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 is a modified polyacrylic acid polymer, the modified polyacrylic acid polymer comprises a first group and a second group, the hydrophilicity of the first group is greater than that of the second group, and the weight-average molecular weight M of the adhesive is greater than or equal to 1 * 10 < 7 > g / mol and less than or equal to 2.2 * 10 < 7 > g / mol.

Description

Technical Field

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

[0002] In lithium-ion batteries, the adhesive of the negative electrode sheet is used to bond the active material. However, the bonding force of the commonly used negative electrode sheet at the interface is still relatively small, and the active material is prone to fall off at the disassembled interface of the negative electrode sheet. Therefore, it is necessary to provide an adhesive with better bonding performance. Summary of the invention

[0003] In view of this, the present application provides an adhesive, a negative electrode plate, a battery and an electrical device, wherein the adhesive has good bonding properties to the active material, so that the negative electrode plate has a large peeling force.

[0004] The present application provides an adhesive, which is a modified polyacrylic acid polymer, wherein the modified polyacrylic acid polymer comprises a first group and a second group, wherein the hydrophilicity of the first group is greater than the hydrophilicity of the second group, and the weight average molecular weight M of the adhesive is in the range of: 1×10 7 g / mol≤M≤2.2×10 7 g / mol.

[0005] Further, the second group is -COOR, and satisfies R=-C x H 2x+1 , the range of x is: 5≤x≤8.

[0006] Furthermore, the first group is a carboxyl group, the second group is an ester group, and in the molecular chain of the modified polyacrylic acid polymer, the ratio a of the number of the second group to the first group is in the range of 0.2≤a≤0.5.

[0007] Furthermore, the structural formula of the adhesive is: , where n is in the range of 4×10 4 ≤n≤10×10 4 , the range of m is: 2×10 4 ≤m≤5×10 4 .

[0008] Furthermore, the viscosity of the aqueous solution of the adhesive with a mass fraction of 1% is greater than or equal to 2×10 5 mPa·s.

[0009] The present application provides a negative electrode plate, which includes: a current collector layer and an active material layer, the active material layer includes an active material and an adhesive provided by the present application, and the active material includes graphite.

[0010] Furthermore, the range of the peel strength σ of the negative electrode sheet after rolling is: 10N / m≤σ≤35N / m.

[0011] Furthermore, in the active material layer, the mass fraction b of the binder is in the range of 0.1%≤b≤1%.

[0012] The present application provides a battery, which includes: a negative electrode plate, a separator, a positive electrode plate and an electrolyte provided in the present application, wherein the electrolyte is used to infiltrate at least a portion of the negative electrode plate, the separator and the positive electrode plate.

[0013] The present application provides an electrical device, which includes a device body and a battery provided in the present application, and the battery supplies power to the device body.

[0014] In the present application, the adhesive is a modified polyacrylic acid polymer, and the modified polyacrylic acid polymer includes a main chain structure formed by connecting repeating units derived from acrylic acid, and the weight average molecular weight of the adhesive is as high as tens of millions. The larger the weight average molecular weight of the adhesive, the longer the main chain structure, which can form long-range adhesion and more hydrogen bonds and physical entanglements, thereby significantly enhancing the interaction between the modified polyacrylic acid polymers. When the adhesive is applied to the negative electrode sheet, it is beneficial to improve the adhesion of the adhesive to the surface of the active material, so that the adhesive has excellent bonding properties. In addition, the modified polyacrylic acid polymer includes a first group and a second group, the hydrophilicity of the first group is greater than the hydrophilicity of the second group, and the first group and the second group are respectively connected to the main chain structure, wherein the first group has a greater hydrophilicity. When the adhesive is applied to the negative electrode sheet, the first group can make the adhesive have better dispersibility, which is convenient for realizing that the adhesive is evenly dispersed in the active material layer of the negative electrode sheet. In addition, the second group has good hydrophobicity and lipophilicity, which is conducive to coating the periphery of graphite. In other words, the second group enhances the affinity between the adhesive and the active material, which is conducive to further improving the bonding performance of the adhesive. The adhesive can be evenly dispersed in the active material layer and arranged in contact with the active material. The adhesive has excellent bonding performance, so that the negative electrode sheet has a large peeling force. Furthermore, the weight average molecular weight M of the adhesive satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol, compared with the conventional weight average molecular weight of 1.5×10 6The weight average molecular weight of the adhesive of the present application is very large, so that the adhesive has high bonding performance and strong suspension performance, which is conducive to bonding more active materials so that the negative electrode plate has a higher energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A schematic diagram of a partial cross-sectional structure of a negative electrode sheet according to an embodiment of the present application; Figure 2 A partial cross-sectional structural schematic diagram of a battery according to an embodiment of the present application; Figure 3 This is a schematic diagram of the structure of an electrical device according to an embodiment of the present application; Figure 4 This is a circuit block diagram of an electrical device according to an embodiment of the present application.

[0017] Description of reference numerals: 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 equipment, 410 - equipment body. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. 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 includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0020] Reference to "embodiment" or "implementation" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment or implementation may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] In lithium-ion batteries, the adhesive of the negative electrode sheet is used to bond the active material. However, the bonding force of the commonly used negative electrode sheet at the interface is still relatively small. Specifically, the mass fraction of the commonly used adhesive in the active material layer is about 2.5%, and its bonding force is about 13N / m. The active material is prone to fall off at the disassembled interface of the negative electrode sheet. Therefore, it is necessary to provide an adhesive with better bonding performance.

[0022] See also Figure 1 The present application provides an adhesive 100, which is a modified polyacrylic acid polymer. The modified polyacrylic acid polymer includes a first group and a second group. The hydrophilicity of the first group is greater than the hydrophilicity of the second group. The weight average molecular weight M of the adhesive 100 is in the range of: 1×10 7 g / mol≤M≤2.2×10 7 g / mol.

[0023] Specifically, the weight average molecular weight M of the adhesive 100 may be, but is not limited to, 1×10 7 g / mol, 1.1×10 7 g / mol, 1.2×10 7 g / mol, 1.3×10 7 g / mol, 1.4×10 7 g / mol, 1.5×10 7 g / mol, 1.6×10 7 g / mol, 1.7×10 7 g / mol, 1.8×10 7 g / mol, 1.9×10 7 g / mol, 2×10 7 g / mol, 2.1×10 7 g / mol and 2.2×10 7 g / mol, etc.

