Composite binder, electrode sheet and preparation method therefor, battery, and electric device

Abstract

Provided are a composite binder, an electrode sheet and a preparation method therefor, a battery, and an electric device. The composite binder comprises polytetrafluoroethylene and polydopamine arranged on at least part of the surface of the polytetrafluoroethylene, wherein the composite binder comprises, in parts by mass: 50-99.99 parts of polytetrafluoroethylene, and 0.01-50 parts of polydopamine. When the composite binder is used for preparing an electrode sheet, the stability of the electrode sheet can be improved, and the electrode sheet can be prepared by means of a dry method, thereby reducing the preparation costs and facilitating the large-scale production.

Description

Composite binder, electrode sheet and preparation method thereof, battery and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite binder, an electrode sheet and a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] In recent years, with the continuous development of new energy industry and automobile industry, people's demand for electric vehicles, electric bicycles and other electric devices is increasing, and the performance requirements are also increasing

[0003] The electrode sheet of the traditional vehicle and battery often needs to use an adhesive to uniformly adhere the electrode active material, conductive agent and other components on the current collector, so as to maintain the stability of the electrode structure during the cycle charging and discharging process. However, the electrode active material such as carbon-based negative electrode active material and silicon-based negative electrode active material will inevitably expand in volume during the cycle charging and discharging process, especially the silicon negative electrode active material has a high degree of volume expansion, which is easy to damage the stability of the electrode structure, thereby causing the cycle performance of the battery to decrease. Moreover, when the traditional adhesive is used to prepare the electrode sheet, solvents such as N-methyl-2-pyrrolidone (NMP) and water are needed to disperse the electrode material so that the electrode material and the binder are uniformly mixed, and subsequent high-temperature drying is needed to remove the solvents to obtain the electrode sheet. The equipment of this electrode preparation process occupies a large area, and the required energy consumption is high. At the same time, N-methyl-2-pyrrolidone is a harmful gas and has a high cost, and a N-methyl-2-pyrrolidone recovery device needs to be set up, which increases the process cost.

[0004] Therefore, the traditional technology still needs to be improved.

[0005] SUMMARY

[0006] Therefore, the traditional technology still needs to be improved.

[0007] In one aspect of the present application, a composite binder is provided, which comprises polytetrafluoroethylene and polydopamine arranged on at least part of the surface of the polytetrafluoroethylene.

[0008] In one aspect of the present application, a composite binder is provided, which comprises polytetrafluoroethylene and polydopamine arranged on at least part of the surface of the polytetrafluoroethylene.

[0009] The polytetrafluoroethylene is coated with polydopamine on at least part of the surface, and the polydopamine contains polar groups such as amine groups and hydroxyl groups, so that more polar groups are loaded on the surface of the composite binder, and the binding capacity is improved. When the composite binder is used to prepare an electrode sheet, the stability of the electrode sheet can be improved, that is, even if the electrode sheet contains a silicon-based negative active material with a large expansion coefficient, the stability of the electrode sheet can also be maintained, so that the cycle performance of the battery is improved.

[0010] The composite binder can be used to prepare an electrode sheet by a dry method, that is, the electrode sheet can be prepared without adding a solvent, so that the preparation process can be simplified, the preparation cost is reduced, and large-scale production is facilitated.

[0011] In some embodiments, the mass fraction of the polytetrafluoroethylene in the total mass of the composite binder is 50% to 99.99%.

[0012] An embodiment of the present application further provides a preparation method of the composite binder, comprising the following steps:

[0013] Raw materials, i.e., polytetrafluoroethylene and a dopamine hydrochloride solution, are provided according to a stoichiometric ratio of the polytetrafluoroethylene and the dopamine hydrochloride solution.

[0014] The polytetrafluoroethylene and the dopamine hydrochloride solution are mixed, and a polymerization reaction is performed to prepare the composite binder.

