Polymer, battery cell, manufacturing method therefor, and electric device

Abstract

The present application provides a polymer, a battery cell, a manufacturing method therefor, a battery device, and an electric device. The polymer comprises a phenyl group, formula (I), a flexible chain segment, and an end group; the end group comprises one or more of a substituted or unsubstituted amide group and a substituted or unsubstituted -NH2, and optionally one or more of a carbonate group, a sulfonate group, a phosphate group, a quaternary ammonium group, and a C6-C18 aryl group; the flexible chain segment comprises one or more of -CH2-O-CH2- and -C(O)O-, and optionally -CH2-; the flexible chain segment is linked to -O- in formula (II); and the end group is linked to the flexible chain segment.

Description

Polymers, battery cells, their manufacturing methods and electrical devices Cross-references to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411517448.0, filed on October 29, 2024, entitled “Polymer, Battery Cell, Method of Manufacturing Thereof and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a polymer, a battery cell, a method for manufacturing the same, and an electrical device thereof. Background Technology

[0003] In secondary batteries, the positive electrode sheet is typically prepared by coating a slurry containing positive electrode active materials onto a current collector and then drying it. Increasing the maximum solid content of the slurry is an important and effective means to reduce drying time, increase electrode coating speed, and improve coating surface density. However, with the further upgrading of secondary battery performance, such as energy density and long lifespan, positive electrode active materials are developing towards nano-scale and optimized carbon coating. Such materials have higher surface energy and are more prone to agglomeration and gel formation in the slurry, which seriously affects the slurry solid content and the production efficiency and quality of the positive electrode sheet. Therefore, how to increase the slurry solid content while ensuring the uniformity of slurry dispersion, thereby effectively increasing the maximum solid content of the slurry, is one of the technical problems that urgently need to be solved in this field.

[0004] Furthermore, to improve the volumetric energy density of secondary batteries, the positive electrode sheet needs to have a higher coating surface density and a higher electrode compaction density. Such electrodes will be subjected to greater stress during core forming, potentially causing the positive electrode sheet to break at corners, which can severely impact the overall self-discharge performance and safety of the battery cell. Therefore, improving the flexibility of positive electrode sheets with high coating surface density and high compaction density, enabling them to withstand greater stress without breaking, is one of the urgent technical problems to be solved in this field. Summary of the Invention

[0005] To improve the dispersion uniformity of the slurry and enhance the flexibility of the positive electrode sheet, this application provides a polymer, a battery cell, a method for manufacturing the same, and an electrical device thereof.

[0006] A first aspect of the present invention provides a polymer comprising phenyl, Flexible segments and end groups, the end groups including one or more of substituted or unsubstituted amide groups, substituted or unsubstituted -NH2 groups, and optionally one or more of carbonate groups, sulfonate groups, phosphate groups, quaternary ammonium groups, and C6-C18 aryl groups; the flexible segments including one or more of -CH2-O-CH2-, -C(O)O-, and optionally -CH2-; the flexible segments are connected to... On the -O-, the end base is connected to the flexible chain segment.

[0007] The carbon-containing coating layer with a certain degree of graphitization on the surface of the positive electrode active material transforms the surface characteristics of the positive electrode active material from polar to non-polar. The N-type end groups are polar groups, which often contain lone pairs of electrons and have strong intermolecular forces on C. They also have van der Waals forces on the carbon layer on the surface of the positive electrode active material and form hydrogen bonds with the residues on the carbon layer surface. This is more conducive to the uniform dispersion of the positive electrode active material in the slurry, thereby improving the stability of the slurry.

[0008] Furthermore, the aforementioned flexible segments not only enhance the polymer's flexibility but also improve it when applied to electrode sheets. In particular, the -CH2-O-CH2- and -C(O)O- segments utilize the spins of CO and CC to reduce the ordered arrangement of binder molecules in the positive electrode slurry, enabling the active material particles to slide better during rolling and further improving the electrode sheet's flexibility. Improved electrode flexibility effectively suppresses breakage at corners, contributing to high energy density in battery cells. Simultaneously, improved dispersion of the positive electrode active material and enhanced electrode sheet flexibility lead to a more stable positive electrode structure, thus also improving the cycle performance of battery cells.

[0009] Furthermore, the phenyl group in the polymer can strengthen the π-π conjugation between the polymer and the conductive agent in the slurry, resulting in better adsorption between the polymer and the conductive agent, and also strengthening the steric hindrance of the molecular chain. This further improves the aggregation of the conductive agent and enhances its dispersion. Moreover, the effect of the phenyl group is not limited to the dispersion of the conductive agent. When the surface of the positive electrode active material has a carbon-containing coating layer, the phenyl group also has the aforementioned effect with the positive electrode active material, thus also improving the dispersion uniformity of the positive electrode active material in the slurry and enhancing the stability of the slurry. In addition, the phenyl group can be better embedded in the molecular chain of the binder, thereby further improving the flexibility of the electrode sheet.

[0010] Meanwhile, the polymer of this application has The group, consisting of maleic acid residues, exhibits low swelling and high electrochemical stability. The polymer contains flexible segments grafted onto the above-mentioned... The side chains are end-capped with the aforementioned end groups, which can be stably adsorbed on the surface of the electrode active material. At the same time, the steric hindrance provided by the molecular chains of the aforementioned flexible segments physically separates the electrode active material particles, preventing particle agglomeration in the slurry. This improves the uniformity of particle dispersion in the slurry and maintains the fluidity of the slurry, reducing the risk of slurry gelation. Therefore, it is beneficial to increase the solid content of the slurry to improve the electrode fabrication efficiency.

[0011] In any embodiment of the first aspect of this application, the polymer comprises the following structural units:

[0012]

[0013] Among them, R 1 and R 2 Each group independently comprises one or more of the following: carbonate group, sulfonate group, phosphate group, substituted or unsubstituted amide group, substituted or unsubstituted -NH2 group, quaternary ammonium group, and C6-C18 aryl group, and R 1 and R 2 At least one of them includes one or more of substituted or unsubstituted amide groups and substituted or unsubstituted -NH2; L 1 and L 2 Each independently includes one or more of -CH2-, -CH2-O-CH2-, and -C(O)O-, and L 1 and L 2 At least one of them includes one or more of -CH2-O-CH2- and -C(O)O-.

[0014] Polymers having the above-mentioned structural units, wherein The synergistic effect of flexible segments and end groups is better, and the two branches provided by maleic acid residues can better provide flexibility to the electrode in space. The end groups connected at the ends of the flexible segments can anchor the active material, thus making the dispersion uniformity of active material particles in the slurry better and the flexibility of the electrode sheet more fully improved.

[0015] In any embodiment of the first aspect of this application, R 1 and R 2 Each independently includes -C(O)OR 11 -SO3R 11 , One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R17 R 18 R 19 Each is independently selected from one or more substituted or unsubstituted C1-C18 alkyl groups; R 12 R 13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; X - To represent a halide anion, F can be selected. - Cl - ,Br - I - One or more of the above aromatic groups can be used. The aromatic groups can also form a relatively stable adsorption on the surface of the positive electrode active material with a carbon-coated layer, thereby more effectively promoting the dispersion of the positive electrode active material in the slurry and improving the stability of the slurry.

[0016] In any embodiment of the first aspect of this application, R 1 and R 2 Each independently includes -C(O)OR 11 -SO3R 11 , One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R 17 R 18 R 19 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups, R 12 R 13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups.

[0017] In any embodiment of the first aspect of this application, R may optionally be used. 1 and R 2 Each independently includes One or more of them, and R 1 and R 2 At least one of them includes R 16 R 17 R 18 R 19 Each is independently selected from one or more alkyl groups selected from H and C4-C12, optionally; R 12 R 13 Each is independently selected from one or more alkyl groups selected from H and C1-C6.