[0024] Optionally, the modified polyacrylic acid polymer may be, but is not limited to, a modified polyacrylic acid polymer or a modified polymethacrylic acid polymer. In the present application, the modified polyacrylic acid polymer is introduced as an example, which should not be construed as a limitation on the modified polyacrylic acid polymer.

[0025] It can be understood that the adhesive 100 includes a main chain and a side chain, the main chain includes a repeating unit derived from acrylic acid, and the first group and the second group are respectively connected to the main chain to form a side chain.

[0026] It can be understood that the hydrophilicity of the first group is greater than that of the second group, the first group has good hydrophilicity, the second group has good hydrophobicity and good lipophilicity, and the lipophilicity of the second group is greater than that of the first group.

[0027] It can be understood that the adhesive 100 is applied to the negative electrode plate 200, and the negative electrode plate 200 includes a current collector layer 210 and an active material layer 220. The active material layer 220 includes an active material and the adhesive 100 of this embodiment. The active material includes graphite. The adhesive 100 is used to bond the active material and to bond the active material layer 220 and the current collector layer 210.

[0028] In this embodiment, the adhesive 100 is a modified polyacrylic acid polymer, which includes a main chain structure formed by connecting repeating units derived from acrylic acid, and the weight average molecular weight of the adhesive 100 is as high as tens of millions. The larger the weight average molecular weight of the adhesive 100, the longer the main chain structure, which can form long-range adhesion and more hydrogen bonds and physical entanglements, thereby significantly enhancing the interaction force between the modified polyacrylic acid polymers. When the adhesive 100 is applied to the negative electrode plate 200, it is beneficial to improve the adhesion of the adhesive 100 on the surface of the active material, so that the adhesive 100 has excellent bonding properties. In addition, the modified polyacrylic acid polymer includes a first group and a second group, the hydrophilicity of the first group is greater than that of the second group, the first group and the second group are respectively connected to the main chain structure, wherein the first group has a greater hydrophilicity, and when the adhesive 100 is applied to the negative electrode plate 200, the first group can make the adhesive 100 have a better dispersibility, which is convenient for achieving the adhesive 100 to be uniformly dispersed in the active material layer 220 of the negative electrode plate 200. In addition, the second group has good hydrophobicity and lipophilicity, which is conducive to coating the periphery of graphite. In other words, the second group enhances the affinity of the adhesive 100 with the active material, thereby facilitating further improving the bonding performance of the adhesive 100. The adhesive 100 can be uniformly dispersed in the active material layer 220 and arranged in contact with the active material, and the adhesive 100 has excellent bonding performance, so that the negative electrode plate 200 has a greater peeling force. Furthermore, the weight average molecular weight M of the adhesive 100 satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol, compared with the conventional weight average molecular weight of 1.5×10 6 The weight average molecular weight of the adhesive 100 of this embodiment is very large, so that the adhesive 100 has high bonding performance and strong suspension performance, which is conducive to bonding more active materials, so that the negative electrode plate 200 has a higher energy density.

[0029] It can be understood that the main chain structure of the modified polyacrylic acid polymer is formed by pure acrylic acid or its derivative polymer. Compared with the random copolymer formed by multiple monomers with different chirality, the modified polyacrylic acid polymer has a higher regularity, which is convenient for forming an adhesive 100 with a larger molecular weight, so that the adhesive 100 has excellent bonding properties.

[0030] In some embodiments, the second group is -COOR, and satisfies R=-C x H2x+1 , the range of x is: 5≤x≤8.

[0031] Specifically, the value of x may be, but is not limited to, 5, 6, 7, 8, etc.

[0032] It is understood that R is selected from an alkyl group having five to eight carbon atoms.

[0033] In this embodiment, the second group is -COOR, and satisfies R=-C x H 2x+1 In other words, in the adhesive 100, the α-hydrogen atom in the carboxyl group of the modified polyacrylic acid polymer has high activity, and the alkane with five to eight carbon atoms replaces the α-hydrogen atom through a free radical reaction or a nucleophilic substitution reaction to form the second group. The second group -COOR includes a non-polar alkyl group, so that the second group shows strong lipophilicity, and as x gradually increases, the lipophilicity of the second group becomes stronger. In this embodiment, x satisfies the range of 5≤x≤8, and the number of carbon atoms of the alkyl group is within a reasonable range. On the one hand, the lipophilicity of the second group is within a reasonable range, so that when the adhesive 100 is applied to the negative electrode plate 200, the adhesive 100 can be arranged in accordance with the active material and coated on the periphery of the active material. The adhesive 100 has good affinity with the active material, which is conducive to the adhesive 100 being evenly dispersed in the active material layer 220 and effectively bonding the active material, so that the adhesive 100 has excellent bonding performance, so that the negative electrode plate 200 has a large peeling force. On the other hand, it can prevent the chain length of the alkyl group from being too long and increasing the difficulty of replacing the α-hydrogen atom, and the adhesive 100 has good preparation performance. When the value of x is too large, the chain length of the alkyl group is too long, and it is difficult for the alkyl group to replace the α-hydrogen atom in the carboxyl group, which increases the difficulty of preparing the second group, which is not conducive to the industrial production of the adhesive 100. When the value of x is too small, the alkyl group contains too few carbon-hydrogen bonds, and the lipophilicity of the second group is weak. When the adhesive 100 is applied to the negative electrode sheet 200, the affinity between the adhesive 100 and the active material is poor, which weakens the bonding effect of the adhesive 100 on the active material, and is not conducive to improving the peeling force of the negative electrode sheet 200.

[0034] In some embodiments, the first group is a carboxyl group, the second group is an ester group, and in the molecular chain of the modified polyacrylic acid polymer, the ratio a of the number of the second group to the first group is in the range of 0.2≤a≤0.5.

[0035] Specifically, the value of the ratio a of the number of the second group to the first group can be, but is not limited to, 0.2, 0.22, 0.25, 0.27, 0.29, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.45, 0.47, 0.49 and 0.5, etc.

[0036] It is understood that the number of the second groups is less than the number of the first groups.

