Adhesive, negative pole piece, battery and electric equipment

Abstract

The invention relates to an adhesive, a negative pole piece, a battery and electric equipment. The adhesive comprises an acrylate-maleimide-acrylate-acrylonitrile copolymer, and the molar fraction n1 of a maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer is greater than or equal to 1% and less than or equal to 4%.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly relates to an adhesive, a negative electrode sheet, a battery, and an electrical device. Background Art

[0002] In an ion battery, the slurry of the negative electrode active material layer is commonly mixed with a sodium carboxymethyl cellulose (CMC) adhesive, a polyacrylic acid (PAA) adhesive, and a styrene-butadiene rubber latex (SBR) adhesive to bond the active material. Among them, the sodium carboxymethyl cellulose adhesive has good dispersibility and thickening properties, which is beneficial to improving the stability of the negative electrode sheet and the cycle performance of the battery. However, due to the influence of the molecular weight, concentration of the sodium carboxymethyl cellulose adhesive or its compatibility with other materials, the prepared negative electrode sheet is relatively brittle, and the flexibility of the negative electrode sheet is poor, thereby affecting the overall performance of the battery. Summary of the Invention

[0003] In view of this, the present application provides an adhesive, a negative electrode sheet, a battery, and an electrical device. When the adhesive is applied to the negative electrode sheet, the negative electrode sheet has good flexibility and is not easily swollen.

[0004] The present application provides an adhesive, which includes an acrylate-maleimide-acrylate-acrylonitrile copolymer. The range of the molar fraction n1 of the maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 1% ≤ n1 ≤ 4%.

[0005] Further, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction n1 of the maleimide unit and the molar fraction n2 of the acrylate unit satisfy the relationship: 4 ≤ n2 / n1 ≤ 60.

[0006] Further, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the acrylate unit is greater than the molar fraction of the acrylate unit, and the molar fraction of the acrylate unit is greater than the molar fraction of the acrylonitrile unit.

[0007] Further, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m1 of the maleimide unit is: 10% ≤ m1 ≤ 20%, and the range of the mass fraction m2 of the acrylate unit is: 30% ≤ m2 ≤ 60%.

[0008] Further, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m3 of the acrylate unit is: 20% ≤ m3 ≤ 40%, and the range of the mass fraction m4 of the acrylonitrile unit is: 3% ≤ m4 ≤ 5%.

[0009] Furthermore, the range of the weight-average molecular weight M of the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 5×10 4 g / mol ≤ M ≤ 20×10 4 g / mol.

[0010] Furthermore, the range of the swelling ratio α of the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 80% ≤ α ≤ 120%.

[0011] Furthermore, the adhesive is an aqueous adhesive, the adhesive further includes water, the acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water, and the pH value of the adhesive at 25 °C satisfies the range: 7.5 ≤ pH ≤ 8.5.

[0012] Furthermore, the range of the solid content β of the adhesive is: 1% ≤ β ≤ 5%, where the solid content of the adhesive is the mass fraction of the acrylate-maleimide-acrylate-acrylonitrile copolymer in the adhesive.

[0013] Furthermore, when the solid content β of the adhesive is 2%, the range of the viscosity μ of the adhesive is: 500 mPa·s ≤ μ ≤ 10000 mPa·s.

[0014] The present application provides a negative electrode plate, which includes: a current collector layer and an active material layer. The active material layer is disposed on at least one side of the current collector layer. The active material layer includes an active material and the adhesive provided by the present application, and the adhesive is used to bond the active material.

[0015] Furthermore, the active material layer further includes a polyacrylic acid binder and a styrene-butadiene rubber binder. In the active material layer, the range of the mass fraction W1 of the adhesive is: 0.5% ≤ W1 ≤ 2%, the range of the mass fraction W2 of the polyacrylic acid binder is: 0% ≤ W2 ≤ 2%, and the range of the mass fraction W3 of the styrene-butadiene rubber binder is: 0.5% ≤ W3 ≤ 1%.

[0016] The present application provides a battery, which includes: the negative electrode plate provided by the present application, a separator, a positive electrode plate, and an electrolyte. The separator is located on one side of the negative electrode plate; the positive electrode plate is located on the side of the separator away from the negative electrode plate; the electrolyte is used to infiltrate at least part of the negative electrode plate, the separator, and the positive electrode plate.

[0017] The present application provides an electrical device, which includes: a device body and the battery provided by the present application, and the battery powers the electrical device.

[0018] In the present application, the adhesive includes an acrylate-maleimide-acrylate-acrylonitrile copolymer, and the acrylate-maleimide-acrylate-acrylonitrile copolymer includes an acrylate unit and a maleimide unit, and the acrylate unit forms a polyacrylate segment, and the maleimide unit forms a polymaleimide segment. Among them, the acrylate monomer is a flexible monomer, so that the acrylate-maleimide-acrylate-acrylonitrile copolymer has good flexibility, which is beneficial to improve the flexibility of the adhesive applied to the negative electrode. But relatively speaking, the molecular chain of the flexible monomer has a higher conformational freedom, and the internal rotation barrier of its single bond is lower. This flexibility allows the molecular chain to be more freely unfolded and stretched in the solvent, so that the degree of swelling of the polyacrylate segment is greater. The maleimide monomer has good rigidity, so that the polymaleimide chain segment is more resistant to deformation, which is beneficial to slow down the swelling degree of the acrylate-maleimide-acrylate-acrylonitrile copolymer, so that the acrylate-maleimide-acrylate-acrylonitrile copolymer has good flexibility and deformation resistance, so as to improve the structural stability of the negative electrode when the adhesive is applied to the negative electrode. In addition, the acrylate-maleimide-acrylate-acrylonitrile copolymer also includes acrylate units and acrylonitrile units. The acrylate forms a polyacrylate chain segment, and the polyacrylate chain segment is obtained by alkalization after the polymerization reaction of the acrylic acid monomer. In other words, the acrylic acid monomer first forms polyacrylic acid through polymerization reaction, and then alkalizes with NaOH or LiOH to obtain the polyacrylic acid chain segment. Polyacrylic acid is a weakly acidic polyelectrolyte. The carboxyl groups on its molecular chain can be partially or completely ionized by adding NaOH or LiOH to form a negatively charged polyion -COO - and H + , while acrylonitrile has a polar group -CN. Acrylonitrile will form -COO in an alkaline solution. - , then the acrylate-maleimide-acrylate-acrylonitrile copolymer is a polymer with ionizable groups on the main chain or side chain, which will ionize polymer ions and small molecule ions with opposite charges, and has the dual structural characteristics of ionization of polymer long chains and small molecule electrolytes. The molecules inside the acrylate-maleimide-acrylate-acrylonitrile copolymer are affected by electrostatic repulsion, the molecular chain stretches and makes the adhesive have a higher viscosity, so as to facilitate the bonding of the active material. In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in the present application, the polyacrylate segment and the polymaleimide segment are used to improve the flexibility and structural stability of the negative electrode when the adhesive is applied to the negative electrode, and the polyacrylate segment and the acrylonitrile segment make the adhesive have better bonding properties to the active material.

[0019] Further, when the molar fraction n1 of maleimide units in the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range of 1% ≤ n1 ≤ 4%, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of maleimide units is within a reasonable range. The polyimide chain segments formed by maleimide units can improve the deformation resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer, avoid excessive swelling of the adhesive, and improve the structural stability of the negative electrode sheet when the adhesive is applied to the negative electrode sheet. In addition, it can also prevent the excessive rigidity of the acrylate-maleimide-acrylate-acrylonitrile copolymer due to too many maleimide units, enabling the negative electrode sheet to maintain good flexibility and improving the cycle stability of the battery when the negative electrode sheet is applied to the battery. When the molar fraction of maleimide units is too large, the maleimide monomer is a rigid monomer, which weakens the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer. When the adhesive is applied to the negative electrode sheet, the negative electrode sheet may become too brittle and hard, ultimately affecting the cycle stability of the battery. When the molar fraction of maleimide units is too small, the polyimide chain segments are difficult to improve the deformation resistance and electrolyte resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer, resulting in easy swelling of the adhesive and reducing the viscosity of the adhesive for bonding the active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for implementation will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 Partial cross-sectional structure schematic diagram of a negative electrode sheet according to an embodiment of the present application;

[0022] Figure 2 Infrared spectrum diagram of an acrylate-maleimide-acrylate-acrylonitrile copolymer according to an embodiment of the present application;

[0023] Figure 3 Partial cross-sectional structure schematic diagram of a battery according to an embodiment of the present application;

[0024] Figure 4 Structural schematic diagram of an electrical device according to an embodiment of the present application;

[0025] Figure 5 Circuit block diagram of an electrical device according to an embodiment of the present application.