[0018] In any embodiment of the first aspect of this application, R is further optionally... 1 and R 2 Each independently includes -C(O)NH2 and [NH4]. + X - And R 1 and R 2 At least one of them includes -C(O)NH2.

[0019] In any embodiment of the first aspect of this application, X - For F - Cl - ,Br - I - One or more of them.

[0020] In any embodiment of the first aspect of this application, L 1 and L 2 Each independently includes C1-C18 alkylene groups and C1-C18 alkylene-NH-R groups. 21 -、-C(O)O-、 any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C10 alkylene groups, where a and b are each independently selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

[0021] In any embodiment of the first aspect of this application, L 1 and L 2 Each independently includes C2-C12 alkylene groups and C4-C12 alkylene groups -NH-R. 21 -、-C(O)O-、 any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C5 alkylene groups, where a and b are each independently selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

[0022] Optionally, in any embodiment of the first aspect of this application, L 1 and L 2Each independently includes C4-C12 alkylene groups, C2-C10 alkylene groups -O(O)C-, and C4-C12 alkylene groups -NH-R. 21 -、 Any one of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C2 alkylene groups, where a is selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

[0023] The polyether segments in the above structure have more suitable steric hindrance and a lower glass transition temperature, which can more effectively reduce the ordered arrangement of binder molecules in the electrode slurry. This helps the active material particles to slide better during rolling, thus improving the flexibility of the electrode sheet. Through these excellent dispersion and flexibility-enhancing effects, the uniformity of particle dispersion in the slurry and the flexibility of the electrode sheet are improved, thereby enhancing the safety performance and ultimate compaction density of the battery cell. This allows for an increase in the active material loading of the battery cell, contributing to a further improvement in the energy density of the battery cell.

[0024] In any embodiment of the first aspect of this application, the polymer has the following structural segments:

[0025]

[0026] Where x is selected from any integer between 5 and 60; y is selected from any integer between 5 and 60.

[0027] In any embodiment of the first aspect of this application, the polymer has the following structural segments:

[0028]

[0029] Where n is selected independently from any integer from 4 to 12, m is selected independently from any integer from 2 to 10, c is selected independently from any integer from 1 to 8, d is selected independently from any integer from 1 to 8, 2≤c+d≤10, x is selected from any integer from 5 to 60, and y is selected from any integer from 5 to 60.

[0030] In any embodiment of the first aspect of this application, the weight-average molecular weight of the polymer is 10,000 to 500,000, and optionally 15,000 to 25,000. Polymers with the above-mentioned weight-average molecular weight disperse more smoothly in binders, and therefore the dispersion effect on solid particles in the slurry is more easily achieved.

[0031] In any embodiment of the first aspect of this application, the elongation at break of the polymer-containing film is 190%-250%, the film comprises the polymer and polyvinylidene fluoride in a mass ratio of 1:9, the polyvinylidene fluoride is Arkema HSV900 polyvinylidene fluoride from France, and the thickness of the film is 3 mm.

[0032] The second aspect of this application provides a battery cell, which includes a positive electrode sheet, the positive electrode sheet including a positive active layer, the positive active layer including a positive active material and a dispersant, the dispersant including the polymer provided in any embodiment of the first aspect above.

[0033] Because the polymer of this application has The group is a maleic anhydride ring-opening structure, which exhibits low swelling and high electrochemical stability. Simultaneously, the polymer contains phenyl groups and flexible segments grafted onto the above-mentioned... The side chains are end-capped with the aforementioned end groups, which can stably adsorb onto the surface of the positive electrode active material. Simultaneously, the steric hindrance provided by the molecular chains of the flexible segments physically separates the positive electrode active material particles, preventing particle aggregation in the slurry. This improves the uniformity of particle dispersion in the slurry, maintains the slurry's fluidity, reduces the risk of slurry gelation, and also helps increase the slurry's solid content, thus improving electrode fabrication efficiency. Furthermore, the aforementioned flexible segments not only give the polymer better flexibility, improving the flexibility of the positive electrode when applied to it, but also, the -CH2-O-CH2- segments utilize the spins of CO and CC to reduce the ordered arrangement of binder molecules in the positive electrode slurry. This helps the positive electrode active material particles slide better during rolling, further improving the flexibility of the positive electrode and reducing cracking at corners.

[0034] In any embodiment of the second aspect of this application, the density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

[0035] In any embodiment of the second aspect of this application, the positive electrode active material includes one or more of nickel-containing lithium transition metal oxides or lithium phosphates with an olivine structure.

[0036] In any embodiment of the second aspect of this application, the olivine-structured lithium phosphate has a carbon-containing coating layer; more preferably, the thickness of the carbon-containing coating layer is 3 nm to 15 nm. This further optimizes its conductivity and avoids the impact of excessive thickness on the specific capacity of the positive electrode active material. More preferably, the graphitization degree of the carbon-containing coating layer is 0.2 to 0.8, and optionally 0.3 to 0.5. This is more conducive to the uniform dispersion of the slurry including the lithium phosphate.

[0037] In any embodiment of the second aspect of this application, the Dv10 particle size of the positive electrode active material is 0.35 μm or larger, the Dv50 particle size is 0.76 μm to 1.76 μm, the Dv90 particle size is 5 μm or smaller, and the Dv99 particle size is 10 μm or smaller. The relatively small particle size of the above-mentioned positive electrode active material results in a higher powder compaction density, which is beneficial for improving the energy density of the positive electrode sheet and thus increasing the volumetric energy density of the battery cell.

[0038] In any embodiment of the second aspect of this application, the weight ratio of the positive electrode active material to the dispersant is 96:1 to 96.9:0.1. Within the above weight ratio range, the dispersant can be fully utilized to improve the dispersion uniformity of the positive electrode active material in the positive electrode active layer, and the positive electrode active material can provide sufficient energy density.

[0039] The third aspect of this application provides a method for manufacturing a battery cell, including a process for preparing a positive electrode sheet. The preparation process includes the following steps: mixing materials including a positive electrode active material, a dispersant, and a solvent to form a positive electrode slurry, wherein the dispersant includes a polymer provided in any embodiment of the first aspect of this application; and using the positive electrode slurry to form a positive electrode active layer on the surface of a positive electrode current collector.

[0040] In any embodiment of the third aspect of this application, the positive electrode active material includes one or more of a nickel-containing lithium transition metal oxide or a lithium phosphate with an olivine structure; optionally, the lithium phosphate with an olivine structure has a carbon-containing coating layer; more preferably, the thickness of the carbon-containing coating layer is 3 nm to 15 nm; further optionally, the graphitization degree of the carbon-containing coating layer is 0.2 to 0.8, and optionally 0.3 to 0.5.

[0041] In any embodiment of the third aspect of this application, the positive electrode active material has a Dv10 particle size of 0.35 μm or more, a Dv50 particle size of 0.2 μm to 1.5 μm, a Dv90 particle size of 0.5 μm or less, and a Dv99 particle size of 10 μm or less.

[0042] In any embodiment of the third aspect of this application, the mass ratio of the positive electrode active material to the dispersant is 96:1 to 96.9:0.1.

[0043] In any embodiment of the third aspect of this application, the solid content of the positive electrode slurry is 65% to 72%.

[0044] In any embodiment of the third aspect, the density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

[0045] The fourth aspect of this application provides an electrical device, including a battery cell or a battery device, wherein the battery cell includes the battery cell provided in any embodiment of the second aspect of this application, and the battery device includes the battery device provided in any embodiment of the third aspect of this application. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0047] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0048] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0049] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0050] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0051] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0052] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0053] The accompanying drawings are not drawn to scale.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0056] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0057] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the polymer, battery cell, manufacturing method thereof, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0058] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0060] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0061] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0062] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0063] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0064] [polymer]

[0065] As described in the background art, when the solid content of the positive electrode slurry increases, the dispersion uniformity of the slurry deteriorates. Furthermore, when the coating surface density or compaction density of the positive electrode sheet increases, the positive electrode sheet becomes less flexible and breaks at corners due to stress. To solve the above problems, the first embodiment of this application provides a polymer comprising phenyl... Flexible segments and end groups, the end groups including one or more of substituted or unsubstituted amide groups, substituted or unsubstituted -NH2 groups, and optionally one or more of carbonate groups, sulfonate groups, phosphate groups, quaternary ammonium groups, and C6-C18 aryl groups; the flexible segments including one or more of -CH2-O-CH2-, -C(O)O-, and optionally -CH2-; the flexible segments are connected to... On the -O-, the end base is connected to the flexible chain segment.

