Battery, positive electrode sheet and slurry, dispersant, and preparation method

Abstract

The present application discloses a battery, a positive electrode sheet and slurry, a dispersant, a preparation method, and an electric device. The battery comprises a positive electrode sheet; the positive electrode sheet comprises a current collector and a positive electrode material layer provided on at least one side of the current collector; the positive electrode material layer comprises a positive electrode active material and a dispersant; the dispersant comprises a polyester compound; the polyester compound comprises a structural unit A and / or a structural unit B; the chemical formula of the structural unit A is (I), and the chemical formula of the structural unit B is (II), wherein R1 and R2 are each independently selected from at least one of a C0 group, a C1-C18 alkyl group, and a C6-C18 aryl group; R3 and R4 are each independently selected from at least one of H, a C1-C18 alkyl group, a C6-C18 aryl group, and an ester group. The dispersant can improve the dispersibility of the positive electrode slurry, and enhance the uniformity and flexibility of the positive electrode sheet, thereby enabling the battery to achieve high capacity and stability.

Description

Battery, positive electrode sheet and slurry, dispersant and preparation method

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410961343.8, filed on July 17, 2024, entitled “Battery, Positive Electrode and Slurry, Dispersant and Preparation Method”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of new energy technology, and in particular to batteries, positive electrode sheets and slurries, dispersants and preparation methods and electrical equipment. Background Technology

[0004] Lithium-ion batteries have high energy density and are widely used in wireless communication, transportation, aerospace, and other fields. In the manufacturing process of lithium-ion batteries, the positive electrode is typically made by coating a positive electrode slurry onto a current collector and then drying it. Therefore, the properties of the positive electrode slurry affect the electrochemical performance and stability of the positive electrode, and consequently, the performance of the battery.

[0005] Insufficient dispersion of the positive electrode slurry reduces the uniformity of the positive electrode sheet, leading to battery capacity loss. Excessive coating thickness and compaction density of the positive electrode slurry result in greater brittleness, reduced stability, and increased susceptibility to cracking. The above statements are for informational purposes only and do not necessarily constitute prior art.

[0006] Summary of the Invention

[0007] The main technical problem solved by this application is to provide a battery, a positive electrode sheet and slurry, a dispersant, a preparation method and an electrical device, which can improve the dispersibility of the positive electrode slurry, improve the uniformity and flexibility of the positive electrode sheet, and enable the battery to have a high capacity retention rate and stability.

[0008] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a battery, the battery including a positive electrode sheet, the positive electrode sheet including a current collector and a positive electrode material layer disposed on at least one side of the current collector, the positive electrode material layer including a positive electrode active material and a dispersant, the dispersant including a polyester compound, the polyester compound including structural unit A and / or structural unit B, the chemical formula of structural unit A being […]. The chemical formula of structural unit B is R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group.

[0009] In this embodiment, the dispersant provided is a polymer with polyester as the main component on the main chain. The ester groups in the polyester are highly polar groups that can generate a strong polarization effect. Furthermore, solvated segments can be introduced into the polyester branches to allow them to fully expand in the solvent system, thereby improving the dispersibility of the positive electrode slurry and the uniformity of the positive electrode sheet. Moreover, the carbon chains in the middle of the ester groups can rotate freely, improving the flexibility of the electrode sheet, thus enabling the battery to have a high capacity retention rate and stability.

[0010] In one embodiment, the chemical formula of the ester group is: Wherein, 0≤a≤6, and R' is selected from any one of C1-C18 alkyl, C6-C18 aryl, polyoxyethylene ether segment, and polyoxyethylene-polyoxypropylene ether copolymer segment. In this embodiment, the introduction of carbon chain or polyether segment can act as a solvation segment to fully extend in the solvent system, playing a steric hindrance role to improve dispersion ability and subsequent stabilization role, preventing particles from re-aggregating after complete dispersion.

[0011] In one embodiment, the polyoxyethylene ether polyoxypropylene ether copolymer segment includes Where 3≤b≤60; 0≤c≤60. Polyoxyethylene ether-polyoxypropylene ether copolymer segments can be used as solvation segments. Within the above-mentioned degree of polymerization, they have good solvation effect and improve dispersion performance.

[0012] In one embodiment, the positive electrode active material includes one or more of lithium iron phosphate and lithium manganese iron phosphate, which can improve the stability of battery performance.

[0013] In one embodiment, the coating amount of the positive electrode material layer is 300-450g / 1540.25mm. 2 In this embodiment, the flexibility of the electrode is improved.

[0014] In one embodiment, the compaction density of the positive electrode material layer is 2.4-2.8 g / cm³. 2 In this embodiment, the flexibility of the electrode is improved.

[0015] In one embodiment, the film resistance of the positive electrode is 0.05Ω-0.30Ω. The low film resistance of the positive electrode helps to reduce the internal resistance of the battery.

[0016] In one embodiment, the polyester compound includes structural unit C and / or structural unit D, wherein the chemical formula of structural unit C is [insert chemical formula here]. The chemical formula of structural unit D is R5 is selected from any one of C1-C18 alkyl and C6-C18 aryl. In this embodiment, the provided polyester compound can be formed by polycondensation of a polyacid and a diol, or by polycondensation of a polyol and a diacid. The carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing a certain degree of flexibility; the flexibility effect can be controlled by regulating the carbon chain.

[0017] In one embodiment, the polyester compound further includes at least one substituent G, which includes any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, or a phosphonic acid group and its derivatives. The substituent G can ionize to produce negative ions, which then adsorb onto the surface of the active material through positive and negative charge interactions, causing electrostatic repulsion between the material particles and achieving dispersion. Alternatively, the substituent G can be a polar group, generating strong interaction forces with the material surface, maintaining a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0018] In one embodiment, G is an end group of the polyester compound. This configuration allows the dispersant to interact better with the active material, thereby improving the dispersion effect.

[0019] In one embodiment, the chemical formula of the carboxylic acid group and its derivatives is: The chemical formulas of and / or sulfonic acid groups and their derivatives are as follows: Wherein, d takes values ​​greater than 1 and less than or equal to 12, and R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, and aromatic ester; the chemical formula of the alkyl group is... The chemical formula of alkyl alcohols is The chemical formula of alkyl hydroxylamine is The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is: The value of e is 1-12, the value of f is 1-16, and the number of carbon atoms in Ar does not exceed 12.

[0020] In this embodiment, C d As a carbon atom chain, it can act as a solvation segment to achieve a solvation effect; when R6 is H, the above group can ionize to produce negative ions, which can then adsorb onto the surface of the active material through the interaction of positive and negative charges, causing electrostatic repulsion between the material particles to achieve the purpose of dispersion; when R6 is alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, or aromatic ester, it can increase the polarity of the substituent group G, generating a stronger interaction force with the material surface, keeping a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0021] In one embodiment, the chemical formula of the phosphonic acid group and its derivatives is: R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester group, and aromatic ester group; the chemical formula of the alkyl group is... The chemical formula of alkyl alcohols is The chemical formula of alkyl hydroxylamine is The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is: The value of e is 1-12, the value of f is 1-16, and the number of carbon atoms in Ar does not exceed 12.

[0022] When R6 is H, the above-mentioned group can ionize to produce negative ions, which can then adsorb onto the surface of the active material through the interaction of positive and negative charges, causing electrostatic repulsion between the material particles and achieving the purpose of dispersion. When R6 is alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, or aromatic ester, it can increase the polarity of the substituent group G, generating a stronger interaction force with the material surface, keeping a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0023] In one embodiment, the dispersant comprises a structure as shown in formula (1) or a structure as shown in formula (2);

[0024] Where n ranges from 3 to 100, and A is a capping group, which includes alkoxy groups. Benzyloxy ester group ester group amide group One or more of the following: hydroxyl group -OH, amino group -NH2, and carboxyl group -COOH, where g is 1-12, and C... h It is an alkyl segment or an aryl segment, where h is 1-18 and R is H, C1-C12 alkyl or C6-C12 aryl.