[0015] In some embodiments, the step of mixing the polytetrafluoroethylene and the dopamine hydrochloride solution comprises the following steps:

[0016] A buffer solution is added to the dopamine hydrochloride solution to make the pH value of the mixed system be 7.5 to 12, and then the polytetrafluoroethylene is added.

[0017] In some embodiments, the temperature of the polymerization reaction is -18°C to 40°C, and the time is 1h to 48h; and / or

[0018] The concentration of the dopamine hydrochloride solution is 0.01g / L to 20g / L.

[0019] Another aspect of the present application provides an electrode sheet, which comprises a current collector and an active layer arranged on at least one surface of the current collector, and the active layer comprises the composite binder or the binder prepared by the preparation method of the composite binder.

[0020] In some embodiments, the active layer further comprises a negative active material and a conductive agent, and the negative active material comprises at least one of a carbon-based negative active material and a silicon-based negative active material.

[0021] In some embodiments, the mass percentage of the composite binder in the active layer is 0.1% to 20%; and / or

[0022] In the active layer, the mass percentage of the negative electrode active material is 60% to 99.8%; and / or

[0023] In the active layer, the mass percentage of the conductive agent is 0.1% to 20%.

[0024] In another aspect of the present application, a method for preparing the electrode sheet is provided, comprising the following steps:

[0025] Mixing the raw materials for preparing the binder to prepare an active mixture;

[0026] Coating the active mixture on at least one surface of the current collector to prepare the electrode sheet.

[0027] In another aspect of the present application, a battery is provided, which comprises the electrode sheet as described above or the electrode sheet prepared by the method as described above.

[0028] In another aspect of the present application, an electric device is provided, which comprises the battery as described above.

[0029] In some embodiments, the electric device comprises a vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are intended to depict only preferred embodiments of the application, and therefore should not be considered to limit the scope of the application in any way. Similarly, like reference numerals are intended to represent like elements throughout the various figures. In the drawings:

[0031] FIG. 1 is a comparison of FT-IR of the composite binder prepared in Example 1 and the raw material polytetrafluoroethylene used therein;

[0032] FIG. 2 is a comparison of UV curves of the composite binder prepared in Example 1 and the raw material polytetrafluoroethylene used therein;

[0033] FIG. 3 is a comparison of XRD of the composite binder prepared in Example 1 and the raw material polytetrafluoroethylene used therein;

[0034] FIG. 4 is a comparison of DSC of the composite binder prepared in Example 1 and the raw material polytetrafluoroethylene used therein;

[0035] FIG. 5 is a comparison of TGA of the composite binder prepared in Example 1 and the raw material polytetrafluoroethylene used therein;

[0036] Figure 6 is a photograph of the electrode sheet prepared in Example 1;

[0037] Figure 7 is an SEM image of the electrode sheet prepared in Example 1;

[0038] Figure 8 is an EDS image of the electrode sheet prepared in Example 1. DETAILED DESCRIPTION

[0039] For the purposes of the present application, a more complete description of the application will be presented. Preferred embodiments of the application are presented in the detailed description. However, the application can be realized in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] Terminology

[0042] Unless otherwise indicated, or unless the context clearly indicates otherwise, terms or phrases used in this document have the meanings presented throughout this section.

[0043] As used herein, the terms "and / or", "or / and", "and / or" are inclusive of any and all combinations of two or more of the associated listed items, and are inclusive of any and all combinations of the associated listed items, including any two of the associated listed items, any more of the associated listed items, or all of the associated listed items. It is noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are combined to connect at least three items, it is understood that in this application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B, and the combination of A and B. For another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (i.e., the technical solution connected by "logical or"), and includes any and all combinations of A, B, C, and D, i.e., includes the combination of any two or any three of A, B, C, and D, and includes the four-item combination of A, B, C, and D (i.e., the technical solution connected by "logical and").

[0044] In the present application, "a plurality of", "a plurality of kinds", "a plurality of times" and the like, if not otherwise specified, refer to more than two or equal to two in number. For example, "one or more" means one or more than two.

