WO2025091717A1 - Binder and preparation method therefor, negative electrode sheet, battery and electric device - Google Patents

Abstract

The present disclosure provides a binder and a preparation method therefor, a negative electrode sheet, a battery and an electric device. The binder comprises a polymer which comprises structural units of formulas (I), (II) and (III) and at least one selected from structural units of formulas (IV), (V) and (VI); R1, R2, R4, R6 and R7 are each independently selected from at least one of H, unsubstituted or substituted C₁-C₂₀ alkyl, unsubstituted or substituted C₁-C₂₀ alkoxy; R3 and R5 are each independently selected from at least one of unsubstituted or substituted C₁-C₂₀alkyl; and substituents in the substituted C₁-C₂₀ alkyl and the substituted C₁-C₂₀ alkoxy are each independently selected from at least one of hydroxyl, halogen or amino.

Description

Binder and preparation method thereof, negative electrode sheet, battery and electrical device

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is based on Chinese patent application with application number 202311423953.4, application date October 31, 2023, and invention name “Binder and preparation method thereof, negative electrode sheet, battery and electrical device”, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into the present disclosure as a reference.

Technical Field

New energy batteries are being used more and more widely in life and industry. For example, new energy vehicles equipped with batteries have been widely used. In addition, batteries are also being increasingly used in areas such as energy storage.

The present disclosure relates to the technical field of lithium batteries, and in particular to a binder and a preparation method thereof, a negative electrode sheet, a battery and an electrical device.

Background Art

In recent years, driven by the dual carbon background and government policies, the rapid development of the new energy vehicle industry and the energy storage industry has led to the rapid development of lithium batteries. Battery energy density is an essential key indicator in the process of lithium battery technology iteration. In previous studies, improving the energy density of batteries mainly focused on the research and development of the main material graphite and increasing the operating voltage of the battery; or achieving high load capacity through thick coating of the pole piece.

However, when preparing the pole piece coating, the thicker the coating, the higher the density, the greater the internal stress, resulting in a larger elastic modulus of the coating. In this case, the stress accumulation cannot be released evenly, resulting in cracking of the pole piece.

Therefore, how to improve the flexibility of the electrode so that the electrode does not crack when thickly coated, thereby improving battery performance has become an urgent problem to be solved in this field.

Summary of the invention

The present disclosure is made in view of the above-mentioned problems, and its purpose is to provide a binder and a preparation method thereof to solve the problems such as cracking of the electrode sheet when thickly coated and the resulting degradation of battery performance. The present disclosure also provides a negative electrode sheet, a battery including the negative electrode sheet, and an electrical device including the battery.

In order to achieve the above-mentioned object, the first aspect of the present disclosure provides a binder, the binder comprising a polymer, the polymer comprising a structural unit represented by formula (I), a structural unit represented by formula (II), a structural unit represented by formula (III), and at least one selected from a structural unit represented by formula (IV), a structural unit represented by formula (V), or a structural unit represented by formula (VI);

in,

R1, R2, R4, R6, and R7 are independently selected from at least one of H, unsubstituted or substituted C ₁ -C ₂₀ alkyl, and unsubstituted or substituted C ₁ -C ₂₀ alkoxy, wherein the substituents in the substituted C ₁ -C ₂₀ alkyl and the substituents in the substituted C ₁ -C ₂₀ alkoxy are independently selected from at least one of hydroxyl, halogen, and amino;

R3 and R5 are independently selected from at least one of unsubstituted or substituted C ₁ -C ₂₀ alkyl groups, and the substituent group in the substituted C ₁ -C ₂₀ alkyl group is selected from at least one of hydroxyl, halogen or amino.

In the embodiment of the present disclosure, through the joint action of the structural unit represented by formula (I), the structural unit represented by formula (II), the structural unit represented by formula (III), and at least one of the structural unit represented by formula (IV), the structural unit represented by formula (V), or the structural unit represented by formula (VI), the binder has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, and prevent the pole piece from cracking when thickly coated, thereby increasing the single-sided coating quality of the negative electrode slurry per unit area on the pole piece.

In any embodiment, R1, R2, R4, R6, and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl;

and/or, R3 is at least one selected from unsubstituted C ₁ -C ₄ alkyl groups;

And/or, R5 is at least one selected from unsubstituted or substituted C ₁ -C ₈ alkyl groups, and the substituent group in the substituted C ₁ -C ₈ alkyl group is hydroxyl group.

The adhesive in these embodiments has further enhanced bonding force, can further reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, and prevent the pole piece from cracking when thickly coated.

In any embodiment, the polymer includes at least one structural unit represented by formula (IV), wherein R4 is selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent group in the substituted C ₁ -C ₈ alkyl is hydroxyl. The acrylate group in the structural unit represented by formula (IV) is not only conducive to enhancing the bonding force of the binder, but also conducive to increasing the wettability of the electrolyte to the electrode.

In any embodiment, the polymer includes at least one structural unit represented by formula (IV) and at least one structural unit represented by formula (V), wherein R4 and R6 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent group in the substituted C ₁ -C ₈ alkyl is hydroxyl. The ester group in the structural unit represented by formula (IV) is not only conducive to enhancing the bonding force of the binder, but also conducive to increasing the wettability of the electrolyte to the electrode. The amide group in the structural unit represented by formula (V) is conducive to enhancing the bonding force of the binder.

In any embodiment, the polymer includes at least one structural unit represented by formula (IV), at least one structural unit represented by formula (V) and at least one structural unit represented by formula (VI), wherein R4, R6 and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent group in the substituted C ₁ -C ₈ alkyl is hydroxyl. The ester group in the structural unit represented by formula (IV) is not only conducive to enhancing the bonding force of the binder, but also conducive to increasing the wettability of the electrolyte to the electrode. The amide group in the structural unit represented by formula (V) and the cyano group in the structural unit represented by formula (VI) are conducive to enhancing the bonding force of the binder.

In any embodiment, in the polymer, the mass percentage of the structural unit represented by formula (I) is 4.5% to 8%, the mass percentage of the structural unit represented by formula (II) is 12% to 21%, the mass percentage of the structural unit represented by formula (III) is 3% to 6.5%, and the mass percentage of at least one of the structural unit represented by formula (IV), the structural unit represented by formula (V) or the structural unit represented by formula (VI) is 68% to 77%. By making the mass percentage of each structural unit within the above range, it is beneficial to further enhance the bonding force of the binder.

In any embodiment, the glass transition temperature of the polymer is -15 to 15° C. By making the glass transition temperature of the polymer within the above range, it is beneficial for the binder to have appropriate flexibility, which in turn helps the electrode to have appropriate flexibility and prevent the electrode from cracking when thickly coated.

In any embodiment, the weight average molecular weight of the polymer is 400,000 to 1,000,000. By making the weight average molecular weight of the polymer within the above range, it is beneficial to make the binder have fluidity suitable for actual production needs.