[0026] Description of the reference numerals in the drawings:

[0027] 100 - Adhesive, 200 - Negative electrode plate, 210 - Current collector layer, 220 - Active material layer, 300 - Battery, 310 - Separator, 320 - Positive electrode plate, 330 - Electrolyte, 400 - Electrical device, 410 - Device body. Detailed implementation manners

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0029] The terms "first", "second", etc. in the specification and claims of the present application and the above - mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non - exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0030] Referring to "embodiment" or "implementation manner" herein means that a specific feature, structure or characteristic described in connection with the embodiment or implementation manner can be included in at least one embodiment of the present application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0031] In the slurry of the negative electrode active material layer in an ion battery, sodium carboxymethyl cellulose (CMC) binder, polyacrylic acid (PAA) binder, and styrene-butadiene rubber (SBR) binder are commonly mixed to bond the active material. Among them, the sodium carboxymethyl cellulose binder has good dispersibility and thickening properties, which is beneficial to improving the stability of the negative electrode sheet and the cycling performance of the battery. However, due to the influence of the molecular weight, concentration of the sodium carboxymethyl cellulose binder, or its compatibility with other materials, some problems may be encountered with the sodium carboxymethyl cellulose binder during the battery preparation process, such as a long powder dissolution time and the resulting electrode sheet being relatively brittle. In addition, although the polyacrylic acid binder has excellent mechanical properties, due to its molecular structure and processing conditions, the polyacrylic acid binder may become hard and brittle during drying and heat treatment, which also affects the flexibility of the negative electrode sheet and ultimately the overall performance of the battery. Further, when the flexibility of the negative electrode sheet is improved, a problem of relatively large swelling may occur, thereby reducing the structural stability of the negative electrode sheet when the binder is applied to the negative electrode sheet.

[0032] Please refer to Figure 1 , the present application provides a binder 100, and the binder 100 includes an acrylate-maleimide-acrylate-acrylonitrile copolymer, and the range of the molar fraction n1 of the maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 1% ≤ n1 ≤ 4%.

[0033] Specifically, the value of the molar fraction n1 of the maleimide unit can be, but is not limited to, 1%, 1.1%, 1.3%, 1.5%, 1.8%, 2%, 2.2%, 2.3%, 2.5%, 2.6%, 2.8%, 3%, 3.2%, 3.5%, 3.7%, 3.8%, and 4%, etc.

[0034] It can be understood that the acrylate-maleimide-acrylate-acrylonitrile copolymer is a random copolymer of a polyacrylate chain segment, a polymaleimide chain segment, a polyacrylate chain segment, and an acrylonitrile chain segment. In other words, the acrylate-maleimide-acrylate-acrylonitrile copolymer includes a polyacrylate chain segment, a polymaleimide chain segment, a polyacrylate chain segment, and an acrylonitrile chain segment, and the polyacrylate chain segment, the polymaleimide chain segment, the polyacrylate chain segment, and the acrylonitrile chain segment form a random copolymer.

[0035] It can be understood that the acrylonitrile chain segment is an oligomer formed by acrylonitrile units.

[0036] It can be understood that the binder 100 is an aqueous binder 100, and the binder 100 further includes water, and the acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water.

[0037] Understandably, the adhesive 100 is applied to the negative electrode plate 200. During the preparation process of the negative electrode plate 200, the adhesive 100 is mixed with the active material to form a slurry, and the slurry is coated on the current collector layer 210 and finally forms the active material layer 220.

[0038] Understandably, the molar fraction of the maleimide unit is the ratio of the amount of substance of the maleimide unit to the sum of the amounts of substance of acrylate, maleimide, acrylate salt, and acrylonitrile.

[0039] Understandably, the function of the maleimide unit is to improve the electrolyte resistance 330 performance, fatigue resistance, and deformation resistance of the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, and can prevent the cracking of the negative electrode plate 200 when the adhesive 100 is applied to the negative electrode plate 200.

[0040] In this embodiment, the adhesive 100 includes an acrylate-maleimide-acrylate salt-acrylonitrile copolymer. The acrylate-maleimide-acrylate salt-acrylonitrile copolymer includes acrylate units and maleimide units, and the acrylate units form a polyacrylate chain segment, and the maleimide units form a polymaleimide chain segment. Among them, the acrylate monomer is a flexible monomer, so that the acrylate-maleimide-acrylate salt-acrylonitrile copolymer has good flexibility, which is beneficial to improving the flexibility of the adhesive 100 applied to the negative electrode plate 200. However, relatively speaking, the molecular chain of the flexible monomer has a high conformational freedom, and the internal rotation barrier of its single bond is low. This flexibility enables the molecular chain to unfold and stretch more freely in the solvent, resulting in a larger swelling degree of the polyacrylate chain segment. The maleimide monomer has good rigidity, so that the polymaleimide chain segment is more resistant to deformation, which is beneficial to slowing down the swelling degree of the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, making the acrylate-maleimide-acrylate salt-acrylonitrile copolymer have both good flexibility and deformation resistance, so as to improve the structural stability of the negative electrode plate 200 when the adhesive 100 is applied to the negative electrode plate 200. In addition, the acrylate-maleimide-acrylate salt-acrylonitrile copolymer also includes acrylate units and acrylonitrile units. The acrylate salt forms a polyacrylate salt chain segment, and the polyacrylate salt chain segment is obtained by alkalization treatment after the acrylate monomer undergoes a polymerization reaction. In other words, the acrylate monomer first forms polyacrylic acid through a polymerization reaction. Polyacrylic acid has a polar group -COOH, and polyacrylic acid is then alkalized with NaOH or LiOH to obtain a polyacrylate salt chain segment. Polyacrylic acid is a weak acidic polyelectrolyte, and the carboxyl groups on its molecular chain can be partially or completely ionized when adding NaOH or LiOH to form polyions -COO with negative charges.- and H + , while acrylonitrile has a polar group -CN, and acrylonitrile segments will form -COO in an alkaline solution - , then the acrylate-maleimide-acrylate-acrylonitrile copolymer is a polymer with ionizable groups on the main chain or side chain, which will ionize into polymer ions and small molecule ions with opposite charges, having the dual structural characteristics of both polymer long chains and small molecule electrolyte ionization. The intermolecular electrostatic repulsion in the acrylate-maleimide-acrylate-acrylonitrile copolymer causes the molecular chains to stretch, making the adhesive 100 have a relatively high viscosity to facilitate the adhesion of the active material. In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in this embodiment, the polyacrylate segments and the polymaleimide segments are used to improve the flexibility and structural stability of the negative electrode sheet 200 when the adhesive 100 is applied to the negative electrode sheet 200, and the acrylate segments and acrylonitrile segments make the adhesive 100 have good adhesion performance to the active material.

[0041] Furthermore, when the molar fraction n1 of the maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range 1% ≤ n1 ≤ 4%, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the maleimide unit is within a reasonable range. The polymaleimide segments formed by the maleimide units can not only improve the deformation resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer to avoid excessive swelling of the adhesive 100 and improve the structural stability of the negative electrode sheet 200 when the adhesive 100 is applied to the negative electrode sheet 200. In addition, it can also prevent the rigidity of the acrylate-maleimide-acrylate-acrylonitrile copolymer from being too large due to excessive maleimide units, enabling the negative electrode sheet 200 to maintain good flexibility and improving the cycle stability of the battery 300 when the negative electrode sheet 200 is applied to the battery 300. When the molar fraction of the maleimide unit is too large, the maleimide monomer is a rigid monomer, which weakens the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer. When the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 may be too brittle and hard, ultimately affecting the cycle stability of the battery 300. When the molar fraction of the maleimide unit is too small, it is difficult for the polymaleimide segments to improve the deformation resistance and electrolyte resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer, resulting in easy swelling of the adhesive 100 and reducing the viscosity of the adhesive 100 for adhering the active material.

[0042] Please refer to Figure 2, optionally, the acrylate-maleimide-acrylate-acrylonitrile copolymer is analyzed by infrared spectroscopy on the surface, and the C=O stretching vibration peak at 1730 cm-1 and the C-O stretching vibration peak at 1110 cm-1 of the polyacrylate chain segment have strong absorption intensities; secondly, the characteristic peaks of the polyacrylate chain segment, the C=O stretching vibration peak at 1710 cm-1, the C-O stretching vibration peak at 1260 cm-1, and the OH stretching vibration peak at 3200 - 3400 cm-1 also show strong absorption; the -CN characteristic peak of the polymaleimide chain segment at 1380 cm-1 and the weak C≡N characteristic peak of the acrylonitrile chain segment at 2240 cm-1 can also be observed, thereby proving that the acrylate-maleimide-acrylate-acrylonitrile copolymer is a random copolymer of the polyacrylate chain segment, the polyacrylate chain segment, the polymaleimide chain segment, and the acrylonitrile chain segment.

[0043] Optionally, in some embodiments, the molecular weight of the maleimide monomer used to form the acrylate-maleimide-acrylate-acrylonitrile copolymer is 1000 g / mol to 2000 g / mol, and the maleimide monomer is a modified maleimide monomer, that is, a monomer derived on the basis of maleimide, which is beneficial to improving the electrolyte resistance performance of the polymaleimide chain segment formed by the maleimide unit, thereby improving the electrolyte resistance performance of the acrylate-maleimide-acrylate-acrylonitrile copolymer. The modified maleimide monomer can be, but is not limited to, MAL-PEG-MAL, that is, a bismaleimide polyethylene glycol compound, and its chemical structure contains two maleimide groups (MAL) and a polyethylene glycol (PEG) chain.