[0025] In this embodiment, the dispersant provided is a polymer with polyester as the main component of its main chain. The ester groups in polyester are highly polar groups, which can generate strong polarization. Multiple closely spaced ester groups can combine to generate strong intermolecular forces on the surface of the material particles, leading to adsorption and the formation of an electric double layer structure on the particle surface, resulting in electrostatic repulsion. Simultaneously, the oxygen heteroatoms on the ester groups can also form hydrogen bonds with the less polar groups on the particle surface. Furthermore, solvated segments can be introduced into the polyester branches to allow them to fully extend in the solvent system, acting as steric hindrance to improve dispersion and subsequent stabilization, preventing the particles from re-aggregating after complete dispersion. Moreover, the carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing a certain degree of flexibility. When applied to electrode sheets, the polyester compound can be embedded into the rigid binder (e.g., PVDF) chain, increasing the slippage ability of the PVDF chain and improving the flexibility of the electrode sheet.

[0026] In one embodiment, the weight percentage of the substituent group G segment in the polyester compound is less than 15%, the weight percentage of the solvated segments R1, R2, R3, R4, and R5 is less than 65%, and the weight percentage of the polyester group is 3%-30%. By controlling the weight percentage of each group in the polyester compound within the above range, good adsorption can be achieved between the dispersant and the material particles, and between the dispersant and the dispersion medium, thereby achieving a better dispersion effect, while also giving the polymer molecular chain better flexibility.

[0027] In one embodiment, the weight-average molecular weight of the polyester compound is 500-100,000. A larger molecular weight of the dispersant can create a stronger steric hindrance, allowing the material particles to be fully dispersed while reducing their re-agglomeration.

[0028] In one embodiment, the weight-average molecular weight of the polyester compound is 2000-50000. When the weight-average molecular weight of the dispersant is within this range, it can further disperse the material particles through physical isolation, while simultaneously reducing the re-agglomeration of the dispersed particles.

[0029] To solve the above-mentioned technical problems, another technical solution adopted in this application is: providing a positive electrode slurry, comprising a positive electrode active material, a dispersant, and a solvent, wherein the dispersant comprises a polyester compound, and the polyester compound comprises structural unit A and / or structural unit B, the chemical formula of structural unit A being […]. The chemical formula of structural unit B is R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group.

[0030] In this embodiment, the positive electrode slurry has good dispersibility, which is beneficial to improving the uniformity and flexibility of the positive electrode sheet.

[0031] In one embodiment, the dispersant accounts for 0.01%-3.0% of the total weight of the positive electrode slurry. When the dispersant accounts for a portion of the total weight of the positive electrode slurry within this range, both the flexibility of the positive electrode sheet and the energy density of the battery can be balanced.

[0032] In one embodiment, the dispersant accounts for 0.03%-2.0% of the total weight of the positive electrode slurry. When the dispersant accounts for a portion of the total weight of the positive electrode slurry within this range, it is possible to further balance the flexibility of the positive electrode sheet and the energy density of the battery.

[0033] In one embodiment, the viscosity of the positive electrode slurry is 4000 mPa·s-30000 mPa·s. When the viscosity of the positive electrode slurry is within this range, the slurry is less prone to sedimentation and has good dispersibility. Simultaneously, the slurry has good leveling properties, which facilitates coating.

[0034] In one embodiment, the solid content of the positive electrode slurry is 55%-65%. This solid content is beneficial for improving the stability of the positive electrode slurry, and can also reduce the coating thickness and lower the battery internal resistance.

[0035] To solve the above-mentioned technical problems, another technical solution adopted in this application is: providing a dispersant comprising a polyester compound, wherein the polyester compound comprises structural unit A and / or structural unit B, and the chemical formula of structural unit A is [insert chemical formula here]. The chemical formula of structural unit B is:

[0036] R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group.

[0037] In this embodiment, the dispersant can improve the dispersibility of the positive electrode slurry, improve the uniformity and flexibility of the positive electrode sheet, and enable the battery to have higher capacity and stability.

[0038] In one embodiment, the polyester compound includes structural unit C and / or structural unit D, wherein the chemical formula of structural unit C is [insert chemical formula here]. The chemical formula of structural unit D is R5 is selected from any one of C1-C18 alkyl and C6-C18 aryl. In this embodiment, the provided polyester compound can be formed by polycondensation of a polyacid and a diol, or by polycondensation of a polyol and a diacid. The carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing a certain degree of flexibility; the flexibility can be enhanced by regulating the carbon chain.

[0039] In one embodiment, the polyester compound further includes at least one substituent G, which includes any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, or a phosphonic acid group and its derivatives. The substituent G can ionize to produce negative ions, which then adsorb onto the surface of the active material through positive and negative charge interactions, causing electrostatic repulsion between the material particles and achieving dispersion. Alternatively, the substituent G can be a polar group, generating strong interaction forces with the material surface, maintaining a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0040] To solve the above-mentioned technical problems, another technical solution adopted in this application is: providing a method for preparing a dispersant, comprising the following steps: providing a polyacid monomer or a polyol monomer, wherein the polyacid monomer includes... Polyol monomers include Wherein, R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group; the polyester compound of any of the above embodiments is obtained by polycondensation reaction of polyacid monomer and diol monomer; or the polyester compound of any of the above embodiments is obtained by polycondensation reaction of polyol monomer and diacid monomer. The dispersant prepared by the above method can improve the dispersibility of the slurry and, when applied to electrode sheets, can improve the flexibility of the positive electrode sheet.

[0041] In one embodiment, the polycondensation reaction is followed by: reacting the polyester compound with a halogen-substituted compound containing a substituent group G to obtain a polyester compound containing a substituent group G; the substituent group G includes any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, and a phosphonic acid group and its derivatives. The substituent group G can ionize to produce negative ions, which can then adsorb onto the surface of the active material through positive and negative charge interactions, causing electrostatic repulsion between the material particles to achieve dispersion; or the substituent group G is a polar group, which can generate strong interaction forces with the material surface, maintaining a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0042] In one embodiment, the molar ratio of the substituent group G to the polyacid monomer is 1:(1-100); the molar ratio of the substituent group G to the polyol monomer is 1:(1-100). With the above settings, the prepared dispersant has better dispersion and softening effects.

[0043] To solve the aforementioned technical problems, another technical solution adopted in this application is to provide an electrical device that includes the aforementioned battery. The electrical device has at least the same advantages as the battery, namely, improved battery life.

[0044] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 is an exploded structural diagram of a battery according to one or more embodiments of this application;

[0047] Figure 2 is an exploded structural diagram of a battery cell according to one or more embodiments of this application;

[0048] Figure 3 is a structural schematic diagram of a vehicle according to one or more embodiments of this application.

[0049] In the attached diagram: 1000, vehicle; 300, motor; 200, controller; 100, battery; 10, housing; 11, first part; 12, second part; 20, battery cell; 21, end cap; 21a, electrode terminal; 22, housing; 23, electrode assembly. Detailed Implementation

[0050] To make the objectives, technical solutions, and effects of this application clearer and more explicit, the embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0052] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0055] Quantities, ratios, and other numerical values ​​are presented in range format in this document. It should be understood that this range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0056] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) may be performed simultaneously in parallel. For example, the method may also 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 steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0057] Lithium-ion batteries, as a new type of green rechargeable battery, are widely used in electric vehicles, energy storage systems, and renewable energy fields. With the new development of lithium-ion batteries in my country, they will inevitably achieve improvements in many aspects.

[0058] Please refer to Figure 1, which is an exploded structural diagram of a battery according to one or more embodiments. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, jointly defining a space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 jointly define the space. Alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0059] In battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, battery 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0060] Each battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0061] Please refer to Figure 2, which is an exploded structural diagram of a battery cell according to one or more embodiments. A battery cell 20 refers to the smallest unit that makes up a battery. As shown in Figure 2, the battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0062] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. In one embodiment, end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that end cap 21 is less prone to deformation under pressure and impact, allowing battery cell 20 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 to output or input electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0063] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, and plastic.