A second aspect of the present disclosure provides a method for preparing the binder as described above, the method comprising:

Adding a monomer corresponding to the structural unit represented by formula (I) and a monomer corresponding to the structural unit represented by formula (II) into a solvent, reacting in the presence of a first surfactant and a first initiator to obtain a first emulsion;

Adding a monomer corresponding to the structural unit represented by formula (III) and at least one monomer selected from the group consisting of a monomer corresponding to the structural unit represented by formula (IV), a monomer corresponding to the structural unit represented by formula (V), and a monomer corresponding to the structural unit represented by formula (VI) to the first emulsion, and reacting in the presence of a second surfactant to obtain a second emulsion;

The second emulsion is heated to react in the presence of a second initiator to obtain a binder.

The binder is prepared by using the monomers corresponding to the above-mentioned structural units as monomer raw materials for polymerization. The obtained binder has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, prevent the pole piece from cracking when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece.

The third aspect of the present disclosure provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises the binder of the first aspect of the present disclosure, or the binder prepared by the method of the second aspect of the present disclosure. By including the binder described above, the flexibility of the plate is improved, so that the plate does not crack when thickly coated.

In any embodiment, the mass percentage of the binder is 1.2% to 2.2% based on the total mass of the negative electrode film layer. By making the mass percentage of the binder within the above range, it is beneficial to improve the flexibility of the electrode sheet, so that the electrode sheet does not crack when thickly coated, and at the same time does not reduce the content of active materials in the negative electrode film layer.

In any embodiment, the negative electrode film layer further includes a stabilizer, and the stabilizer includes at least one of sodium carboxymethyl cellulose, sodium alginate or sodium cyclodextrin. The inclusion of the stabilizer facilitates the dispersion of the negative electrode active material in the negative electrode film layer.

The fourth aspect of the present disclosure provides a battery, comprising the negative electrode sheet of the third aspect of the present disclosure, wherein the battery has an improved battery energy density.

The fifth aspect of the present disclosure provides an electric device, comprising the battery according to the fourth aspect of the present disclosure. The electric device has a durable power supply.

The present disclosure provides a binder, the binder comprising a polymer, the polymer comprising a structural unit represented by formula (I), a structural unit represented by formula (II), and a structural unit represented by formula (III), and at least one selected from a structural unit represented by formula (IV), a structural unit represented by formula (V), or a structural unit represented by formula (VI). Through the joint action of the above structural units, the binder has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, prevent the pole piece from cracking when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece. Thus, for a battery prepared using the binder, the DC impedance of the battery can be reduced, and the energy density, cycle performance, and storage performance of the battery can be improved.

The present disclosure also provides a method for preparing the above-mentioned binder. In this method, a monomer corresponding to the structural unit represented by formula (I), a monomer corresponding to the structural unit represented by formula (II), a monomer corresponding to the structural unit represented by formula (III), and at least one monomer selected from the monomer corresponding to the structural unit represented by formula (IV), the monomer corresponding to the structural unit represented by formula (V), or the monomer corresponding to the structural unit represented by formula (VI) is used as a monomer raw material to prepare the binder, and the binder obtained thereby has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, make the pole piece not crack when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece. Thus, for a battery prepared using the binder, the DC impedance of the battery can be reduced, and the energy density, cycle performance, and storage performance of the battery can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a cross-linked network of a binder according to an embodiment of the present disclosure.

FIG2 shows a schematic diagram of hydrogen bonding of a binder according to an embodiment of the present disclosure. In the upper part of FIG2 , a strong hydrogen bond with large bond energy is formed between the exemplary stabilizer CMC-Na itself; the lower left part of FIG2 shows a reversible hydrogen bond formed between the binder according to an embodiment of the present disclosure and the exemplary stabilizer CMC-Na; the lower right part of FIG2 shows that the polar groups of the binder according to an embodiment of the present disclosure form hydrogen bonds of both strong and weak strength with each other.

FIG. 3 is a schematic diagram of a battery cell according to an embodiment of the present disclosure.

FIG. 4 is an exploded view of the battery cell according to the embodiment of the present disclosure shown in FIG. 3 .

FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present disclosure.

FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present disclosure.

FIG. 7 is an exploded view of the battery pack according to the embodiment of the present disclosure shown in FIG. 6 .

FIG. 8 is a schematic diagram of an electric device using a battery as a power source according to an embodiment of the present disclosure.

Description of reference numerals:
1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly.

DETAILED DESCRIPTION

Hereinafter, the embodiments of the binder and preparation method thereof, negative electrode plate, battery and electric device disclosed in the present invention are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter claimed for protection in the present disclosure.

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

If not otherwise specified, all embodiments and optional embodiments of the present disclosure may be combined with each other to form a new technical solution.

Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form a new technical solution.

If not otherwise specified, all steps of the present disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

In the related art, in order to improve the energy density of the battery, one method that can be used is to apply a thick coating of active material on the pole piece to achieve a high load, thereby increasing the amount of active material per unit area of the negative pole piece. However, when preparing the active material coating, the thicker the coating, the higher the density, the greater the internal stress, resulting in a larger elastic modulus of the coating, and the stress accumulation cannot be released evenly, which leads to cracking of the pole piece. When the thickness of the pole piece coating is increased, the evaporation of water during the drying process of the pole piece will also cause local accumulation and release of internal stress in the pole piece, which can easily cause the pole piece to crack, resulting in a low pole piece quality rate, and the assembled battery cell will also have the risk of lithium precipitation.

In order to solve the above problems, the previous solution is to add plasticizers during the preparation of negative electrode slurry to improve the flexibility of the electrode. However, this method has some disadvantages and risks. For example, additional delivery pipelines are required; excessive addition will deteriorate the battery performance; during high-speed thick coating, some plasticizers are highly hydrophilic, and the residual amount of small plasticizer molecules in the electrode is high, which will deteriorate the battery performance and cannot ensure the dryness of the electrode; the addition of plasticizers will also reduce the content of negative electrode active materials in the negative electrode slurry.

Based on this, the present disclosure proposes a binder and a preparation method thereof, a negative electrode sheet, a battery and an electrical device. The present disclosure and optional implementation methods are described in more detail below.

Binder

The present disclosure provides a binder, the binder comprising a polymer, the polymer comprising a structural unit represented by formula (I), a structural unit represented by formula (II), a structural unit represented by formula (III), and at least one selected from a structural unit represented by formula (IV), a structural unit represented by formula (V), or a structural unit represented by formula (VI);

Wherein, R1, R2, R4, R6, and R7 are independently selected from at least one of H, unsubstituted or substituted C ₁ -C ₂₀ alkyl, and unsubstituted or substituted C ₁ -C ₂₀ alkoxy, wherein the substituent groups in the substituted C ₁ -C ₂₀ alkyl and the substituent groups in the substituted C ₁ -C ₂₀ alkoxy are independently selected from at least one of hydroxyl, halogen, and amino.

R3 and R5 are independently selected from at least one of unsubstituted or substituted C ₁ -C ₂₀ alkyl groups, and the substituent group of the substituted C ₁ -C ₂₀ alkyl group is selected from at least one of hydroxyl, halogen or amino.