[0066] The surface of the positive electrode active material has a graphitized carbon-containing coating layer. The surface properties of the positive electrode active material change from polar to non-polar. The N-type end groups are polar groups, which often contain lone pairs of electrons. They have strong intermolecular forces on C and van der Waals forces on the carbon layer of the positive electrode active material. They also form hydrogen bonds with the residues on the carbon layer surface, which is more conducive to the uniform dispersion of the positive electrode active material in the slurry.

[0067] Furthermore, the aforementioned flexible segments not only enhance the polymer's flexibility but also improve it when applied to electrode sheets. In particular, the -CH2-O-CH2- and -C(O)O- segments utilize the spins of CO and CC to reduce the ordered arrangement of binder molecules in the positive electrode slurry, enabling the active material particles to slide better during rolling and further improving the electrode sheet's flexibility. Improved electrode flexibility effectively suppresses breakage at corners, contributing to high energy density in battery cells. Simultaneously, improved dispersion of the positive electrode active material and enhanced electrode sheet flexibility lead to a more stable positive electrode structure, thus also improving the cycle performance of battery cells.

[0068] Furthermore, the phenyl group in the polymer can strengthen the π-π conjugation between the polymer and the conductive agent in the slurry, resulting in better adsorption between the polymer and the conductive agent, and also strengthening the steric hindrance of the molecular chain. This further improves the aggregation of the conductive agent and enhances its dispersion. Moreover, the effect of the phenyl group is not limited to the dispersion of the conductive agent. When the surface of the positive electrode active material has a carbon-containing coating layer, the phenyl group also has the aforementioned effect with the positive electrode active material, thus also improving the dispersion uniformity of the positive electrode active material in the slurry and enhancing the stability of the slurry. In addition, the phenyl group can be better embedded in the molecular chain of the binder, thereby further improving the flexibility of the electrode sheet.

[0069] Meanwhile, the polymer of this application has The polymer contains maleic acid residues, and this structure exhibits low swelling and high electrochemical stability. Flexible segments are grafted into the polymer as described above. The side chains are end-capped with the aforementioned end groups, which can be stably adsorbed on the surface of the electrode active material. At the same time, the steric hindrance provided by the molecular chains of the aforementioned flexible segments physically separates the electrode active material particles, preventing particle agglomeration in the slurry. This improves the uniformity of particle dispersion in the slurry and maintains the fluidity of the slurry, reducing the risk of slurry gelation. Therefore, it is beneficial to increase the solid content of the slurry to improve the electrode fabrication efficiency.

[0070] The term "a certain group" as described in this application includes or is selected from a variety of groups. The selected groups can be freely combined. For example, "the flexible segment includes one or more of -CH2-O-CH2-, -C(O)O-, and optionally -CH2-" can include multiple segments formed by -CH2-O-CH2-, multiple segments formed by -C(O)O-, or segments formed by one or more -CH2- and one or more -CH2- and one or more -CH2-O-CH2-, or segments formed by one or more -CH2- and one or more -C(O)O-.

[0071] In some embodiments, the polymer has the following structural units:

[0072]

[0073] Among them, R 1 and R 2 Each group independently comprises one or more of the following: carbonate group, sulfonate group, phosphate group, amide group, substituted or unsubstituted -NH2 group, quaternary ammonium group, and C6-C18 aryl group, and R 1 and R 2 At least one of them includes one or more of substituted or unsubstituted amide groups and substituted or unsubstituted -NH2; L 1 and L 2 Each independently includes one or more of -CH2-, -CH2-O-CH2-, and -C(O)O-, and L 1 and L 2 At least one of them includes one or more of -CH2-O-CH2- and -C(O)O-.

[0074] The above L 1 and L 2 As a flexible chain segment, R 1 and R 2 As an end base.

[0075] Polymers having the above-mentioned structural units, wherein The synergistic effect of flexible segments and end groups is better, and the two branches provided by maleic acid residues can better provide flexibility to the electrode in space. The end groups connected at the ends of the flexible segments can anchor the active material, thus making the dispersion uniformity of active material particles in the slurry better and the flexibility of the electrode sheet more fully improved.

[0076] In some implementations, R 1 and R 2 Each independently includes -C(O)OR 11 -SO3R 11 , One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R 17 R 18 R 19 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; R 12 R13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; X - To represent a halide anion, F can be selected. - Cl - ,Br - I - One or more of them.

[0077] When R 1 and / or R 2 When aromatic groups with symmetrical structures are selected, the π-π bond interaction between the aromatic groups and the conductive agent exhibits stronger intermolecular forces, allowing the polymer to be better adsorbed onto the surface of the conductive agent particles. These aromatic groups also form a relatively stable adsorption relationship with the surface of the positive electrode active material with a carbon-coated layer, thereby more effectively promoting the dispersion of the positive electrode active material in the slurry and improving the slurry's stability.

[0078] In some implementations, R 1 and R 2 Each independently includes -C(O)OR 11 -SO3R 11 , One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R 17 R 18 R 19 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups, R 12 R 13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; X - For F - Cl - ,Br - I - One or more of them.

[0079] In some implementations, R can optionally 1 and R 2 Each independently includes One or more of them, and R 1 and R 2 At least one of them includes R 16 R 17 R 18R 19 Each is independently selected from one or more alkyl groups selected from H and C4-C12, optionally; R 12 R 13 Each is independently selected from one or more alkyl groups selected from H and C1-C6; X - For F - Cl - ,Br - I - One or more of them.

[0080] In some implementations, R is further optionally 1 and R 2 Each independently includes -C(O)NH2 and [NH4]. + X - And R 1 and R 2 At least one of them includes -C(O)NH2; X - For F - Cl - ,Br - I - One or more of them.

[0081] To better enhance the flexibility provided by the flexible chain segment, in some implementations, L 1 and L 2 Each independently includes C1-C18 alkylene groups and C1-C18 alkylene-NH-R groups. 21 -、-C(O)O- any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C10 alkylene groups, where a and b are each independently selected from any integer from 2 to 10 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10); 2 ≤ c + d ≤ 10, c > 0 and d > 0 (e.g., c is 1, 2, 3, 4, 5, 6, 7, 8, or 9, and d is 1, 2, 3, 4, 5, 6, 7, 8, or 9). In some embodiments, L 1 and L 2 Each independently includes C2-C12 alkylene groups and C4-C12 alkylene groups -NH-R. 21 -、-C(O)O-、 any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21Including C0-C5 alkylene groups, where a and b are each independently selected from any integer from 2 to 10; 2 ≤ c + d ≤ 10, c > 0 and d > 0. In some embodiments, L 1 and L 2 Each independently includes C4-C12 alkylene groups, C2-C10 alkylene groups -O(O)C-, and C4-C12 alkylene groups -NH-R. 21 -、 Any one of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C2 alkylene groups, where a is selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

[0082] The polyether segments in the above structure have more suitable steric hindrance and a lower glass transition temperature, which can more effectively reduce the ordered arrangement of binder molecules in the electrode slurry. This helps the active material particles to slide better during rolling, thus improving the flexibility of the electrode sheet. Through these excellent dispersion and flexibility-enhancing effects, the uniformity of particle dispersion in the slurry and the flexibility of the electrode sheet are improved, thereby enhancing the safety performance and ultimate compaction density of the battery cell. This allows for an increase in the active material loading of the battery cell, contributing to a further improvement in the energy density of the battery cell.