[0064] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode plates, and typically a separator is provided between the positive and negative electrode plates. The portions of the positive and negative electrode plates containing active material constitute the main body of the electrode assembly, while the portions of the positive and negative electrode plates without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current loop.

[0065] In some embodiments, the positive electrode includes a current collector and a positive active layer disposed on the current collector.

[0066] The positive electrode active layer includes a positive electrode active material, which may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2, also known as NCM 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0067] In one embodiment, the positive electrode active material includes lithium manganese iron phosphate (LiFe). x Mn 1-xLithium iron phosphate (LiPO4), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), and high-nickel layered materials Li 1+y (Ni a Co b Mn 1-a-b-c B c ) 1-y O2; where 0.05≤y≤0.05, 0.85≤a≤0.95, 0.01≤b≤0.10, 0≤c≤0.05, and B is Zn. 2+ Mg 2+ Al 3+ Cr 3+ ,Sc 3+ Ga 3+ La 3+ Sm 3+ Ti 4+ Zr 4+ Nb 5+ W 6+ One or more of them.

[0068] In one embodiment, the active layer of the positive electrode material further includes a conductive agent and a binder; the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, Ketjen black, and acetylene black; the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, acrylate, and polyurethane.

[0069] A conductive agent imparts conductivity to the electrode. The positive electrode conductive material can include any conductive material as long as it does not cause a chemical change. Positive electrode conductive materials include, but are not limited to, carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. In one embodiment, the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, Ketjen black, and acetylene black.

[0070] The adhesive improves the adhesion stability of the active layer and reduces the probability of powder shedding. The adhesive can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). In one embodiment, the adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, acrylate, and polyurethane.

[0071] In one embodiment, the active layer of the positive electrode material further includes the dispersant of any of the foregoing embodiments, or a dispersant prepared using the preparation method of the dispersant of any of the foregoing embodiments. The dispersant is beneficial for improving the uniformity and flexibility of the positive electrode sheet.

[0072] In some embodiments, the negative electrode includes a current collector and a negative electrode active layer disposed on the current collector.

[0073] The negative electrode active layer includes negative electrode active materials, which include, but are not limited to, carbon-based negative electrode materials, silicon-based negative electrode materials, tin-based negative electrode materials, lithium titanate negative electrode materials, and lithium metal negative electrode materials; specifically, including but not limited to graphite materials, silicon-carbon materials, graphite-silicon suboxide materials, nano-silicon materials, silicon suboxide materials, and tin-based materials; more specifically, including natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys.

[0074] In some embodiments, the negative electrode active layer may further include a binder, a conductive agent, and other optional additives. As examples, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers. As examples, the binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). As examples, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0075] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0076] In one embodiment, the electrolyte includes one or more of carbonate solvents and ether solvents.

[0077] Carbonates are typically small-molecule cyclic or chain carbonates; including but not limited to one or more of ethylene carbonate, propylene carbonate, butene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluorocarbonates; and may also be at least one ester solvent selected from γ-butyrolactone, dimethyl sulfite, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl acetate, and fluorocarboxylic acid esters.

[0078] Ether solvents include, but are not limited to, one or more of dimethyl ether, diethyl ether, tetrahydrofuran, methyltetrahydrofuran, ethylene oxide, 1,3-dioxolane, fluoroethers, DME (ethylene glycol dimethyl ether), DEE (ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), TRGDME (triethylene glycol dimethyl ether), TEGDME (tetraethylene glycol dimethyl ether), dipropyl ether, and dibutyl ether.

[0079] In other embodiments, the electrolyte may further comprise any one or a mixture of several of amine solvents, sulfone solvents, and nitrile solvents. Amine solvents include at least one of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide. Sulfone solvents include at least one of dimethyl sulfoxide, sulfolane, diphenyl sulfoxide, thionyl chloride, and dipropyl sulfone. Nitrile solvents include at least one of acetonitrile, succinic anionizer, adiponitrile, and glutaronitrile. A high-voltage resistant electrolyte is preferred, as its acidity decreases under high voltage, facilitating the transport of active ions, significantly reducing side reactions on the electrode surface, and improving battery stability.

[0080] In some embodiments, the electrolyte further includes an electrolyte salt, which may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0081] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0082] As mentioned earlier, the electrode assembly is the component in a battery cell where electrochemical reactions occur. The electrode assembly is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The positive electrode sheet includes a current collector and a positive active layer disposed on the current collector. The positive active layer includes positive active material, conductive agent, and binder, etc. In the preparation process of the positive electrode sheet, the positive active material, conductive agent, and binder are first thoroughly mixed in a solvent to obtain a positive electrode slurry; then, the positive electrode slurry is coated onto the current collector, dried, and cold-pressed to obtain the positive electrode sheet.

[0083] Therefore, the properties of the cathode slurry significantly affect the performance of the cathode electrode. In the cathode slurry, the solid content affects its stability; within a certain range, the higher the solid content, the higher the stability. Furthermore, a high solid content slurry can reduce coating thickness and lower battery internal resistance. However, high solid content slurries have insufficient dispersibility and are prone to gelation, which reduces the uniformity of the cathode electrode and leads to battery capacity loss.

[0084] Furthermore, increasing the coating thickness of the positive electrode slurry and the compaction density of the positive electrode sheet are beneficial to improving the energy density of the battery. However, with a large coating thickness and high compaction density, the flexibility of the positive electrode sheet will decrease, leading to reduced stability and increased susceptibility to cracking.

[0085] Accordingly, this application provides a dispersant that improves the dispersibility of the positive electrode slurry, enhances the uniformity and flexibility of the positive electrode sheet, and thus enables the battery to have higher capacity and stability. This dispersant can be applied to the positive electrode sheet of a battery; that is, this application provides a battery comprising a positive electrode sheet, the positive electrode sheet comprising a current collector and a positive electrode material layer disposed on at least one side of the current collector, the positive electrode material layer comprising a positive electrode active material and a dispersant, the dispersant comprising a polyester compound, the polyester compound comprising structural unit A or structural unit B, the chemical formula of structural unit A being […]. The chemical formula of structural unit B is R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group.

[0086] Wherein, C0 refers to a group containing 0 carbon atoms, that is, the ester groups at both ends are directly connected to the middle carbon atom, C1-C18 alkyl refers to an alkyl chain containing 1 to 18 carbon atoms, and C6-C18 aryl refers to an aryl chain containing 6 to 18 carbon atoms.

[0087] In this embodiment, the dispersant is selected from polymers with polyester as the main component. The ester groups in polyester are highly polar groups, which can generate strong polarization. Multiple closely spaced ester groups can combine to generate strong intermolecular forces on the surface of the material particles, leading to adsorption and the formation of an electric double layer structure on the particle surface, resulting in electrostatic repulsion. Simultaneously, the oxygen heteroatoms on the ester groups can also form hydrogen bonds with the less polar groups on the particle surface. Furthermore, solvated segments can be introduced into the polyester branches to allow them to fully expand in the solvent system, acting as steric hindrance to improve dispersion and subsequent stabilization, preventing the particles from re-aggregating after complete dispersion. Moreover, the carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing the dispersant with a certain degree of flexibility. When applied to electrode sheets, the polyester compound can embed into the rigid binder (e.g., PVDF) chain, increasing the slippage ability of the PVDF chain and improving the flexibility of the electrode sheet. This type of battery has good uniformity and flexibility in the positive electrode sheet, making it less prone to breakage, thus resulting in high battery capacity and stability. Furthermore, without compromising the structural stability of the positive electrode sheet, the coating thickness and compaction density of the positive electrode sheet can be increased, thereby improving the energy density of the battery.

[0088] In this embodiment, the polyester compound is a polymer obtained by polycondensation of polyols and polyacids. The polyester compound provided can be formed by polycondensation of a polyacid and a diol, or by polycondensation of a polyol and a diacid.