“C ₁ -C ₂₀ alkyl” refers to a straight or branched aliphatic hydrocarbon group having 1 to 20 carbon atoms. Optional C ₁ -C ₂₀ alkyl includes a straight or branched C ₁ -C ₁₀ alkyl group having 1 to 10 carbon atoms. Optional C ₁ -C ₂₀ alkyl includes a straight or branched C ₁ -C ₈ alkyl group having 1 to 8 carbon atoms. Optional C ₁ -C ₂₀ alkyl includes a straight or branched C 1 -C _{6 alkyl group having 1 to 6 carbon} atoms. Optional C ₁ -C ₂₀ alkyl includes a straight or branched C ₁ -C ₄ alkyl group having 1 to 4 carbon atoms. Optional C ₁ -C ₂₀ alkyl includes a C ₁ -C ₂ alkyl group having 1 to 2 carbon atoms. Examples of C ₁ -C ₂₀ alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, and decyl.

“C ₁ -C ₂₀ alkoxy” refers to “C ₁ -C ₂₀ alkyloxy”, wherein the “C ₁ -C ₂₀ alkyl” portion is the same as the definition of the above-mentioned “C ₁ -C ₂₀ alkyl”. Optional C ₁ -C ₂₀ alkoxy includes C ₁ -C ₁₀ alkoxy. Optional C ₁ -C ₂₀ alkoxy includes C ₁ -C ₈ alkoxy. Optional C ₁ -C ₂₀ alkoxy includes C ₁ -C ₆ alkoxy. Optional C ₁ -C ₂₀ alkoxy includes C ₁ -C ₄ alkoxy. Optional C ₁ -C ₂₀ alkoxy includes C ₁ -C ₂ alkoxy. Examples of C ₁ -C ₂₀ alkoxy include, but are not limited to, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, and decyloxy.

The "structural unit represented by formula (I)" may include more than one structural unit represented by formula (I). For example, the binder in the embodiment of the present disclosure may include a structural unit represented by formula (I) in which R1 is H; or the binder in the embodiment of the present disclosure may include structural units represented by formula (I) in which R1 is H and R1 is methyl at the same time. The expressions "structural unit represented by formula (II)", "structural unit represented by formula (III)", "structural unit represented by formula (IV)", "structural unit represented by formula (V)" and "structural unit represented by formula (VI)" shall be interpreted in the same way.

"Unsubstituted" means that the group in question has no substituent groups.

"Substituted" means that the group in question has a substituent. Examples of the substituent include, but are not limited to, hydroxyl (OH), halogen (F, Cl, Br, I), amino (NH ₂ ), cyano (CN), nitro (NO ₂ ), C ₁ -C ₁₀ alkylamino, phenyl (Ph). When a group is substituted, it may have more than one substituent, for example, 1, 2 or 3 substituents. For example, a substituted group may have 1 or 2 substituents.

The present disclosure found that the main stress for cracking the pole piece comes from the strong hydrogen bonds formed between stabilizers such as sodium carboxymethyl cellulose (CMC-Na). The side chains of the binder in the embodiment of the present disclosure include at least one polar group selected from carboxyl, ester, amide, and cyano. Although the mechanism is not clear, in the process of coating the negative electrode slurry including the binder of the embodiment of the present disclosure on the negative electrode current collector, the binder itself undergoes thermal cross-linking to form a uniform network as schematically shown in Figure 1, and more contact sites can be provided on the surface of the active material. The polar groups at these contact sites can form reversible hydrogen bonds with different bond energies with the hydroxyl and carboxyl groups of stabilizers such as CMC-Na (Figure 2), which greatly reduces the possibility of forming strong hydrogen bonds with large bond energies and non-rotatable bonds between stabilizers such as CMC-Na (Figure 2). At the same time, the polar groups on the side chains of the binder form hydrogen bonds with different bond energies (Figure 2) with each other, which are both strong and weak. During the drying process of the electrode, weak hydrogen bonds with low bond energy will break due to local accumulation of drying stress, and then heal after the stress is released. Strong hydrogen bonds with high bond energy are not easy to break, thus maintaining the overall integrity of the electrode structure.

The structural unit represented by formula (I) is derived from a rigid monomer, which enables the binder to maintain a good spatial expansion structure, so that excessive deformation of the molecular chain will not occur during the drying process of the pole piece, which will adversely affect the cohesion. Therefore, by including the structural unit represented by formula (I), the cohesion of the binder can be enhanced, thereby enhancing the cohesion of the pole piece.

The structural unit represented by formula (II) includes a carboxyl group. The structural unit represented by formula (IV), the structural unit represented by formula (V) or the structural unit represented by formula (VI) respectively includes an ester group, an amide group and a cyano group. The polar groups included in these structural units can form reversible hydrogen bonds with the stabilizer in the slurry or these polar groups can form hydrogen bonds with different bond energies with each other. During the drying process of the pole piece, these hydrogen bonds are conducive to the uniform release of the accumulated stress of the pole piece.

Moreover, during the drying process of the electrode, the siloxane in the structural unit represented by formula (III) hydrolyzes and condenses to produce Si-O-Si bonds, which, on the one hand, crosslinks the linear structure into a three-dimensional structure, and on the other hand, the Si-O bonds can rotate 360 degrees, reducing the stress during the drying process of the electrode. accumulation.

Therefore, through the joint action of the structural unit represented by formula (I), the structural unit represented by formula (II), and the structural unit represented by formula (III), as well as at least one of the structural unit represented by formula (IV), the structural unit represented by formula (V), or the structural unit represented by formula (VI), the binder in the embodiment of the present disclosure has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, prevent the pole piece from cracking when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece.

In some embodiments, R1, R2, R4, R6, and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl. For example, R1, R2, R4, R6, and R7 are independently selected from at least one of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl.

In some embodiments, R3 is selected from at least one of unsubstituted C ₁ -C ₄ alkyl groups. For example, R3 is selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, or tert-butyl.

In some embodiments, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl groups. Here, the substituents in the substituted C ₁ -C ₈ alkyl groups include, but are not limited to, hydroxyl groups. Alternatively, R5 is selected from at least one of unsubstituted C ₁ -C ₈ alkyl groups. For example, R5 is selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, hexyl, heptyl, octyl, and isooctyl. Alternatively, R5 is selected from at least one of hydroxy-substituted C ₁ -C ₈ alkyl groups. For example, R5 is selected from at least one of hydroxy-substituted methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, hexyl, heptyl, octyl, and isooctyl.

The adhesive in these embodiments has further enhanced bonding force, can further reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, and prevent the pole piece from cracking when thickly coated.

In some embodiments, the polymer includes at least one structural unit represented by formula (IV), wherein R4 is selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, and R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituents in the substituted C ₁ -C ₈ alkyl include but are not limited to hydroxyl. Examples of R4 and R5 are as described above and will not be repeated here.

"The polymer includes at least one structural unit represented by formula (IV)" means that the polymer may include more than one structural unit represented by formula (IV). For example, the polymer may simultaneously include structural units represented by formula (IV) in which R4 is H and R5 is isooctyl; R4 is H and R5 is ethyl; R4 is H and R5 is butyl; R4 is methyl and R5 is methyl; and R4 is H and R5 is ethyl substituted with hydroxyl. However, the present invention is not limited thereto.

