CN117642890A

CN117642890A - Adhesive and application thereof

Info

Publication number: CN117642890A
Application number: CN202280014080.9A
Authority: CN
Inventors: 杨丙梓; 程丛; 陈均桄; 裴海乐; 张盛武; 王星会
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2024-03-01
Also published as: WO2024000100A1

Abstract

The present application relates to a binder, a slurry containing the binder, and an electrode sheet, a secondary battery, a battery module, a battery pack, and an electric device related thereto. The adhesive has the advantages of good adhesive property, low swelling rate and high cohesive force, and the prepared pole piece is not easy to crack, turn up and the like in the drying process.

Description

Adhesive and application thereof

Technical Field

The application relates to the technical field of secondary batteries, in particular to an adhesive, slurry containing the adhesive, and an electrode plate, a secondary battery, a battery module, a battery pack and an electric device related to the adhesive.

Background

In recent years, the application range of secondary batteries is becoming wider and wider, and for example, the secondary batteries can be applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, and various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like. With the wide application of secondary batteries, the requirements of battery performance are also increasing.

However, the adhesive used for preparing the battery pole piece in the prior art has insufficient adhesive force, low cohesive force and high swelling ratio of the formed adhesive film, so that the pole piece is easy to crack and turn up in the drying process, the obtained pole piece has poor brittleness and other problems, and the electrical property of the secondary battery is seriously influenced.

Therefore, there is still a need for an improvement in the binder used to prepare the electrode tabs in order to obtain a secondary battery having better electrical properties.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a binder, a slurry containing the binder, and an electrode sheet, a secondary battery, a battery module, a battery pack, and an electric device related thereto, which aim to improve the problems occurring when using the binder of the related art, thereby improving the electric performance of the secondary battery.

To achieve the above object, the present application provides in a first aspect a binder comprising a graft polymer comprising as a main chain a copolymer of formula I and grafted onto the main chain a siloxane of formula II:

wherein R is ₁ 、R ₂ And R is ₃ Each independently selected from at least one of hydrogen and C1-C6 alkyl, optionally each independently selected from at least one of hydrogen and methyl;

R ₄ selected from C (=O) OLi, C (=O) ONa, CN, C (=O) NH ₂ And at least one of carbonyloxy C1-C6 alkyl, optionally at least one selected from C (=o) OLi, C (=o) ONa and CN;

R ₅ selected from C (=O) OLi, C (=O) ONa, CN, C (=O) NH ₂ And at least one of carbonyloxy C1-C6 alkyl, optionally selected from C (=O) NH ₂ And at least one of a carbonyloxy C1-C6 alkyl group;

R ₆ at least one selected from COOH, OH, CN and carbonyloxy C1-C6 alkyl hydroxy, optionally at least one selected from OH and carbonyloxy C1-C6 alkyl hydroxy;

wherein x, y are each independently an integer from 0 to 5000, optionally an integer from 500 to 1500; x and y are not both 0;

z is an integer from 100 to 3000, optionally from 200 to 1500;

wherein R is ₇ At least one selected from the group consisting of C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 alkylazide, C1-C6 alkylamino, C1-C6 alkylcarboxy, C1-C6 alkylhydroxy, C1-C6 alkylepoxy and C1-C6 alkylmercapto, optionally at least one selected from the group consisting of C1-C6 alkylamino, C1-C6 alkylcarboxy and C1-C6 alkylepoxy;

R ₈ and R is ₉ Each independently selected from at least one of C1-C6 alkyl and C1-C6 alkyloxy;

R ₁₀ is a C1-C6 alkyl group.

In any embodiment, the weight percent of the copolymer of formula I in the graft polymer is from 90% to 99.9%.

In any embodiment, the silicone of formula II has a grafting ratio in the graft polymer of from 0.1% to 5%.