[0083] In some embodiments, the polymer has the following structural segments:

[0084]

[0085] Where x is selected from any integer from 5 to 60; y is selected from any integer from 5 to 60. The above-mentioned branched structure is formed on the maleic anhydride ring-opening structure, i.e., maleic acid residue, of the styrene-maleic anhydride copolymer. The high chemical stability and low swelling properties of maleic acid residues allow the steric hindrance effect of the above-mentioned branched structure to be fully utilized.

[0086] In some embodiments, the polymer has any one or more of the following structural segments:

[0087]

[0088] Where n is selected independently from any integer from 4 to 12, m is selected independently from any integer from 2 to 10, c is selected independently from any integer from 1 to 8, d is selected independently from any integer from 1 to 8, 2≤c+d≤10, x is selected from any integer from 5 to 60, and y is selected from any integer from 5 to 60.

[0089] In some embodiments, the polymer has any one or more of the following structural segments:

[0090]

[0091] In some embodiments, the weight-average molecular weight of the polymer is 10,000 to 500,000, optionally 15,000 to 25,000, 14,000 to 22,000, or 15,000 to 22,000. Polymers with the above-mentioned weight-average molecular weight disperse more smoothly in binders, thus making it easier to achieve the desired dispersion effect on solid particles in the slurry.

[0092] In some embodiments, the elongation at break of the polymer-containing film is 190%-250% (optionally 190%-230%). The film comprises a polymer and polyvinylidene fluoride in a mass ratio of 1:9, wherein the polyvinylidene fluoride is Arkema HSV900 polyvinylidene fluoride from France, and the film thickness is 3 mm. The polymer of this application improves the toughness of the film, thereby improving the elongation at break of the film.

[0093] The above-mentioned adhesive film can be prepared by referring to the following method:

[0094] The polymers were mixed with PVDF (Arkema HSV900) at a mass ratio of 1:9. After stirring in NMP solvent, the mixture was dissolved into a 7% solid content adhesive solution. The solution was then ultrasonically removed to remove air bubbles generated during the stirring process. The solution was poured into a molding mold and dried at 100°C to form an adhesive film with a thickness of 3 mm.

[0095] Film breaking elongation test: The film sample prepared above is made into a 5*15mm strip, fixed at both ends of the clamp, and stretched longitudinally using a SHK-A102 double column tensile testing machine with a double lever arm. The length at break is recorded. Breaking elongation = length at break / original length of film * 100%.

[0096] The following schematically illustrates the preparation method of the above polymer.

[0097] The prepolymer shown in formula (II), the compound shown in formula (III), and the styrene-maleic anhydride copolymer shown in formula (IV) were grafted together to obtain the aforementioned polymer.

[0098] Formula (II) is HO-L 1 -R 1 Equation (III) is HO-L 2 -R 2 , where L 1 R 1 L 2 R 2 The definition is the same as above.

[0099] Equation (IV) is The definitions of x and y are the same as above.

[0100] The molar ratios of the prepolymer shown in formula (II), the compound shown in formula (III), and the styrene-maleic anhydride copolymer shown in formula (IV) can be selected according to the set grafting target.

[0101] The grafting reaction described above is carried out in a solvent, such as butanone.

[0102] To promote grafting, a polymerization inhibitor is added to the reaction system, such as p-hydroxyanisole (MEHQ). In some embodiments, the polymerization inhibitor is 0.1%-1% of the mass of the styrene-maleic anhydride copolymer.

[0103] To accelerate the grafting reaction rate, a catalyst is added to the reaction system, such as triethylamine (TEA). In some embodiments, the mass of the catalyst is 0.5%–3% of the mass of the styrene-maleic anhydride copolymer.

[0104] The prepolymer shown in formula (II) and the compound shown in formula (III) can be prepared by conventional methods, which will not be described in detail in this application.

[0105] [Battery cell]

[0106] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0107] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0108] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0109] The second embodiment of this application provides a battery cell, which includes a positive electrode sheet, a positive electrode active layer, a positive electrode active material, and a dispersant, wherein the dispersant includes any polymer provided in the first embodiment above.

[0110] Because the polymer of this application has the above-mentioned advantages, it can improve the dispersion uniformity of active materials in the positive electrode and the flexibility of the positive electrode, thereby improving the cycle performance of the battery cell.

[0111] Because the dispersant in this application improves the stability of the positive electrode active material in the slurry and the flexibility of the positive electrode sheet, it can increase the areal density and / or compaction density of the positive electrode active layer, thereby improving the energy density of the battery cell. In some embodiments, the areal density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

[0112] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of 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 iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (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) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0113] In some embodiments, the aforementioned positive electrode active material includes one or more of nickel-containing lithium transition metal oxides or lithium phosphates with an olivine structure.

[0114] In some embodiments, the lithium phosphate with an olivine structure has a carbon-containing coating to improve its conductivity.

[0115] In some embodiments, the thickness of the carbon coating layer is 3nm to 15nm, such as 3nm, 5nm, 7nm, 10nm, 12nm or 15nm, and can be selected as 5nm to 10nm, to further optimize its conductivity and avoid the impact of excessive thickness on the specific capacity of the positive electrode active material.

[0116] In some embodiments, the degree of graphitization of the carbon-containing coating layer is 0.2 to 0.8, such as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and optionally 0.3 to 0.5. Lithium phosphates with higher graphitization exhibit a shift in surface properties from polar to nonpolar. The end groups containing nitrogen (N) are polar groups, often containing lone pairs of electrons, resulting in stronger intermolecular forces on carbon. They exert van der Waals forces on the surface carbon layer of the lithium phosphate and form hydrogen bonds with the residues on the carbon layer surface, which is more conducive to the uniform dispersion of slurries containing lithium phosphates.

[0117] The degree of graphitization was characterized using a HORIBA Jobin Yvon high-resolution Raman spectrometer (LabRAM HR Evlution, France). After background subtraction, the spectra were fitted using the following Gaussian function. Raman spectroscopy test conditions: wavelength 532 nm, scanning range 200-4000 cm⁻¹. -1 Accumulate twice, measuring 10 points for each sample, and use the average value to fit the result:

[0118]

[0119] In the above formula, G represents the degree of graphitization, Ai, Vi, and wi represent the peak intensity, peak position, and peak width of the test sample, respectively, and V refers to the peak position of a completely non-graphitized sample.

[0120] Due to the dispersing effect of the polymer in this application, agglomeration of small-particle-size positive electrode active materials is avoided, enabling the positive electrode active materials to achieve good dispersion within a small particle size range. In some embodiments, the Dv10 particle size of the positive electrode active material is above 0.35 μm, the Dv50 particle size is 0.76 μm to 1.76 μm, the Dv90 particle size is below 5 μm, and the Dv99 particle size is below 10 μm. The aforementioned positive electrode active materials have relatively small particle sizes, thus exhibiting high powder compaction density, which is beneficial for improving the energy density of the positive electrode sheet, and consequently, improving the volumetric energy density of the battery cell.

[0121] Dv10, Dv50, and Dv90 all represent volume average particle size. Taking Dv50 as an example, it indicates that the particle size of 50% of the volume of particles in the powder particle size distribution does not exceed the current value; that is, the median particle size. The particle size of the sample can be analyzed using a laser diffraction particle size analyzer. For specific methods, refer to GB / T19077-2016.

[0122] The use of dispersants can lead to a decrease in the proportion of positive electrode active material. To minimize the loss of battery energy density caused by the use of dispersants, in some embodiments, the weight ratio of positive electrode active material to dispersant is 96:1 to 96.9:0.1, such as 96:1, 96.3:0.7, 96.3:0.5, 96.7:0.3, or 96.9:0.1, with a possible ratio of 96.3:0.7 to 96.7:0.3. Within the above weight ratio range, the dispersant can be fully utilized to improve the dispersion uniformity of the positive electrode active material in the positive electrode active layer, while the positive electrode active material can provide sufficient energy density.