Although the mechanism is not clear, the acrylate groups in the binder in these embodiments increase the wettability of the electrode by the electrolyte.

In some embodiments, the polymer includes at least one structural unit represented by formula (IV) and at least one structural unit represented by formula (V), wherein R4 and R6 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent group in the substituted C ₁ -C ₈ alkyl includes but is not limited to hydroxyl. Examples of R4, R6 and R5 are as described above and will not be repeated here.

Although the mechanism is not clear, the acrylate groups in the binder in these embodiments increase the wettability of the electrolyte to the electrode. In addition, polar groups such as amide groups are added to the side chains, which enhances the bonding force of the binder.

In some embodiments, the polymer includes at least one structural unit represented by formula (IV), at least one structural unit represented by formula (V), and at least one structural unit represented by formula (VI), wherein R4, R6, and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, and R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituents in the substituted C ₁ -C ₈ alkyl include hydroxyl, but are not limited thereto. Examples of R4, R6, R7, and R5 are as described above and will not be repeated here.

Although the mechanism is not clear, the structural unit side chains of the binder in these embodiments include at least one polar group among carboxyl, amide, cyano, and ester. These polar groups form reversible hydrogen bonds with different bond energies with stabilizers such as CMC-Na. During the drying process of the pole piece, weak hydrogen bonds will break due to local accumulation of drying stress, and heal again after the stress is released. Strong hydrogen bonds are not easy to break, thereby maintaining the overall integrity of the pole piece.

In some embodiments, in the polymer, the mass percentage of the structural unit represented by formula (I) is 4.5% to 8%, optionally 5% to 7.5%, optionally 5.5% to 7.0%, optionally 6.0% to 6.5%; the mass percentage of the structural unit represented by formula (II) is 12% to 21%, optionally 14% to 20%, optionally 15% to 19%, optionally 16% to 18%; the mass percentage of the structural unit represented by formula (III) is 3% to 6.5%, optionally 3.5% to 6%, optionally 4% to 5%; and the mass percentage of at least one of the structural unit represented by formula (IV), the structural unit represented by formula (V) or the structural unit represented by formula (VI) is 68% to 77%, optionally 69% to 76%, optionally 70% to 75%, optionally 71% to 74%.

Although the mechanism is not clear, controlling the mass percentage of at least one of the structural unit represented by formula (I), the structural unit represented by formula (II), the structural unit represented by formula (III), and the structural unit represented by formula (IV), the structural unit represented by formula (V), or the structural unit represented by formula (VI) within the above range is beneficial for making the glass transition temperature of the polymer within the range of The molecular chains of the binder are kept in a certain space and in the drying process of the pole piece, so as to evenly release the stress accumulation caused by the volatilization of water during the drying process. The appropriate amount of silane chains is conducive to controlling the crosslinking degree to a desired level. The structural unit represented by formula (I) is derived from a rigid monomer, and including an appropriate amount of the structural unit represented by formula (I) is conducive to improving the cohesion of the binder.

In some embodiments, the glass transition temperature of the polymer is -15 to 15°C, optionally -14 to 10°C, optionally -13 to 8°C, optionally -11 to 6°C, optionally -9 to 4°C, optionally -7 to 2°C, optionally -5 to 0°C.

Although the mechanism is not yet clear, the glass transition temperature Tg of the polymer reflects the flexibility of the binder and affects the flexibility of the electrode to a certain extent. The electrode with a certain flexibility is the ideal electrode. If the electrode is too soft, it will lead to insufficient cohesion and large rebound of the electrode. If the electrode is too hard, it will easily crack. Controlling the glass transition temperature of the polymer within the above range is conducive to making the binder have appropriate flexibility, which in turn helps the electrode have appropriate flexibility, so that the electrode does not crack when thickly coated, and increases the single-sided coating quality of the negative electrode slurry per unit area on the electrode.

In some embodiments, the weight average molecular weight of the polymer is 400,000 to 1,000,000, optionally 450,000 to 900,000, optionally 450,000 to 800,000, optionally 450,000 to 700,000, optionally 450,000 to 600,000.

Although the mechanism is not yet clear, controlling the weight average molecular weight of the polymer within the above range is beneficial to making the binder have fluidity suitable for actual production needs.

Preparation method of adhesive

The present disclosure also provides a method for preparing the above-mentioned adhesive, which comprises the following steps.

The monomer corresponding to the structural unit represented by formula (I) and the monomer corresponding to the structural unit represented by formula (II) are added to a solvent, and reacted in the presence of a first surfactant and a first initiator to prepare a first emulsion.

A monomer corresponding to the structural unit represented by formula (III) and at least one monomer selected from the monomer corresponding to the structural unit represented by formula (IV), the monomer corresponding to the structural unit represented by formula (V) or the monomer corresponding to the structural unit represented by formula (VI) are added to the first emulsion, and reacted in the presence of a second surfactant to obtain a second emulsion.

The second emulsion is heated to react in the presence of a second initiator to prepare the adhesive of the present disclosure.

In some embodiments, the solvent may be a commonly used solvent in the art, such as deionized water, but is not limited thereto.

In some embodiments, the first surfactant and the second surfactant may be the same or different, and surfactants commonly used in the art may be used. For example, the surfactant may include at least one of nonylphenol polyoxyethylene ether ammonium sulfate and polyoxyethylene lauryl alcohol ether, but is not limited thereto.

In some embodiments, the first initiator and the second initiator may be the same or different, and initiators commonly used in the art may be used. For example, the initiator may include at least one of ammonium persulfate, potassium persulfate, sodium persulfate, dibenzoyl peroxide, hydrogen peroxide/rongalite, tert-butyl hydroperoxide/rongalite, but is not limited thereto. Alternatively, the first initiator may include ammonium persulfate. Alternatively, the second initiator may include at least one of ammonium persulfate or tert-butyl hydroperoxide/rongalite.

In some embodiments, the second emulsion may be heated to 70 to 100° C. Alternatively, the second emulsion may be heated to 80 to 90° C., but is not limited thereto.

Although the mechanism is not clear, in this method, a monomer corresponding to the structural unit represented by formula (I), a monomer corresponding to the structural unit represented by formula (II), a monomer corresponding to the structural unit represented by formula (III), and a monomer corresponding to the structural unit represented by formula (IV), a monomer corresponding to the structural unit represented by formula (V), or a monomer corresponding to the structural unit represented by formula (VI) are used as monomer raw materials for polymerization to prepare a binder. The obtained binder has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, prevent the pole piece from cracking when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece. Therefore, for a battery prepared using the binder, the DC impedance of the battery can be reduced, and the energy density, cycle performance, and storage performance of the battery can be improved.

Regarding the reaction conditions such as reaction temperature, reaction time, reaction pressure, reagent addition amount, and other optional reagents (for example, molecular weight regulator, pH regulator, etc.) and their addition amounts in the above method, those skilled in the art can select and adjust them according to actual needs, which will not be elaborated here.

Negative electrode slurry composition

The present disclosure also provides a negative electrode slurry composition. The negative electrode slurry composition includes a negative electrode active material, the binder and stabilizer described above. The main function of the binder is to play a bonding role between the negative electrode active materials and between the negative electrode active materials and the substrate. The stabilizer mainly plays a suspending role during the stirring process of the negative electrode slurry, so that the active material such as graphite will not settle during the stirring process.