In any embodiment, the copolymer of formula I is a terpolymer formed by copolymerizing three monomers, wherein the first monomer is lithium (meth) acrylate, sodium (meth) acrylate, or acrylonitrile; the second monomer is C1-C6 alkyl (meth) acrylate, acrylamide or acrylonitrile; the third monomer is hydroxy C1-C6 alkyl (meth) acrylate.

In any embodiment, the molar ratio of the first monomer, the second monomer, and the third monomer is (0.5-3): (0.5-2): 1, optionally (0.8-2.5): (0.6-1.5): 1.

in any embodiment, the terpolymer is selected from at least one of poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-propyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-pentyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-acrylamide-hydroxymethyl acrylate), poly (acrylonitrile-methyl acrylate-hydroxymethyl acrylate), and poly (sodium acrylate-acrylonitrile-hydroxymethyl acrylate).

In any embodiment, the siloxane of formula II is selected from at least one of 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and 3-aminopropyl tripropoxysilane.

In any embodiment, the binder is in the form of an aqueous emulsion, wherein the weight percent of the graft polymer in the aqueous emulsion is from 5% to 50%, alternatively from 10% to 40%.

In any embodiment, the viscosity of the binder is from 100 mPa-s to 20000 mPa-s, optionally from 500 mPa-s to 2000 mPa-s.

A second aspect of the present application provides a method of preparing the binder of the first aspect of the present application, wherein the method comprises the steps of:

Step (1): reacting a copolymer of formula I with a halogenated C1-C6 alkyl epoxy compound in the presence of a base, the reaction being carried out in the presence of a solvent;

step (2): after optional removal of the solvent and addition of water, the siloxane of formula II and optionally the surfactant are then added and stirred.

In any embodiment, the weight ratio of copolymer of formula I to halogenated C1-C6 alkyl epoxy compound is 1 (0.005-0.1), optionally 1 (0.01-0.05).

In any embodiment, the molar ratio of halogenated C1-C6 alkyl epoxy compound to siloxane of formula II is 1 (0.5-2), alternatively 1 (0.8-1.5), and alternatively 1 (0.9-1.2).

In any embodiment, the halogenated C1-C6 alkyl epoxy compound is epichlorohydrin;

in any embodiment, the base is selected from at least one of sodium hydride and sodium hydroxide, optionally sodium hydride;

in any embodiment, the molar ratio of the halogenated C1-C6 alkyl epoxy compound to the base is 1 (0.5-2), alternatively 1 (0.8-1.5), and further alternatively 1 (0.9-1.2) 1.

A third aspect of the present application provides a slurry comprising a binder as described in the first aspect of the present application or a binder prepared according to the method of the second aspect of the present application.

In any embodiment, the slurry comprises 0.5% to 5% by weight of the binder.

A fourth aspect of the present application provides an electrode sheet comprising a current collector and a film layer formed from the slurry of the third aspect of the present application disposed on at least one surface of the current collector.

A fifth aspect of the present application provides a secondary battery comprising the electrode tab of the fourth aspect of the present application.

A sixth aspect of the present application provides a battery module comprising the secondary battery of the fifth aspect of the present application.

A seventh aspect of the present application provides a battery pack comprising the battery module of the sixth aspect of the present application.

An eighth aspect of the present application provides an electric device including at least one selected from the secondary battery of the fifth aspect of the present application, the battery module of the sixth aspect of the present application, or the battery pack of the seventh aspect of the present application.

The adhesive has good adhesive property, high cohesive force, low swelling rate of the formed adhesive film, difficult cracking, curling and other problems of the pole piece prepared from the adhesive in the drying process, and the prepared secondary battery also has good capacity retention rate.

Drawings

Fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 1.

Fig. 3 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 4 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 5 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 4.

Fig. 6 is a schematic view of an electric device in which the secondary battery according to an embodiment of the present application is used as a power source.