[0123] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0124] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0125] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] [Negative electrode plate]

[0127] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0128] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0129] As an example, the negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0130] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0131] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0132] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0133] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0134] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0135] In some embodiments, the negative electrode active layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0136] In some embodiments, the negative electrode active layer may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0137] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0138] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0139] [Electrolytes]

[0140] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0141] Liquid electrolytes include electrolyte salts and solvents.

[0142] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0143] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0144] 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 additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0145] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0146] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0147] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0148] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0149] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0150] [Isolation Component]

[0151] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0152] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0153] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. 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. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0154] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and isolate the positive and negative electrodes. In some embodiments, the positive electrode, negative electrode, and separator are fabricated into an electrode assembly using a winding or stacking process.

[0155] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0156] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0157] In some implementations, the electrode assembly is a stacked structure.

[0158] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0159] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0160] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0161] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0162] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0163] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0164] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0165] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0166] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0167] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0168] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0169] Figure 1 shows a square-structured battery cell 5 as an example.

[0170] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be closed by covering the opening. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0171] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0172] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0173] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0174] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0175] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0176] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0177] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0178] [Manufacturing method of a single battery cell]

[0179] The third embodiment of this application also provides a method for manufacturing a battery cell, including a process for preparing a positive electrode sheet, the preparation process including the following steps:

[0180] Materials including a positive electrode active material, a dispersant, and a solvent are mixed to form a positive electrode slurry, wherein the dispersant includes any polymer provided in the first embodiment described above;

[0181] A positive electrode active layer is formed on the surface of the positive electrode current collector using a positive electrode slurry.

[0182] Since the polymer of this application can alleviate the agglomeration of the positive electrode active material when used as a dispersant, it can make the positive electrode active material more uniformly dispersed in the solvent. Therefore, the dispersion of the positive electrode active material in the formed positive electrode active layer is also more uniform, thereby improving the performance of the battery cell.

[0183] The positive electrode active material described above is the same as the positive electrode active material in the second embodiment described above, and will not be described again here.

[0184] The use of dispersants can lead to a decrease in the proportion of positive electrode active material. In order to minimize the loss of battery energy density caused by the use of dispersants, in some embodiments, the weight ratio of positive electrode active material to dispersant is 96:1 to 97:0.1. Within the above weight ratio range, the dispersant can be fully utilized to improve the dispersion uniformity of the positive electrode active material in the positive electrode slurry, and the positive electrode active material can be used to provide sufficient energy density.

[0185] Due to the dispersant, the prepared slurry does not separate into layers, exhibits no significant viscosity rebound upon standing, shows no sedimentation during slow stirring, and does not gel. Therefore, the solid content of the cathode slurry can be increased; in some embodiments, the solid content of the cathode slurry is 65%–72%. This increases the solid content of the cathode slurry by approximately 6% compared to the solid content without the dispersant, while maintaining the slurry's stability. Therefore, it not only facilitates uniform coating of the cathode slurry but also helps to shorten the drying time after coating.

[0186] Solid content test:

[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] Because the dispersant in this application improves the stability of the positive electrode active material in the slurry and the flexibility of the positive electrode sheet, it can increase the areal density and / or compaction density of the positive electrode active layer, thereby improving the energy density of the battery cell. In some embodiments, the areal density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

[0190] [Battery Device]

[0191] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0192] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0193] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0194] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary battery cells 5 can be fixed in place using fasteners.

[0195] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0196] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0197] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0198] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0199] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0200] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0201] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0202] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0203] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0204] [Electrical appliances]

[0205] In addition, this application also provides an electrical device, which includes a battery cell or battery device provided in this application. The battery cell or battery device can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0206] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0207] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0208] [Example]

[0209] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0210] Polymer preparation examples

[0211] Preparation Example 1

[0212] Step 1)

[0213] Hydroxyacetamide (0.4% of the total mass of ethylene oxide and propylene oxide monomers) and concentrated sulfuric acid (0.3% of the total mass of ethylene oxide and propylene oxide monomers) were weighed and added into the reactor. The reactor lid was closed and the fixing bolts were tightened with a wrench. The reactor was evacuated and purged three times with high-purity nitrogen. Ethylene oxide and propylene oxide were added sequentially in a molar ratio of n:m to carry out a block polymerization reaction. The reaction pressure was maintained at 0.3±0.05 MPa and the temperature at 115±5℃. After reacting for 5 hours at 115±5℃, intermediate product 1 was generated. The reaction route is as follows:

[0214]

[0215] Step 2)

[0216] Hydroxyacetamide was subjected to a condensation reaction by bubbling ammonia (NH3) into it and heating for 6 hours. Then, HO(CH2)4Cl was added, and a substitution reaction was carried out at room temperature under alkaline conditions for 6 hours. This process was repeated once, and intermediate 2 was prepared according to the following reaction route:

[0217] R 3 It is -(CH2)4-, and n is 2.

[0218] Step 3)

[0219] Styrene-maleic anhydride copolymer (SMA) with a maleic anhydride to phenyl molar ratio of 1:1 was selected as the parent material for grafting. The reaction solvent was butanone (MEK), and the molar ratios n(SMA):n(intermediate product 1):n(intermediate product 2) were 1:1:1. The polymerization inhibitor, p-hydroxyanisole (MEHQ), was used at 0.2% of the mass of SMA. The reaction temperature was 80℃, the modification time was 6 h, and the catalyst, triethylamine (TEA), was used at 1% of the mass of SMA, yielding polymer 1. The repeating segment structure of polymer 1 is as follows:

[0220]

[0221] Preparation Example 2

[0222] Step 1) is the same as step 1 in preparation example 1.

[0223] Step 2) Add POCl3 to a four-necked flask equipped with a thermometer, stirrer and hydrogen chloride gas collection device. Add HO(CH2)4OH dropwise while stirring. Keep the reaction temperature below 20℃. After stirring for 20 min, raise the temperature to 40-50℃. The ratio of n(POCl3):n(HO(CH2)4OH) is about 1.4. After reacting for about 6 h, add a certain amount of distilled water dropwise to the system and react at 60℃ for 5 h.

[0224] Step 3) Select styrene-maleic anhydride copolymer SMA (where the molar ratio of maleic anhydride to phenyl is 1:1) as the parent material for grafting. The reaction solvent is methyl ethyl ketone (MEHQ). The molar ratio of SMA to intermediate product from step 1 is 1:1:1. The polymerization inhibitor MEHQ is used at a mass of 0.2% relative to SMA. The reaction temperature is 80℃, the modification time is 6h, and the catalyst is triethylamine (TEA) at a mass of 1% relative to SMA.

[0225] The repeating segment structure of polymer 2 is as follows:

[0226] Preparation Example 3

[0227] Step 1) is the same as step 1 in preparation example 1.

[0228] Step 2) Select styrene-maleic anhydride copolymer SMA (where the molar ratio of maleic anhydride to phenyl is 1:1) as the parent material for grafting. The reaction solvent is methyl ethyl ketone (MEHQ), the molar ratio of SMA to intermediate product in step 1 is 1:2, the polymerization inhibitor MEHQ is 0.2% of the mass of SMA, the reaction temperature is 80℃, the modification time is 6h, and the catalyst is 1% of the mass of SMA.

[0229] The repeating segment structure of polymer 3 is as follows:

[0230] Preparation Example 4

[0231] Step 1) is the same as step 1 in preparation example 1.

[0232] Step 2) Acylchloroacetamide + ethylene glycol are added and a substitution reaction is carried out at room temperature and under alkaline conditions for 6 hours to prepare intermediate product 2 according to the following reaction route.