In some embodiments, the mass percentage of the binder may be 1.2% to 2.2%, optionally 1.4 to 2.0%, or optionally 1.6 to 1.8%, relative to the total solid content of the negative electrode slurry composition.

In some embodiments, the weight percentage of the stabilizer relative to the total solid content of the negative electrode slurry composition may be 0.5% to 1.2%, optionally 0.6 to 1.1%, optionally 0.8 to 1.0%.

In some embodiments, the stabilizer is selected from substances including groups such as hydroxyl groups and carboxyl groups that can form hydrogen bonds. For example, the stabilizer may include but is not limited to sodium carboxymethyl cellulose, sodium alginate, and sodium cyclodextrin. Alternatively, the stabilizer may include but is not limited to sodium carboxymethyl cellulose, sodium alginate, sodium hydroxypropyl cyclodextrin, sodium carboxymethyl cyclodextrin, sodium hyperbranched cyclodextrin, sodium sulfobutyl-β-cyclodextrin, etc.

The polar groups in the binder in the disclosed embodiment form hydrogen bonds with different bond energies with the hydroxyl, carboxyl and other hydrogen-bonding groups in these stabilizers, greatly reducing the possibility of hydrogen bonds between the stabilizers themselves. During the drying process of the pole piece, the weak hydrogen bonds with low bond energy will break due to the local accumulation of drying stress, and then heal after the stress is released. The strong hydrogen bonds with high bond energy are not easy to break, thereby maintaining the integrity of the overall structure of the pole piece. As a result, the pole piece will not crack when thickly coated, and the single-sided coating quality of the negative electrode slurry per unit area on the pole piece will be increased.

Negative electrode

The present disclosure also provides a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes the binder described above, or a binder prepared by the method described above.

In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the binder may be 1.2% to 2.2%, optionally 1.4 to 2.0%, or optionally 1.6 to 1.8%.

In some embodiments, the negative electrode film layer further comprises a stabilizer. The stabilizer is selected from substances including groups such as hydroxyl groups and carboxyl groups that can form hydrogen bonds. For example, the stabilizer includes but is not limited to sodium carboxymethyl cellulose, sodium alginate, and sodium cyclodextrin. Alternatively, the stabilizer includes but is not limited to sodium carboxymethyl cellulose, sodium alginate, sodium hydroxypropyl cyclodextrin, sodium carboxymethyl cyclodextrin, sodium hyperbranched cyclodextrin, sodium sulfobutyl-β-cyclodextrin, and the like.

In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the stabilizer may be 0.5% to 1.2%, optionally 0.6 to 1.1%, or optionally 0.8 to 1.0%.

As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

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

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

In some embodiments, the negative electrode film layer may further include other binders. These binders 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) or carboxymethyl chitosan (CMCS).

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

In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener.

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

In addition, the battery and the electric device of the present disclosure will be described below with reference to the drawings as appropriate.

In one embodiment of the present disclosure, a battery is provided, which includes a binder selected from the above-mentioned binder, a binder prepared by the above-mentioned method, or the above-mentioned negative electrode sheet.

The term "battery" mentioned in this article refers to a battery cell, a battery module or a battery pack. Each of these is described below.

Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time to make Ions pass through.

Positive electrode

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

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

In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present disclosure is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO ₂ ), lithium nickel oxide (such as LiNiO ₂ ), lithium manganese oxide (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM ₅₂₃ ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM 622 ), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), and LiNi _0.8 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.1 Al _0.05 O ₂ ) and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this disclosure, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

In the list of positive electrode materials in the present disclosure, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

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

In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

Negative electrode

The negative electrode plate is as described above and will not be described again here.

Electrolytes

The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present disclosure has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

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

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

Isolation film

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

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

In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The present disclosure has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. For example, FIG3 is a battery cell 5 of a square structure as an example.

In some embodiments, referring to FIG. 4 , the outer package may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

FIG5 is a battery module 4 as an example. Referring to FIG5 , in the battery module 4, a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

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

FIG6 and FIG7 are battery packs 1 as an example. Referring to FIG6 and FIG7 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

In addition, the present disclosure further provides an electric device, the electric device comprising the battery provided by the present disclosure. The battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

FIG8 is an example of an electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery pack or a battery module may be used.

As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

Example

Hereinafter, embodiments of the present disclosure are described. The embodiments described below are exemplary and are only used to explain the present disclosure, and should not be construed as limiting the present disclosure. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

Preparation of binder

Example 1

1.1 According to weight, 18 parts of deionized water, 0.06 parts of dodecyl mercaptan, and 0.4 parts of nonylphenol polyoxyethylene ether ammonium sulfate are mixed in a reaction kettle and heated to 60°C. Then 1.2 parts of styrene and 3 parts of acrylic acid are added. After the addition is complete, the pH is adjusted to about 7 with sodium bicarbonate. Then the temperature is raised to 75°C, 0.2 parts of initiator ammonium persulfate are added, and the reaction is carried out for 1 hour. After that, the temperature is lowered to 40°C to obtain the first emulsion.

1.2 Add 20 parts of deionized water, 0.09 parts of dodecyl mercaptan, and 0.18 parts of polyoxyethylene lauryl alcohol ether to the first emulsion by weight. Then heat to 60°C, stir for 0.5h, then add 3.3 parts of isooctyl acrylate (2-EHA), 2 parts of ethyl acrylate (EA), 1.8 parts of butyl acrylate (BA), 4.1 parts of methyl methacrylate, 2.6 parts of hydroxyethyl acrylate, and 0.9 parts of vinyl triethoxysilane, and stir thoroughly for 1h. After stirring thoroughly, cool to 40°C, then add 0.2 parts of nonylphenol polyoxyethylene ether ammonium sulfate, stir evenly, and obtain the second emulsion.

1.3 Heat the second emulsion to 80-90°C with stirring, keep the temperature at 80-90°C, add 0.2 parts of ammonium persulfate solution dropwise, and react for 2.5 hours after the addition is complete. Then, cool the reaction mixture to 50°C, add 0.12 parts of Rongbai and 0.08 parts of tert-butyl hydroperoxide, and keep the temperature for 2 hours. Then cool, adjust the pH value to about 7 with sodium bicarbonate, and discharge the material to obtain a binder emulsion.

Example 2 to Example 14

The same preparation method as in Example 1 was used, except that the type and amount of monomers added were different. The specific type and amount of monomers added, the molecular weight and glass transition temperature of the obtained polymer are shown in Table 1 below.

The difference between Example 2 and Example 1 is that vinyltrimethoxysilane is used instead of vinyltriethoxysilane in Example 1.

The difference between Example 3 and Example 1 is that methyl methacrylate is used instead of the ester monomers of isooctyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and hydroxyethyl acrylate used in Example 1.

The difference between Example 4 and Example 1 is that isooctyl acrylate is used instead of the ester monomers isooctyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and hydroxyethyl acrylate used in Example 1.

The difference between Examples 5 to 12 and Example 1 is that the added amounts of various monomers are different.