[0037] In the molecular chain of the modified polyacrylic acid polymer provided in this embodiment, the main chain structure is formed by connecting repeating units derived from acrylic acid, the first group is a carboxyl group, the second group is an ester group, and the first group and the second group are connected to the main chain structure respectively. Among them, the hydrophilicity of the carboxyl group is stronger than the hydrophilicity of the ester group, and the first group can make the adhesive 100 have better dispersibility, which is convenient for uniformly dispersing the adhesive 100 in the active material layer 220 and effectively bonding the active material. The second group is an ester group and includes an alkyl group with five to eight carbon atoms. The second group has good lipophilicity, which enhances the affinity of the adhesive 100 with the active material. The first group and the second group cooperate with each other so that the adhesive 100 can be uniformly dispersed in the active material layer 220 and set in contact with the active material. The adhesive 100 has excellent bonding performance, so that the negative electrode sheet 200 has a large peeling force. In the molecular chain of the modified polyacrylic acid polymer, the number of the first group may represent the number of unsubstituted acrylic acid monomers, and the number of the second group may represent the number of alkyl-substituted acrylic acid derivative monomers. When the number ratio a of the second group to the first group satisfies the range of 0.2≤a≤0.5, the number of the second group and the number of the first group are both within a reasonable range. When the adhesive 100 is applied to the negative electrode sheet 200, the adhesive 100 can maintain good dispersion performance and have good affinity with the active material, so that the adhesive 100 can be evenly dispersed in the active material layer 220 and arranged in contact with the active material. The adhesive 100 has excellent bonding performance to the active material, so that the negative electrode sheet 200 has a large peeling force. When the ratio of the number of the second group to the first group is too large, the number of the second group is too large, and accordingly, in the molecular chain of the modified polyacrylic acid polymer, the number of alkyl-substituted acrylic acid derivative monomers is too large, and the adhesive 100 has good lipophilicity with the active material, but its dispersion performance is weakened, and the adhesive 100 may agglomerate and reduce the bonding effect to the active material, increasing the probability of part of the active material falling off from the active material layer 220. When the ratio of the number of the second group to the first group is too small, the number of the second group is too small, and accordingly, in the molecular chain of the modified polyacrylic acid polymer, the number of alkyl-substituted acrylic acid derivative monomers is too small, and the lipophilicity of the adhesive 100 is poor, so that the affinity between the adhesive 100 and the active material is reduced, and the bonding performance of the adhesive 100 to the active material is also weakened.

[0038] In some embodiments, the structural formula of the adhesive 100 is: , where n is in the range of 4×104 ≤n≤10×10 4 , the range of m is: 2×10 4 ≤m≤5×10 4 .

[0039] Specifically, the value of n can be, but is not limited to, 4×10 4 4.2×10 4 , 4.5×10 4 4.8×10 4 , 5×10 4 , 5.2×10 4 , 5.6×10 4 , 6×10 4 , 6.2×10 4 , 6.5×10 4 , 6.8×10 4 ,7×10 4 , 7.2×10 4 , 7.5×10 4 , 8×10 4 , 8.2×10 4 , 8.5×10 4 ,9×10 4 , 9.2×10 4 , 9.5×10 4 , 9.6×10 4 , 9.8×10 4 and 10×10 4 wait.

[0040] Specifically, the value of m may be, but is not limited to, 2×10 4 , 2.2×10 4 , 2.4×10 4 , 2.6×10 4 , 3×10 4 , 3.2×10 4 , 3.6×10 4 , 4×10 4 4.2×10 4 , 4.3×10 4 , 4.5×10 4 4.8×10 4 and 5×10 4 wait.

[0041] In this embodiment, the structural formula of the adhesive 100 is , the adhesive 100 includes a main chain and a plurality of side chains, each of the side chains is connected to the main chain, the main chain is a full carbon chain, that is, a repeating unit formed by a plurality of acrylic acids, and the plurality of repeating units have the same or similar structure, so as to improve the regularity of the modified polyacrylic acid polymer, and facilitate the formation of an adhesive 100 with an extremely high weight average molecular weight, so that the adhesive 100 has very excellent bonding performance. In addition, the adhesive 100 also includes a plurality of side chains, some of which include a first group carboxyl group, and some of which include a second group, an ester group substituted by an alkyl group, the first group has good hydrophilicity, so that the adhesive 100 has good dispersibility, and the second group has good lipophilicity, so that the adhesive 100 has good affinity with the active material. The first group and the second group cooperate with each other so that the adhesive 100 can be evenly dispersed in the active material layer 220, and can be coated on the surface of the active material and arranged in contact with the active material, thereby achieving effective bonding to the active material and improving the peeling force of the negative electrode sheet 200. Further, in the structural formula of the adhesive 100, n satisfies the range of 4×10 4 ≤n≤10×10 4 , m satisfies the range 2×10 4 ≤m≤5×10 4 , the value of n and the value of m are within a reasonable range. On the one hand, by adjusting the number of n and the number of m, the adhesive 100 has a higher weight average molecular weight and satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol, so that the adhesive 100 has high bonding performance and strong suspension performance, which is conducive to bonding more active materials, so that the negative electrode sheet 200 has a higher energy density. On the other hand, by regulating the number of n and the number of m respectively, the dispersion performance of the adhesive 100 and the affinity for the active material can be balanced, so that the adhesive 100 can be evenly dispersed in the active material layer 220 and tightly coated on the periphery of the active material to give full play to the bonding effect on the active material, the adhesive 100 shows excellent bonding performance, and the negative electrode sheet 200 has a larger peeling force.

[0042] Optionally, the value of n+m satisfies the range: 6×10 4 ≤n+m≤15×10 4 .

[0043] Specifically, the value of n+m may be, but is not limited to, 6×10 4 ,7×10 4 , 8×10 4 ,9×10 4, 10×10 4 , 11×10 4 , 12×10 4 , 13×10 4 , 14×10 4 and 15×10 4 wait.

[0044] In this embodiment, the value of n+m satisfies the range: 6×10 4 ≤n+m≤15×10 4 , so that the weight average molecular weight of the adhesive 100 satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol, which is conducive to bonding more active materials to meet the needs of the negative electrode sheet 200 with higher capacity density.

[0045] Optionally, the structural formula of the adhesive 100 further satisfies the relationship: 0.2≤m / n≤0.5.

[0046] Specifically, the value of m / n may be, but is not limited to, 0.2, 0.22, 0.25, 0.27, 0.29, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.45, 0.47, 0.49, and 0.5, etc.

[0047] In this embodiment, the structural formula of the adhesive 100 satisfies the relationship 0.2≤m / n≤0.5, and accordingly, the number of the second group and the number of the first group are both within a reasonable range. When the adhesive 100 is applied to the negative electrode sheet 200, the adhesive 100 can maintain good dispersion performance and have good affinity with the active material, so that the adhesive 100 can be evenly dispersed in the active material layer 220 and be arranged in contact with the active material. The adhesive 100 has excellent bonding performance to the active material, so that the negative electrode sheet 200 has a large peeling force.