[0089] Specifically, polyester compounds can be obtained by polycondensation reaction of polybasic acid monomers with diols. For example, diacid monomers can be selected. To prepare polyester compounds, structural unit A is formed in the polyester compounds. Alternatively, polyester compounds can be obtained by polycondensation reaction of polyol monomers and diacids. For example, diol monomers can be used. To prepare polyester compounds, structural unit B is formed in the polyester compounds. It can be that a polyester compound contains only structural unit A, a polyester compound contains only structural unit B, or a polyester compound contains both structural units A and B.

[0090] In one embodiment, R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl. R1 and R2 are located on the main chain of the polyester compound and are disposed between two ester groups. By selecting the above-mentioned carbon chain structure, the carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing a certain degree of flexibility to the dispersant; by regulating the carbon chain, the flexibility effect can be enhanced.

[0091] In one embodiment, R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester groups. R3 and R4 are branched groups of the polyester compound and can be introduced into the polyester compound as solvation segments. The solvation segments have good compatibility with the dispersion medium (usually an organic solvent, such as N-methylpyrrolidone), can fully expand in the dispersion medium system, play a steric hindrance role to improve dispersion ability and subsequent stabilization role, and prevent the particles from re-aggregating after complete dispersion.

[0092] In one embodiment, the chemical formula of the ester group is: Wherein, 0≤a≤6, and R' is selected from any one of C1-C18 alkyl, C6-C18 aryl, polyoxyethylene ether segment, and polyoxyethylene polyoxypropylene ether copolymer segment.

[0093] Among them, C a This refers to a carbon chain structure with 'a' carbon atoms, which can be an alkyl chain structure. The number of carbon atoms ranges from 0 to 6. When the number of carbon atoms is 0, the ester group is directly connected to the main chain of the polyester compound.

[0094] In this embodiment, the introduction of carbon chains or polyether segments in R3 and R4 can act as solvation segments that fully expand in the solvent system, playing a steric hindrance role to improve dispersion ability and subsequent stabilization role, preventing particles from re-aggregating after complete dispersion.

[0095] In one embodiment, the polyoxyethylene ether polyoxypropylene ether copolymer segment includes Where 3≤b≤60; 0≤c≤60. Polyoxyethylene ether-polyoxypropylene ether copolymer segments can be used as solvation segments. Within the above-mentioned degree of polymerization, they have good solvation effect and improve dispersion performance.

[0096] In one embodiment, the polyester compound includes structural unit C or structural unit D, wherein the chemical formula of structural unit C is [insert chemical formula here]. The chemical formula of structural unit D is R5 is selected from any one of C1-C18 alkyl and C6-C18 aryl.

[0097] As mentioned earlier, polyester compounds can be obtained by polycondensation reaction of polybasic acid monomers with diols. Alternatively, polyester compounds can be obtained by polycondensation reaction of polyol monomers with diacids. For example, diacid monomers can be used. To prepare polyester compounds, with diacid monomers The diol in the reaction can be Structural unit C is formed in polyester compounds: Diol monomers can also be used. To prepare polyester compounds, diol monomers The dicarboxylic acid in the reaction can be Structural unit D is formed in the polyester compound:

[0098] In this embodiment, R5, as the carbon chain between two ester groups in the polyester compound molecule, can rotate freely, providing a certain degree of flexibility to the dispersant; by regulating the carbon chain, the flexibility effect can be enhanced.

[0099] In one embodiment, the polyester compound further includes at least one substituent group G, which includes any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, or a phosphonic acid group and its derivatives.

[0100] The substituent group G can ionize to produce negative ions, which can then adsorb onto the surface of polar materials through the interaction of positive and negative charges, causing electrostatic repulsion between material particles and achieving dispersion. Alternatively, if the substituent group G is a polar group, it can generate strong interaction forces with the material surface, keeping a certain distance between material particles and further improving the dispersion effect of the dispersant.

[0101] In some embodiments, the substituent G is any one of a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group. In this case, the substituent G can ionize into negative ions. Different substituent Gs ionize into different negative ions. By controlling the type of substituent G, different types of negative ions can be ionized, and the forces generated are also different. Thus, adsorption is achieved on the surfaces of materials with different polarities through the interaction of positive and negative charges, causing electrostatic repulsion between material particles and achieving the purpose of dispersion.

[0102] In some embodiments, the substituent G is any one of a carboxylic acid group derivative, a sulfonic acid group derivative, or a phosphonic acid group derivative. When the active hydrogen on the carboxylic acid group, sulfonic acid group, or phosphonic acid group is replaced by other substituents, derivatives of the corresponding groups are obtained. In this case, the substituent G is a polar group, which can generate strong interaction forces with the material surface, maintaining a certain distance between material particles, thereby improving the dispersion effect of the dispersant.

[0103] In one embodiment, the substituent G may further include a cationic group or an aromatic nonpolar group. The cationic group can generate electrostatic interactions with negatively charged materials, causing electrostatic repulsion between material particles and achieving dispersion. The aromatic nonpolar group has excellent adsorption properties for carbon-coated materials, enabling such material particles to maintain a certain distance, thereby further improving the dispersion effect of the dispersant.

[0104] In one embodiment, the chemical formula of the carboxylic acid group and its derivatives is: The chemical formulas of and / or sulfonic acid groups and their derivatives are as follows: Wherein, d takes values ​​greater than 1 and less than or equal to 12, and R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, and aromatic ester; the chemical formula of the alkyl group is... The chemical formula of alkyl alcohols is The chemical formula of alkyl hydroxylamine is The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is: The value of e is 1-12, the value of f is 1-16, and the number of carbon atoms in Ar does not exceed 12.

[0105] In this embodiment, C d The carbon chain with d carbon atoms can be an alkyl chain. It can act as a solvation segment to achieve a solvation effect. When R6 is H, the above group can ionize to produce negative ions, which can then adsorb onto the material surface through the interaction of positive and negative charges, causing electrostatic repulsion between the material particles and achieving the purpose of dispersion. When R6 is alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, or aromatic ester, it can increase the polarity of the substituent group G, generating a stronger interaction force with the material surface, keeping a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0106] In one embodiment, the phosphonic acid group and its derivatives include diester phosphonic acid and its derivatives or monoester phosphonic acid and its derivatives, wherein the chemical formula of diester phosphonic acid and its derivatives is [insert chemical formula here]. The chemical formulas of monophosphonic acid esters and their derivatives are as follows: R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester group, and aromatic ester group; the chemical formula of the alkyl group is... The chemical formula of alkyl alcohols is The chemical formula of alkyl hydroxylamine is The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is: The value of e is 1-12, the value of f is 1-16, and the number of carbon atoms in Ar does not exceed 12.

[0107] When R6 is H, the above-mentioned group can ionize to produce negative ions, which can then adsorb onto the material surface through the interaction of positive and negative charges, causing electrostatic repulsion between the material particles and achieving the purpose of dispersion. When R6 is alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester, or aromatic ester, it can increase the polarity of the substituent group G, generating a stronger interaction force with the material surface, keeping a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0108] In one embodiment, diester phosphonic acid and its derivatives are flanked by symmetrical polyester segments.

[0109] Substituent group G, acting as an anchoring group, can be adsorbed onto the surface of material particles through ionic bonds, hydrogen bonds, and van der Waals forces, maintaining a certain distance between the material particles and thus further improving the dispersion effect of the dispersant.

[0110] In one embodiment, G is an end group of the polyester compound. This configuration allows the dispersant to interact better with the material, improving the dispersion effect.

[0111] In this context, terminal groups refer to the groups at the ends of the polymer molecular chains. Substituent groups G are attached to the ends of the polyester compound's main chain. Therefore, a polyester compound molecule can have a maximum of two Gs, preferably one G. When the substituent group G is a diester phosphonic acid or its derivative, symmetrical polyester chain segments are attached to both ends of G.

[0112] In one embodiment, polyester segments may be prepared first, and then substituent groups G may be introduced at the ends of the polyester segments.

[0113] In one embodiment, the dispersant comprises a structure as shown in formula (1) or a structure as shown in formula (2);

[0114] Where n ranges from 3 to 100, and A is a capping group, which includes alkoxy groups. Benzyloxy ester group ester group amide group One or more of the following: hydroxyl group -OH, amino group -NH2, and carboxyl group -COOH, where g is 1-12, and C... h It is an alkyl segment or an aryl segment, where h is 1-18 and R is H, C1-C12 alkyl or C6-C12 aryl.