The difference between Example 13 and Example 1 is that acrylamide monomer is further added in step 1.2, specifically, 0.2 parts by weight of acrylamide monomer replaces 0.1 parts by weight of isooctyl acrylate and 0.1 parts by weight of butyl acrylate in Example 1.

The difference between Example 14 and Example 1 is that acrylamide and acrylonitrile monomers are further added in step 1.2, specifically, 0.2 parts by weight of acrylamide monomer and 0.1 parts by weight of acrylonitrile replace 0.1 parts by weight of isooctyl acrylate, 0.1 parts by weight of butyl acrylate and 0.1 parts by weight of methyl methacrylate in Example 1.

Comparative Example 1

The binder used in Comparative Example 1 is polyacrylic acid (PAA, weight average molecular weight 700,000, glass transition temperature 50° C.), a commonly used binder in the art.

Weight average molecular weight test method

The test was conducted using a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141). A polystyrene solution sample with a mass fraction of 3.0% was used as a reference, and a matching chromatographic column was selected (oily: Styragel HT5 DMF7.8*300mm+Styragel HT4). A 3.0% polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day for use. During the test, tetrahydrofuran was first drawn with a syringe and rinsed, and repeated several times. Then 5 ml of the experimental solution was drawn, the air in the syringe was removed, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the injection port. Data was obtained after the indication stabilized.

Glass transition temperature test method

The test was carried out using a differential scanning calorimeter (DSC), NETZSCH/DSC200F3/STA449F3.

Prepare the adhesive film and weigh about 30 mg of sample; gently place the alumina crucible with the sample on the sample position of the bracket, heat it to 60°C at a heating rate of 5°C/min, then cool it down to -30°C naturally, and then heat it to 60°C at the same heating rate for the second time. Collect data and draw heat flow curves. Determine the glass transition temperature based on the curve.

Table 1: Types of monomers added in Examples 1 to 14, amounts added (in parts by weight), and weight percentages (wt%) relative to the total monomer addition amount

Note: The symbol “/” indicates that the corresponding monomer is not added.

Here, “monomer (I)”, “monomer (II)”, “monomer (III)”, “monomer (IV)”, “monomer (V)” and “monomer (VI)” respectively represent the monomer corresponding to the structural unit represented by formula (I), the monomer corresponding to the structural unit represented by formula (II), the monomer corresponding to the structural unit represented by formula (III), the monomer corresponding to the structural unit represented by formula (IV), the monomer corresponding to the structural unit represented by formula (V) and the monomer corresponding to the structural unit represented by formula (VI).

The meanings of the abbreviations in Table 1 are as follows:

TEOS: Vinyltriethoxysilane

VTMOS: Vinyltrimethoxysilane

2-EHA: 2-ethylhexyl acrylate

EA: Ethyl acrylate

BA: Butyl acrylate

MMA: Methyl Methacrylate

HEA: Hydroxyethyl acrylate

Performance and test results

(I) Coating window test

The coating window refers to the maximum single-sided coating mass of the negative electrode slurry per unit area that can be achieved on the electrode without cracking the electrode.

Coating Window Test of Adhesive of Example 1

The negative electrode active material graphite, the conductive agent conductive carbon, the stabilizer sodium carboxymethyl cellulose CMC-Na, and the binder in Example 1 were weighed according to the weight ratio shown in Table 2 (the binder content in Example 1 was increased from 1.2% to 2.2%), and stirred in deionized water to obtain each negative electrode slurry. The solid content in each negative electrode slurry was 40%.

The prepared negative electrode slurry was uniformly coated on the negative electrode current collector copper foil by the same extrusion coating machine at a coating speed of 50 m/min. The specific coating method is as follows.

The coating weight was increased gradually with a single-sided coating weight of 160 mg/1540.25 ^mm2 and a unit increase of 10 mg/1540.25 ^mm2 . The coated negative electrode sheet was dried and then observed for cracking. If cracking occurred, the previous coating weight was taken as the maximum coating weight. If cracking did not occur, the coating weight was continued to be increased until cracking was observed. The maximum coating weight of the prepared negative electrode slurry was thus measured, and the test results are shown in Table 2.

Coating Window Test of Adhesives of Examples 1 to 14 and Comparative Example 1

The negative electrode slurry was prepared using the binders of Examples 1 to 14 and the binder of Comparative Example 1, and the maximum single-sided coating mass per unit area that can be achieved without cracking the pole piece was tested when the binder content was 1.2% and 2.2%, respectively. When the binder content was 1.2%, graphite, binder, CMC-Na and conductive agent conductive carbon were uniformly mixed according to the weight percentage of 97%: 1.2%: 1.2%: 0.6% and dispersed in deionized water to form a negative electrode slurry; when the binder content was 2.2%, graphite, binder, CMC-Na and conductive agent conductive carbon were uniformly mixed according to the weight percentage of 96%: 2.2%: 1.2%: 0.6% and dispersed in deionized water to form a negative electrode slurry. The solid content of the negative electrode slurry was 40%.

The prepared negative electrode slurry was uniformly coated on the negative electrode current collector copper foil by the same extrusion coater, and the coating speed was 50 m/min. The specific coating method was as described above. The maximum coating mass of the prepared negative electrode slurry was measured, and the test results are shown in Table 3.

(II) Negative electrode sheet adhesion and cohesion test

The negative electrode active material graphite, conductive agent conductive carbon, stabilizer sodium carboxymethyl cellulose CMC-Na, binder in Examples 1 to 14 and binder in Comparative Example 1 were respectively prepared into negative electrode slurries, wherein the weight percentages of graphite, binder, CMC-Na and conductive agent were 97%:1.2%:1.2%:0.6%, that is, the content of binder relative to the total solid content of the negative electrode slurry was 1.2%. The prepared negative electrode slurry was uniformly coated on the negative electrode current collector copper foil by the same coating machine, and the coating mass was 160mg/1540.25mm2 ^. After drying and cold pressing, the negative electrode sheet was obtained, and the bonding force and cohesion of the negative electrode sheet thus prepared were tested. The test results are shown in Table 3.

Negative electrode related parameter test

1. Negative electrode sheet adhesion test process

Equipment model: Zhongzhi testing tensile machine (model LXG2-LLCS-0009), specific test process:

Take the electrode to be tested, cut a 30mm wide * 90-150mm long adhesive strip with a blade, and stick the double-sided adhesive on the steel plate. The tape size is 20mm wide * 90-150mm long. Stick the cut electrode strip on the double-sided adhesive with the test side facing up. Roll three times in the same direction with a roller. Turn on the power of the tensile machine, fix the end of the steel plate without the electrode with the lower clamp, ensure that the steel plate is placed vertically with the base, and the bottom of the steel plate is flush with the base. Fold the electrode stuck on the steel plate upward and fix it with the upper clamp. Pre-pull about 5mm first, then "clear" the "force" and "displacement" parameters, so that the above two parameters are zero, click the start button to start the test, and then record the test results. Repeat the test three times, calculate the average value N1 (unit: N/20mm), and the final bonding force size = N1*50. The test results are shown in Table 3.