[0048] In some embodiments, the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% is greater than or equal to 2×10 5 mPa·s.

[0049] It can be understood that, in the aqueous solution containing the adhesive 100 provided in the present application, the mass of the adhesive 100 is 1% of the mass of the aqueous solution.

[0050] In this embodiment, the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% is greater than or equal to 2×10 5mPa·s, the viscosity of the aqueous solution exceeds 200,000 mPa·s, which has extremely high viscosity. When the adhesive 100 is applied to the negative electrode sheet 200, the adhesive 100 can effectively bond the active material, and in order to meet the requirements of the negative electrode sheet 200 with high energy density, the adhesive 100 can also bond enough active materials.

[0051] Optionally, in some embodiments, the preparation method of the adhesive 100 includes: S101, providing monomers of acrylic acid and its derivative monomers and adding them into a reaction kettle.

[0052] It can be understood that the monomer acrylic acid and its derivative monomers include acrylic acid and acrylic acid in which the carboxyl group is partially substituted.

[0053] S102, adding part of acrylic acid monomer and its derivatives to the aqueous solution at the first temperature, adding 20% ​​by mass of initiator and 7% to 8% by mass of emulsifier after passing nitrogen, and gradually heating the reaction temperature to a second temperature which is greater than the first temperature, and starting to drop the remaining acrylic acid monomer and alkyl alcohol monomer having 5 to 8 carbon atoms to obtain a modified polyacrylic acid polymer.

[0054] Optionally, the first temperature satisfies the range of 45°C to 55°C. Specifically, the value of the first temperature may be, but is not limited to, 45°C, 46°C, 48°C, 50°C, 52°C, 53°C, 54°C, 55°C, etc. Preferably, the first temperature is 50°C.

[0055] Optionally, the initiator is ammonium persulfate solution.

[0056] Optionally, the emulsifier includes lithium dodecyl sulfate. It can be understood that the emulsifier with a mass fraction of 7% to 8% means that the mass fraction of lithium dodecyl sulfate in the emulsifier is 7% to 8%.

[0057] Optionally, the second temperature satisfies the range of 65°C to 75°C. Specifically, the value of the second temperature may be, but is not limited to, 65°C, 66°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, etc. Preferably, the second temperature is 70°C.

[0058] It can be understood that when part of the acrylic acid monomers are added to the aqueous solution at the first temperature, the plurality of acrylic acid monomers undergo a polymerization reaction to form a main chain structure.

[0059] It can be understood that, when the remaining acrylic acid monomer and the alkyl alcohol monomer having 5 to 8 carbon atoms are added dropwise at the end, the acrylic acid monomer part forms the main chain structure, and the hydrogen on the carboxyl group of the acrylic acid monomer is replaced by -C x H2x+1 Replace, wherein x satisfies the range 5≤x≤8.

[0060] S103, washing the modified polyacrylic acid polymer 2 to 3 times.

[0061] S104, neutralizing the modified polyacrylic acid polymer with sodium carbonate or sodium hydroxide.

[0062] S105, drying and granulation to obtain the adhesive 100 provided in the present application. The adhesive 100 is a modified polyacrylic acid polymer, which includes a first group and a second group, wherein the hydrophilicity of the first group is greater than the hydrophilicity of the second group, and the weight average molecular weight M of the adhesive 100 is in the range of: 1×10 7 g / mol≤M≤2.2×10 7 g / mol.

[0063] The adhesive 100 obtained by the above preparation method is a polyacrylic acid polymer, and the adhesive 100 includes a main chain structure connected by repeating units derived from acrylic acid, and the weight average molecular weight of the adhesive 100 is as high as tens of millions. 5 to 8 alkyl alcohol monomers replace the hydroxyl group of acrylic acid to form a side chain structure connected to the main chain. In other words, the first group is a carboxyl group, and the second group is formed by replacing the carboxyl group with an alkyl alcohol. The first group enables the adhesive 100 to have better dispersibility, which is convenient for the adhesive 100 to be evenly dispersed in the active material layer 220. The second group has good lipophilicity, which is convenient for coating on the surface of graphite and has good affinity with the active material, so that the adhesive 100 can give full play to its bonding performance.

[0064] Some embodiments of the present application further provide a negative electrode plate 200 , which includes: a current collector layer 210 and an active material layer 220 , wherein the active material layer 220 includes an active material and an adhesive 100 provided in the present application, wherein the active material includes graphite.

[0065] It can be understood that the active material layer 220 is arranged on at least one side of the current collector layer 210; in some embodiments, the number of layers of the active material layer 220 is one layer, and the active material layer 220 is arranged on one side of the current collector layer 210; in other embodiments, the number of layers of the active material layer 220 is two layers, and the two active material layers 220 are respectively arranged on opposite sides of the current collector layer 210.

[0066] In this embodiment, the negative electrode sheet 200 includes a current collector layer 210 and an active material layer 220, and the active material layer 220 includes an active material and an adhesive 100 provided in the present application. On the one hand, the adhesive 100 is a modified polyacrylic acid polymer and includes a first group and a second group. The hydrophilicity of the first group is greater than that of the second group. The first group and the second group cooperate with each other so that the adhesive 100 has both good dispersion performance, which facilitates the uniform dispersion of the adhesive 100 in the active material layer 220 of the negative electrode sheet 200, and has a greater affinity with the active material graphite, so that the adhesive 100 has excellent bonding performance to the active material, and the negative electrode sheet 200 has a greater peeling force. On the other hand, the weight average molecular weight M of the adhesive 100 satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol. Compared with the conventional adhesive 100, the weight average molecular weight of the adhesive 100 provided in the present application is extremely large, so that the adhesive 100 has high bonding performance and strong suspension performance, which is conducive to bonding more active materials, so that the negative electrode plate 200 has a higher energy density, which is conducive to improving the performance of the negative electrode plate 200.

[0067] In some embodiments, the peel strength σ of the negative electrode sheet 200 after rolling is in the range of 10 N / m≤σ≤35 N / m.