FIG. 7 is an infrared spectrum of a graft polymer of example 1 of the present application, in which the characteristic peak 1087cm ^-1 Indicating that the copolymer was grafted with a silicone compound.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 roof assembly

Detailed Description

Hereinafter, embodiments of the binder, the slurry containing the binder, and the electrode tabs, secondary batteries, battery modules, battery packs, and electric devices related thereto of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

Unless otherwise specified, in the present application, all operations were carried out at normal temperature (25 ℃) and normal pressure (101 kPa).

The inventors have found in studies that when a binder in the prior art, particularly a poly (meth) acrylic acid-based binder is used, the positive electrode sheet prepared from the binder has problems of high brittleness, poor flexibility, low cohesive force, high swelling coefficient in an electrolyte, and the like. However, the inventors have unexpectedly found that the resulting adhesive can significantly improve the above problems after grafting a silicone-containing compound onto a poly (meth) acrylic polymer. This improvement is particularly advantageous for use cases requiring thick coatings and high compaction densities.

Without being bound by any theory, the inventors believe that when the adhesive of the present application is used in the preparation of an aqueous slurry, during the process of coating the slurry on a current collector and drying, the concentration of the adhesive gradually increases due to the solvent in the slurry being carried away during the drying process, the concentration of the silicon hydroxyl groups formed by the hydrolysis of the grafted siloxane on each backbone increases, and the probability of contact between the silicon hydroxyl groups increases. Two adjacent silicon hydroxyl groups are dehydrated in the drying process to form Si-O-Si covalent bonds, so that a stronger irreversible cross-linked network is generated, the cohesive energy of active substances in the pole piece is improved, and the adhesive force between the active substances and the conductive agent is enhanced. Meanwhile, on the interface where the slurry contacts the current collector, the silicon hydroxyl in the adhesive and the hydroxyl in the current collector can form Si-O-R covalent bond in the drying and dehydration process, so that the bonding strength of the active substance and the current collector is improved.

In addition, as the main chain is grafted with siloxane, the siloxane can be hydrolyzed to form silicon hydroxyl groups under acidic, alkaline and other conditions, and weak hydrogen bond interaction is formed between the silicon hydroxyl groups of each molecular chain, so that the adhesive can generate reversible crosslinking in the slurry. The reversible crosslinking can gel the slurry in the static process of the anode slurry and the cathode slurry, prevent different components in the slurry from floating or settling due to different densities, improve the stability and uniformity of the slurry, and prolong the storage time of the slurry. Meanwhile, as the adhesive has lower loading capacity in the slurry and a large amount of solvent is contained in the slurry, the weak hydrogen bond interaction can only generate extremely low interaction force, the hydrogen bond interaction can be destroyed under the action of extremely small external shearing force, the reversible crosslinking fracture is caused, the slurry recovers the original fluidity and rheological property, and the slurry has better processability.

To this end, a first aspect of the present application provides a binder comprising a graft polymer comprising as a backbone a copolymer of formula I and grafted to the backbone a siloxane of formula II:

wherein x, y are each independently an integer from 0 to 5000, optionally an integer from 100 to 4000, still optionally an integer from 200 to 3000, still further optionally an integer from 500 to 1500; x and y are not both 0;

z is an integer from 100 to 3000, alternatively from 150 to 2500, alternatively from 180 to 2000, and further alternatively from 200 to 1500;

R ₁₀ is a C1-C6 alkyl group.

In the present application, it is understood that "C1-C6 alkyl" refers to a straight or branched hydrocarbon having from 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1, 2-dimethylpropyl, 1-dimethylpropyl, 2-dimethylpropyl, 1-ethylpropyl, hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1, 2-dimethylpropyl, 1, 3-dimethylbutyl, 1, 4-dimethylbutyl, 2, 3-dimethylbutyl, 1-dimethylbutyl, 2-dimethylbutyl, 3-dimethylbutyl, 1, 2-trimethylpropyl, 1, 2-trimethylpropyl, 1-ethylbutyl and 2-ethylbutyl. Alkyl groups having 1 to 4 carbon atoms are also optional, such as, inter alia, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl.

