0409] The cycle test process is as follows:

[0410] Allow the battery cell to rest at 25°C for 2 hours, ensuring the cell temperature is 25°C. Charge the battery cell at 0.33°C to a voltage of V2 at 25°C, then allow it to rest for 0.5 hours. Discharge the battery cell at 0.33°C to a voltage of V1 at 25°C, recording the capacity at this point as Cn. After allowing it to rest for 0.5 hours, repeat the above steps until the number of cycles, n, reaches 40 cls.

[0411] After cycling for 40 cls according to the above steps, Cn / C0 is recorded as the cycle capacity retention rate, which is used as an indicator to evaluate the battery cycle performance.

[0412] 3) Full battery cycle test:

[0413] At a constant temperature of 45°C, charge the full battery at 1C from 2.5V to 4.3V. Then, charge at constant voltage at 4.3V until the current is less than or equal to 0.05mA. Let it rest for 5 minutes, then discharge at 1C to 2.5V. Record the discharge capacity at this point as D0. Repeat the charge and discharge cycle until the discharge capacity drops to 80% of D0. Record the number of cycles the battery has completed.

[0414] 3. Analysis of test results of various embodiments and comparative examples

[0415] Table 1

[0416] From the comparison between the embodiments and the comparative examples, it can be seen that the embodiments all include the polymer dispersant shown in Formula I, which can effectively increase the maximum solid content of the slurry, shorten the filtration time, improve the production efficiency and quality of the electrode, and improve the flexibility of the electrode.

[0417] From the comparison between Examples 1-4 and Example 5, it can be seen that the organic segment of R2 containing at least one of an amide group and an amino group can further increase the maximum solid content of the slurry.

[0418] From the comparison between Examples 6-7 and Example 1, it can be seen that the end group of R2 containing at least one of -C(O)-NH2 and -CH2-NH2 can more effectively exert the dispersing effect of the polymer and increase the maximum solid content of the slurry compared with other end groups.

[0419] From the comparison between Example 7 and Example 17, it can be seen that at least one of R1 and R3 containing a poly(ethylene oxide-propylene oxide) polyether segment can more effectively exert a dispersing and softening effect than a polyethylene oxide polyether segment, further improving the maximum solid content of the slurry and the flexibility of the electrode.

[0420] From the comparison between Example 19 and Example 7, it can be seen that when both R1 and R3 are polyether segments, the slurry filtration time can be further reduced and the electrode flexibility can be improved compared with when only one of the two is a polyether segment.

[0421] From the comparison of Examples 7-11, it can be seen that a polymer with a weight average molecular weight of 2000-5000 can further exert the dispersing effect, increase the maximum solid content of the slurry, and shorten the filtration time.

[0422] Table 2

[0423] From the comparison between Example 22 and Example 19, Example 25 and Example 7, and Example 23 and Example 21, it can be seen that the end groups of the polyether segments include phenyl groups, which can further improve the dispersibility of the slurry.

[0424] Table 3

[0425] As shown in Examples 12-15, a polymer content of 0.1% to 2.0% by weight, based on the total dry mass of the positive electrode slurry, results in a slurry with a high maximum solids content, a short filtration time, and high flexibility. A polymer content of 0.2% to 1.0% by weight, based on the total dry mass of the positive electrode slurry, further balances the processing performance of the electrode sheet with the energy density of the battery.

[0426] Table 4

[0427] From the comparison between Example 7 and Example 20, it can be seen that the inclusion of a vinylidene fluoride polymer with a weight average molecular weight of not less than 700,000 as a binder in the positive electrode slurry can further reduce the amount of binder used and improve the flexibility of the electrode.

[0428] Table 5

[0429] From the comparison between Example 7 and Example 18, it can be seen that phosphate polymers can more effectively increase the solid content of the slurry, shorten the filtration time, and improve the flexibility of the electrode compared to phosphite polymers; and phosphate polymers have better stability, and can effectively improve the cycle capacity retention rate of the battery on the basis of improving the dispersibility of the slurry.

[0430] Table 6

[0431] From the comparison of Examples 26-28 and Comparative Examples 3-5, it can be seen that the polymers provided in the embodiments of the present application can more effectively improve the dispersibility of the positive electrode active material with a high degree of order in the carbon coating layer, and simultaneously improve the processability, cycle stability and gram capacity of the battery by matching the dispersant with the surface coating layer of the positive electrode active material.

[0432] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A polymer, wherein The polymer comprises a structure shown in Formula I, Wherein X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment; and R2 comprises an organic segment.