[0045] In the present application, the terms "first", "second", "third", "fourth" and the like in "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the technical features indicated. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0046] In the present application, among the technical features described in an open manner, both the closed technical solution consisting of the listed features and the open technical solution containing the listed features are included.

[0047] In the present application, with respect to a numerical interval (i.e. a numerical range), if not otherwise specified, the distribution of the selectable values within the numerical interval is considered to be continuous and includes both numerical end points (i.e. the minimum value and the maximum value) of the numerical interval and every value between the two numerical end points. If not otherwise specified, when a numerical interval refers only to integers within the numerical interval, including both end point integers of the numerical range and every integer between the two end points, it is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe a feature or a property, these numerical ranges can be combined. In other words, unless otherwise indicated, the numerical ranges disclosed herein are to be understood as including any and all sub-ranges subsumed therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" is allowed to broadly include numerical interval types such as percentage interval, ratio interval, value interval, etc.

[0048] In the present application, the temperature parameter, if not otherwise specified, allows for constant temperature treatment and also allows for variation within a certain temperature interval. It should be understood that the constant temperature treatment allows for fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0049] In the present application, "room temperature" or "ambient temperature" refers to 10°C to 35°C, further to 20°C to 30°C.

[0050] The mass or weight of the related components mentioned in the embodiment of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the mass or weight of each component. Therefore, as long as the content of the related components in the embodiment of the present application is proportionally enlarged or reduced, it is within the scope disclosed in the embodiment of the present application. Specifically, the mass or weight mentioned in the embodiment of the present application can be μg, mg, g, kg and other units commonly known in the chemical field.

[0051] One embodiment of the present application provides a composite binder, which comprises polytetrafluoroethylene and polydopamine arranged on at least part of the surface of the polytetrafluoroethylene,

[0052] According to the mass fraction, the composite binder comprises 50 parts to 99.9 parts of polytetrafluoroethylene and 0.1 parts to 50 parts of the polydopamine.

[0053] In the composite binder, the polydopamine is coated on at least part of the surface of the polytetrafluoroethylene, and the polydopamine contains polar groups such as amine groups and hydroxyl groups, so that more polar groups are loaded on the surface of the composite binder, and the adhesion capacity of the composite binder is improved. When the composite binder is used to prepare an electrode sheet, the stability of the electrode sheet can be improved. Even if the electrode sheet contains a silicon-based negative active material with a large expansion coefficient, the electrode sheet can also maintain good stability, thereby improving the cycle performance of the battery.

[0054] Moreover, the composite binder can be used to prepare an electrode sheet by a dry method, that is, the electrode sheet can be prepared without adding a solvent. In this way, the preparation process can be simplified, the preparation cost can be reduced, and large-scale production is facilitated.

[0055] In some embodiments, the mass proportion of the polytetrafluoroethylene is 50% to 99.99% based on the total mass of the composite binder.

[0056] The “50% to 99.99%” includes the minimum value and the maximum value in the range, and every value between the minimum value and the maximum value. Specific examples include, but are not limited to, the following point values in the embodiments: 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%; or a range composed of any two numerical values.

[0057] In another aspect of the present application, a method for preparing the composite binder is provided, comprising steps S10-S20.

[0058] In step S10, raw materials, polytetrafluoroethylene and dopamine hydrochloride solution, are provided according to stoichiometric ratio of polytetrafluoroethylene and dopamine hydrochloride.

[0059] In step S20, the polytetrafluoroethylene and the dopamine hydrochloride solution are mixed and subjected to a polymerization reaction to prepare the composite binder.

[0060] During the polymerization reaction, the dopamine hydrochloride is polymerized to form polydopamine and is loaded on the surface of the polytetrafluoroethylene.

[0061] In some embodiments, the step of mixing the polytetrafluoroethylene and the dopamine hydrochloride solution comprises the following steps:

[0062] A buffer solution is added to the dopamine hydrochloride solution to make the pH value of the mixed system 7.5-12, and then the polytetrafluoroethylene is added.