In some embodiments, the number average molecular weight of the grafted polymer is 50,000 to 1,000,000, alternatively 100,000 to 800,000, and still alternatively 150,000 to 600,000.

In some embodiments, the weight percent of the copolymer of formula I in the graft polymer is from 90% to 99.9%, alternatively from 90.5% to 98.5%, further alternatively from 91% to 98%, based on the total weight of the graft polymer.

In some embodiments, the weight percent of the siloxane of formula II in the graft polymer is from 0.1% to 10%, alternatively from 0.5% to 8%, and still alternatively from 1% to 6%, based on the total weight of the graft polymer.

In some embodiments, the copolymer of formula I has a number average molecular weight of 20,000 to 500,000, alternatively 50,000 to 400,000, and still alternatively 100,000 to 350,000.

In some embodiments, the siloxane of formula II has a relative molecular weight of 50 to 500, alternatively 100 to 400, and still alternatively 150 to 350.

In the present application, the number average molecular weight is determined by Gel Permeation Chromatography (GPC) using tetrahydrofuran as a eluent in accordance with GB/T21863-2008 Gel Permeation Chromatography (GPC).

In some embodiments, the silicone of formula II has a grafting ratio in the graft polymer of 0.1 to 5%, alternatively 0.5 to 3.5%, and still alternatively 0.8% to 3%. In the present application, the expression "grafting ratio" is understood to mean the ratio of the molar quantity of comonomer grafted to the molar quantity of total comonomer in the grafted polymer. For example, in the preparation of the graft polymer, the copolymer of formula I used as the backbone is polymerized from a total of 10 moles of comonomer, whereas in the subsequent grafting using only 0.1 moles of siloxane of formula II, it is understood that the grafting ratio here is 0.1/10 x 100% = 1%.

In the present application, it is understood that the reaction between the copolymer of formula I and the siloxane of formula II may be carried out directly, for example, the copolymer of formula I contains groups on the branches that can react directly with alkenyl, alkynyl, azido, amino, carboxyl, hydroxyl, epoxy or mercapto groups on the siloxane of formula II; in the case where the copolymer of formula I cannot be reacted directly with the siloxane compound of formula II, the copolymer of formula I may be reacted first with an intermediate compound containing two functional groups which are reactive with both the functional groups of formula I and the functional groups of formula II, and then with the siloxane of formula II, by means of which the copolymer of formula I is grafted with the siloxane of formula II, the reactions involved being known to the person skilled in the art.

In some embodiments, when R in formula I ₆ In the case of COOH, R in formula II ₇ At least one selected from the group consisting of C1-C6 alkylamino, C1-C6 alkylcarboxy, C1-C6 alkylhydroxy, C1-C6 alkylepoxy and C1-C6 alkylmercapto, in which case R ₆ And R is R ₇ Grafting may be performed by forming amide, anhydride, or ester linkages by methods well known in the art.

In some embodiments, when R in formula I ₆ In the case of OH, R in formula II ₇ At least one selected from the group consisting of C1-C6 alkylcarboxy, C1-C6 alkylhydroxy, C1-C6 alkylepoxy and C1-C6 alkylmercapto, in which case R ₆ And R is R ₇ Grafting may be performed by formation of ester linkages, condensation, or ring opening by methods well known in the art.

In some embodiments, when R in formula I ₆ In the case of CN, R in formula II ₇ Selected from C1-C6 alkyl azido, in which case R ₆ And R is R ₇ Grafting may be performed by cycloaddition reactions occurring by methods well known in the art.

In some embodiments, when R in formula I ₆ R in formula II in the case of a carbonyloxy C1-C6-alkyl hydroxy group ₇ At least one selected from the group consisting of C1-C6 alkylcarboxy, C1-C6 alkylhydroxy, C1-C6 alkylepoxy and C1-C6 alkylmercapto, in which case R ₆ And R is R ₇ Grafting may be performed by formation of ester linkages, condensation, or ring opening by methods well known in the art.