[0044] It can be understood that maleimide with a molecular weight of 1000 g / mol to 2000 g / mol undergoes free radical copolymerization with monomers such as acrylic acid, acrylate, and acrylonitrile to generate an acrylate-maleimide-acrylate-acrylonitrile copolymer. The carbon-carbon double bonds in each monomer participate in free radical polymerization, and the active functional group of maleimide for free radical polymerization is the olefin double bond on the imide ring, and the imide structure does not participate in the reaction.

[0045] Optionally, the acrylate monomer used to form the acrylate-maleimide-acrylate-acrylonitrile copolymer can be, but is not limited to, methyl acrylate and butyl acrylate.

[0046] In some embodiments, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction n1 of the maleimide unit and the molar fraction n2 of the acrylate unit satisfy the relationship: 4 ≤ n2 / n1 ≤ 60.

[0047] Specifically, the value of n2 / n1 can be, but is not limited to, 4, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, 52, 53, 55, 58, 60, etc.

[0048] It can be understood that the molar fraction of the acrylate unit is the ratio of the amount of substance of the acrylate unit to the total amount of substance of acrylate, maleimide, acrylate salt, and acrylonitrile.

[0049] In this embodiment, the adhesive 100 includes an acrylate-maleimide-acrylate salt-acrylonitrile copolymer. The acrylate unit and the maleimide unit cooperate with each other to make the adhesive 100 have good flexibility and resistance to deformation, so as to improve the structural stability of the negative electrode tab 200 when the adhesive 100 is applied to the negative electrode tab 200. When the molar fraction n1 of the maleimide unit and the molar fraction n2 of the acrylate unit satisfy the relational expression 4 ≤ n2 / n1 ≤ 60, in the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, the molar fractions of the maleimide unit and the acrylate unit are both within a reasonable range. On the one hand, in the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, the molar fraction of the acrylate unit is relatively large, so the main component of the acrylate-maleimide-acrylate salt-acrylonitrile copolymer is the polyacrylate chain segment. The polyacrylate chain segment can improve the flexibility of the adhesive 100 when applied to the negative electrode tab 200, which is beneficial to adapting to the volume expansion of the active material during charge and discharge, thereby reducing the shedding of the active material and improving the cycle stability of the battery 300. Moreover, the acrylate unit is an ester, which shows good wetting performance for active materials such as graphite, which is beneficial to improving the affinity of the adhesive 100 for the active material, thereby improving the adhesion effect of the adhesive 100 on the active material. On the other hand, the polyimide chain segment formed by the maleimide cooperates with the polyacrylate chain segment to prevent the acrylate-maleimide-acrylate salt-acrylonitrile copolymer from swelling too much. In other words, the polyimide chain segment can improve the electrolyte 330 resistance performance of the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, so that the adhesive 100 is resistant to deformation, can adapt to the volume expansion of the active material during charge and discharge, and improve the structural stability of the negative electrode tab 200 when the adhesive 100 is applied to the negative electrode tab 200.

[0050] Understandably, when the negative electrode sheet 200 is applied to the negative electrode sheet 200, the negative electrode sheet 200 has good flexibility. During the charge and discharge process of the battery 300, the negative electrode sheet 200 with good flexibility can adapt to the volume expansion and contraction of the active material, reducing problems such as fracture of the negative electrode sheet 200 and shedding of the active material caused by stress concentration, thereby enabling the battery 300 to have good cycle stability.

[0051] Optionally, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction n2 of the acrylate unit ranges from: 15% ≤ n2 ≤ 60%.

[0052] Specifically, the value of the molar fraction n2 of the acrylate unit can be, but is not limited to, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 36%, 38%, 39%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, and 60%, etc.

[0053] In this embodiment, when the molar fraction of the acrylate unit satisfies the range of 15% ≤ n2 ≤ 60%, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the acrylate unit is within a reasonable range. The polyacrylate segment formed by the acrylate unit can improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer, so that when the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 has good flexibility, which is beneficial to adapting to the volume expansion of the active material during charge and discharge, thereby reducing the shedding of the active material and improving the cycle stability of the battery 300. When the molar fraction of the acrylate unit is too large, although the polyacrylate segment can improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer and its affinity with the active material, correspondingly, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the mass fractions of other components such as the maleimide unit, acrylate unit and acrylonitrile unit are too small. If the mass fraction of the maleimide unit is too small, it may lead to poor electrolyte 330 resistance performance of the adhesive 100, that is, when the adhesive 100 is applied to the negative electrode sheet 200, the swelling degree of the negative electrode sheet 200 may be relatively large. If the mass fractions of the acrylate unit and the acrylonitrile unit are too small, it may lead to poor dispersion performance of the adhesive 100, which is not conducive to the uniform dispersion of the adhesive 100 and the active material, thereby weakening the adhesion performance of the adhesive 100 to the active material. When the molar fraction of the acrylate unit is too small, the polyacrylate segment is difficult to improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer. When the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 is relatively brittle in flexibility and is prone to problems such as fracture of the negative electrode sheet 200 and shedding of the active material during charge and discharge, reducing the cycle stability of the battery 300.

[0054] In some embodiments, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the acrylate unit is greater than the molar fraction of the acrylate unit, and the molar fraction of the acrylate unit is greater than the molar fraction of the acrylonitrile unit.

[0055] It can be understood that in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the acrylate unit is the largest.

[0056] It can be understood that the molar fraction of the acrylate unit is the ratio of the amount of substance of the acrylate unit to the sum of the amounts of substance of the acrylate, maleimide, acrylate and acrylonitrile.

[0057] Understandably, the molar fraction of the acrylonitrile unit is the ratio of the amount of substance of the acrylonitrile unit to the total amount of substance of the acrylate, maleimide, acrylate salt, and acrylonitrile. In the acrylate-maleimide-acrylate salt-acrylonitrile copolymer provided in this embodiment, the molar fraction of the acrylate unit is greater than the molar fraction of the acrylate salt unit, and the molar fraction of the acrylate unit is greater than the molar fraction of the acrylonitrile unit. Then, in the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, the polyacrylate chain segment is the main component, and the components of the polymaleimide chain segment, polyacrylate salt chain segment, and acrylonitrile chain segment are all within a reasonable range. The polyacrylate salt chain segment and polyacrylate chain segment endow the adhesive 100 with excellent dispersion performance, so that in the slurry formed by the adhesive 100 and the active material, the adhesive 100 can be uniformly dispersed around the active material and effectively bond the active material, and finally the adhesive 100 has excellent adhesion to the active material. The maleimide unit and acrylate unit cooperate with each other, so that the acrylate-maleimide-acrylate salt-acrylonitrile copolymer has both high flexibility and deformation resistance, and finally improves the flexibility and structural stability of the adhesive 100 when applied to the negative electrode sheet 200.

[0058] In some embodiments, in the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, the mass fraction m1 of the maleimide unit ranges from 10% ≤ m1 ≤ 20%. In other words, the mass fraction m1 of the polymaleimide chain segment ranges from 10% ≤ m1 ≤ 20%.

[0059] Specifically, the value of the mass fraction m1 of the maleimide unit can be, but is not limited to, 10%, 10.2%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, and 20%, etc.

[0060] Understandably, in the acrylate-maleimide-acrylate salt-acrylonitrile copolymer, the maleimide unit forms a polymaleimide chain segment.

[0061] In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in this embodiment, when the mass fraction m1 of the maleimide unit satisfies the range of 10% ≤ m1 ≤ 20%, the mass fraction of the polymaleimide segment is within a reasonable range. The polymaleimide segment can not only improve the deformation resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer to avoid excessive swelling of the adhesive 100, but also improve the structural stability of the negative electrode plate 200 when the adhesive 100 is applied to the negative electrode plate 200. In addition, it can also prevent the excessive mass content of the polymaleimide segment from making the acrylate-maleimide-acrylate-acrylonitrile copolymer too rigid, so that the negative electrode plate 200 can maintain good flexibility and improve the cycle stability of the battery 300 when the negative electrode plate 200 is applied to the battery 300. When the mass fraction of the maleimide unit is too large, correspondingly, there are too many maleimide monomers in the prepared polymaleimide segment. Since the maleimide monomer is a rigid monomer, the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer is weakened, which may cause the negative electrode plate 200 to be too brittle and hard when the adhesive 100 is applied to the negative electrode plate 200, and ultimately affect the cycle stability of the battery 300. When the mass fraction of the maleimide unit is too small, it is difficult for the polymaleimide segment to improve the deformation resistance and electrolyte resistance of the acrylate-maleimide-acrylate-acrylonitrile copolymer, resulting in easy swelling of the adhesive 100 and a decrease in the viscosity of the adhesive 100 for bonding the active material.