[0115] The choice of the capping group depends on whether the last group is a hydroxyl group (alcohol-capped) or a carboxyl group (acid-capped). For example, if the last group is a hydroxyl group (alcohol-capped), then it can be... If the final group is a carboxyl group (acid-capped), then it can be... It could also be

[0116] In this embodiment, the dispersant provided is a polymer with polyester as the main component of its main chain. The ester groups in polyester are highly polar groups, which can generate strong polarization. Multiple closely spaced ester groups can combine to generate strong intermolecular forces on the surface of the material particles, leading to adsorption and the formation of an electric double layer structure on the particle surface, resulting in electrostatic repulsion. Simultaneously, the oxygen heteroatoms on the ester groups can also form hydrogen bonds with the less polar groups on the particle surface. Furthermore, solvated segments can be introduced into the polyester branches to allow them to fully extend in the solvent system, acting as steric hindrance to improve dispersion and subsequent stabilization, preventing the particles from re-aggregating after complete dispersion. Moreover, the carbon chain between the two ester groups in the polyester compound molecule can rotate freely, providing a certain degree of flexibility. When applied to electrode sheets, the polyester compound can be embedded into the rigid binder (e.g., PVDF) chain, increasing the slippage ability of the PVDF chain and improving the flexibility of the electrode sheet.

[0117] In one embodiment, the weight percentage of the substituent group G segment in the polyester compound is less than 15%, the weight percentage of the solvation segments R1, R2, R3, R4, and R5 is less than 65%, and the weight percentage of the polyester group is 3%-30%. By controlling the weight percentage of each group in the polyester compound within the above range, good adsorption can be achieved between the dispersant and the material particles, and between the dispersant and the dispersion medium, thereby achieving a better dispersion effect and giving the polymer molecular chain better flexibility.

[0118] In one embodiment, the weight-average molecular weight of the polyester compound is 500-100,000. For example, it can be 500, 3,000, 10,000, 25,000, 30,000, 40,000, 60,000, 80,000, 100,000, etc., or a range consisting of any two of the above values, such as 10,000-30,000, 25,000-50,000, 70,000-85,000, 90,000-100,000, etc. A larger molecular weight of the dispersant can generate a stronger steric hindrance effect, allowing the material particles to be fully dispersed while reducing their re-agglomeration.

[0119] In one embodiment, the weight-average molecular weight of the polyester compound is 2000-50000. For example, it can be 2000, 3000, 8000, 10000, 25000, 30000, 40000, 50000, etc., or a range consisting of any two of the above values, such as 2000-5000, 5000-15000, 15000-35000, 35000-50000, etc. When the weight-average molecular weight of the dispersant is within the above range, it can further disperse the material particles through physical isolation, while reducing the re-agglomeration of the dispersed particles.

[0120] The dispersant with the above structure can achieve good dispersion of the positive electrode material; when applied to the positive electrode sheet, it can improve the stability and flexibility of the positive electrode sheet, thereby reducing the capacity loss of the battery.

[0121] In one embodiment, the positive electrode active material includes one or more of lithium iron phosphate and lithium manganese iron phosphate. The aforementioned positive electrode active material interacts with the dispersant in the positive electrode material layer, maintaining a certain distance between the positive electrode active material particles and achieving good dispersion.

[0122] In one embodiment, the film resistance of the positive electrode is 0.05Ω-0.30Ω. The film resistance of the positive electrode can be 0.05Ω, 0.10Ω, 0.135Ω, 0.15Ω, 0.20Ω, 0.25Ω, 0.30Ω, etc., or a range consisting of any two of the above values, such as 0.05Ω-0.10Ω, 0.135Ω-0.20Ω, 0.20Ω-0.30Ω, etc. A low film resistance of the positive electrode is beneficial for reducing the internal resistance of the battery.

[0123] This application also provides a method for preparing a dispersant, comprising the following steps: providing a polyacid monomer or a polyol monomer, wherein the polyacid monomer includes... Polyol monomers include Wherein, R1 and R2 are selected from at least one of C0, C1-C18 alkyl, and C6-C18 aryl; R3 and R4 are selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, and ester group; the polyester compound of any of the above embodiments is obtained by polycondensation reaction of polyacid monomer and diol monomer; or the polyester compound of any of the above embodiments is obtained by polycondensation reaction of polyol monomer and diacid monomer. The dispersant prepared by the above method can improve the dispersibility of the slurry and, when applied to electrode sheets, can improve the flexibility of the positive electrode sheet.

[0124] In one embodiment, the polycondensation reaction is followed by: reacting the polyester compound with a halogen-substituted compound containing a substituent group G to obtain a polyester compound containing a substituent group G; the substituent group G includes any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, and a phosphonic acid group and its derivatives. The substituent group G can ionize to produce negative ions, which can then adsorb onto the surface of a polar material through the interaction of positive and negative charges, causing electrostatic repulsion between the material particles to achieve dispersion; or the substituent group G is a polar group, which can generate strong interaction forces with the material surface, maintaining a certain distance between the material particles, thereby further improving the dispersion effect of the dispersant.

[0125] In one embodiment, the molar ratio of the substituent group G to the polyacid monomer is 1:(1-100); the molar ratio of the substituent group G to the polyol monomer is 1:(1-100). By controlling the weight percentage of each group in the polyester compound within the above range, good adsorption can be achieved between the dispersant and the material particles, and between the dispersant and the dispersion medium, so as to achieve a better dispersion effect, while making the polymer molecular chain more flexible.

[0126] In one application scenario, the dispersant provided in this application can be used as an additive in electrode material slurries. For example, it can be applied to the positive electrode slurry of lithium-ion batteries.

[0127] Taking lithium iron phosphate (LFP) as the active material as an example, in existing lithium-ion battery cathode slurries, the high solid content leads to insufficient dispersibility and easy gelation. With the continuous development of LFP production technology and the increasing demand for higher energy density, LFP particle size is constantly decreasing, specific surface area is constantly increasing, and surface energy is rising, making it difficult for particles to disperse. Furthermore, under thick coating and high compaction density, the electrode's flexibility is poor, leading to cracking issues.

[0128] Based on this, a dispersant of this application is applied to the cathode slurry of lithium iron phosphate (LFP) batteries. The ester groups in the polyester mainly exert a strong adsorption effect on the particles in the system through hydrogen bonding, coordination, or strong intermolecular forces. At the same time, the long chains on the branches act as solvation segments, playing a steric hindrance role to stabilize the dispersed particles. Furthermore, the introduction of polar anchoring groups G into the branched polyester dispersant structure makes the adsorption effect more significant and further improves the dispersion performance.

[0129] In this embodiment, the dispersion mechanism of the dispersant is as follows: A branched polymer capable of multi-site adsorption is designed for the polar surface of LFP powder. G is a polar anchoring group that acts on the surface of polar LFP particles. At the same time, the main chain is mainly polyester, and the ester groups in the polyester are strongly polar groups that can generate strong polarization. Multiple ester groups that are close together can combine together to generate strong intermolecular forces on the particle surface and thus adsorb, forming a double electric layer structure on the particle surface to generate electrostatic repulsion. At the same time, the oxygen heteroatoms on the ester groups can also form hydrogen bonds with the residues on the weakly polar coated carbon on the LFP particle surface. Meanwhile, carbon chains or polyether segments are introduced into the polyester branches, which act as solvation segments and fully extend in the NMP system, playing a steric hindrance role to improve the dispersion ability and subsequent stabilization role, preventing the particles from re-aggregating after complete dispersion.

[0130] The dispersant's flexibility mechanism is as follows: the carbon chain between the two ester groups can rotate freely, providing a certain degree of flexibility. In addition, the carbon chain or polyether segment on the side chain is also a good flexible group that can be embedded into the PVDF chain, increasing the slippage ability of the PVDF chain and improving the flexibility of the electrode.