In some embodiments, when the copolymer of formula I contains a reactive unsaturation, R in the siloxane of formula II ₇ Can be C1-C6 alkenyl or C1-C6 alkynyl.

In some embodiments, when R ₆ And R is R ₇ Without any space therebetweenWhen the reaction is carried out directly, it is possible to achieve grafting by introducing intermediate compounds.

In some embodiments, the intermediate compound may be a small molecule compound (e.g., a relative molecular weight less than 500) or a polymer (e.g., a number average molecular weight greater than 1000 to less than 10,000). For a particular class of intermediate compounds, one skilled in the art can vary the reactive groups contained in the copolymer of formula I with R in the siloxane of formula II ₇ Is specifically selected.

In some embodiments, when R in formula I ₆ Is OH or carbonyloxy C1-C6 alkyl hydroxy, R in formula II ₇ In the case of C1-C6 alkylamino, R can be first of all ₆ The hydroxyl on the copolymer reacts with intermediate compound halogenated C1-C6 alkyl epoxy under alkaline condition, so that the functional group containing epoxy group is grafted on the side chain of the copolymer firstly, and then the epoxy functional group is reacted with R ₇ The amino groups of (2) react to effect grafting.

In the present application, the term "halogenated C1-C6 alkyl epoxy" refers to a halogenated C1-C6 alkyl group having one epoxy group.

In some embodiments, the halogenated C1-C6 alkyl epoxy is epichlorohydrin.

In some embodiments, the copolymer of formula I comprises at least two, optionally three, polymeric units of:

wherein m is an integer from 0 to 50, optionally an integer from 1 to 5; n may have the values of x, y and z described above.

In some embodiments, the copolymer of formula I is a terpolymer formed by copolymerizing three monomers, wherein the first monomer is lithium (meth) acrylate, sodium (meth) acrylate, or acrylonitrile; the second monomer is C1-C6 alkyl (meth) acrylate, acrylamide or acrylonitrile; the third monomer is hydroxy C1-C6 alkyl (meth) acrylate.

In the present application, it is understood that the polymerized units in the copolymers of the formula I The copolymers of the formula I can be formed by copolymerization in random, block, alternating or grafted fashion.

The application copolymerizes two or more polymer monomers in random, block, alternate, grafting and other modes to form the multipolymer, and the multipolymer can obtain ideal mechanical, chemical and electrochemical properties through regulating and controlling the types and the proportions of the monomers, thereby meeting the requirements of pole piece production.

In some embodiments, the copolymer of formula I is a terpolymer formed by copolymerizing three monomers, wherein the first monomer is lithium (meth) acrylate, sodium (meth) acrylate, or acrylonitrile; the second monomer is C1-C6 alkyl (meth) acrylate, acrylamide or acrylonitrile; the third monomer is hydroxyl C1-C6 alkyl (methyl) acrylate, wherein the mole ratio of the first monomer to the second monomer to the third monomer is (0.5-3): 0.5-2): 1, optionally (0.8-2.5): 0.6-1.5): 1, optionally (1.3-2.0): 0.6-1): 1.

step (2): after optional removal of the solvent and addition of water, the siloxane of formula II (e.g., wherein R ₇ Is a C1-C6 alkylamino group; r is R ₈ And R is ₉ Is C1-C6 alkyloxy; r is R ₁₀ Is C1-C6 alkyl) and optionally a surfactantStirring.

In some embodiments, the weight ratio of copolymer of formula I to halogenated C1-C6 alkyl epoxy compound is 1 (0.005-0.1), alternatively 1 (0.008-0.05), further alternatively 1 (0.01-0.03), and still further alternatively 1 (0.01-0.02).

In some embodiments, the reactions in steps (1) and (2) are performed under an inert gas (e.g., nitrogen or argon) atmosphere.

In some embodiments, in step (1), the reaction is carried out at 10 ℃ to 50 ℃, optionally 20 ℃ to 40 ℃.