[0062] In some embodiments, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m2 of the acrylate unit is: 30% ≤ m2 ≤ 60%. In other words, the range of the mass fraction m2 of the polyacrylate segment is: 30% ≤ m2 ≤ 60%.

[0063] It can be understood that in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the acrylate unit forms a polyacrylate segment.

[0064] Specifically, the value of the mass fraction m2 of the acrylate unit can be, but is not limited to, 30%, 32%, 33%, 35%, 38%, 40%, 42%, 43%, 45%, 48%, 50%, 52%, 53%, 55%, 57%, 59%, 60%, etc.

[0065] In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in this embodiment, when the mass fraction m2 of the acrylate unit satisfies the range of 30% ≤ m2 ≤ 60%, the mass fraction of the polyacrylate chain segment is within a reasonable range. The polyacrylate chain segment can improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer, so that when the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 has good flexibility, which is beneficial to adapting to the volume expansion of the active material during charge and discharge, thereby reducing the shedding of the active material and improving the cycle stability of the battery 300. When the mass fraction of the acrylate unit is too large, although the polyacrylate chain segment can improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer and its affinity with the active material, correspondingly, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the mass fractions of other components such as the maleimide unit, acrylate unit and acrylonitrile unit are too small. If the mass fraction of the maleimide unit is too small, it may lead to poor electrolyte 330 resistance performance of the adhesive 100, that is, when the adhesive 100 is applied to the negative electrode sheet 200, the swelling degree of the negative electrode sheet 200 may be relatively large. If the mass fractions of the acrylate unit and the acrylonitrile unit are too small, it may lead to poor dispersion performance of the adhesive 100, which is not conducive to the uniform dispersion of the adhesive 100 and the active material, thereby weakening the adhesion performance of the adhesive 100 to the active material. When the mass fraction of the acrylate unit is too small, the polyacrylate chain segment is difficult to improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer. When the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 is relatively brittle in flexibility, and problems such as fracture of the negative electrode sheet 200 and shedding of the active material are likely to occur during charge and discharge, reducing the cycle stability of the battery 300.

[0066] In some embodiments, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m3 of the acrylate unit is 20% ≤ m3 ≤ 40%. In other words, the range of the mass fraction m3 of the polyacrylate chain segment is: 20% ≤ m3 ≤ 40%.

[0067] Specifically, the value of the mass fraction m3 of the polyacrylate chain segment can be, but is not limited to, 20%, 22%, 23%, 25%, 28%, 30%, 31%, 32%, 33%, 34%, 36%, 37%, 38%, 39% and 40%, etc.

[0068] It can be understood that in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the acrylate unit forms a polyacrylate chain segment.

[0069] In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in this embodiment, when the mass fraction m3 of the acrylate unit satisfies the range of 20% ≤ m3 ≤ 40%, the mass fraction of the polyacrylate chain segment is within a reasonable range. In other words, the mass fraction of the polyacrylate chain segment formed by alkalization treatment from polyacrylic acid is within a reasonable range. The polyacrylate chain segment has ionizable groups. Due to the influence of electrostatic repulsion among the internal molecules of the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molecular chains are stretched, making the adhesive 100 have a relatively high viscosity, which is convenient for bonding the active material. The polyacrylate chain segment can improve the dispersion performance of the adhesive 100. When the mass fraction of the acrylate unit is too large, correspondingly, the mass fraction of other components such as the polyacrylate chain segment in the acrylate-maleimide-acrylate-acrylonitrile copolymer may decrease, thereby weakening the flexibility of the negative electrode sheet 200 when the adhesive 100 is applied to the negative electrode sheet 200. When the mass fraction of the acrylate unit is too small, even after alkalization treatment, there are still fewer ionizable groups in the acrylate-maleimide-acrylate-acrylonitrile copolymer, and the acrylate-maleimide-acrylate-acrylonitrile copolymer is less affected by electrostatic repulsion, resulting in difficulty in effectively increasing the viscosity of the adhesive 100 and weakening the bonding effect of the adhesive 100 on the active material.

[0070] In the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m4 of the acrylonitrile unit is: 3% ≤ m4 ≤ 5%. In other words, the range of the mass fraction m4 of the acrylonitrile chain segment is: 3% ≤ m4 ≤ 5%.

[0071] Specifically, the value of the mass fraction m4 of the acrylonitrile unit can be, but is not limited to, 3%, 3.1%, 3.2%, 3.3%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.5%, 4.7%, 4.9%, and 5%, etc.

[0072] In the acrylate-maleimide-acrylate-acrylonitrile copolymer provided in this embodiment, the mass fraction m4 of the acrylonitrile satisfies the range of 3% ≤ m4 ≤ 5%. The mass fraction of the acrylonitrile unit is within a reasonable range. The acrylonitrile has high polarity and good intermolecular force, which can enhance the adhesion performance of the binder 100 to the active material. When the mass fraction of the acrylonitrile unit is too large, the structure of the acrylonitrile is relatively rigid, which may make the binder 100 harder and more brittle, and is not conducive to improving the flexibility of the negative electrode sheet 200. When the mass fraction of the acrylonitrile unit is too small, the viscosity of the binder 100 may be weakened, thereby reducing the bonding performance of the binder 100 to the active material.

[0073] In some embodiments, the range of the weight-average molecular weight M of the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 5×10 4 g / mol ≤ M ≤ 20×10 4 g / mol. In other words, the range of the weight-average molecular weight of the acrylate-maleimide-acrylate-acrylonitrile copolymer is from 50,000 to 200,000.

[0074] Specifically, the value of the weight-average molecular weight M of the acrylate-maleimide-acrylate-acrylonitrile copolymer can be, but is not limited to, 5×10 4 g / mol, 6×10 4 g / mol, 7×10 4 g / mol, 8×10 4 g / mol, 9×10 4 g / mol, 10×10 4 g / mol, 11×10 4 g / mol, 12×10 4 g / mol, 13×10 4 g / mol, 14×10 4 g / mol, 16×10 4 g / mol, 17×10 4 g / mol, 19×10 4 g / mol, and 20×10 4 g / mol, etc.

[0075] In this embodiment, when the weight-average molecular weight M of the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range of 5×10 4 g / mol ≤ M ≤ 20×10 4When it is g / mol, the weight-average molecular weight of the acrylate-maleimide-acrylate-acrylonitrile copolymer is within a reasonable range. On the one hand, when the acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water, the acrylate-maleimide-acrylate-acrylonitrile copolymer has the dual structural characteristics of a high-molecular long chain and the ionization of a small-molecule electrolyte. The high-molecular long chain is more stretched under the action of electrostatic repulsion, so that the adhesive 100 has a relatively large viscosity, which is convenient for the adhesive 100 to effectively bond the active material. On the other hand, the acrylate-maleimide-acrylate-acrylonitrile copolymer has good flexibility, which is convenient for improving the flexibility of the negative electrode plate 200. When the weight-average molecular weight of the acrylate-maleimide-acrylate-acrylonitrile copolymer is too large, it may lead to poor solubility and dispersibility of the adhesive 100, and the problem of uneven dispersion occurs during the pulping process, affecting the uniformity of the negative electrode plate 200. When the weight-average molecular weight of the acrylate-maleimide-acrylate-acrylonitrile copolymer is too small, even after alkalization treatment, the chain segment of the acrylate-maleimide-acrylate-acrylonitrile copolymer is not long enough, and the degree of stretching under the action of electrostatic repulsion is not enough, so that the viscosity of the adhesive 100 is still low, which is not conducive to effectively bonding the active material.

[0076] In some embodiments, the swelling ratio α of the acrylate-maleimide-acrylate-acrylonitrile copolymer ranges from: 80% ≤ α ≤ 120%.

[0077] Specifically, the value of the swelling ratio α of the acrylate-maleimide-acrylate-acrylonitrile copolymer can be, but is not limited to, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 100%, 102%, 105%, 108%, 110%, 112%, 115%, 118%, and 200%, etc.

[0078] It can be understood that the swelling ratio refers to the degree of volume or mass expansion of a high-molecular polymer in a solvent. In this application, the swelling ratio of the acrylate-maleimide-acrylate-acrylonitrile copolymer is the degree of volume expansion of the acrylate-maleimide-acrylate-acrylonitrile copolymer in the adhesive 100.

[0079] In this embodiment, when the swelling rate α of the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range of 80% ≤ α ≤ 120%, the swelling rate of the acrylate-maleimide-acrylate-acrylonitrile copolymer is within a reasonable range. Although the acrylate-maleimide-acrylate-acrylonitrile copolymer contains a relatively large amount of flexible monomer acrylate, it is adjusted by the maleimide monomer with a relatively large rigidity so that the acrylate-maleimide-acrylate-acrylonitrile copolymer is more resistant to deformation. When the acrylate-maleimide-acrylate-acrylonitrile copolymer is applied to the negative electrode tab 200 and assembled in the battery 300, the negative electrode tab 200 has good flexibility to avoid risks such as fracture due to excessive brittleness of the negative electrode tab 200. And when the electrolyte 330 infiltrates the negative electrode tab 200, the swelling degree of the acrylate-maleimide-acrylate-acrylonitrile copolymer is within a reasonable range so that the adhesive 100 can effectively bond the active material.