2. Negative electrode cohesion test process

Take the electrode to be tested, cut a 30mm wide * 90-150mm long adhesive strip with a blade, and stick the double-sided adhesive on the steel plate. The tape size is 20mm wide * 90-150mm long. Stick the cut electrode strip on the double-sided adhesive with the test surface facing up. Stick a low-viscosity green tape with a width of 20mm and a length greater than the length of the strip by 80-200mm evenly on the surface of the test surface, and roll it three times in the same direction with a roller. Turn on the power of the tensile testing machine, fix the end of the steel plate without the electrode with the lower clamp, ensure that the steel plate is placed vertically with the base, and the bottom of the steel plate is flush with the base. Fold the green glue with hard paper upwards and fix it with the upper clamp. Pre-pull about 5mm, then "clear" the "force" and "displacement" parameters. After the above two parameters are reset to zero, click the start button to start the test, and then record the test results. The test was repeated three times, and the average value N1 (unit: N/20 mm) was calculated, and the final cohesive force size = N1*50. The test results are shown in Table 3.

(III) Battery performance test

Preparation of negative electrode

The negative electrode active material graphite, the conductive agent conductive carbon, the stabilizer sodium carboxymethyl cellulose CMC-Na, the binder in Examples 1 to 14 and the binder in Comparative Example 1 were respectively prepared into negative electrode slurries, wherein the weight percentages of graphite, binder, CMC-Na and conductive agent were 97%:1.2%:1.2%:0.6%, that is, the content of the binder relative to the total solid content of the negative electrode slurry was 1.2%. The prepared negative electrode slurry was uniformly coated on the negative electrode current collector copper foil by the same coating machine, and the coating mass was 160mg/1540.25mm2, ^and the prepared negative electrode sheet was obtained after drying and cold pressing.

Preparation of positive electrode

The positive electrode active material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , the conductive agent Super-P and the binder polyvinylidene fluoride were stirred and dispersed in N-methylpyrrolidone at a mass ratio of 96:2:2 to prepare a positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector aluminum foil and compacted by a cold press to obtain a positive electrode sheet.

Preparation of electrolyte

Lithium salt LiPF ₆ is added to a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 35:65, and mixed evenly to obtain an electrolyte. The molar concentration of LiPF ₆ in the electrolyte is 1 mol/L.

Isolation film

The isolation membrane is a 12 μm thick polyethylene porous membrane.

Preparation of lithium-ion batteries

The prepared negative electrode sheet, the isolation film and the positive electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell, which is then inserted into a battery casing. After baking, liquid injection, standing, packaging, formation, capacity division and other processes, a lithium-ion battery is obtained.

Battery performance test

1. Battery DCR performance test

The test process of DCR@25℃ at room temperature is as follows: at 25℃, charge the battery to 4.3V at a constant current of 0.33C, then charge at a constant voltage of 4.3V to a current of 0.05C, let it stand for 60s, and then discharge at 0.33C to SOC=50% (remaining power). After standing for 5min, record the voltage V1, and then discharge at 3C for 30s, record the voltage V2, then the battery's DCR@25℃=(V1-V2)/3C.

The low temperature DCR @ -25 ℃ test process is as follows: At 25 ℃ (charging at room temperature), charge the battery to 4.3V at a constant current of 0.33C. Then charge at a constant voltage of 4.3V to a current of 0.05C, let it stand for 60s, and then discharge at 0.33C to SOC = 50%. After leaving it at -25℃ for 2h, record the voltage V3, and then discharge at 0.36C for 30s, record the voltage V4, then the battery's DCR@-25℃＝(V3-V4)/0.36C.

2. Battery cycle performance test

The cycle performance test process of lithium-ion batteries is as follows: the lithium-ion battery is charged to 4.25V at a constant current of 0.33C at a constant temperature of 25℃, 45℃, and 60℃, then charged at a constant voltage of 4.25V until the current drops to 0.05C, and then discharged to 2.8V at a constant current of 0.33C to obtain the first cycle discharge capacity (C ₀ ). This charge and discharge is repeated until the 500th cycle, and the discharge capacity after 500 cycles is obtained, which is recorded as C _n .

Capacity retention rate = discharge specific capacity after 500 cycles (C _n )/first cycle discharge specific capacity (C ₀ ).

3. Storage performance test of lithium-ion batteries

The storage performance test process of lithium-ion batteries is as follows:

The lithium-ion battery was charged at 25° C. at a constant current of 0.33 C to 4.25 V, then charged at a constant voltage until the current became 0.05 C, and then discharged at a constant current of 0.33 C to 2.8 V to obtain an initial discharge specific capacity (C ₀ ).

Afterwards, at 25°C, the battery was charged to 4.25V at a constant current of 0.33C, and then charged at a constant voltage until the current became 0.05C, and the battery was placed in a furnace at a constant temperature of 45°C. After 120 days of storage, the battery was taken out and left to stand at 25°C for 12 hours, and the capacity was tested, and the battery was discharged to 2.8V at a constant current of 0.33C to obtain the discharge specific capacity ( _Cn ) after 120 days of storage.

Capacity retention rate = discharge specific capacity after storage for 120 days (C _n )/initial discharge specific capacity (C ₀ ).

The test results of the above battery performance are shown in Table 4.

Table 2 shows that the negative electrode slurry was made using the binder of Example 1, and the maximum coating mass per unit area that can be achieved without cracking the electrode sheet was tested when the binder content increased from 1.2% to 2.2%, which is referred to as the coating window.

Table 2: Negative electrode slurry prepared using the binder of Example 1 and its coating window

The test results are shown in the last column of Table 2. The results show that when the binder content changes from 1.2% to 2.2%, the maximum coating mass basically shows an increasing trend with the increase of the binder content, specifically from 210mg/ ^1540.25mm2 to 290mg/ ^1540.25mm2 . This shows that within the tested binder content range, the maximum coating mass is related to the binder content in the negative electrode slurry, and the higher the binder content, the greater the maximum coating mass that can be achieved.

Table 3 uses the binders of Examples 1 to 14 and the binder of Comparative Example 1 to make negative electrode slurries, and tests the maximum single-sided coating mass (i.e., coating window) per unit area that can be achieved without cracking the pole piece when the binder content is 1.2% and 2.2%, respectively. When the binder content is 1.2%, graphite, binder, CMC-Na and conductive agent are uniformly mixed according to the weight percentage of 97%: 1.2%: 1.2%: 0.6% and dispersed in deionized water to form a negative electrode slurry; when the binder content is 2.2%, graphite, binder, CMC-Na and conductive agent are uniformly mixed according to the weight percentage of 96%: 2.2%: 1.2%: 0.6% and dispersed in deionized water to form a negative electrode slurry. Among them, the binder of Comparative Example 1 is a commonly used binder polyacrylic acid (PAA) in the art.

In Table 3, the binders of Examples 1 to 14 and the binder of Comparative Example 1 were used to prepare negative electrode slurries, wherein the binder content was 1.2%. Negative electrode sheets were prepared with a coating mass of 160 mg/1540.25 mm ² , and the bonding force and cohesion of the negative electrode sheets prepared in this way were tested.