[0063] In some embodiments, the mixing is performed under stirring.

[0064] In some embodiments, the polymerization reaction is performed at a temperature of -18℃-40℃ for 1h-48h.

[0065] In some embodiments, the concentration of the dopamine hydrochloride solution is 0.01g / L-20g / L.

[0066] In some embodiments, the buffer solution comprises a Tris-HCl buffer solution.

[0067] In some embodiments, after the step of the polymerization reaction, the following step is further included:

[0068] The product of the polymerization reaction is subjected to solid-liquid separation, and the solid product is washed and dried with water. Further, the drying can be performed by heating or by freeze-drying.

[0069] In another embodiment of the present application, an electrode sheet is provided, which comprises a current collector and an active layer provided on at least one surface of the current collector, and the active layer comprises the composite binder or the binder prepared by the method for preparing the composite binder.

[0070] In some embodiments, the active layer further comprises a negative active material and a conductive agent, and the negative active material comprises at least one of a carbon-based negative active material and a silicon-based negative active material.

[0071] The silicon-based negative active material includes a silicon-oxygen negative active material with a molecular formula of SiOx, wherein x is any value between 0 and 2. Non-limiting examples include silicon monoxide and silicon dioxide.

[0072] The carbon-based negative active material can be any carbon negative active material commonly used in the art, including but not limited to at least one of mesocarbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, and soft carbon.

[0073] The conductive agent can be any conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor grown carbon fiber VGCF, carbon nanotube CNTs, and graphene, and a composite conductive agent thereof.

[0074] In some embodiments, the mass percentage of the composite binder in the active layer is 0.1% to 20%.

[0075] In some embodiments, the mass percentage of the negative active material in the active layer is 60% to 99.8%.

[0076] In some embodiments, the mass percentage of the conductive agent in the active layer is 0.1% to 20%.

[0077] Another embodiment of the present application further provides a method for preparing the electrode sheet, including steps S30-S40.

[0078] Step S30: mixing the raw materials including the binder to prepare an active mixture.

[0079] Step S40: coating the active mixture on at least one surface of the current collector to prepare the electrode sheet.

[0080] The composite binder can be used to prepare the electrode sheet by a dry method, i.e., the electrode sheet can be prepared without adding a solvent. In this way, the preparation process can be simplified, the preparation cost can be reduced, and mass production can be facilitated.

[0081] Another embodiment of the present application further provides a battery including the electrode sheet or the electrode sheet prepared by the method.

[0082] In some embodiments, the electrode sheet is a negative electrode sheet; further, the battery further includes a positive electrode sheet, a separator, and an electrolyte.

[0083] The positive electrode sheet, the separator, and the electrolyte can be any positive electrode sheet, separator, and electrolyte commonly used in the art for various secondary batteries, which will not be described herein.

[0084] Yet another embodiment of the present application also provides a power consuming device, which further comprises the above-mentioned battery.

[0085] In some embodiments, the power consuming device comprises a vehicle; specifically including but not limited to an electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle.

[0086] The present application will be described in connection with specific embodiments below, but the present application is not limited to the following embodiments, and it should be understood that the appended claims generalize the scope of the present application, and those skilled in the art should realize that certain changes made to the embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0087] Specific embodiments

[0088] The following are specific embodiments.

[0089] Embodiment 1

[0090] (1) Provide the corresponding raw materials according to the stoichiometric ratio of 50 parts of polytetrafluoroethylene and 50 parts of polydopamine: polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (4 g / L).

[0091] Add buffer salt: tris(hydroxymethyl) aminomethane hydrochloride to the dopamine hydrochloride solution, adjust the pH of the solution to 8.5, then slowly add polytetrafluoroethylene powder, high-speed stirring, 0℃ polymerization for 15h; after the reaction is completed, filter and wash the solid with water for several times until the filtrate is clear and transparent, then dry the solid at 120℃ under vacuum for 10h to obtain a composite adhesive.