[0080] Preferably, the swelling rate α of the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range of 60% ≤ α ≤ 100%.

[0081] In some embodiments, the adhesive 100 is an aqueous adhesive 100. The adhesive 100 further includes water. The acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water. The pH value of the adhesive 100 at 25°C satisfies the range: 7.5 ≤ pH ≤ 8.5.

[0082] Specifically, the pH value of the adhesive 100 at 25°C can be, but is not limited to, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, and 8.5, etc.

[0083] In this embodiment, the adhesive 100 is an aqueous adhesive 100. The acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water, which facilitates the mixing of the adhesive 100 with the active material to form a slurry, thereby facilitating the uniform mixing of the adhesive 100 with the active material and achieving effective bonding. After the copolymerization reaction of acrylic acid monomer, acrylonitrile monomer, acrylate monomer and maleimide monomer, a polyelectrolyte aqueous solution is prepared. At this time, the viscosity of the polyelectrolyte aqueous solution is relatively low, about 10 mPa·s. In order to increase the viscosity of the adhesive 100, an alkaline solution such as NaOH or LiOH is added to the polyelectrolyte aqueous solution so that the chain segment of polyacrylic acid formed by the copolymerization of acrylic acid monomers carries a negatively charged group -COO -, further, under the action of electrostatic repulsion, the chain segments are dispersed, and the viscosity of the polyelectrolyte aqueous solution is gradually increased to form the adhesive 100. Wherein, the pH value of the adhesive 100 at 25°C satisfies the range of 7.5≤pH≤8.5. In other words, the adhesive 100 is alkaline, and a large amount of alkaline solution is added to the polyelectrolyte aqueous solution, so that polyacrylic acid can form the polyacrylic acid salt chain segment, improve the dispersion performance of the adhesive 100, and finally improve the adhesion performance of the adhesive 100 to the active material. If the pH value of the adhesive 100 is too low, on the one hand, the amount of alkaline solution added to the polyelectrolyte aqueous solution is too small, and the acrylate-maleimide-acrylate-acrylonitrile copolymer still contains a large amount of polyacrylic acid. Polyacrylic acid will agglomerate in water due to hydrogen bonding, so that the dispersion performance of the polyacrylic acid is much weaker than the dispersion performance of the polyacrylic acid salt segment, and the dispersion performance of the adhesive 100 is reduced. On the other hand, the carboxylic acid and ions ionized from the acrylate-maleimide-acrylate-acrylonitrile copolymer are also relatively small. In other words, the electrostatic repulsion between the molecules of the acrylate-maleimide-acrylate-acrylonitrile copolymer is weakened, which is not conducive to the improvement of the viscosity of the adhesive 100. If the pH value of the adhesive 100 is too high, too much NaOH or LiOH is added, and accordingly, the positively charged active ions are excessive, so that the negatively charged carboxylic acid and ions are shielded, and the electrostatic repulsion between the segments with carboxylic acid and ions is weakened, which is also not conducive to the improvement of the viscosity of the adhesive 100.

[0084] It can be understood that when the adhesive 100 is applied to the negative electrode plate 200 and assembled in a lithium-ion battery, the alkaline solution added to the polyelectrolyte aqueous solution is LiOH. When the adhesive 100 is applied to the negative electrode plate 200 and assembled in a sodium-ion battery, the alkaline solution added to the polyelectrolyte aqueous solution is NaOH.

[0085] In some embodiments, the solid content β of the adhesive 100 is in the range of 1%≤β≤5%, wherein the solid content of the adhesive 100 is the mass fraction of the acrylate-maleimide-acrylate-acrylonitrile copolymer in the adhesive 100 .

[0086] Specifically, the solid content β of the adhesive 100 may be, but is not limited to, 1%, 1.2%, 1.3%, 1.5%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.3%, 3.5%, 3.8%, 4%, 4.2%, 4.4%, 4.5%, 4.8%, 4.9% and 5%, etc.

[0087] In this embodiment, when the solid content β of the adhesive 100 satisfies the range of 1% ≤ β ≤ 5%, the solid content of the adhesive 100 is within a reasonable range, so that the adhesive 100 has both a relatively high viscosity and good flexibility. When the adhesive 100 is applied to the negative electrode sheet 200, the adhesive 100 has good adhesion to the active material, so that the negative electrode sheet 200 has good flexibility and structural stability.

[0088] In some embodiments, when the solid content β of the adhesive 100 is 2%, the range of the viscosity μ of the adhesive 100 is: 500 mPa·s ≤ μ ≤ 10000 mPa·s.

[0089] Specifically, the value of the viscosity μ of the adhesive 100 can be, but is not limited to, 500 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 6000 mPa·s, 6500 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, etc.

[0090] In this embodiment, when the mass fraction of the acrylate-maleimide-acrylate-acrylonitrile copolymer in the adhesive 100 is 2%, the viscosity μ of the adhesive 100 satisfies the range of 500 mPa·s ≤ μ ≤ 10000 mPa·s. The adhesive 100 has a relatively high viscosity. The adhesive 100 in this embodiment ensures the viscosity of the adhesive 100 while improving the flexibility of the adhesive 100, so that the adhesive 100 can firmly bond the active material. When the adhesive 100 is applied to the negative electrode sheet 200, the negative electrode sheet 200 has good flexibility, and the adhesive 100 has good adhesion to the active material. During the charge and discharge process of the battery 300, the flexible negative electrode sheet 200 can adapt to the volume expansion and contraction of the active material, reducing problems such as fracture of the negative electrode sheet 200 and shedding of the active material caused by stress concentration, thereby enabling the battery 300 to have good cycle stability.

[0091] Preferably, when the solid content β of the adhesive 100 is 2%, the range of the viscosity μ of the adhesive 100 is: 2000 mPa·s ≤ μ ≤ 7000 mPa·s.

[0092] Please refer to Figure 1, this application provides a negative electrode plate 200, the negative electrode plate 200 includes a current collector layer 210 and an active material layer 220, the active material layer 220 is disposed on at least one side of the current collector layer 210, the active material layer 220 includes an active material and an adhesive 100 provided by this application, and the adhesive 100 is used for bonding the active material.

[0093] Optionally, in some embodiments, the active material layer 220 is one layer, and the active material layer 220 is disposed on one side of the current collector layer 210. In other embodiments, the active material layer 220 is two layers, and the two active material layers 220 are respectively disposed on opposite sides of the current collector layer 210.

[0094] In this embodiment, during the preparation process of the negative electrode plate 200, the adhesive 100 and the active material form a slurry, which is coated on the surface of the current collector layer 210, and the negative electrode plate 200 is formed after rolling. The adhesive 100 of this application includes an acrylate-maleimide-acrylate-acrylonitrile copolymer, and the acrylate-maleimide-acrylate-acrylonitrile copolymer is a copolymer formed by a polyacrylate chain segment, a polymaleimide chain segment, a polyacrylate chain segment, and an acrylonitrile chain segment. The polyacrylate chain segment has good flexibility, which is beneficial to improving the flexibility of the negative electrode plate 200; the polymaleimide chain segment is more resistant to deformation, so that the adhesive 100 is more resistant to deformation, so as to improve the structural stability of the adhesive 100 and the negative electrode plate 200. The polyacrylate chain segment and the acrylonitrile chain segment are dispersed under the action of electrostatic repulsion to improve the dispersion performance and viscosity of the adhesive 100. In other words, the adhesive 100 has good flexibility while maintaining a high viscosity, so that the negative electrode plate 200 has good flexibility and overall performance. When the negative electrode plate 200 is applied to a battery 300, it can adapt to the volume expansion and contraction of the active material during charge and discharge, so that the battery 300 has good cycle stability.

[0095] In some embodiments, the active material layer 220 further includes a polyacrylic acid binder and a styrene-butadiene rubber binder. In the active material layer 220, the mass fraction W1 of the adhesive 100 ranges from 0.5% ≤ W1 ≤ 2%, the mass fraction W2 of the polyacrylic acid binder ranges from 0% ≤ W2 ≤ 2%, and the mass fraction W3 of the styrene-butadiene rubber binder ranges from 0.5% ≤ W3 ≤ 1%.

[0096] Specifically, the value of the mass fraction W1 of the binder 100 can be, but is not limited to, 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc.

[0097] Specifically, the value of the mass fraction W2 of the polyacrylic acid binder can be, but is not limited to, 0%, 0.1%, 0.3%, 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc. When the mass fraction W2 of the polyacrylic acid binder is 0%, the polyacrylic acid binder is not included in the active material layer 220.

[0098] Specifically, the value of the mass fraction W3 of the styrene-butadiene rubber binder can be, but is not limited to, 0.5%, 0.52%, 0.55%, 0.58%, 0.6%, 0.62%, 0.65%, 0.7%, 0.72%, 0.75%, 0.8%, 0.82%, 0.85%, 0.9%, 0.92%, 0.95%, 0.98%, 1%, etc.