[0131] Based on this, the polyester compound dispersant provided in this application introduces anchoring groups and polar groups into the molecule to enhance the adsorption between the polymer and the surface of particles with different polarities, thereby improving the dispersion performance. At the same time, a steric hindrance solvated segment is introduced to act as a steric hindrance, preventing the powder from re-agglomerating after dispersion and solving the problem of insufficient dispersibility and easy gelation of slurries with high solids content.

[0132] Furthermore, by introducing flexible segments into the polymer molecules, the polymer tends to be linear, reducing intermolecular sliding resistance and improving flexibility. This addresses the problem of poor electrode flexibility leading to electrode cracking under thick-coated high-density conditions.

[0133] In other embodiments, the dispersant provided in this application can also be applied to slurries of other positive electrode active materials. For example, the substituent G can form hydrogen bonds with the phosphate groups on the surface of positive electrode active materials such as lithium iron phosphate and lithium manganese iron phosphate, and with the hydroxyl groups on the surface of ternary positive electrode active materials; it can also form hydrogen bonds with functional groups such as hydroxyl and carboxyl groups on the surface of conductive agents such as carbon nanotubes and graphene. That is, dispersants with different molecular structures can be selected according to the type of positive electrode active material.

[0134] This application also provides a positive electrode slurry, which includes a positive electrode active material, a dispersant, and a solvent. The dispersant is the dispersant of any of the above embodiments or a dispersant prepared using the preparation method of the dispersant of any of the above embodiments. The positive electrode slurry has good dispersibility, which is beneficial to improving the uniformity and flexibility of the positive electrode sheet.

[0135] In one embodiment, the dispersant accounts for 0.01%-3.0% of the total weight of the positive electrode slurry. For example, it can be 0.01%, 0.05%, 0.1%, 0.16%, 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, etc., or a range of any two of the above values, such as 0.01%-0.05%, 0.1%-0.16%, 0.1%-0.2%, 0.8%-1.0%, 2.5%-3.0%, etc.

[0136] When the dispersant accounts for a portion of the total weight of the positive electrode slurry within the aforementioned range, the positive electrode slurry can achieve a better dispersion effect and improve the flexibility of the positive electrode sheet. At the same time, reducing the impact of the dispersant on the proportion of the positive electrode active material is beneficial to increasing the mass proportion of the positive electrode active material and improving the energy density and specific capacity of the battery.

[0137] In one embodiment, the dispersant accounts for 0.03%-2.0% of the total weight of the positive electrode slurry. For example, it can be 0.03%, 0.05%, 0.1%, 0.16%, 0.2%, 0.25%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, etc., or a range of any two of the above values, such as 0.03%-0.05%, 0.1%-0.16%, 0.2%-0.25%, 0.8%-1.0%, 1.5%-2.0%, etc.

[0138] When the dispersant accounts for a portion of the total weight of the cathode slurry within the aforementioned range, the cathode slurry achieves a better dispersion effect and reduces the impact of the dispersant on the proportion of the cathode active material. This is beneficial for increasing the mass proportion of the cathode active material and improving the energy density and specific capacity of the battery.

[0139] In one embodiment, the viscosity of the positive electrode slurry is 4000 mPa·s-30000 mPa·s. For example, it could be 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 6000 mPa·s, 8000 mPa·s, 10000 mPa·s, 12500 mPa·s, 15000 mPa·s, 20000 mPa·s, 22000 mPa·s, 26000 mPa·s, 29500 mPa·s, 30000 mPa·s, etc., or a range consisting of any two of the above values, such as 4000 mPa·s-4500 mPa·s, 6000 mPa·s-8000 mPa·s, 12500 mPa·s-15000 mPa·s, 22000 mPa·s-26000 mPa·s, 29500 mPa·s-30000 mPa·s, etc.

[0140] When the viscosity of the positive electrode slurry is within the above range, the slurry is not prone to sedimentation and has good dispersibility. At the same time, the slurry has good leveling properties, which is helpful for coating.

[0141] In one embodiment, the solid content of the positive electrode slurry is 55%-65%. For example, it can be 55%, 55.6%, 56.4%, 58%, 60%, 62.3%, 62.5%, 63%, 65%, etc., or a range of any two of the above values, such as 55%-55.6%, 56.4%-60%, 62.3%-65%, etc. The above solid content is beneficial for improving the stability of the positive electrode slurry, and can also reduce the coating thickness and lower the battery's internal resistance.

[0142] In some embodiments, the preparation method of the positive electrode slurry is as follows: the positive electrode active material, conductive agent, binder, dispersant, solvent and other functional components are added to the mixing tank in a certain proportion and in a certain order of addition, and after dispersion and mixing, a slurry suspension system is obtained.

[0143] The prepared positive electrode slurry does not separate into layers, has no obvious viscosity rebound upon standing, does not settle when slowly stirred, and does not exhibit gelation.

[0144] This application also provides a positive electrode sheet, which includes a current collector and a positive electrode material layer disposed on the current collector. The positive electrode material layer includes a positive electrode active material and a dispersant. The dispersant is a dispersant according to any of the above embodiments or a dispersant prepared using the preparation method of the dispersant according to any of the above embodiments. The positive electrode sheet exhibits good uniformity and flexibility; without compromising the structural stability of the positive electrode sheet, the coating thickness and compaction density of the positive electrode sheet can be increased, thereby improving the energy density of the battery.

[0145] In some embodiments, the positive electrode slurry of any of the above embodiments is coated onto the positive electrode current collector, dried in an oven to obtain a positive electrode film, and then cold-pressed according to the designed compaction thickness to obtain a positive electrode sheet.

[0146] In some embodiments, the application of the electrochemical device of this application is not particularly limited, and it can be used in any electronic device known in the prior art. The battery disclosed in the embodiments of this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. That is, an electrical device is provided. In some embodiments, the electrical device of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large storage batteries and lithium-ion capacitors, etc.

[0147] Electrical equipment can be equipped with individual battery cells, battery modules, or battery packs depending on its usage requirements.

[0148] Please refer to Figure 3, which is a structural schematic diagram of a vehicle according to one or more embodiments. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0149] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0150] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0151] Example 1:

[0152] (I) Preparation of dispersants

[0153] (1) Polycondensation is carried out using tricarboxylic acid and diol as monomers. In this process, a small amount of alcohol is added to first carry out an esterification reaction with the tricarboxylic acid to obtain a branched dicarboxylic acid containing ester groups.

[0154] (2) The dicarboxylic acid and diol then undergo a polycondensation reaction under concentrated sulfuric acid catalysis to obtain a branched polyester product. The degree of polymerization can be controlled by adjusting the reaction conditions and feed ratio. The degree of polymerization can be increased by appropriately extending the reaction time and increasing the reaction temperature. Then, the hydroxyl group at one end of the polyester reacts with the halogenated product under alkaline catalysis to achieve end capping. Then, two molecules of end capped polyester undergo a phosphonate esterification reaction with phosphorus oxychloride to obtain a phosphonate product with a symmetrical structure. Finally, it undergoes a hydrolysis reaction with a small amount of water in the system to obtain dispersant 1.

[0155] (II) Preparation of Lithium-ion Batteries

[0156] 1. The positive electrode active material lithium iron phosphate, conductive agent acetylene black, binder PVDF, and dispersant 1 are weighed in a weight ratio of 97.5:1.5:0.5:0.5. After being thoroughly mixed in an N-methylpyrrolidone solvent system, the mixture is coated onto Al foil using extrusion coating or transfer coating, dried, and cold-pressed to obtain the positive electrode sheet.

[0157] 2. The negative electrode active material artificial graphite, conductive agent acetylene black, binder carboxymethyl cellulose, and dispersant styrene-butadiene rubber are thoroughly mixed in a deionized water solvent system at a weight ratio of 96:2:1:1. The mixture is then coated onto Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0158] 3. Using PE porous polymer film as the separator. The positive electrode, separator, and negative electrode are wound in sequence and according to size to form a cell. After encapsulation, electrolyte injection, formation, and degassing, a lithium-ion battery is obtained.