In some embodiments, in step (1), the copolymer of formula I may be reacted with a base for 1 to 5 hours prior to the addition of the halogenated C1-C6 alkyl epoxy compound.

In some embodiments, the halogenated C1-C6 alkyl epoxy compound is epichlorohydrin.

In some embodiments, the solvent is selected from at least one of toluene, methylene chloride, chloroform, acetone, and N, N' -dimethylformamide.

In some embodiments, the base is selected from at least one of sodium hydride and sodium hydroxide, optionally sodium hydride.

In some embodiments, the molar ratio of the halogenated C1-C6 alkyl epoxy compound to the base is 1 (0.5-2), alternatively 1 (0.8-1.5), and still alternatively 1 (0.9-1.2) 1.

In some embodiments, in step (2), after the addition of the siloxane of formula II and optionally the surfactant, the resulting mixture is stirred at 30 ℃ to 60 ℃, optionally 35 ℃ to 55 ℃, for a period of 10 hours to 50 hours, optionally 11 hours to 30 hours.

In some embodiments, the molar ratio of the halogenated C1-C6 alkyl epoxy compound to the siloxane of formula II is 1 (0.5-2), alternatively 1 (0.8-1.5), and alternatively 1 (0.9-1.2).

In some embodiments, the weight ratio of the copolymer of formula I to the water is 1 (0.5-6), alternatively 1 (1-5), further alternatively 1 (1.5-4), further alternatively 1 (2-3).

In some embodiments, the weight ratio of water to surfactant is 1 (0.05-0.5), alternatively 1 (0.06-0.3), and alternatively 1 (0.08-0.2).

In some embodiments, the binder is in the form of an aqueous emulsion, wherein the weight percent of the graft polymer in the aqueous emulsion is from 5% to 50%, alternatively from 10% to 40%, and still alternatively from 20% to 32%, based on the total weight of the aqueous emulsion.

In this application, unless otherwise indicated, all water used is deionized water.

In some embodiments, the viscosity of the binder is from 100 mPa-s to 20000 mPa-s, optionally from 500 mPa-s to 2000 mPa-s.

In this application, the viscosity of the adhesive can be tested at 25℃using the spin method according to standard GB/T10247-2008. The standard specifically operates as follows: filling the beaker or vessel with the sample to be tested, ensuring that no air bubbles are introduced, and if necessary, evacuating to eliminate the air bubbles. If the sample volatilizes or is easily absorbed by moisture, the beaker or the container is sealed in the constant temperature process. The beaker or holder of ready sample is placed in a constant temperature bath to ensure that the time is sufficient to reach the prescribed temperature. And selecting a proper rotor to ensure that the reading is 20-90% of the maximum measuring range. For the No. 63 rotor, the viscosity of 1000 mpa.s is less than or equal to 10000 mpa.s, the torque percentage of 20 percent is less than or equal to 90 percent, if the viscosity result is NG, the No. 64 rotor is used, and the following results are simultaneously satisfied: 10000 mpa.s < viscosity, 20% or more and 90% or less of torque percentage. The rotor groove is flush with the liquid level during the test. After the instrument viscosity reading is stable after 5min, the motor is stopped, the motor is started again after the rotor is stopped, the second test is performed until the deviation of the continuous two test data relative to the average value is not more than 3%, and the result is the average value of the two measurement values.

Herein, the test may include the steps of:

the rotor was selected based on the sample viscosity using a rotational viscometer. The viscometer is slowly lowered by using a viscometer lifting frame, and the rotor is controlled to be immersed in the liquid until the mark on the rotor is leveled with the liquid level. Test temperature: 25 ℃, rotation speed: 12rpm. And (5) pressing a measurement key to start measurement, and reading the viscosity value after the data is kept stable for 5 minutes.