2. The polymer according to claim 1, wherein The organic segment of R2 contains at least one of an amide group, an amino group, and an aromatic group.

3. The polymer according to claim 1 or 2, wherein The organic chain segment of R2 also includes C 2-12 Hydrocarbon.

4. The polymer according to any one of claims 1 to 3, wherein R2 comprises the structure shown in Formula II Among them, R4 and R5 are randomly copolymerized, and R4 includes C 2-12 Alkylidene, C 3-13 At least one of the amide groups, R5 includes At least one of; Wherein, q1, q2, q3, q4 each independently include any integer between 0 and 4, R6 a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

5. The polymer according to any one of claims 1 to 4, wherein R2 comprises the structure shown in Formula III Among them, R6 includes C 2-12 Alkylene, R7 includes middle At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

6. The polymer according to any one of claims 1 to 5, wherein The terminal group of R2 includes at least one of -C(O)-NH2 and -CH2-NH2.

7. The polymer according to any one of claims 1 to 6, wherein At least one of R1 and R3 comprises a polyether segment, and optionally, both R1 and R3 comprise a polyether segment.

8. The polymer according to any one of claims 1 to 7, wherein At least one of R1 and R3 comprises a polyether segment represented by formula IV Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50.

9. The polymer according to any one of claims 1 to 8, wherein The terminal groups of the polyether segments include aromatic groups.

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

11. The polymer according to any one of claims 1 to 10, wherein The polymer includes at least one of the polymers represented by the following formula: Wherein, at least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50, R6 and R4 each independently include C 4-8 Alkylene, C 4-8 At least one of alkenylene groups.

12. The polymer according to claim 11, wherein The terminal groups of the polyether segments include aromatic groups.

13. The polymer according to any one of claims 1 to 10, wherein The polymer is shown in the following formula: Wherein, R2 comprises at least one of hydrogen, aryl, substituted or unsubstituted alkyl, and an organic segment containing an amino group or an amide group, At least one of R1 and R3 comprises a block copolymer polyether segment represented by formula IV Wherein EO represents -CH2-CH2-O-, PO represents -CH(CH3)-CH2-O-, 4≤m1≤50, 4≤n1≤50, and the terminal group of the polyether segment includes phenyl.

14. The polymer according to any one of claims 1 to 13, wherein The weight average molecular weight of the polymer is 1000-10000, and can be optionally 2000-5000.

15. A method for preparing a polymer, wherein: The preparation method comprises: The compound represented by formula VI is reacted with R3OH, R1OH, water, and a polymerizable monomer containing an unsaturated bond to prepare a polymer having a structure represented by formula I. Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all contain halogen; R1 and R3 each independently contain at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 contains a polyether segment or a polyester segment; and R2 includes an organic segment.

16. The preparation method according to claim 15, wherein: The preparation method comprises the following steps: The compound represented by formula VI is reacted with R3OH, R1OH and water to prepare the intermediate product represented by formula VII. The intermediate product is subjected to a second reaction with a polymerization monomer containing at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond to prepare the polymer.

17. The preparation method according to claim 16, wherein: The second reaction specifically comprises the following steps: The intermediate product undergoes an addition reaction with at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and then undergoes a substitution reaction with a halogen-substituted organic alcohol; The polymer is prepared by cycling the addition reaction and substitution reaction in sequence for multiple times; Wherein, R2 comprises the structure shown in formula III Among them, R6 includes C 2-12 Hydrocarbyl, R7 includes At least one of; wherein, q5 and q6 each independently include any integer between 0-4, 1≤n≤6.

18. The preparation method according to claim 16, wherein: The preparation method further comprises the following steps: The intermediate product is subjected to a third reaction with (i) at least one of an amide containing an unsaturated bond and an amine containing an unsaturated bond, and (ii) at least one of a hydrocarbon monomer containing an unsaturated bond and a cyclic amide monomer to prepare the polymer, wherein R2 comprises a structure shown in Formula II: Among them, R4 and R5 are randomly copolymerized, and R4 includes C 2-12 Hydrocarbon, C 3-13 At least one of the amide groups, R5 includes At least one of; Wherein, q1, q2, q3, q4 each independently include any integer between 0 and 4, R6 a 、R6 b Contains hydrogen, C 1-4 At least one of the alkyl groups, 1≤s≤6, 1≤t≤10.