[0159] Example 2:

[0160] The polyester preparation was the same as in Example 1, except that the ratio of phosphorus oxychloride to polyester segments was controlled at 1:1.05 during phosphonate esterification.

[0161] Example 3:

[0162] The preceding steps are the same as in Example 1. The anchoring group step is also carried out under alkaline catalysis, reacting with ClC4H9COOH to introduce the anchoring group. The subsequent steps are also the same as in Example 1.

[0163] Example 4:

[0164] The preceding steps are the same as in Example 1. The anchoring group step is also performed under alkaline catalysis, reacting with ClC4H9SO3H to introduce the anchoring group. Subsequent steps are also the same as in Example 1.

[0165] Examples 5-8:

[0166] The difference from Example 1 is that the solvation segment groups R1, R2, R3, R4, and R5 of the dispersant are changed.

[0167] Examples 9-10:

[0168] The difference from Example 1 is that the degree of polymerization of the polyester compound is adjusted.

[0169] Example 11:

[0170] The difference from Example 1 is that the main chain structure of the polyester compound was adjusted.

[0171] Example 12:

[0172] The difference from Example 1 is that the amount of dispersant added is adjusted.

[0173] Comparative example:

[0174] 1. The positive electrode active material lithium iron phosphate, conductive agent acetylene black, binder PVDF, and dispersant styrene-butadiene rubber are weighed in a weight ratio of 97.5:1.5:0.5:0.5. After being thoroughly mixed in an N-methylpyrrolidone solvent system, the mixture is coated onto Al foil by extrusion coating or transfer coating, dried, and cold-pressed to obtain the positive electrode sheet.

[0175] 2. The negative electrode active material artificial graphite, conductive agent acetylene black, binder carboxymethyl cellulose, and dispersant styrene-butadiene rubber are thoroughly mixed in a deionized water solvent system at a weight ratio of 96:2:1:1. The mixture is then coated onto Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0176] 3. Using PE porous polymer film as the separator. The positive electrode, separator, and negative electrode are wound in sequence and according to size to form a cell. After encapsulation, electrolyte injection, formation, and degassing, a lithium-ion battery is obtained.

[0177] Performance testing

[0178] 1. Material Characterization

[0179] (1) Infrared characterization of dispersants

[0180] The battery was disassembled, and the positive electrode was removed. An organic solvent was used to treat the material layers of the positive electrode to remove inorganic materials, dissolving and separating the organic matter. Chromatographic separation was then used to purify the organic compound, which was then subjected to qualitative testing. Measurements were taken using a Bruker Tensor 37 infrared spectrometer. The sample solution was either dropped onto a potassium bromide tablet or mixed with the sample during grinding and then pressed into a tablet, using a spectrally pure potassium bromide tablet as a carrier. The infrared scanning range was 4000 cm⁻¹. -1 up to 400cm -1 The scanning resolution is 16cm. -1 Repeat the scan 16 times.

[0181] (2) Dispersant weight-average molecular weight test

[0182] A Waters 2695 Isocratic HPLC gel electrophoresis system (differential refractive index detector 2141) was used. A 3.0% polystyrene solution was used as a reference, and a matched column was selected (oil-based: Styragel HT5 DMF7.8*300mm + Styragel HT4). A 3.0% polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. For testing, tetrahydrofuran was first used to flush the syringe, repeated several times. Then, 5 ml of the experimental solution was drawn, air was expelled from the syringe, and the needle tip was dried. Finally, the sample solution was slowly injected into the injection port. Data was acquired after the reading stabilized.

[0183] (3) Degree of aggregation test

[0184] After obtaining the weight-average molecular weight data of the dispersant, the degree of polymerization of the dispersant is obtained by combining it with the mass of the monomer.

[0185] 2. Positive electrode slurry performance testing

[0186] (1) Solid content of slurry

[0187] Weigh the copper foil in the weight loss rate measuring instrument and record the weight as M0, then zero the instrument.

[0188] Take a small amount of positive electrode slurry, coat it onto copper foil, and then weigh it in a moisture analyzer, recording it as M1; close the equipment and start drying; after the drying is completed, record the weighing data as M2, and calculate the solid content, which is (M2-M0) / (M1-M0).

[0189] (2) Slurry stability test

[0190] After re-stirring the slurry for 30 minutes, take a certain amount of slurry and pour it into the sample bottle of the stability tester. After placing the sample bottle, close the test tower lid and open the test tower lid. The test interface will start to show the scanning curve, and the sample stability test will begin. The test will continue for more than 72 hours to complete the test.

[0191] (3) Slurry viscosity

[0192] Use a rotational viscometer, model DV-2TLV Bollerfei viscometer. When using it, select the appropriate rotor according to the viscosity of the slurry, and adjust the parameter to 12 r / min. After the measurement starts, pay attention to the reading on the screen. When the number no longer jumps significantly and the measurement progress on the right rises from the bottom to the top, record the data.

[0193] 3. Battery performance test

[0194] (1) Brittleness test of positive electrode sheet

[0195] Take a defect-free positive electrode sheet and cut it longitudinally into samples with a length and width of 20cm and a width of 2.5cm. The number of samples should be at least 8. First, pre-fold the sample in half. Then, place the sample on the testing platform and roll it once with a 2kg cylindrical roller. If light is transmitted, the number of folds is counted as one. If light is not transmitted, repeat the reverse folding and rolling process. Observe the crease against the light to check for light transmission or breakage. Record the actual number of folds and take the average as the test result.

[0196] (2) Diaphragm resistance

[0197] Cut the dried positive electrode slurry (film layer) into small round pieces with a diameter of 3mm from the left, center, and right sides of the positive electrode sheet. Turn on the power of the electrode resistance meter, place the probe at the appropriate position on the electrode resistance meter, click the "start" button, and wait for the reading to stabilize before taking the reading. Test two positions for each small round piece, and finally calculate the average of the six measurements, which is the resistance of the electrode film layer.

[0198] (3) First Coulomb efficiency

[0199] At 25°C, the batteries of the above embodiments and comparative examples were charged at a constant current rate of 0.1C to a voltage of 4.3V. The charging capacity at this time was recorded as the first charge capacity of the secondary battery. After resting for 5 minutes, the batteries were discharged at a constant current rate of 0.1C to a voltage of 2.0V and then rested for 5 minutes. This is one charge-discharge cycle. The discharge capacity of this cycle was recorded as the first discharge capacity of the secondary battery, which is the initial capacity of the secondary battery.

[0200] The first-cycle coulombic efficiency (%) of a secondary battery = first-cycle discharge capacity / first-cycle charge capacity × 100%.

[0201] (4) Capacity retention rate during 45℃ cycling

[0202] At 45°C, the batteries in the examples and comparative examples were charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to rest for 10 minutes, and then discharged to 2.5V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle was recorded. The battery capacity retention rate after each cycle was: Pn = Cn / C0 × 100%.

[0203] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=100. The battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 300 cycles under the above test conditions, i.e., the value of P300.

[0204] Table 1. Parameters of dispersants in each embodiment and comparative example. Note: The feed ratio refers to the molar ratio of polyacid monomers, polyol monomers, and halogenated compounds; "EO" refers to polyoxyethylene ether segments, "PO" refers to polyoxypropylene ether segments, and polyester type indicates the main chain structure of the polyester compound, as shown in Formula 1. Equation 2 is "Ratio" refers to the proportion of the dispersant to the total weight of the positive electrode slurry.

[0205] Table 2 Performance parameters of each embodiment and comparative example Note: "Electrode brittleness" refers to the number of times the electrode is folded in half to transmit light; "capacity retention rate" refers to the capacity retention rate after 300 cycles at 45℃.

[0206] III. Analysis of Test Results of Positive Electrode and Battery

[0207] The data from the above embodiments show that the dispersant provided in this application can achieve good dispersion of the positive electrode slurry. When applied to the positive electrode sheet, it gives the positive electrode sheet good flexibility, which is beneficial to improving the stability of the battery. It also reduces the resistance of the positive electrode sheet, which is beneficial to improving the battery's first efficiency and capacity retention rate.