[0068] Specifically, the value of the peel strength σ of the negative electrode sheet 200 after rolling can be but is not limited to 10N / m, 12N / m, 13N / m, 15N / m, 16N / m, 18N / m, 20N / m, 21N / m, 22N / m, 24N / m, 25N / m, 27N / m, 29N / m, 30N / m, 31N / m, 32N / m, 33N / m, 34N / m and 35N / m, etc.

[0069] It can be understood that the peel strength of the negative electrode sheet 200 after rolling can represent the bonding strength between the active material layer 220 and the current collector layer 210 after the negative electrode sheet 200 is rolled, and can also represent the bonding performance of the adhesive 100 to the active material. Accordingly, the greater the peel strength of the negative electrode sheet 200, the greater the bonding strength between the active material layer 220 and the current collector layer 210, and the better the bonding performance of the adhesive 100 to the active material.

[0070] In this embodiment, when the peel strength σ of the negative electrode sheet 200 after rolling satisfies the range of 10N / m≤σ≤35N / m, the negative electrode sheet 200 has a large peel strength after rolling. In other words, in the active material layer 220, the adhesive 100 has a good bonding performance to the active material to prevent the active material from falling off from the active material layer 220, thereby improving the cycle stability of the battery 300 when the negative electrode sheet 200 is applied to the battery 300. In addition, the adhesive 100 located on the surface of the active material layer 220 facing the current collector layer 210 can also be used to bond the active material layer 220 to the current collector layer 210, so that when the negative electrode sheet 200 is applied to the battery 300 and the battery 300 is in a charge and discharge cycle, the active material layer 220 can be prevented from falling off from the current collector layer 210 due to the embedding and extraction of active ions, which is conducive to extending the service life of the negative electrode sheet 200.

[0071] The compaction density range of the negative electrode plate 200 provided in this embodiment is: 1.5 g / cm 3 Up to 1.6g / cm 3 Specifically, the compaction density of the negative electrode plate 200 may be, but is not limited to, 1.5 g / cm 3 , 1.52g / cm 3 , 1.54g / cm 3 , 1.56g / cm 3 , 1.58g / cm 3 , and 1.6g / cm 3 Preferably, the compaction density of the negative electrode sheet 200 is 1.5 g / cm 3 .

[0072] In some embodiments, in the active material layer 220 , the mass fraction b of the binder 100 is in the range of 0.1%≤b≤1%.

[0073] Specifically, the mass fraction b of the adhesive 100 may be, but is not limited to, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9% and 1%.

[0074] It can be understood that, in the active material layer 220 , the mass fraction b of the binder 100 is the ratio of the mass of the binder 100 to the mass of the active material layer 220 .

[0075] In the active material layer 220 of the negative electrode plate 200 provided in this embodiment, when the mass fraction b of the adhesive 100 satisfies the range of 0.1%≤b≤1%, the mass fraction of the adhesive 100 is within a reasonable range. On the one hand, the adhesive 100 can be evenly dispersed in the active material layer 220 and coated on the surface of the active material. The adhesive 100 has good bonding properties to the active material to prevent the active material from falling off from the active material layer 220, so that the negative electrode plate 200 has a large peeling force. On the other hand, it can avoid that the mass fraction of the active material is too small due to the excessive mass fraction of the adhesive 100, and the negative electrode plate 200 has a higher energy density. When the mass fraction b of the adhesive 100 is too large, correspondingly, the mass fraction of the active material in the active material layer 220 is too low, which is not conducive to the improvement of the energy density of the negative electrode plate 200. When the mass fraction b of the adhesive 100 is too small, the adhesive property of the adhesive 100 to the active material is weakened, and the risk of a part of the active material falling off from the active material layer 220 is increased.

[0076] See also Figure 2 The present application provides a battery 300, which includes: a negative electrode plate 200, a separator 310, a positive electrode plate 320 and an electrolyte 330 provided in the present application, and the electrolyte 330 is used to infiltrate at least part of the negative electrode plate 200, the separator 310 and the positive electrode plate 320.

[0077] It can be understood that the negative electrode sheet 200, the separator 310 and the positive electrode sheet 320 are stacked in sequence and then wound.

[0078] It can be understood that the electrolyte 330 includes active ions, and during the charge and discharge cycle of the battery 300 , the active ions are transferred between the positive electrode plate 320 and the negative electrode plate 200 .

[0079] Optionally, the battery 300 is a lithium-ion battery, and the active ions are lithium ions.

[0080] In this embodiment, the battery 300 includes the negative electrode sheet 200 provided in this 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 transmitted between the positive electrode sheet 320 and the negative electrode sheet 200 to realize the charge and discharge process of the battery 300. The active material layer 220 of the negative electrode sheet 200 provided in this application includes an active material and an adhesive 100. The adhesive 100 can be uniformly dispersed in the active material layer 220 and has a large affinity for the active material, so that the adhesive 100 and the active material have excellent bonding performance, the negative electrode sheet 200 has a large peeling force, and the active material is not easy to fall off from the active material layer 220, so that the battery 300 has good cycle stability.

[0081] The technical solution of this application is further introduced in the following with multiple embodiments: Example 1 to Example 9, Comparative Example 1 to Comparative Example 6: 1. Preparation of adhesive 100: Provide monomers of acrylic acid and its derivatives and add them into a reaction kettle, add part of acrylic acid monomers and its derivatives into a 50° C. aqueous solution, introduce nitrogen, add a 20% by mass initiator ammonium persulfate solution and a 7% to 8% by mass emulsion lithium dodecyl sulfate, gradually heat the reaction to 70° C., start to dropwise add the remaining acrylic acid monomers and an alkyl alcohol monomer with 5 to 8 carbon atoms, so as to obtain a modified polyacrylic acid polymer.

[0082] The modified polyacrylic acid polymer obtained above was washed, neutralized, dried, and granulated to obtain the adhesive 100 of Examples 1 to 9 and Comparative Examples 1 to 6.

[0083] The weight average molecular weight M of the adhesive 100 is measured by any one of gel permeation chromatography (GPC), static light scattering, mass spectrometry, etc., which is not limited here. In the second group -COOR of the adhesive 100, R=-C x H 2x+1 The value of x can be measured by any one of nuclear magnetic resonance, gel permeation chromatography (GPC), infrared spectroscopy, elemental molecule, X-ray photoelectron spectroscopy, and atomic force microscopy, and is not limited here.

[0084] Wherein, in the second group -COOR of the adhesive 100 of Examples 1 to 9 and Comparative Examples 1 to 6, R=-C x H 2x+1The value of x, the value of the weight average molecular weight M of the adhesive 100, and the value of the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% are shown in Table 1.