[0092] (2) Adhesive characterization:

[0093] 1: Fourier transform infrared spectroscopy test is performed on the raw material polytetrafluoroethylene (denoted as PTFE-1) and the prepared composite adhesive (denoted as PTFE-2), and the infrared spectrum comparison chart is shown in Figure 1, the abscissa represents wavelength (Wavelength, cm -1 ), and the ordinate is the transmittance (Transmitance, %).

[0094] 2: Ultraviolet and visible absorption spectrum (ultraviolet and visible spectrum, abbreviated as UV) test is performed on the raw material polytetrafluoroethylene (denoted as PTFE-1) and the prepared composite adhesive (denoted as PTFE-2), and the UV curve comparison is shown in Figure 2, the abscissa represents wavelength (Wavelength, nm), and the ordinate is absorbance (Absorbance).

[0095] 3: The raw material polytetrafluoroethylene (denoted as PTFE-1) and the prepared composite binder (denoted as PTFE-2) were respectively subjected to X-ray diffraction (XRD) test, and the X-ray diffraction (XRD) comparison chart is shown in FIG. 3, wherein the abscissa represents the angle (2θ), and the ordinate is the diffraction intensity (Intensity).

[0096] 4: The raw material polytetrafluoroethylene (denoted as PTFE-1) and the prepared composite binder (denoted as PTFE-2) were respectively subjected to differential scanning calorimetry (DSC) test, and the differential scanning calorimetry (DSC) comparison chart is shown in FIG. 4, wherein the abscissa represents the time (Time), and the ordinate is the power difference, also known as heat flow rate (dH / dt, mW).

[0097] 5: The raw material polytetrafluoroethylene (denoted as PTFE-1) and the prepared composite binder (denoted as PTFE-2) were respectively subjected to thermogravimetric analyzer (TGA) test, and the thermogravimetric analysis (TGA) comparison chart is shown in FIG. 5, wherein the abscissa represents the temperature (Temperature, ℃), and the ordinate is the mass fraction (Weight, %).

[0098] (3) The composite binder electrode sheet was used, and the raw materials were uniformly mixed according to the mass ratio of ternary material (NCM523): conductive carbon black: composite binder of 95:3:2, and were fully ground and rolled on the current collector to obtain the electrode sheet, and the physical map is shown in FIG. 6, and the electron microscope map (SEM) is shown in FIG. 7.

[0099] The energy dispersive X-ray spectrometer (EDS) was used to test the active layer of the electrode sheet, and the energy dispersive X-ray spectrum (EDS) is shown in FIG. 8, wherein the label spectrum of C element, N element, O element and F element is shown from left to right.

[0100] (4) Performance test, the specific steps are as follows:

[0101] S1: The adhesive strength of the electrode sheet was tested according to the 180° peeling experiment test (GB-T2790-1995 national standard), and the specific results are shown in Table 1.

[0102] Example 2

[0103] Example 2 is different from example 1, and the difference is only that step (1) is as follows:

[0104] According to the stoichiometric ratio of 50 parts of polytetrafluoroethylene and 50 parts of polydopamine, the corresponding raw materials, polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (2g / L) were provided.

[0105] The dopamine hydrochloride solution was added with a buffer salt: tris(hydroxymethyl)aminomethane hydrochloride, the pH of the solution was adjusted to 8.5, then polytetrafluoroethylene powder was slowly added, high-speed stirring, polymerization at 0°C for 12h; after the reaction was completed, the solid was filtered and washed with water for multiple times until the filtrate was clear and transparent, then the solid was dried at 120°C under vacuum for 10h to obtain the composite adhesive.

[0106] The other steps were the same as in Example 1, and the specific test results can be seen in Table 1.

[0107] Example 3

[0108] Example 3 was different from Example 1, and the only difference was that step (1) was as follows:

[0109] The corresponding raw materials were provided according to the stoichiometric ratio of 50 parts of polytetrafluoroethylene and 50 parts of polydopamine: polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (2g / L).