[0208] Furthermore, the dispersion effect of the dispersant can be adjusted by controlling the type of anchoring group, the type of solvation segment, the degree of polymerization of the dispersant, and the amount added: Comparing Examples 1-4, different anchoring groups G all showed good effects, among which diester phosphonic acid (Example 1) was better than monoester phosphonic acid (Example 2); Comparing Examples 1, 5-8, different solvation segments were screened, and those containing polyoxyethylene ether and polyoxypropylene ether segments (Example 1) were better than pure polyoxyethylene ether and alkyl segments (Examples 5-7), and even better than alkyl segments and alkyl segments (Example 5); Comparing Examples 1, 9-10, polyester compounds with different degrees of polymerization all showed good effects; Comparing Examples 1, 12, polyester compounds with different amounts added all showed good effects.

[0209] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A battery, wherein, The battery includes a positive electrode sheet including a current collector and a positive electrode material layer provided on at least one side of the current collector, the positive electrode material layer including a positive electrode active material and a dispersing agent, the dispersing agent including a polyester compound, the polyester compound including structural unit A and / or structural unit B, the structural unit A having a chemical formula of the structural unit B having a chemical formula of wherein R1, R2 are independently selected from at least one of C0, C1-C18 alkyl, C6-C18 aryl, ester group; R3, R4 are independently selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, ester group.

2. The battery of claim 1, wherein, The chemical formula of the ester group is wherein 0≤a≤6, R' is selected from any one of C1-C18 alkyl, C6-C18 aryl, polyoxyethylene ether segment, polyoxyethylene polyoxypropylene ether copolymer segment.

3. The battery of claim 2, wherein, The polyoxyethylene polyoxypropylene ether copolymer segment includes wherein 3≤b≤60; 0≤c≤60.

4. The battery of any one of claims 1-3, wherein, the positive active material comprises one or more of lithium iron phosphate, lithium manganese iron phosphate.

5. The battery of any one of claims 1-4, wherein, The coating amount of the positive electrode material layer is 300-450 g / 1540.25 mm 2 .

6. The battery of any one of claims 1-5, wherein, The compacted density of the positive electrode material layer is 2.4-2.8 g / cm 2 .

7. The battery of any one of claims 1-6, wherein, the sheet resistance of the positive electrode tab is 0.05 Ω-0.30 Ω.

8. The battery of any one of claims 1 to 7, wherein, The polyester compound includes structural unit C and / or structural unit D, the chemical formula of the structural unit C is The chemical formula of the structural unit D is wherein R5 is selected from any one of C1-C18 alkyl, C6-C18 aryl, ester group.

9. The battery of any one of claims 1 to 8, wherein, the polyester compound further comprises at least one substituent group G, the G comprises any one of a carboxylic acid group and its derivative, a sulfonic acid group and its derivative, a phosphonic acid group and its derivative.

10. The battery of claim 9, wherein, the G is an end group of the polyester compound.

11. The battery of claim 9 or 10, wherein, The chemical formula of the carboxylic acid group and its derivatives is and / or The chemical formula of the sulfonic acid group and its derivatives is wherein d is in a range of greater than 1 and less than or equal to 12, R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester group, aromatic ester group; The alkyl group has the formula The alkyl alcohol has the chemical formula The alkylhydroxylamine has the chemical formula The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is e is in a range of 1-12, f is in a range of 1-16, and the number of carbon atoms in Ar is no more than 12.

12. The battery of claim 9 or 10, wherein, The chemical formula of the phosphonic acid group and its derivatives is wherein R6 is selected from any one of H, alkyl, alkyl alcohol, alkyl hydroxylamine, aliphatic ester group, aromatic ester group; The alkyl group has the formula The alkyl alcohol has the chemical formula The alkylhydroxylamine has the chemical formula The chemical formula of the fatty ester group is The chemical formula of the aromatic ester group is e is in a range of 1-12, f is in a range of 1-16, and the number of carbon atoms in Ar is no more than 12.

13. The battery of any one of claims 1 to 12, wherein, The dispersant includes a structure as shown in formula (1) or a structure as shown in formula (2); wherein n has a value ranging from 3 to 100, A is a capping group, said capping group comprising an alkoxy group phenylalkyloxy ester group ester group amido one or several of hydroxyl -OH, amino -NH2 and carboxyl -COOH, g has a value of 1 to 12, C h is an alkyl segment or an aryl-containing segment, h has a value of 1 to 18, R is H, C1-C12 alkyl or C6-C12 aryl.

14. The battery of claim 13, wherein, the weight percentage of the substituent group G segment in the polyester compound is less than 15%, the weight percentage of the solvent chain segments R1, R2, R3, R4, R5 is less than 65%, and the weight percentage of the polyester group is 3%-30%.

15. The battery of any one of claims 1 to 14, wherein, the weight average molecular weight of the polyester compound is 500-100000.

16. The battery of claim 15, wherein, the weight average molecular weight of the polyester compound is 2000-50000.

17. A positive electrode slurry, wherein, A positive electrode active material, a dispersing agent, and a solvent, the dispersing agent including a polyester compound, the polyester compound including structural unit A and / or structural unit B, the structural unit A having a chemical formula of the structural unit B having a chemical formula of wherein R1, R2 are independently selected from at least one of C0, C1-C18 alkyl, C6-C18 aryl; R3, R4 are independently selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, ester group.

18. The positive electrode slurry of claim 17, wherein, the dispersant accounts for 0.01%-3.0% of the total weight of the positive electrode slurry.

19. The positive electrode slurry of claim 18, wherein, the dispersant accounts for 0.03%-2.0% of the total weight of the positive electrode slurry.

20. The positive electrode slurry of any one of claims 17-19, wherein, the viscosity of the positive electrode slurry is 4000 mPa·s-30000 mPa·s.

21. The positive electrode slurry of any one of claims 17-19, wherein, the solid content of the positive electrode slurry is 55%-65%.

22. A dispersant, wherein, comprising a polyester compound comprising structural unit A and / or structural unit B, the chemical formula of the structural unit A is the chemical formula of the structural unit B is wherein R1, R2 are independently selected from at least one of C0, C1-C18 alkyl, C6-C18 aryl; R3, R4 are independently selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, ester group.

23. The dispersant of claim 22, wherein, The polyester compound includes structural unit C and / or structural unit D, the chemical formula of the structural unit C is The chemical formula of the structural unit D is wherein R5 is selected from any one of C1-C18 alkyl, C6-C18 aryl.

24. The dispersant of claim 22 or 23, wherein, The polyester compound further comprises at least one substituent group G, which comprises any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, a phosphonic acid group and its derivatives.

25. A method of preparing a dispersant, wherein, comprising the steps of: A polyacid monomer or a polyol monomer is provided, the polyacid monomer comprising The polyol monomer includes wherein R1, R2are independently selected from at least one of C0, C1-C18 alkyl, C6-C18 aryl; R3, R4are independently selected from at least one of H, C1-C18 alkyl, C6-C18 aryl, ester group; polycondensation of the polybasic acid monomer with a dibasic alcohol monomer to obtain the polyester compound of any one of claims 22-24; or polycondensation of the polyhydric alcohol monomer with a dibasic acid monomer to obtain the polyester compound of any one of claims 22-24.

26. The method of claim 25, wherein the dispersant is prepared by the process of: The polycondensation reaction is followed by: reacting the polyester compound with a halogen-substituted compound containing substituent group G to obtain a polyester compound containing substituent group G; The substituent group G comprises any one of a carboxylic acid group and its derivatives, a sulfonic acid group and its derivatives, a phosphonic acid group and its derivatives.

27. The method of claim 25 or 26, wherein the dispersant is prepared by: The molar ratio of substituent group G to polybasic acid monomer is 1:(1-100); the molar ratio of substituent group G to polyhydric alcohol monomer is 1:(1-100).

28. An electrical device, comprising: The electric device comprises the battery of any one of claims 1-16.

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