[0099] In this embodiment, the active material layer 220 includes a polyacrylic acid binder, a styrene-butadiene rubber binder, and the binder 100 provided in the present application. The polyacrylic acid binder and the styrene-butadiene rubber binder have a greater viscosity compared to the binder 100 provided in the present application. Correspondingly, the binder 100 provided in the present application has better flexibility. The polyacrylic acid binder, the styrene-butadiene rubber binder, and the binder 100 provided in the present application cooperate with each other. On the one hand, it can improve the bonding effect on the active material and prevent the active material from falling off the active material layer 220 during charge and discharge. On the other hand, it can also improve the flexibility of the negative electrode sheet 200 to adapt to the volume expansion and contraction of the active material, reduce the fracture of the negative electrode sheet 200 caused by stress concentration, and is beneficial to improving the cycle stability of the battery 300. The binder 100 in this embodiment can replace the sodium carboxymethyl cellulose binder 100 and reduce the amount of the polyacrylic acid binder to improve the problem that the sodium carboxymethyl cellulose binder 100 and the polyacrylic acid binder are relatively hard and brittle. While ensuring the bonding performance to the active material, it improves the flexibility of the negative electrode sheet 200 and ultimately affects the performance of the battery 300.

[0100] Specifically, when the mass fraction W1 of the adhesive 100 satisfies the range of 0.5% ≤ W1 ≤ 2%, the mass fraction of the adhesive 100 is within a reasonable range, so that the adhesive 100 can improve the flexibility of the negative electrode sheet 200 and ensure the adhesion performance of the negative electrode sheet 200 to the active material. When the mass fraction W1 of the adhesive 100 is too small, in the active material layer 220, the contents of the polyacrylic acid adhesive and the styrene-butadiene rubber adhesive are relatively large. Although the adhesion performance to the active material can be maintained, the flexibility of the negative electrode sheet 200 is weakened, and the negative electrode sheet 200 may be relatively brittle, increasing the risk of fracture of the negative electrode sheet 200 or shedding of the active material. When the mass fraction W1 of the adhesive 100 is too large, in the active material layer 220, the contents of the polyacrylic acid adhesive and the styrene-butadiene rubber adhesive are too small, weakening the adhesion performance to the active material.

[0101] Optionally, the softness range of the negative electrode sheet 200 is: 90 mN to 130 mN.

[0102] Specifically, the value of the softness of the negative electrode sheet 200 can be, but is not limited to, 90 mN, 92 mN, 95 mN, 98 mN, 100 mN, 105 mN, 108 mN, 110 mN, 112 mN, 115 mN, 116 mN, 118 mN, 120 mN, 122 mN, 125 mN, 128 mN, and 130 mN, etc.

[0103] In this embodiment, when the softness of the negative electrode sheet 200 satisfies the range of 90 mN to 130 mN, the negative electrode sheet 200 has good flexibility, so that when the negative electrode sheet 200 is applied to the battery 300, the negative electrode sheet 200 can be prevented from breaking, and when the volume of the active material expands or contracts, the negative electrode sheet 200 can adapt to the volume change of the active material and prevent the active material from shedding. The negative electrode sheet 200 has good structural stability, and also improves the cycle stability of the battery 300 when the negative electrode sheet 200 is applied to the battery 300.

[0104] Please refer to Figure 3 , this application provides a battery 300, which includes: the negative electrode sheet 200 provided by this application, a separator 310, a positive electrode sheet 320, and an electrolyte 330. The separator 310 is located on one side of the negative electrode sheet 200; the positive electrode sheet 320 is located on the side of the separator 310 away from the negative electrode sheet 200; the electrolyte 330 is used to infiltrate at least part of the negative electrode sheet 200, the separator 310, and the positive electrode sheet 320.

[0105] Optionally, in some embodiments, the battery 300 is a lithium-ion battery, and in other embodiments, the battery 300 is a sodium-ion battery.

[0106] It can be understood that after the negative electrode sheet 200, the separator 310, and the positive electrode sheet 320 are stacked in sequence, they are wound.

[0107] It can be understood that the electrolyte 330 includes active ions, and during the charge and discharge cycles of the battery 300, the active ions are transported between the positive electrode sheet 320 and the negative electrode sheet 200.

[0108] Optionally, in some embodiments, the battery 300 is a lithium-ion battery 300, and the active ions are lithium ions. In other embodiments, the battery 300 is a sodium-ion battery 300, and the active ions are sodium ions.

[0109] In this embodiment, the battery 300 includes the negative electrode sheet 200 provided by the present application, as well as a separator 310, a positive electrode sheet 320, and an electrolyte 330. The electrolyte 330 is used to infiltrate at least part of the negative electrode sheet 200, the separator 310, and the positive electrode sheet 320, so that the active ions are transported between the positive electrode sheet 320 and the negative electrode sheet 200, realizing the charge and discharge process of the battery 300. The active material layer 220 of the negative electrode sheet 200 provided by the present application includes an active material and the binder 100 provided by the present application. The binder 100 has good flexibility while maintaining a high viscosity, and at the same time, the acrylate-maleimide-acrylate-acrylonitrile copolymer is not easily swollen, so that the negative electrode sheet 200 has good flexibility and overall performance. When the negative electrode sheet 200 is applied to the battery 300, it can adapt to the volume expansion and contraction of the active material during the charge and discharge process, so that the battery 300 has good cycle stability.

[0110] The technical solution of the present application will be further introduced in multiple embodiments as follows:

[0111] Embodiments 1 to 5, Comparative Examples 1 to 5:

[0112] 1. Preparation of the binder 100:

[0113] Provided are acrylic monomers, acrylonitrile monomers, acrylic monomers, maleimide monomers, and water. The above monomers are dispersed in water and subjected to a free radical polymerization reaction to prepare an aqueous polyelectrolyte solution. Among them, the aqueous polyelectrolyte solution includes an acrylate-maleimide-acrylic acid-acrylonitrile copolymer. Further, the aqueous polyelectrolyte solution is alkalized with LiOH so that polyacrylic acid forms lithium polyacrylate, generating the acrylate-maleimide-acrylate-acrylonitrile copolymer, thereby obtaining the adhesives 100 of Examples 1 to 5 and Comparative Examples 1 to 5.

[0114] Among them, the value of the molar fraction n1 of maleimide units, the value of the molar fraction n2 of acrylate units, the value of n2 / n1, and the value of the swelling ratio α of the acrylate-maleimide-acrylate-acrylonitrile copolymer are shown in Table 1.

[0115] 2. Preparation of the negative electrode sheet 200:

[0116] Examples 1 to 5 and Comparative Example 5:

[0117] By weight fraction ratio, 96 parts of active material (graphite), 1 part of conductive agent (conductive carbon black), and a part of the adhesive 100 are dry-mixed for 30 minutes, then a part of polyacrylic acid binder is added, 30 parts of pure water are added and mixed evenly for 60 minutes, then the remaining polyacrylic acid binder is added, and 30 parts of pure water are added for high-speed dispersion, and then styrene-butadiene rubber binder is added. After uniform dispersion, the slurry of the active material layer 220 of the negative electrode sheet 200 is obtained. The slurry is uniformly coated on one surface of a current collector layer 210 (copper foil) with a thickness of 6 μm. After drying, cold pressing, slitting, and cutting, the negative electrode sheets 200 of Examples 1 to 5 and Comparative Example 5 are obtained. The compaction density of the negative electrode sheet 200 is 1.5 g / cm 3 。

[0118] Among them, the adhesive 100 of Example 1 is applied to the negative electrode sheet 200 of Example 1, the adhesive 100 of Example 2 is applied to the negative electrode sheet 200 of Example 2, and so on.

[0119] Among them, in the active material layer 220, the value of the mass fraction W1 of the adhesive 100, the value of the mass fraction W2 of the polyacrylic acid binder, and the value of the mass fraction W3 of the styrene-butadiene rubber binder are shown in Table 2.

[0120] Comparative Examples 1 to 4:

[0121] By weight fraction ratio, 96 parts of active material (graphite), 1 part of conductive agent (conductive carbon black), partial binder 100 and / or sodium carboxymethyl cellulose (CMC) binder were dry-mixed for 30 minutes, then partial polyacrylic acid binder was added, 30 parts of pure water was added and mixed evenly for 60 minutes. Then the remaining polyacrylic acid binder was added, and another 30 parts of pure water was added for high-speed dispersion. Then styrene-butadiene rubber binder was added. After uniform dispersion, the slurry of the active material layer 220 of the negative electrode sheet 200 was obtained. The slurry was evenly coated on one surface of the current collector layer 210 (copper foil) with a thickness of 6 μm. After drying, cold pressing, slitting and cutting, the negative electrode sheets 200 of Comparative Example 1 to Comparative Example 4 were obtained. The compaction density of the negative electrode sheet 200 was 1.5 g / cm 3 .