[0110] The dopamine hydrochloride solution was added with a buffer salt: tris(hydroxymethyl)aminomethane hydrochloride, the pH of the solution was adjusted to 8.5, then polytetrafluoroethylene powder was slowly added, high-speed stirring, polymerization at -10°C for 12h; after the reaction was completed, the solid was filtered and washed with water for multiple times until the filtrate was clear and transparent, then the solid was dried at 120°C under vacuum for 10h to obtain the composite adhesive.

[0111] The other steps were the same as in Example 1, and the specific test results can be seen in Table 1.

[0112] Example 4

[0113] Example 4 was different from Example 1, and the only difference was that step (1) was as follows:

[0114] (1) The corresponding raw materials were provided according to the stoichiometric ratio of 50 parts of polytetrafluoroethylene and 50 parts of polydopamine: polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (4g / L).

[0115] The dopamine hydrochloride solution was added with a buffer salt: tris(hydroxymethyl)aminomethane hydrochloride, the pH of the solution was adjusted to 8.5, then polytetrafluoroethylene powder was slowly added, high-speed stirring, polymerization at 0°C for 15h; after the reaction was completed, the solid was filtered and washed with water for multiple times until the filtrate was clear and transparent, then freeze-drying was performed to obtain the composite adhesive.

[0116] The other steps were the same as in Example 1, and the specific test results can be seen in Table 1.

[0117] Example 5

[0118] Example 5 is different from Example 1 only in that step (1) is as follows:

[0119] (1) The corresponding raw materials, polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (4 g / L), are provided according to the stoichiometric ratio of 99 parts of polytetrafluoroethylene and 1 part of polydopamine.

[0120] The buffer salt, tris(hydroxymethyl)aminomethane hydrochloride, is added to the dopamine hydrochloride solution, the pH of the solution is adjusted to 8.5, and then the polytetrafluoroethylene powder is slowly added and stirred at high speed. The polymerization reaction is carried out at 0°C for 15 h. After the reaction is completed, the solid is filtered and washed with water for multiple times until the filtrate is clear and transparent, and then freeze-drying is performed to obtain the composite adhesive.

[0121] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0122] Example 6

[0123] Example 6 is different from Example 1 only in that step (1) is as follows:

[0124] (1) The corresponding raw materials, polytetrafluoroethylene (PTFE) powder and dopamine hydrochloride solution (4 g / L), are provided according to the stoichiometric ratio of 75 parts of polytetrafluoroethylene and 25 parts of polydopamine.

[0125] The buffer salt, tris(hydroxymethyl)aminomethane hydrochloride, is added to the dopamine hydrochloride solution, the pH of the solution is adjusted to 8.5, and then the polytetrafluoroethylene powder is slowly added and stirred at high speed. The polymerization reaction is carried out at 0°C for 15 h. After the reaction is completed, the solid is filtered and washed with water for multiple times until the filtrate is clear and transparent, and then freeze-drying is performed to obtain the composite adhesive.

[0126] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0127] Example 7

[0128] Example 7 is different from Example 1 only in that step (3) is as follows:

[0129] The above composite adhesive electrode sheet is used, and the raw materials are uniformly mixed according to the mass ratio of ternary material (NCM523): conductive carbon black: polytetrafluoroethylene composite adhesive of 90:5:5, and are fully ground and rolled on the current collector to obtain the electrode sheet.

[0130] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0131] Example 8

[0132] Example 8 is different from Example 1 only in that step (3) is as follows:

[0133] The above composite binder electrode sheet is used, and the raw materials are uniformly mixed in a mass ratio of graphite: conductive carbon black: composite binder of 90:5:5, are fully ground, and are rolled on the current collector to obtain the electrode sheet.

[0134] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0135] Comparative Example 1

[0136] Comparative Example 1 is basically the same as Example 1, except that in Comparative Example 1, the composite binder in step (3) of Example 1 is replaced by the same mass of polytetrafluoroethylene in step (3).