Table 3: Coating window of each binder and the bonding and cohesive strength of the negative electrode sheet

It can be seen from Table 3 that compared with the binder used in Comparative Example 1, the maximum coating mass of the negative electrode slurry prepared using the binder of Examples 1 to 14 of the present disclosure on the current collector is increased. Similarly, compared with the binder used in Comparative Example 1, the bonding force and cohesion of the negative electrode sheets prepared using the binder of Examples 1 to 14 of the present disclosure are increased to varying degrees. These results show that the binder of the present disclosure can reduce or eliminate stress accumulation in the electrode sheet, enhance the bonding force and cohesion of the electrode sheet, and thus improve the thick coating performance of the negative electrode slurry on the current collector, so as to achieve the electrode sheet without cracking when thickly coated.

Table 4 shows the electrochemical performance test of the secondary battery.

Table 4: Electrochemical performance test of secondary batteries

As can be seen from Table 4, compared with the battery using the binder of Comparative Example 1, the batteries using the binders of Examples 1 to 14 of the present disclosure have better DC impedance at 25°C and -25°C, capacity retention after 500 cycles at 25°C, 45°C and 60°C, and capacity retention after 120 days of storage. This shows that the use of the binder of the present disclosure helps to reduce DC impedance and increase electron migration speed. rate, thereby improving the battery's cycle performance and storage performance.

According to the above results, compared with the adhesive of comparative example 1, the adhesives of embodiments 1 to 14 of the present disclosure have excellent bonding strength, and thus the maximum coating quality of the pole pieces prepared using these adhesives is higher, and thick coating can be achieved without cracking, thereby improving the battery energy density.

In terms of electrochemical performance, the DCR of the battery prepared by using the binder of Examples 1 to 14 of the present disclosure is significantly improved at room temperature and low temperature, which can improve the charging and discharging efficiency of the battery and increase the service life of the battery. The 500 cycles of room temperature and high temperature cycles and the 120-day high temperature storage capacity retention rate are better than the control example, which broadens the practical application scenarios of the battery.

It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and embodiments having substantially the same structure as the technical idea and exerting the same effects within the scope of the technical solution of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main purpose of the present disclosure, various modifications that can be thought of by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

Industrial Applicability

The present disclosure provides a binder in an embodiment, the binder includes a polymer, the polymer includes a structural unit represented by formula (I), a structural unit represented by formula (II), and a structural unit represented by formula (III), and at least one selected from a structural unit represented by formula (IV), a structural unit represented by formula (V), or a structural unit represented by formula (VI). Through the joint action of the above structural units, the binder has enhanced bonding force, can reduce or eliminate stress accumulation in the pole piece, improve the flexibility of the pole piece, prevent the pole piece from cracking when thickly coated, and increase the single-sided coating quality of the negative electrode slurry per unit area on the pole piece. Thus, for a battery prepared using the binder, the DC impedance of the battery can be reduced, and the energy density, cycle performance, and storage performance of the battery can be improved.

Claims (14)

A binder comprising a polymer, the polymer comprising a structural unit represented by formula (I), a structural unit represented by formula (II), a structural unit represented by formula (III), and at least one selected from a structural unit represented by formula (IV), a structural unit represented by formula (V), or a structural unit represented by formula (VI);
in, R1, R2, R4, R6, and R7 are independently selected from at least one of H, unsubstituted or substituted C ₁ -C ₂₀ alkyl, and unsubstituted or substituted C ₁ -C ₂₀ alkoxy, wherein the substituents in the substituted C ₁ -C ₂₀ alkyl and the substituents in the substituted C ₁ -C ₂₀ alkoxy are independently selected from at least one of hydroxyl, halogen, and amino; R3 and R5 are independently selected from at least one of unsubstituted or substituted C ₁ -C ₂₀ alkyl groups, and the substituent group in the substituted C ₁ -C ₂₀ alkyl group is selected from at least one of hydroxyl, halogen or amino. The binder according to claim 1, wherein R1, R2, R4, R6, and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl; and/or, R3 is at least one selected from unsubstituted C ₁ -C ₄ alkyl groups; And/or, R5 is at least one selected from unsubstituted or substituted C ₁ -C ₈ alkyl groups, and the substituent group in the substituted C ₁ -C ₈ alkyl group is hydroxyl group. The binder according to claim 1 or 2, wherein the polymer comprises at least one structural unit represented by formula (IV), wherein R4 is selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent in the substituted C ₁ -C ₈ alkyl is hydroxyl. The binder according to any one of claims 1 to 3, wherein the polymer comprises at least one structural unit represented by formula (IV) and at least one structural unit represented by formula (V), wherein R4 and R6 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent in the substituted C ₁ -C ₈ alkyl is hydroxyl. The binder according to any one of claims 1 to 4, wherein the polymer comprises at least one structural unit represented by formula (IV), at least one structural unit represented by formula (V) and at least one structural unit represented by formula (VI), wherein R4, R6 and R7 are independently selected from at least one of H and unsubstituted C ₁ -C ₄ alkyl, R5 is selected from at least one of unsubstituted or substituted C ₁ -C ₈ alkyl, and the substituent in the substituted C ₁ -C ₈ alkyl is hydroxyl. The binder according to any one of claims 1 to 5, wherein, in the polymer, the mass percentage of the structural unit represented by formula (I) is 4.5% to 8%, the mass percentage of the structural unit represented by formula (II) is 12% to 21%, the mass percentage of the structural unit represented by formula (III) is 3% to 6.5%, and the mass percentage of at least one selected from the structural unit represented by formula (IV), the structural unit represented by formula (V) or the structural unit represented by formula (VI) is 68% to 77%. The binder according to any one of claims 1 to 6, wherein the glass transition temperature of the polymer is -15 to 15°C. The binder according to any one of claims 1 to 7, wherein the weight average molecular weight of the polymer is 400,000 to 1,000,000. A method for preparing the binder according to any one of claims 1 to 8, the method comprising: Adding a monomer corresponding to the structural unit represented by formula (I) and a monomer corresponding to the structural unit represented by formula (II) into a solvent, reacting in the presence of a first surfactant and a first initiator to obtain a first emulsion; Adding a monomer corresponding to the structural unit represented by formula (III) and at least one monomer selected from the group consisting of a monomer corresponding to the structural unit represented by formula (IV), a monomer corresponding to the structural unit represented by formula (V), and a monomer corresponding to the structural unit represented by formula (VI) to the first emulsion, and reacting in the presence of a second surfactant to obtain a second emulsion; The second emulsion is heated to react in the presence of a second initiator to obtain a binder. A negative electrode plate, comprising a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises the binder described in any one of claims 1 to 8, or a binder prepared by the method described in claim 9. The negative electrode plate according to claim 10, wherein the mass percentage of the binder is 1.2% to 2.2% based on the total mass of the negative electrode film layer. The negative electrode plate according to claim 10 or 11, wherein the negative electrode film layer further comprises a stabilizer, and the stabilizer comprises at least one of sodium carboxymethyl cellulose, sodium alginate or sodium cyclodextrin. A battery comprising the negative electrode sheet according to any one of claims 10 to 12. An electrical device comprising the battery according to claim 13.