19. A method for preparing a polymer, wherein: The preparation method comprises: The compound represented by formula VI is reacted with raw materials including R3OH and R1OH to prepare a polymer having a structure represented by formula I, Wherein, X includes a phosphate group or a phosphite group, X1, X2, and X3 all include halogen; R1 and R3 each independently include at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 includes a polyether segment, and the end group of at least one of the polyether segments includes an aromatic group; R2 includes an organic segment.

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

21. A positive electrode slurry, wherein: The invention comprises a dispersant, wherein the dispersant comprises the polymer according to any one of claims 1 to 14 or the polymer prepared by the preparation method according to any one of claims 15 to 19.

22. The positive electrode slurry according to claim 21, wherein The positive electrode slurry includes a positive electrode active material, and the positive electrode active material includes at least one of lithium phosphate and its carbon-modified materials; optionally, the positive electrode active material includes at least one of lithium iron phosphate and its doped materials, lithium iron manganese phosphate and its doped materials, carbon-coated materials of lithium iron phosphate and its doped materials, and carbon-coated materials of lithium iron manganese phosphate and its doped materials.

23. The positive electrode slurry according to claim 21 or 22, wherein: The positive electrode active material comprises a core and a carbon coating layer, wherein the carbon coating layer covers at least a portion of the surface of the core, wherein the carbon coating layer has a sp 2 Hybridized carbon atoms with sp 3 The molar ratio of hybridized carbon atoms is not less than 0.2, and may be not less than 0.5, and may be not less than 0.

8.

24. The positive electrode slurry according to claim 23, wherein: The thickness of the carbon coating layer is not greater than 15 nm; optionally, the thickness of the carbon coating layer is not greater than 10 nm; optionally, the thickness of the carbon coating layer is 4 nm-8 nm.

25. The positive electrode slurry according to any one of claims 21 to 24, wherein Based on the total mass of dry materials in the positive electrode slurry, the mass content of the polymer is 0.1%-2.0%, and can be optionally 0.2%-1.0%.

26. The positive electrode slurry according to any one of claims 21 to 25, wherein The positive electrode slurry includes a binder, and the binder includes a vinylidene fluoride polymer with a weight average molecular weight of not less than 300,000. Optionally, the weight average molecular weight of the binder is 700,000-9,000,000.

27. The positive electrode slurry according to any one of claims 21 to 26, wherein The maximum solid content of the positive electrode slurry is not less than 60%, and can be selected from 60% to 80%.

28. A positive electrode sheet, wherein: The positive electrode plate includes a positive electrode film layer, which is prepared by the positive electrode slurry described in any one of claims 21 to 27 or the positive electrode film layer includes a dispersant, and the dispersant includes a polymer described in any one of claims 1 to 14 or a polymer prepared by the preparation method described in any one of claims 15 to 19.

29. The positive electrode sheet according to claim 28, wherein: The positive electrode sheet has a compaction density of 2.6 g / cm 3 The number of folding times is not less than 2 times, and can be selected as 3-6 times.

30. The positive electrode sheet according to claim 28 or 29, wherein: The surface density of the positive electrode sheet is not less than 300 mg / 1540.25 cm 2 , optional: 300mg / 1540.25cm 2 -600mg / 1540.25cm 2 .

31. The positive electrode sheet according to any one of claims 28 to 30, wherein: The positive electrode film layer includes a dispersant, and the dispersant includes a structure shown in Formula I, wherein X comprises a phosphate group or a phosphite group, R1 and R3 each independently comprise at least one of a polyether segment, a polyester segment, hydrogen, and a hydrocarbon group, and at least one of R1 and R3 comprises a polyether segment or a polyester segment, and R2 comprises an organic segment; optionally, the organic segment of R2 comprises at least one of an amide group and an amino group, and optionally, the end group of the polyether segment comprises an aromatic group; The positive electrode active material includes lithium iron phosphate and its doping material, lithium iron manganese phosphate and its doping material, carbon coating material of lithium iron phosphate and its doping material, lithium iron manganese phosphate and its doping material At least one of the carbon-coated materials of its doping materials; optionally, the positive electrode active material includes at least one of lithium manganese iron phosphate and its doping materials, lithium manganese iron phosphate and its carbon-coated materials of its doping materials; Based on the total mass of the positive electrode film layer, the mass content of the dispersant is 0.1%-2.0%, and can be optionally 0.2%-1.0%.

32. A secondary battery, wherein: A positive electrode sheet comprising any one of claims 28 to 31.

33. An electrical device, wherein: Includes the secondary battery as described in claim 32.

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