[0233] Step 3) Select styrene-maleic anhydride copolymer SMA (where the molar ratio of maleic anhydride to phenyl is 1:1) as the parent material for grafting. The reaction solvent is methyl ethyl ketone (MEHQ). The molar ratio of SMA to intermediate product from step 1 is 1:1:1. The polymerization inhibitor MEHQ is used at a mass of 0.2% relative to SMA. The reaction temperature is 80℃, the modification time is 6h, and the catalyst is triethylamine (TEA) at a mass of 1% relative to SMA.

[0234] The repeating segment structure of polymer 4 is as follows:

[0235] Preparation Example 5

[0236] Step 1) Add POCl3 and HO(CH2) to a four-necked flask equipped with a thermometer, stirrer, and hydrogen chloride gas collection device. 18 After adding OH, stir thoroughly, keeping the reaction temperature below 20℃. After stirring for 20 minutes, raise the temperature to 40-50℃, where n(POCl3):n(HO(CH2)). 18 The OH group is 1.2-1.5. After reacting for 6-7 hours, a certain amount of distilled water is added dropwise to the system, and the reaction is carried out at 60℃ for 5 hours.

[0237] Step 2) Select styrene-maleic anhydride copolymer SMA (where the molar ratio of maleic anhydride to phenyl is 1:1) as the parent material for grafting. The reaction solvent is butanone, and the molar ratios n(SMA):n(intermediate product from step 1):n(n-octadecyl alcohol) = 1:1:1. The polymerization inhibitor p-hydroxyanisole (MEHQ) is used at a mass of 0.2% relative to SMA. The reaction temperature is 80℃, the modification time is 6h, and the catalyst triethylamine (TEA) is used at a mass of 1% relative to SMA.

[0238] The repeating segment structure of polymer 5 is as follows:

[0239] Preparation Example 6

[0240] Step 1) Same as step 1) in Preparation Example 5

[0241] Step 2) Select styrene-maleic anhydride copolymer SMA (where the molar ratio of maleic anhydride to phenyl is 1:1) as the parent material for grafting. The reaction solvent is methyl ethyl ketone (MEHQ), the molar ratio of SMA to intermediate product from step 1 is 2:1, the polymerization inhibitor MEHQ is 0.2% of the mass of SMA, the reaction temperature is 70℃, the modification time is 6h, and the catalyst is 1% of the mass of SMA.

[0242] The repeating segment structure of polymer 6 is as follows:

[0243] The polymers described above were characterized.

[0244] Infrared characterization:

[0245] Measurements were performed using a Bruker Tensor 37 infrared spectrometer. The sample solution was either dropped onto a potassium bromide tablet or mixed with the powder after grinding and then compressed 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.

[0246] The main peak positions of the infrared spectra of Preparation Examples 1 to 6 are as follows:

[0247] The IR values ​​of polymer 1 (neat) are: 2948, 2865, 1733(s), 1670(s), 1470, 1393, 1275, 1223, 1107(s), 889. 1733(s) is the characteristic peak of the amide bond, 1670(s) is the characteristic peak of the ester group, and 1107(s) is the characteristic peak of the ether bond.

[0248] The IR values ​​of polymer 2 (neat) are: 2950, ​​2863, 1735(s), 1671(s), 1473, 1398, 1268, 1275, 1111(s), 873. 1735(s) is the characteristic peak of the amide bond, 1671(s) is the characteristic peak of the ester group, and 1111(s) is the characteristic peak of the ether bond.

[0249] The IR values ​​of polymer 3 (neat) are: 2945, 2867, 1736(s), 1674(s), 1475, 1392, 1268, 1268, 1103(s), 880. 1736(s) is the characteristic peak of the amide bond, 1674(s) is the characteristic peak of the ester group, and 1103(s) is the characteristic peak of the ether bond.

[0250] The IR values ​​of polymer 4 (neat) are: 2943, 2870, 1739(s), 1681(s), 1477, 1386, 1268, 1262, 1102(s), 882. 1739(s) is the characteristic peak of the amide bond, 1681(s) is the characteristic peak of the ester group, and 1102(s) is the characteristic peak of the ether bond.

[0251] The IR values ​​of polymer 5 (neat) are: 2943, 2867, 1685(s), 1501(s), 1465, 1358(s), 1268, 1135(s), 950, 885. 1685(s) is the characteristic peak of the ester group, and 1358(s) and 1135(s) are the characteristic peaks of the phosphate ester.

[0252] The IR values ​​of polymer 6 (neat) are: 2946, 2870, 1677(s), 1506(s), 1468, 1354(s), 1268, 1117(s), 955, 878. 1677(s) is the characteristic peak of the ester group, and 1354(s) and 1117(s) are the characteristic peaks of the phosphate ester.

[0253] Weight-average molecular weight test:

[0254] A Waters 2695 Isocratic HPLC gel electrophoresis system (differential refractive index detector 2141) was used. A 3.0% (w / w) polystyrene solution was used as a reference, and a matched column (oil-based: Styragel HT5 DMF7.8*300mm + Styragel HT4) was selected. 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. After the reading stabilized, data were acquired, collected, and calculated using the following formula.

[0255]

[0256] M w m is the weight-average molecular weight. i It is the molecular mass, M i It is the relative molecular mass, n i It has M i The number of molecules of mass, w i It is the quality score.

[0257] The test results are recorded in Table 1.

[0258] Performance testing:

[0259] Each of the above polymers was mixed with PVDF (Arkema HSV900) at a mass ratio of 1:9. After stirring in NMP solvent, the mixture was dissolved into a 7% solid content adhesive solution. After sonication, the air bubbles generated during the stirring process were removed. The solution was poured into a molding mold and dried at 100°C to form an adhesive film with a thickness of 3 mm.

[0260] Film melting enthalpy test: Thermogravimetric analysis of the film was performed using a DTG-60AH thermogravimetric analyzer.

[0261] 1. Sample preparation: Weigh approximately 50 mg of the above-prepared film into an Al2O3 crucible and level it.

[0262] 2. Parameter settings: Nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min

[0263] 3. Temperature rise program: 10℃ / min, 20℃~800℃, obtain DSC curve, and record the area enclosed by the TG peak as the melting enthalpy of the film in Table 1.

[0264] Film breaking elongation test: The film sample prepared above was cut into 5*15mm strips and fixed at both ends of the clamp. The SHK-A102 double column tensile testing machine was used to stretch the film longitudinally with a double lever arm. The length at which it broke was recorded. Breaking elongation = length at break / original length of film * 100%. The results are recorded in Table 1.

[0265] Table 1

[0266] As can be seen from the data in Table 1, regardless of the molecular weight, the melting enthalpy of the films containing polymers 1 to 4 is significantly lower than that of the films containing polymers 4 and 5, and the elongation at break of the films containing polymers 1 to 4 is significantly higher than that of the films containing polymers 4 and 5, indicating that polymers 1 to 4 have better flexibility than polymers 5 and 6.

[0267] Example 1: Preparation of battery cells

[0268] (1) Preparation of positive electrode sheet

[0269] The positive electrode active material, binder polyvinylidene fluoride (PVDF), conductive agent acetylene black, and dispersant (polymer 1) were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 96.5:1:2:0.5 and thoroughly mixed to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode current collector, followed by drying, cold pressing to form a positive electrode active layer, and slitting to obtain the positive electrode sheet. The areal density of the positive electrode active layer was 400 mg / 1540.25 mm². 2 Compacted density 2.65 g / cm³ 3 .

[0270] (2) Preparation of negative electrode sheet

[0271] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a mass ratio of 95:2:2:1 and then uniformly mixed with the deionized water to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated onto the negative electrode current collector copper foil, dried, and then the negative electrode film was obtained. After cold pressing and slitting, the negative electrode sheet was obtained.