In some embodiments, the aqueous emulsion comprises 40% to 90%, alternatively 50% to 80%, and still alternatively 60% to 75% water by weight. Compared with the traditional slurry, which is necessary to use an organic solvent such as N-methyl pyrrolidone, the adhesive of the application uses deionized water as the solvent, thereby avoiding environmental pollution caused by using the organic solvent. Meanwhile, deionized water is used as a solvent, so that the production cost of the pole piece can be greatly reduced.

In some embodiments, the binder is in the form of an aqueous emulsion having a solids content of 10% to 60%, alternatively 20% to 55%, further alternatively 25% to 45%, still further alternatively 28% to 36%.

The solids content of the binder can be tested according to the following method:

the binder of weight M1 was taken and placed in an oven and dried at 120 ℃ for 48 hours, after which weight M2, solids content = M2/m1×100%.

In some embodiments, the aqueous emulsion comprises from 0.5% to 10%, from 1 to 9%, alternatively from 3% to 8% by weight of surfactant, based on the total weight of the aqueous emulsion. The surfactant is at least one selected from sodium dodecyl sulfonate, tristyryl phosphate, sulfate, fatty alcohol polyglycol ether and sodium alkyl succinate.

In some embodiments, the terpolymer is selected from at least one of poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-propyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-pentyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-acrylamide-hydroxymethyl acrylate), poly (acrylonitrile-methyl acrylate-hydroxymethyl acrylate), and poly (sodium acrylate-acrylonitrile-hydroxymethyl acrylate).

In some embodiments, the siloxane of formula II is selected from at least one of a siloxane comprising an amino group, a carboxyl group, and an epoxy group, and optionally from at least one of a trimethoxysilane, a triethoxysilane, and a tripropoxysilane comprising an amino group.

In some embodiments, the siloxane of formula II is selected from at least one of 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and 3-aminopropyl tripropoxysilane.

In some embodiments, the graft polymer is selected from at least one of the following:

wherein x is an integer from 0 to 5000; optionally an integer from 500 to 1500;

y is an integer from 0 to 5000; optionally an integer from 500 to 1500;

z is an integer from 200 to 3000, optionally from 300 to 1500, and optionally from 225 to 1050; further optionally an integer from 525 to 750;

a is an integer from 200 to 800; optionally an integer from 500 to 700;

alternatively, a/z is from 0.80 to 0.99, alternatively from 0.85 to 0.98.

By way of example, the following shows a synthetic route pattern for one specific graft polymer of the present application:

as an example, the graft polymer is a schematic representation of the crosslinked structure formed after hydrolysis and dehydration during use

The copolymer has grafted main chain several siloxane with alkyl radical capable of being hydrolyzed to form silicon hydroxyl radical under acid, alkali and other conditions, and the grafted silicon has hydroxyl radicals capable of producing hydrogen bond interaction to produce micro cross-linking between the polymer molecular weight of the adhesive. Under the condition of subsequent drying and dehydration, two adjacent silicon hydroxyl groups are dehydrated in the drying process to form Si-O-Si covalent bonds so as to generate a stronger irreversible cross-linked network, improve the cohesive energy of active substances in the pole piece and strengthen the adhesive force between the active substances and the conductive agent.

In some embodiments, the slurry comprises from 0.5% to 10%, alternatively from 1% to 5%, by weight of the binder, based on the total weight of the slurry.

In some embodiments, the slurry is a positive electrode slurry comprising 0.5% to 10%, optionally 1% to 5%, of the binder of the present application, based on 100 parts by weight deionized water; 80% to 99%, optionally 85% to 98%, of a positive electrode active material; 0.5% to 5%, optionally 1% to 3%, of a conductive agent; 0% to 5%, optionally 0.5% to 2% of a stabilizer.

In some embodiments, the slurry is a negative electrode slurry comprising 0.5% to 10%, optionally 1% to 5%, of the binder of the present application, based on 100 parts by weight deionized water; 92% to 98%, optionally 95% to 97%, of a negative active material; 0.5% to 5%, optionally 1% to 2%, of a conductive agent; 0.1% to 5%, optionally 0.5% to 2% of a stabilizer.