[0085] The test method for the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% is as follows: The viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% was tested by a rotational viscometer, and the specific steps were as follows: ① First install the 63# rotor, adjust the instrument level and calibrate the zero position; ② Process the sample to be tested into a state suitable for the test, pour it into the sample pool, and ensure that the liquid level reaches the specified position and there are no bubbles; ③ Set the speed to 6 rpm and the measurement time to 3 min, keep the sample at a temperature of 25°C, start the instrument for measurement, and record the viscosity data after stabilization.

[0086] 2. Preparation of negative electrode sheet 200: Active material (graphite), conductive agent (conductive carbon black), binder 100 and solvent (water) are kneaded into negative electrode slurry, and active material layer 220 is coated on bottom coating current collector layer 210 (copper foil) by coating machine, and water is removed by high temperature baking, and the obtained electrode sheet is rolled to obtain negative electrode sheets 200 of Examples 1 to 9 and Comparative Examples 1 to 6. The compaction density of negative electrode sheet 200 is 1.5 g / cm 3 After the negative electrode sheet 200 is manufactured, the number ratio a of the second group to the first group can be obtained inversely. The values ​​of the number ratio a of the second group to the first group in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1.

[0087] The test method for the ratio a of the number of the second group -COOR to the number of the first group -COOH in the adhesive 100 is as follows: Use a scraper of appropriate size to scrape powder from the upper, middle and lower layers of the cleaned negative electrode sheet 200, and ensure that the scraping force is uniform to avoid damaging the negative electrode sheet 200. Then, the scraped powder is fully mixed and dried to remove moisture interference. Then, an infrared spectrum test is performed to accurately identify the characteristic absorption peaks of the carboxyl group and the ester group, calculate the peak intensity by the integral area method, and deduct the background signal. Finally, the number ratio a is calculated based on the peak intensity ratio.

[0088] 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, the adhesive 100 of Comparative Example 1 is applied to the negative electrode sheet 200 of Comparative Example 1, and so on.

[0089] 3. Preparation of battery 300: A positive electrode sheet 320 , a separator 310 and an electrolyte 330 are provided, wherein the positive electrode sheet 320 , the separator 310 and the electrolyte 330 are conventional formulas in the art and are not limited here.

[0090] The positive electrode sheet 320, the separator 310, and the negative electrode sheet 200 are stacked in order so that the separator 310 is located between the positive electrode sheet 320 and the negative electrode sheet 200 to play an isolating role, and then they are wound into a bare electrode assembly; after welding the pole ears, the bare battery 300 is placed in an outer packaging shell, and after drying, the above-mentioned electrolyte 330 is injected, and after vacuum packaging, standing, forming, shaping, etc., finally, implementation batteries 1 to implementation batteries 9 and comparison batteries 1 to comparison batteries 6 are prepared.

[0091] Among them, the negative electrode sheet 200 of Example 1 is assembled in the implementation battery 1, the negative electrode sheet 200 of Example 2 is assembled in the implementation battery 2, the negative electrode sheet 200 of Comparative Example 1 is assembled in the comparative battery 1, and so on.

[0092] The following Table 1 is a table of structures and performance parameters of the adhesive 100 of Examples 1 to 7 and Comparative Examples 1 to 4.

[0093]

[0094] Furthermore, in the negative electrode plates 200 of Examples 1 to 9 and Comparative Examples 1 to 6, styrene-butadiene rubber adhesive is also included. The adhesive 100 of this embodiment and the styrene-butadiene rubber adhesive constitute the adhesive, that is, the mass fraction of the adhesive 100 and the mass fraction of the styrene-butadiene rubber adhesive are the total content of the adhesive.

[0095] Among them, the mass of the adhesive 100 added to the negative electrode sheet in Examples 1 to 9 and Comparative Examples 1 to 6 is the same, and the active material (graphite), conductive agent (conductive carbon black), adhesive 100, styrene-butadiene rubber (SBR), and thickener CMC are added to water in a ratio of 96.5:1.0:0.2:0.8:0.5 and formed into a negative electrode slurry through a kneading process.

[0096] Among them, in Example 1, Example 8, Example 9, Comparative Example 5 and Comparative Example 6, the mass fraction of the conductive agent is 1%, the mass fraction of the styrene-butadiene rubber adhesive is 0.8%, the mass fraction of the adhesive 100 is as shown in Table 2, the sum of the mass fraction of the conductive agent, the mass fraction of the active material and the total content of the adhesive is 1, and the mass fraction of the active material changes with the value of the mass fraction of the adhesive. In addition, the other parameter conditions of Example 8, Example 9, Comparative Example 5 and Comparative Example 6 are the same as those of Example 1. Specifically, the preparation parameters of Example 1, Example 8, Example 9, Comparative Example 5 and Comparative Example 6 are as shown in Table 2.

[0097]

[0098] Performance test of negative electrode sheet 200 and battery 300: 1. Peeling force test of negative electrode sheet 200: The negative electrode sheets 200 of Examples 1 to 9 and Comparative Examples 1 to 6 were tested for peel strength using a tensile testing machine, and the testing 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 a strip of 200 mm × 25 mm. A group of samples generally requires 3 to 5 test strips to be prepared; 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 make it firmly bonded to the test steel plate; Step 3, make one end of the test strip flush with the steel plate, with slightly wider double-sided tape on both sides, and parallelly and centrally adhere it to the other side of the double-sided tape, and use a roller to roll it 3 times in one direction to make it fit flat, manually peel off 5 mm to 10 mm from the bottom, and use a tensile testing machine with a 90° clamp to peel it off to obtain the peeling force of the test strip.

[0099] The peeling force of the test strip can characterize the peeling force of the negative electrode sheet 200 , and more specifically, 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 bonding performance of the adhesive 100 .

[0100] The peel strength refers to the peeling force required for the bonding surface of the adhesive 100 of unit width in the direction perpendicular to the bonding surface. In other words, the peel strength is the ratio of the peeling force to the width of the bonding surface of the adhesive 100. In the present application, the peel strength of the negative electrode sheet 200 is the ratio of the peeling force to the width (20 mm) of the test strip, thereby obtaining the peel strength values ​​of the negative electrode sheets 200 of Examples 1 to 9 and Comparative Examples 1 to 6.

[0101] The peel strength values ​​of the negative electrode sheets 200 of Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Table 3.