[0122] Among them, the binder 100 of Comparative Example 1 was applied to the negative electrode sheet 200 of Comparative Example 1, the binder 100 of Comparative Example 2 was applied to the negative electrode sheet 200 of Comparative Example 2, and so on.

[0123] Among them, in the active material layer 220, the mass fraction value W1 of the binder 100, the mass fraction value W2 of the polyacrylic acid binder, the mass fraction value W3 of the styrene-butadiene rubber binder, and the mass fraction value of the sodium carboxymethyl cellulose binder are shown in Table 2.

[0124] 3. Preparation of battery 300:

[0125] A positive electrode sheet 320, a separator 310 and an electrolyte 330 are provided. The positive electrode sheet 320, the separator 310 and the electrolyte 330 are of conventional formulations in the art and are not limited herein.

[0126] The above positive electrode sheet 320, separator 310 and negative electrode sheet 200 are stacked in sequence, so that the separator 310 is between the positive electrode sheet 320 and the negative electrode sheet 200 to play an isolation role, and then wound into a bare electrode assembly; after welding the electrode tabs, the bare battery 300 is placed in an outer packaging shell, dried and then the above electrolyte 330 is injected. After vacuum packaging, standing, forming, shaping, etc., the implementation batteries 1 to 5 and the comparative batteries 1 to 5 are finally prepared.

[0127] Among them, the negative electrode sheet 200 of Example 1 was assembled into the implementation battery 1, the negative electrode sheet 200 of Example 2 was assembled into the implementation battery 2, the negative electrode sheet 200 of Comparative Example 1 was assembled into the comparative battery 1, and so on.

[0128] The following Table 1 is a table of the structure and performance parameters of the binder 100 and the negative electrode sheet 200 of Examples 1 to 5 and Comparative Examples 1 to 5.

[0129] Table 1: Structure and performance parameters of the adhesive 100 and the negative electrode sheet 200 in Examples 1 to 5 and Comparative Examples 1 to 5.

[0130]

[0131]

[0132] Performance test of the negative electrode sheet 200:

[0133] 1. Softness test of the negative electrode sheet 200:

[0134] The negative electrode sheets 200 obtained in the above examples were cut into the same size (25 mm × 130 mm), with three parallel samples in each group for testing. The instrument test was based on the stress-strain curve test method. The negative electrode sheet 200 was fixed on the test device, and the electric telescopic rod moved vertically at a certain rate. At the same time, the stress and strain (pressure-displacement) of the negative electrode sheet 200 under different deformation degrees were measured. By recording the corresponding relationship between the displacement value of the electric telescopic rod in the vertical direction and the pressure value received at its top, the "stress-strain curve" of the electrode sheet was obtained to obtain the softness of the negative electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 5. Among them, the softness values of the negative electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Table 2.

[0135] It can be understood that the smaller the softness value, the softer the negative electrode sheet 200, and the better the flexibility of the negative electrode sheet 200.

[0136] 2. Peel strength test of the negative electrode sheet 200:

[0137] The peel strength of the negative electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 5 was tested using a tensile machine. The test method was as follows: Step 1, lay the negative electrode sheet 200 flat, and use a ruler and a utility knife to prepare the negative electrode sheet 200 into long strips with a specification of 200 mm × 25 mm. Usually, 3 to 5 test long strips need to be prepared for a group of samples; Step 2, stick one side of the double-sided tape to the middle of the steel plate, and roll it back and forth with a roller 3 times to firmly bond it to the test steel plate; Step 3, align one end of the test long strip with the steel plate, with the double-sided tape slightly wider on both sides, and fit it parallel and centered to the other side of the double-sided tape. Roll it with a roller 3 times in one direction to make it fit flat. Manually peel the test long strip 5 mm to 10 mm from the bottom, and use a tensile machine with a 180° clamp for peeling to obtain the peel force of the test long strip.

[0138] Among them, the peeling force of the test strip can characterize the peeling force of the negative electrode sheet 200. More specifically, it can characterize the peeling force between the active material layer 220 and the current collector layer 210 in the negative electrode sheet 200. The greater the peeling force of the negative electrode sheet 200, the better the adhesion performance of the adhesive 100.

[0139] The peeling strength refers to the peeling force required per unit width of the adhesive surface of the adhesive 100 in the direction perpendicular to the adhesive surface. In other words, the peeling strength is the ratio of the peeling force to the width of the adhesive surface of the adhesive 100. In this application, the peeling strength of the negative electrode sheet 200 is the ratio of the peeling force of the test strip to the width (25 mm), and thus the peeling strength values of the negative electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 5 are obtained.

[0140] Among them, the peeling strength values of the negative electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Table 2.

[0141] 3. Cycling performance test of the battery 300:

[0142] Perform a constant power charge-discharge cycling test on the above-mentioned Embodiment Batteries 1 to 5 and Comparative Batteries 1 to 5 on a charge-discharge instrument. The test temperature is 25°C, the charge-discharge rate is 0.5C (the magnitude of the charge-discharge current is usually represented by the charge-discharge rate, and the calculation formula for the charge-discharge current is: charge-discharge power = the voltage plateau of the battery 300 (3.2V) × the rated capacity of the battery 300), and the charge-discharge voltage window is 2.5V to 3.65V (that is, the charge cut-off voltage of the battery 300 is 3.65V, and the discharge cut-off voltage of the battery 300 is 2.5V; generally, it is considered that when the charge cut-off voltage ≥ 4V, the charge cut-off voltage of the battery 300 is relatively high). Calculate the capacity retention rate after 1000 cycles. The calculation formula is: capacity retention rate after the Nth cycle = (discharge capacity after the Nth cycle / discharge capacity of the first cycle) × 100%.

[0143] Among them, usually, a complete charge-discharge is called a charge-discharge cycle, that is, the battery 300 first charges from 2.5V to 3.65V, and then discharges from 3.65V to 2.5V, thus forming a charge-discharge cycle. Cycling N times means repeating the above process N times.

[0144] Among them, the capacity retention rate values of Embodiment Batteries 1 to 5 and Comparative Batteries 1 to 5 after 1000 cycles are shown in Table 2.

[0145] The following Table 2 shows the performance parameters of the negative electrode sheets 200 and the battery 300 in Examples 1 to 5 and Comparative Examples 1 to 5.

[0146] Table 2: Performance parameters of the negative electrode sheets 200 and batteries 300 of Examples 1 to 5 and Comparative Examples 1 to 5.

[0147] Examples and Comparative Examples Softness (mN) Peel Strength (N / m) Capacity Retention Rate after 1000 Cycles (%) Example 1 98.58 11.43 97.48 Example 2 94.36 11.20 97.40 Example 3 96.83 11.25 97.43 Example 4 97.52 11.47 97.49 Example 5 95.21 11.12 97.38 Comparative Example 1 124.00 12.34 97.41 Comparative Example 2 120.20 11.98 97.44 Comparative Example 3 113.10 11.52 97.47 Comparative Example 4 106.80 11.32 97.50 Comparative Example 5 95.07 10.87 92.54

[0148] It can be understood that in Table 2, the capacity retention rate after 1000 cycles in Example 1 is the capacity retention rate of the implemented battery 1 after 1000 cycles, the capacity retention rate after 1000 cycles in Example 2 is the capacity retention rate of the implemented battery 2 after 1000 cycles, the capacity retention rate after 1000 cycles in Comparative Example 1 is the capacity retention rate of the comparative battery 1 after 1000 cycles, and so on.

[0149] It can be understood that in the active material layer 220 of Example 5, the mass fraction W2 of the polyacrylic acid binder is 0%, then the active material layer 220 in Example 5 does not include the polyacrylic acid binder.

[0150] Please refer to Table 1 and Table 2. From the data of Examples 1 to 5 and Comparative Examples 1 to 4, it can be seen that the active material layer 220 in Examples 1 to 5 includes the binder 100, polyacrylic acid binder, and styrene-butadiene rubber binder provided in the present application, and does not include sodium carboxymethyl cellulose binder. While the active material layer 220 in Comparative Example 1 does not include the binder 100 provided in the present application. Although the active material layer 220 in Comparative Examples 2 to 4 includes the binder 100 provided in the present application, its mass fraction is too small, and it includes sodium carboxymethyl cellulose binder. This results in: the softness of the negative electrode sheets 200 in Examples 1 to 5 is less than that of the negative electrode sheets 200 in Comparative Examples 1 to 4. This is because: in Examples 1 to 5, the binder 100 provided in the present application contains more acrylate units, and the acrylate units and maleimide units cooperate with each other, so that the binder 100 in Examples 1 to 5 has better flexibility and is not easily swollen. Therefore, the softness of the negative electrode sheets 200 in Examples 1 to 5 is smaller and not easily broken, and the corresponding batteries 300 have better cycle stability.