[0137] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0138] Comparative Example 2

[0139] Comparative Example 2 is basically the same as Example 8, except that in Comparative Example 2, the composite binder in step (3) of Example 8 is replaced by the same mass of polytetrafluoroethylene in step (3).

[0140] The other steps are the same as those in Example 1, and the specific test results are shown in Table 1.

[0141] The composition of each example and each comparative example is shown in Table 1.

[0142] Table 1 Note: " / " represents the absence of the substance.

[0143] As can be seen from the data in Table 1, the composite binder prepared by the technical solution of the present application has excellent binding ability, and when the composite binder is used to prepare an electrode sheet, the stability of the electrode sheet can be improved, thereby improving the cycle performance of the battery.

[0144] Moreover, the composite binder can be used to prepare an electrode sheet by a dry method, i.e., the electrode sheet can be prepared without adding a solvent, so that the preparation process can be simplified, the preparation cost can be reduced, and large-scale production is facilitated.

[0145] The technical features of the above-described examples can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-described examples are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the present disclosure.

[0146] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A composite binder, characterized by, The composite binder comprises polytetrafluoroethylene and polydopamine arranged on at least part of the surface of the polytetrafluoroethylene; The composite binder comprises 50 parts to 99.99 parts of the polytetrafluoroethylene and 0.01 parts to 50 parts of the polydopamine in terms of mass fraction.

2. The composite binder of claim 1, wherein, The mass fraction of the polytetrafluoroethylene in the total mass of the composite binder is 50% to 99.99%.

3. The method of producing a composite binder according to any one of claims 1 to 2, wherein The method comprises the following steps: The raw materials, i.e., polytetrafluoroethylene and dopamine hydrochloride solution, are provided in stoichiometric proportion of the polytetrafluoroethylene and the polydopamine. The polytetrafluoroethylene is mixed with the dopamine hydrochloride solution to perform polymerization reaction and prepare the composite binder.

4. The method of claim 3, wherein the composite binder is prepared by mixing the components in the following order: the polyol, the polyisocyanate, the chain extender, the crosslinker, and the catalyst. The step of mixing the polytetrafluoroethylene with the dopamine hydrochloride solution comprises the following steps: The buffer solution is added to the dopamine hydrochloride solution to make the pH value of the mixed system 7.5 to 12, and then the polytetrafluoroethylene is added.

5. The method of preparing a composite binder according to any one of claims 3 to 4, wherein The polymerization reaction is performed at a temperature of -18°C to 40°C for 1h to 48h; and / or The concentration of the dopamine hydrochloride solution is 0.01g / L to 20g / L.

6. An electrode sheet characterized by The electrode sheet comprises a current collector and an active layer arranged on at least one surface of the current collector, and the active layer comprises the composite binder of any one of claims 1 to 2 or the binder prepared by the method of any one of claims 3 to 5.

7. The electrode patch of claim 6, wherein, The active layer further comprises a negative active material and a conductive agent, and the negative active material comprises at least one of a carbon-based negative active material and a silicon-based negative active material.

8. The electrode patch of claim 7, wherein, In the active layer, the mass fraction of the composite binder is 0.1% to 20%; and / or In the active layer, the mass fraction of the negative active material is 60% to 99.8%; and / or In the active layer, the mass fraction of the conductive agent is 0.1% to 20%.

9. The method of producing an electrode sheet according to any one of claims 6 to 8, characterized by, The method comprises the following steps: The raw materials for preparing the binder are mixed to prepare an active mixture; The active mixture is coated on at least one surface of the current collector to prepare the electrode sheet.

10. A battery, characterized by The battery comprises the electrode sheet of any one of claims 6 to 8 or the electrode sheet prepared by the method of claim 9.

11. An electrical device, characterized by The electric device comprises the battery of claim 10.

12. The powered device of claim 11, wherein, The electric device comprises a vehicle.

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