[0102] 3. Battery 300 cycle performance test: The above-mentioned implementation batteries 1 to implementation batteries 9 and comparison batteries 1 to comparison batteries 6 were subjected to constant power charge and discharge cycle tests on a charge and discharge instrument. The test temperature was 25°C, the charge and discharge rate was 0.5P (the size of the charge and discharge current is usually expressed by the charge and discharge rate, and the calculation formula of the charge and discharge current is: charge and discharge power = voltage platform of battery 300 (3.2V) × rated capacity of battery 300), the charge and discharge voltage window was 2.5V to 3.65V (that is, the charge cut-off voltage of battery 300 was 3.65V, and the discharge cut-off voltage of battery 300 was 2.5V; it is generally believed that when the charge cut-off voltage is ≥4V, the charge cut-off voltage of battery 300 is higher), and the capacity retention rate after 1000 cycles was calculated. The calculation formula is: capacity retention rate after the Nth cycle = (discharge capacity after the Nth cycle / discharge capacity of the first cycle) × 100%.

[0103] A complete charge and discharge is usually called a charge and discharge cycle, that is, the battery 300 is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming a charge and discharge cycle. Cycle N times means repeating the above process N times.

[0104] The values ​​of the capacity retention rates of implementation batteries 1 to implementation batteries 9 and comparison batteries 1 to comparison batteries 6 after 1000 cycles are shown in Table 3.

[0105] The following Table 3 shows the performance parameters of the negative electrode sheets 200 of Examples 1 to 9 and Comparative Examples 1 to 6 and the performance parameters of Implementation Batteries 1 to 9 and Comparative Batteries 1 to 6.

[0106]

[0107] Among them, in Comparative Example 6, since the mass fraction of the adhesive 100 is too large, the viscosity of the slurry is too high and cannot be coated, so its peel strength cannot be measured.

[0108] Please refer to Table 1 and Table 3. From the data of Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that under the same other conditions, the weight average molecular weight M of the adhesive 100 of Examples 1 to 3 satisfies the range of 1×10 7 g / mol≤M≤2.2×10 7 g / mol, while the weight average molecular weight M of the adhesive 100 of Comparative Examples 1 to 3 is less than 1×10 7g / mol, which makes the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% in Examples 1 to 3 much greater than the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% in Comparative Examples 1 to 3, and the peel strength of the negative electrode sheet 200 of Examples 1 to 3 is much greater than the peel strength of the negative electrode sheet 200 of Comparative Examples 1 to 3, and the capacity retention rate of the implementation battery 1 to the implementation battery 3 after 1000 cycles is greater than the capacity retention rate of the comparative battery 1 to the comparative battery 3 after 1000 cycles. This is because: the weight average molecular weight of the adhesive 100 of Examples 1 to 3 is within a reasonable range, and correspondingly, the main chain structure of the adhesive 100 is relatively long, which can form long-range adhesion, as well as more hydrogen bonds and physical entanglements, so that the adhesive 100 has high adhesion performance and strong suspension performance, can adhere to more active materials, and has a better adhesive 100 effect on the active materials, so as to prevent the active materials from falling off from the active material layer 220, and make the corresponding battery 300 have better cycle stability. In Comparative Examples 1 to 3, the weight average molecular weight of the adhesive 100 is still relatively small, and accordingly, the length of its main chain structure is relatively short, and the long-range adhesion effect formed by the adhesive 100 is relatively poor, which weakens the adhesive performance of the adhesive 100 on the active material. During the charge and discharge process of the battery 300 , the active material may fall off from the active material layer 220 and affect the cycle stability of the battery 300 , so that the capacity retention rate of the comparative batteries 1 to 3 after 1000 cycles is relatively low.

[0109] Further, it can be seen from the data of Examples 3 to 5 and Comparative Example 4 that, under the same other conditions, the second group of the adhesive 100 of Examples 3 to 5 includes an alkyl group having 5 to 8 carbon atoms. In other words, the second group is -COOR and satisfies R=-C x H 2x+1, the range of x is: 5≤x≤8. In comparative example 4, the value of x is less than 5, which makes: the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% in Examples 3 to 5 is greater than the viscosity of the aqueous solution of the adhesive 100 with a mass fraction of 1% in comparative example 4, and the peel strength of the negative electrode sheet 200 of Examples 3 to 5 is greater than the peel strength of the negative electrode sheet 200 of comparative example 4, and the capacity retention rate of the implementation battery 3 to the implementation battery 5 after 1000 cycles is greater than the capacity retention rate of the comparative battery 4 after 1000 cycles. Further, in Examples 3 to 5, x satisfies the reasonable range of 5≤x≤8, and as x gradually increases, the bonding performance of the adhesive 100 to the active material is gradually enhanced, so that the peel strength of the corresponding negative electrode sheet 200 is gradually increased. This is because: in the adhesive 100 of Examples 3 to 5, x satisfies the range of 5≤x≤8, the number of carbon atoms of the alkyl group is within a reasonable range, the lipophilicity of the alkoxy group and the lipophilicity of the second group are within a reasonable range, so that when the adhesive 100 is applied to the negative electrode sheet 200, the adhesive 100 can be arranged in contact with the active material and coated on the periphery of the active material, and the adhesive 100 has good affinity with the active material, which is conducive to the adhesive 100 being uniformly dispersed in the active material layer 220 and effectively bonding the active material, so that the adhesive 100 has excellent bonding performance, so that the negative electrode sheet 200 has a large peeling force. In the adhesive 100 of Comparative Example 4, the value of x is too small, the carbon-hydrogen bonds contained in the alkyl group are too few, the lipophilicity of the alkyl group is weak, and the lipophilicity of the second group is weak. When the adhesive 100 is applied to the negative electrode sheet 200, the affinity between the adhesive 100 and the active material is poor, which weakens the bonding effect of the adhesive 100 on the active material, thereby reducing the peel strength of the negative electrode sheet 200 of comparative example 4. Accordingly, the cycle stability of comparative battery 4 is poor.