[0151] More specifically, please refer to Examples 1 to 3 and Comparative Examples 1 to 4. When the total mass fraction of the binder 100, polyacrylic acid binder, styrene-butadiene rubber binder, and sodium carboxymethyl cellulose binder is constant, as the mass fraction of the binder 100 gradually increases and the mass fraction of the sodium carboxymethyl cellulose binder gradually decreases, the softness of the corresponding negative electrode sheet 200 gradually decreases, and the capacity retention rate of the corresponding battery 300 after 1000 cycles is higher. This shows that: the sodium carboxymethyl cellulose binder is relatively hard and brittle after drying, and using the binder 100 provided in the present application can significantly improve the flexibility of the negative electrode sheet 200, which is convenient for preparing flexible electrodes.

[0152] More specifically, please refer to Examples 1 to 3. Under the same other conditions, if the total mass fraction of the binder 100 provided in the present application, the mass fraction of the polyacrylic acid binder, and the mass fraction of the styrene-butadiene rubber binder is constant, the greater the mass fraction of the binder 100, the smaller the softness of the corresponding negative electrode sheet 200, that is, the corresponding negative electrode sheet 200 has better flexibility, indicating that the binder 100 also has better flexibility compared to the conventional polyacrylic acid binder, facilitating the preparation of flexible electrodes.

[0153] In addition, the negative electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 5 all have relatively large peel strengths, that is, the binder 100 provided in the present application also has good adhesion performance, and can ensure the flexibility of the negative electrode sheet 200 while improving the flexibility of the negative electrode sheet 200.

[0154] Further, please refer to Embodiment 3 to Embodiment 5, and Comparative Example 5. Under the same other conditions, in the adhesive 100 of Embodiment 3 to Embodiment 5, the molar fraction n1 of the maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer satisfies the range 1% ≤ n1 ≤ 4%, the molar fraction n2 of the acrylate unit satisfies the range 15% ≤ n2 ≤ 60%, and satisfies the relationship 4 ≤ n2 / n1 ≤ 60. In Comparative Example 5, the value of the molar fraction n2 of the acrylate unit is too large and the value of n2 / n1 is too large. This makes the swelling rate α of the acrylate-maleimide-acrylate-acrylonitrile copolymer in Embodiment 3 to Embodiment 5 smaller than the swelling rate α of the acrylate-maleimide-acrylate-acrylonitrile copolymer in Comparative Example 5, and the softness of the negative electrode sheet 200 in Embodiment 3 to Embodiment 5 is greater than the softness of the negative electrode sheet 200 in Comparative Example 5. The peel strength of the negative electrode sheet 200 in Embodiment 3 to Embodiment 5 is greater than the peel strength of the negative electrode sheet 200 in Comparative Example 5. The capacity retention rate of Battery 3 to Battery 5 after 1000 cycles is greater than the capacity retention rate of Comparative Battery 5 after 1000 cycles. This is because: Although the polyacrylate chain segment formed by the acrylic acid unit can improve the flexibility of the acrylate-maleimide-acrylate-acrylonitrile copolymer and its affinity with the active material, correspondingly, if the molar fraction of the acrylate unit is too large, in the acrylate-maleimide-acrylate-acrylonitrile copolymer, the mass fractions of other components such as the maleimide unit, acrylate unit, and acrylonitrile unit are too small. If the mass fraction of the maleimide unit is too small, it may result in poor electrolyte 330 resistance performance of the adhesive 100, thereby causing a relatively large swelling degree of the negative electrode sheet 200 in Comparative Example 5. If the mass fractions of the acrylate unit and the acrylonitrile unit are too small, it may result in poor dispersion performance of the adhesive 100, which is not conducive to the uniform dispersion of the adhesive 100 and the active material, thereby weakening the adhesion performance of the adhesive 100 to the active material, and thus making the peel strength of the negative electrode sheet 200 in Comparative Example 5 smaller and the softness smaller.

[0155] Please refer to Figure 4 and Figure 5 , the present application provides an electrical device 400, and the electrical device 400 includes: a device body 410 and the battery 300 provided by the present application, and the battery 300 supplies power to the electrical device 400.

[0156] It can be understood that the battery 300 is electrically connected to the electrical device 400.

[0157] In this embodiment, the battery 300 includes the negative electrode sheet 200 provided by the present application. The binder 100 of the negative electrode sheet 200 has good adhesion to the active material, and the negative electrode sheet 200 has good flexibility, which can reduce the situation that the negative electrode sheet 200 breaks due to excessive brittleness. The negative electrode sheet 200 and the battery 300 have a long service life, and the battery 300 has good cycle stability to provide stable electric energy for the electrical device 400, which is beneficial to improving the user experience.

[0158] Optionally, the electrical device 400 in the embodiment of the present application may be, but is not limited to, portable electronic devices such as mobile phones, tablet computers, laptop computers, desktop computers, smart bracelets, smart watches, e-readers, game consoles, etc. It may also be transportation means such as cars, trucks, sedans, freight trucks, bullet trains, high-speed rails, and electric scooters. In addition, it may also be various household appliances, etc. The Figure 4 electrical device 400 in the embodiment of the present application is an energy storage battery cabinet.

[0159] It can be understood that the electrical device 400 described in this embodiment is only one form of the electrical device 400 applied by the battery 300, and should not be construed as a limitation on the electrical device 400 provided by the present application, nor should it be construed as a limitation on the electrical device 400 provided by each embodiment of the present application.

[0160] In the present application, the mention of "embodiment" and "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in each embodiment of the present application can be combined arbitrarily without contradiction to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An adhesive, characterized in that, The adhesive includes an acrylate-maleimide-acrylate-acrylonitrile copolymer, and the range of the molar fraction n1 of the maleimide unit in the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 1% ≤ n1 ≤ 4%.

2. The adhesive according to claim 1, wherein In the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction n1 of the maleimide unit and the molar fraction n2 of the acrylate unit satisfy the relational expression: 4 ≤ n2 / n1 ≤ 60.

3. The adhesive according to claim 1, wherein In the acrylate-maleimide-acrylate-acrylonitrile copolymer, the molar fraction of the acrylate unit is greater than the molar fraction of the acrylate salt unit, and the molar fraction of the acrylate unit is greater than the molar fraction of the acrylonitrile unit.

4. The adhesive according to claim 1, characterized in that, In the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m1 of the maleimide unit is: 10% ≤ m1 ≤ 20%, and the range of the mass fraction m2 of the acrylate unit is: 30% ≤ m2 ≤ 60%.

5. The adhesive according to claim 1, wherein In the acrylate-maleimide-acrylate-acrylonitrile copolymer, the range of the mass fraction m3 of the acrylate salt unit is: 20% ≤ m3 ≤ 40%, and the range of the mass fraction m4 of the acrylonitrile unit is: 3% ≤ m4 ≤ 5%.

6. The adhesive according to any one of claims 1 to 5, characterized in that, The range of the weight-average molecular weight M of the acrylate-maleimide-acrylate-acrylonitrile copolymer is: 5×10 4 g / mol ≤ M ≤ 20×10 4 g / mol.

7. The adhesive according to any one of claims 1 to 5, characterized in that, The swelling ratio α of the acrylate-maleimide-acrylate-acrylonitrile copolymer ranges from: 80% ≤ α ≤ 120%.

8. The adhesive according to any one of claims 1 to 5, characterized in that, The adhesive is an aqueous adhesive. The adhesive further includes water. The acrylate-maleimide-acrylate-acrylonitrile copolymer is dispersed in water. The pH value of the adhesive at 25 °C satisfies the range: 7.5 ≤ pH ≤ 8.

5.

9. The adhesive according to any one of claims 1 to 5, characterized in that, The solid content β of the adhesive ranges from: 1% ≤ β ≤ 5%, where the solid content of the adhesive is the mass fraction of the acrylate-maleimide-acrylate-acrylonitrile copolymer in the adhesive.

10. The adhesive according to claim 9, characterized in that, When the solid content β of the adhesive is 2%, the viscosity μ of the adhesive ranges from: 500 mPa·s ≤ μ ≤ 10000 mPa·s.

11. A negative electrode plate, characterized in that, The negative electrode plate includes: a current collector layer; and an active material layer, the active material layer is disposed on at least one side of the current collector layer, the active material layer includes an active material and the adhesive according to any one of claims 1 to 10, and the adhesive is used to bond the active material.

12. The negative electrode sheet according to claim 11, characterized in that, The active material layer further includes a polyacrylic acid binder and a styrene-butadiene rubber binder. In the active material layer, the range of the mass fraction W1 of the adhesive is: 0.5% ≤ W1 ≤ 2%, the range of the mass fraction W2 of the polyacrylic acid binder is: 0% ≤ W2 ≤ 2%, and the range of the mass fraction W3 of the styrene-butadiene rubber binder is: 0.5% ≤ W3 ≤ 1%.

13. A battery, characterized in that, The battery includes: the negative electrode plate according to claim 11 or 12; a separator, the separator is located on one side of the negative electrode plate; a positive electrode plate, the positive electrode plate is located on the side of the separator away from the negative electrode plate; and an electrolyte, the electrolyte is used to infiltrate at least part of the negative electrode plate, the separator and the positive electrode plate.

14. An electrical device, characterized in that, The electrical device includes: a device body; and the battery according to claim 13, which powers the electrical device.

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