[0272] (3) Preparation of electrolyte

[0273] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed uniformly at a volume ratio of 3 / 7 to form an organic solvent. LiPF6 is dissolved in the organic solvent to prepare a solution with a mass content of 12.5%. The mixture is stirred evenly to obtain the corresponding electrolyte.

[0274] (4) Preparation of the isolation membrane: conventional polypropylene membrane is used as the isolation membrane.

[0275] (5) Preparation of lithium-ion batteries

[0276] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain an electrode assembly. The electrode assembly is placed in the battery casing, dried, and then injected with electrolyte. After formation and settling processes, a lithium-ion battery cell is obtained.

[0277] The positive electrode active material, positive electrode slurry, and battery cell of Example 1 were tested as follows.

[0278] Parameter testing methods

[0279] Test of the thickness of the carbon coating layer of the positive electrode active material:

[0280] The thickness of the carbon layer on the surface of a single particle sample was measured using a high-resolution transmission electron microscope (Tecnai G2 F30 S-Twin). Ten thickness values ​​were taken and averaged to obtain the thickness of the carbon-containing coating layer.

[0281] Graphitization degree test of the carbon-containing coating layer of the positive electrode active material:

[0282] The degree of graphitization was characterized using a HORIBA Jobin Yvon high-resolution Raman spectrometer (LabRAM HR Evlution, France). After background subtraction, the following Gaussian function was used for fitting the spectra. Raman spectroscopy testing conditions: wavelength 532 nm, scanning range 200-4000 cm⁻¹, two measurements taken cumulatively, 10 points per sample, and average values ​​used for fitting. In the above formula, G represents the degree of graphitization, Ai, Vi, and wi represent the peak intensity, peak position, and peak width, respectively, and V refers to the peak position of a completely non-graphitized peak.

[0283] Volumetric particle size distribution test of positive electrode active material:

[0284] For the analysis of sample particle size using a laser diffraction particle size analyzer, please refer to GB / T19077-2016 for specific methods.

[0285] Solid content test of cathode slurry:

[0286] Weigh the copper foil in the weight loss rate measuring instrument and record it as M0, then zero the instrument. Take a small amount of positive electrode slurry, coat it onto the copper foil, and then weigh it in the moisture analyzer and record it as M1. Close the instrument 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).

[0287] Positive electrode slurry viscosity test:

[0288] The rotational viscometer used was a DV-2TLV Bollerfei viscometer. When using it, select the appropriate rotor based on the slurry viscosity and adjust the parameter to 12 r / min. After starting the measurement, observe the screen reading. When the number stops fluctuating significantly and the measurement progress on the right side rises from the bottom to the top, record the data. After standing for 24 hours, retest and record the viscosity after 24 hours.

[0289] Test methods for battery (cell or electrode) performance

[0290] Positive electrode sheet brittleness test:

[0291] 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.

[0292] 60℃ Cyclic Capacity Retention

[0293] At 60°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 = C n / C0×100% During this test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 100th cycle corresponds to n=100. The battery capacity retention rate data corresponding to Example 1 in Table 1 are the data measured after 400 cycles under the above test conditions.

[0294] The positive electrode active material used in Example 1 is carbon-coated lithium iron phosphate (denoted as LiFePO4@C), and the test results of relevant parameters are recorded in Table 2.

[0295] Table 2

[0296] In Examples 2 to 4, polymer 2 to 4 were used to replace polymer 1 in Example 1, and all other aspects were the same as in Example 1.

[0297] Comparative Example 1

[0298] Polymer 5 was used to replace polymer 1 in Example 1, and all other aspects were the same as in Example 1.

[0299] Comparative Example 2

[0300] Polymer 6 was used to replace polymer 1 in Example 1, and all other aspects were the same as in Example 1.

[0301] Comparative Example 3

[0302] Polymer 1 was not added, the proportion of positive electrode active material added was 97%, and the rest was the same as in Example 1.

[0303] The results of parameter testing and battery performance testing are recorded in Table 3.

[0304] Table 3

[0305] The data comparison in Table 3 shows that Examples 1 to 4, with a higher solid content, have lower viscosity than Comparative Examples 1 to 3. Even after 24 hours of storage, the viscosity increase is less than that of Comparative Examples 2 to 3, indicating that the added polymers 1 to 4 are more conducive to maintaining the stability of the slurry. Moreover, the brittleness of the positive electrode sheets of Examples 1 to 4 is significantly better than that of the positive electrode sheets of Comparative Examples 1 to 3, indicating that polymers 1 to 4 are more conducive to improving the flexibility of the positive electrode sheet than polymers 5 and 6, and thus are also more conducive to improving the cycle performance of the battery cells.

[0306] The following investigation examines the effects of dispersant dosage on the viscosity of the cathode slurry, the brittleness of the cathode sheet, and the cycle performance of the battery cell.

[0307] Examples 5 to 8 are based on Example 1, with adjustments made to the amount of dispersant and the amount of positive electrode active material. The details are recorded in Table 4, and the test results are also recorded in Table 4.

[0308] Comparative Example 4 adjusts the amount of dispersant and positive electrode active material based on Comparative Example 1. The specific details are recorded in Table 4, and the test results are also recorded in Table 4.

[0309] Comparative Example 5 was based on Comparative Example 2, with adjustments made to the amount of dispersant and the amount of positive electrode active material. The details are recorded in Table 4, and the test results are also recorded in Table 4.

[0310] Table 4

[0311] The data comparison in Table 4 shows that as the amount of dispersant increases to 0.5%, the viscosity of the positive electrode slurry decreases, and this decreasing trend continues after 24 hours of standing. Further increases in dispersant content lead to a gradual increase in the viscosity of the positive electrode slurry, which also increases after 24 hours of standing, but remains lower than when no dispersant is added. The increased dispersant content reduces the brittleness of the positive electrode sheet, indicating that the addition of dispersant improves the flexibility of the positive electrode sheet.

[0312] The following investigation examines the effect of dispersants on the dispersibility of cathode active materials with different degrees of graphitization.

[0313] Carbon coating layers of varying thicknesses were formed on the surface of the lithium iron phosphate cathode active material used in Example 1. The graphitization degree of the carbon coating layers was adjusted by changing the sintering temperature, resulting in carbon-coated lithium iron phosphate cathode active materials for Examples 9 to 13. The thickness of the carbon coating layers was taken as an integer, and the graphitization degree was taken as one decimal place, all of which are recorded in Table 5. The composition of the remaining battery cells was the same as in Example 1. The viscosity test results of the formed cathode slurry are recorded in Table 5.

[0314] Table 5

[0315] The data comparison in Table 5 shows that as the degree of graphitization increases and the thickness of the carbon coating layer decreases, the viscosity increase of the cathode slurry after standing for 24 hours first decreases and then increases. This is because although the dispersant's effect is enhanced by increasing the degree of graphitization on the same carbon content, it is more difficult to achieve a high degree of graphitization as the carbon coating layer thickness in the cathode active material increases. Limited by the thickness of the carbon coating layer, the dispersant's effect on the cathode active material is also affected. That is, after the carbon coating layer thickness reaches below 7 nm, the amount of graphitized carbon that can interact with the dispersant decreases as the thickness decreases, resulting in a weakening of the improvement in slurry dispersibility and thus an increase in slurry viscosity.

[0316] The following investigation examines the effect of dispersants on the dispersion of positive electrode active materials with different particle size distributions.

[0317] The material composition of the positive electrode active material in Example 14 is the same as that in Example 1. The particle size distribution is recorded in Table 6, and the viscosity test results of the positive electrode slurry are recorded in Table 6.

[0318] Table 6

[0319] Small-particle positive electrode active materials have a large specific surface area and high surface energy. The increased proportion of Dv50 and Dv10 particles leads to a greater number of small particles, which tend to aggregate within the slurry, causing gelation. The dispersant added in this application anchors to the particle surface and physically separates the particles using the steric hindrance of its side chains, preventing particle aggregation and effectively controlling the viscosity of the positive electrode slurry, thereby improving the slurry's stability.