[0110] Furthermore, it can be seen from the data of Example 1, Example 6 and Example 7 that, under the same other conditions, as the value of the ratio a of the number of the second group to the first group increases, the bonding performance of the adhesive 100 to the active material gradually increases, so that the peel strength of the corresponding negative electrode sheet 200 gradually increases, and the capacity retention rate of the corresponding battery 300 after 1000 cycles gradually increases. This is because: when the number of the second group and the first group is reasonable, the adhesive 100 can maintain good dispersion performance and have good affinity with the active material, so that the adhesive 100 can be evenly dispersed in the active material layer 220 and arranged in contact with the active material. The adhesive 100 has excellent bonding performance to the active material, so that the negative electrode sheet 200 has a large peeling force. When the value of the number ratio of the second group to the first group is too large, the adhesive 100 has good lipophilicity with the active material, but its dispersion performance is weakened, and the adhesive 100 may agglomerate and reduce the bonding effect on the active material, increasing the probability of part of the active material falling off from the active material layer 220, thereby reducing the peel strength of the corresponding negative electrode sheet 200, and further affecting the cycle performance of the corresponding battery 300. When the value of the number ratio of the second group to the first group is too small, the lipophilicity of the adhesive 100 is poor, so that the affinity between the adhesive 100 and the active material is reduced, and the bonding performance of the adhesive 100 to the active material is also weakened, thereby reducing the peel strength of the corresponding negative electrode sheet 200, and further affecting the cycle performance of the corresponding battery 300.

[0111] Further, referring to Tables 1 to 3, it can be seen from the data of Example 1, Example 8, Example 9, Comparative Example 5 and Comparative Example 6 that, under the same other conditions, in the active material layer 220 of the corresponding negative electrode sheet 200, the mass fraction b of the adhesive 100 in Example 1, Example 8 and Example 9 satisfies the range of 0.1%≤b≤1%, while the mass fraction of the adhesive 100 in Comparative Example 5 is too small, and the mass fraction of the adhesive 100 in Comparative Example 6 is too large, so that the peel strength of the negative electrode sheet 200 of Example 1, Example 8 and Example 9 is greater than the peel strength of the negative electrode sheet 200 of Comparative Example 5, and the capacity retention rate of the implementation battery 1, the implementation battery 8 and the implementation battery 9 after 1000 cycles is greater than the capacity retention rate of the comparative battery 5 after 1000 cycles, while in Comparative Example 6, due to the excessive mass fraction of the adhesive 100, the slurry viscosity is too large and cannot be coated, so its peel strength cannot be measured. This is because: the mass fraction of the adhesive 100 is within a reasonable range. On the one hand, the adhesive 100 can be evenly dispersed in the active material layer 220 and coated on the surface of the active material. The adhesive 100 has good bonding properties to the active material to prevent the active material from falling off from the active material layer 220, so that the negative electrode sheet 200 has a larger peeling force. On the other hand, it can avoid that the mass fraction of the active material is too small due to the excessive mass fraction of the adhesive 100. The negative electrode sheet 200 has a higher energy density, so that the corresponding negative electrode sheet 200 has a larger peeling strength. When the mass fraction of the adhesive 100 is too large or too small, the peeling strength of the negative electrode sheet 200 will be reduced, which will then affect the cycle performance of the corresponding battery 300.

[0112] See also Figure 3 and Figure 4 The present application provides an electrical device 400 , which includes a device body 410 and a battery 300 provided in the present application, and the battery 300 supplies power to the device body 410 .

[0113] It can be understood that the battery 300 is electrically connected to the device body 410 .

[0114] In this embodiment, the battery 300 includes the negative electrode plate 200 provided in the present application. The adhesive 100 of the negative electrode plate 200 has good bonding properties to the active material, so that the negative electrode plate 200 has a large peeling force. The battery 300 has good cycle stability, so as to provide stable electric energy for the electrical device 400, which is beneficial to improving user experience.

[0115] Optionally, the power-consuming device 400 of the embodiment of the present application may be, but is not limited to, a portable electronic device such as a mobile phone, a tablet computer, a laptop computer, a desktop computer, a smart bracelet, a smart watch, an e-reader, a game console, etc. It may also be a vehicle such as a car, a truck, a car, a truck, a truck, a motor vehicle, a high-speed train, an electric vehicle, etc. In addition, it may also be various household appliances, etc. The present application Figure 3 The electrical equipment 400 of the embodiment is an energy storage battery cabinet.

[0116] It can be understood that the electric device 400 described in this embodiment is only a form of the electric device 400 used by the battery 300, and should not be understood as a limitation on the electric device 400 provided in this application, nor should it be understood as a limitation on the electric device 400 provided in each embodiment of this application.

[0117] Mentioning "embodiment" and "implementation method" in this application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, provided that there is no contradiction between them.

[0118] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the above preferred implementation modes, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. An adhesive, characterized in that: The adhesive is a modified polyacrylic acid polymer, which includes a first group and a second group, wherein the hydrophilicity of the first group is greater than that of the second group, and the weight average molecular weight M of the adhesive is in the range of: 1×10 7 g / mol≤M≤2.2×10 7 g / mol.

2. The adhesive according to claim 1, characterized in that The second group is -COOR, and satisfies R=-C x H 2x+1 , the range of x is: 5≤x≤8.

3. The adhesive according to claim 1, characterized in that The first group is a carboxyl group, the second group is an ester group, and in the molecular chain of the modified polyacrylic acid polymer, the range of the quantity ratio a of the second group to the first group is: 0.2≤a≤0.

5.

4. The adhesive according to claim 2, characterized in that The structural formula of the adhesive is: , where n is in the range of 4×10 4 ≤n≤10×10 4 , the range of m is: 2×10 4 ≤m≤5×10 4 .

5. The adhesive according to any one of claims 1 to 4, characterized in that: The viscosity of the aqueous solution of the adhesive with a mass fraction of 1% is greater than or equal to 2×10 5 mPa·s.

6. A negative electrode plate, characterized in that: The negative electrode plate comprises: a current collector layer; and An active material layer, comprising an active material and the binder according to any one of claims 1 to 5, wherein the active material comprises graphite.

7. The negative electrode sheet according to claim 6, characterized in that: The range of the peel strength σ of the negative electrode sheet after rolling is: 10N / m≤σ≤35N / m.

8. The negative electrode sheet according to claim 6, characterized in that: In the active material layer, the mass fraction b of the binder is in the range of 0.1%≤b≤1%.

9. A battery, characterized in that: The battery comprises: The negative electrode sheet according to any one of claims 6 to 7; Diaphragm; A positive electrode; and An electrolyte is used to soak at least a portion of the negative electrode plate, the separator and the positive electrode plate.

10. An electrical device, characterized in that: The electrical equipment includes: The device itself; and The battery as claimed in claim 9, wherein the battery is used to power the device body.

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