[0320] A comparison of particle size in Examples 1 and 14 reveals that as particle size decreases, the viscosity of the cathode slurry increases with the same dispersant addition ratio. However, even compared to Comparative Example 3, the viscosity remains relatively low after standing for 24 hours, indicating that the dispersant in this application plays a role in reducing viscosity and improving stability.

[0321] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A polymer, said polymer comprising phenyl, The flexible segment and end group, the end group comprising one or more of substituted or unsubstituted amide groups, substituted or unsubstituted -NH2 groups, and optionally one or more of carbonate groups, sulfonate groups, phosphate groups, quaternary ammonium groups, and C6-C18 aryl groups, the flexible segment comprising one or more of -CH2-O-CH2-, -C(O)O-, and optionally -CH2-, the flexible segment being connected to the... On the -O-, the end base is connected to the flexible chain segment.

2. The polymer according to claim 1, wherein, The polymer comprises the following structural units: Among them, R 1 and R 2 Each group independently comprises one or more of the following: carbonate group, sulfonate group, phosphate group, substituted or unsubstituted amide group, substituted or unsubstituted -NH2 group, quaternary ammonium group, and C6-C18 aryl group, and R 1 and R 2 At least one of them includes one or more of substituted or unsubstituted amide groups and substituted or unsubstituted -NH2; L 1 and L 2 Each independently includes one or more of -CH2-, -CH2-O-CH2-, and -C(O)O-, and L 1 and L 2 At least one of them includes one or more of -CH2-O-CH2- and -C(O)O-.

3. The polymer according to claim 2, wherein, R 1 and R 2 Each independently includes -C(O)OR 11 -SO3R 11 , One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R 17 R 18 R 19 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; R 12 R 13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups; X - To represent a halide anion, F can be selected. - Cl - ,Br - I - One or more of them.

4. The polymer according to claim 3, wherein, R 1 and R 2 Each independently includes -C(O)OR 11 、-SO3R 11 、 One or more of them, and R 1 and R 2 At least one of them includes R 11 R 14 R 15 R 16 R 17 R 18 R 19 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups, R 12 R 13 Each is independently selected from one or more of H, substituted or unsubstituted C1-C18 alkyl groups.

5. The polymer according to claim 3, wherein, R 1 and R 2 Each independently includes One or more of them, and R 1 and R 2 At least one of them includes R 16 R 17 R 18 R 19 Each is independently selected from one or more alkyl groups selected from H and C4-C12, R 12 R 13 Each is independently selected from one or more alkyl groups selected from H and C1-C6.

6. The polymer according to claim 3, wherein, R 1 and R 2 Each independently includes -C(O)NH2 and [NH4]. + X - And R 1 and R 2 At least one of them includes -C(O)NH2; X - For F - Cl - ,Br - I - One or more of them.

7. The polymer according to any one of claims 2 to 6, wherein, L 1 and L 2 Each independently includes C1-C18 alkylene groups and C1-C18 alkylene-NH-R groups. 21 -、-C(O)O-、 Any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C10 alkylene groups, where a and b are each independently selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

8. The polymer according to any one of claims 2 to 6, wherein, L 1 and L 2 Each independently includes C2-C12 alkylene groups and C4-C12 alkylene groups -NH-R. 21 -、-C(O)O-、 Any one or more of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C5 alkylene groups, where a and b are each independently selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

9. The polymer according to any one of claims 2 to 6, wherein, L 1 and L 2 Each independently includes C4-C12 alkylene groups, C2-C10 alkylene groups -O(O)C-, and C4-C12 alkylene groups -NH-R. 21 -、 Any one of them, and L 1 and L 2 At least one of them includes Any one or more of them, R 21 Including C0-C2 alkylene groups, where a is selected from any integer from 2 to 10; 2≤c+d≤10, c>0 and d>0.

10. The polymer according to any one of claims 2 to 9, wherein, The polymer has the following structural segments: in, x is selected from any integer between 5 and 60; y is selected from any integer between 5 and 60.

11. The polymer according to claim 1, wherein, The polymer has the following structural segments: Where n is selected independently from any integer from 4 to 12, m is selected independently from any integer from 2 to 10, c is selected independently from any integer from 1 to 8, d is selected independently from any integer from 1 to 8, 2≤c+d≤10, x is selected from any integer from 5 to 60, and y is selected from any integer from 5 to 60.

12. The polymer according to any one of claims 1 to 11, wherein, The weight-average molecular weight of the polymer is 10,000 to 500,000.

13. The polymer according to any one of claims 1 to 12, wherein, The elongation at break of the film containing the polymer is 190%-250%, the film comprises the polymer and polyvinylidene fluoride in a mass ratio of 1:9, and the thickness of the film is 3 mm.

14. A battery cell, said battery cell comprising a positive electrode, wherein, The positive electrode sheet includes a positive active layer, the positive active layer includes a positive active material and a dispersant, and the dispersant includes the polymer according to any one of claims 1 to 13.

15. The battery cell according to claim 14, wherein, The density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

16. The battery cell according to claim 14 or 15, wherein, The positive electrode active material includes one or more of nickel-containing lithium transition metal oxides or lithium phosphates with an olivine structure.

17. The battery cell according to claim 16, wherein, The lithium phosphate with the olivine structure has a carbon-containing coating layer; the thickness of the carbon-containing coating layer is 3 nm to 15 nm; and / or, the degree of graphitization of the carbon-containing coating layer is 0.2 to 0.

8.

18. The battery cell according to any one of claims 14 to 17, wherein, The positive electrode active material has a Dv10 particle size of 0.35 μm or larger, a Dv50 particle size of 0.76 μm to 1.76 μm, a Dv90 particle size of 5 μm or smaller, and a Dv99 particle size of 10 μm or smaller.

19. The battery cell according to any one of claims 14 to 18, wherein, The weight ratio of the positive electrode active material to the dispersant is 96:1 to 96.9:0.

1.

20. A method for manufacturing a single battery cell, comprising a process for preparing a positive electrode sheet, wherein, The preparation process includes the following steps: Materials comprising a positive electrode active material, a dispersant, and a solvent are mixed to form a positive electrode slurry, wherein the dispersant comprises the polymer according to any one of claims 1 to 13; The positive electrode active layer is formed on the surface of the positive electrode current collector using the positive electrode slurry.

21. The manufacturing method according to claim 20, wherein, The positive electrode active material includes one or more of nickel-containing lithium transition metal oxides or lithium phosphates with an olivine structure.

22. The manufacturing method according to claim 21, wherein, The lithium phosphate with olivine structure has a carbon-containing coating layer; the thickness of the carbon-containing coating layer is 3 nm to 15 nm and / or the degree of graphitization of the carbon-containing coating layer is 0.2 to 0.

8.

23. The manufacturing method according to any one of claims 20 to 22, wherein, The positive electrode active material has a particle size of Dv10 above 0.35 μm, Dv50 has a particle size of 0.2 μm to 1.5 μm, Dv90 has a particle size of less than 0.5 μm, and Dv99 has a particle size of less than 10 μm.

24. The manufacturing method according to any one of claims 20 to 23, wherein, The mass ratio of the positive electrode active material to the dispersant is 96:1 to 96.9:0.

1.

25. The manufacturing method according to any one of claims 20 to 24, wherein, The solid content of the positive electrode slurry is 65% to 72%.

26. The manufacturing method according to any one of claims 20 to 25, wherein, The density of the positive electrode active layer is 300 mg / 1540.25 mm. 2 -450mg / 1540.25mm 2 And / or a compacted density of 2.55 g / cm³ 3 -2.7g / cm 3 .

27. An electrical device comprising a single battery cell, wherein, The battery cell comprises the battery according to any one of claims 14 to 19.

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