In some embodiments, the stabilizing agent is selected from the group consisting of soluble polysaccharides and derivatives thereof, such as methylcellulose and salts thereof, xanthan gum and salts thereof, chitosan and salts thereof, alginic acid and salts thereof. The positive electrode active material, the negative electrode active material, and the conductive agent will be described in detail below.

[ Positive electrode sheet ]

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

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

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

In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ )、 LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further comprises a binder of the present application.

In some embodiments, the content in the binder positive electrode film layer is 0.1 to 5 mass%, alternatively 0.5 to 2 mass%.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ negative electrode sheet ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

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

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

In some embodiments, the negative electrode film layer further comprises a binder of the present application.

In some embodiments, the binder negative electrode film layer is present in an amount of 0.1 to 5 mass%, alternatively 0.5 to 2 mass%.

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as stabilizers (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder of the present application, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

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

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

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

In some embodiments, the electrolyte further optionally includes an additive. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, and the like.

[ isolation Membrane ]

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 2, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

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

Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

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

Fig. 4 and 5 are battery packs 1 as an example. Referring to fig. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device, which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 6 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

Examples (example)

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

[ Infrared Spectrometry test ]

According to the standard GB/T6040-2002 infrared spectroscopy method, an IS10 Fourier transform infrared spectrometer of Nigao (Nicolet) corporation of America IS used.

[ test of film tensile Property ]

The tensile property test of the adhesive film is referred to national standard GB/T1040-1992.

[ test for swelling Property of adhesive film ]

The adhesive of the present invention was dried, and after the obtained adhesive film was completely dried, it was cut into an object having a specific shape and weighing about 0.5g, immersed in an electrolyte (the same electrolyte as used in a secondary battery hereinafter), sealed, placed in an ambient temperature of 70 c, and the surface-dried electrolyte was taken out at 7 days intervals, weighed and recorded.

[ Positive plate appearance test ]

The appearance of the prepared positive electrode sheet was observed and classified according to the following criteria:

if the appearance has no abnormal phenomena such as scratches, salient points and the like, the appearance is marked as excellent;

if the appearance scratch is less than or equal to 1 part and no metal or no protruding point is exposed at less than or equal to 3 parts, the mark is good;

if the scratch is greater than 1 or the bump is > 3, it is marked as bad.

[ adhesion test ]

I.e. 180 ° peel strength. And taking the positive pole piece to be tested, wherein the pole piece has good appearance and does not allow appearance bad products. Samples 30mm wide by 140mm long were taken with a razor blade. A special double faced adhesive tape nitto.no5000ns was attached to the steel plate with a tape width of 20mm and a length of 120mm. The cut pole piece sample with fixed size is stuck on a double-sided adhesive tape, the test surface is downward, and then the pole piece sample is rolled three times by a 3kg press roller along the same direction on the surface of the pole piece. Paper tape with the width equal to the pole piece and the length greater than the length of the sample by 120mm is inserted under the pole piece and fixed by using crepe adhesive. Then the sample is fixed on a testing machine, one end of the steel plate, which is not attached with the pole piece, is fixed by a lower clamp, the paper tape is folded upwards and fixed by an upper clamp, the axial direction of the pole piece is consistent with the force application direction, the testing machine loads at a stripping speed of 10mm/min until the pole piece breaks, the testing is stopped, the maximum load force is recorded as F (unit N), the pole piece width L=20 mm, and the stripping strength F1 (unit N/m) is calculated according to f1=F/L.

[ cohesion test ]

I.e. 180 ° shear strength test. And taking the positive pole piece to be tested, wherein the pole piece has good appearance and does not allow appearance bad products. A specimen 30mm wide by 130mm long was cut with a blade. A special double faced adhesive tape nitto.no5000ns was attached to the steel plate with a tape width of 20mm and a length of 130mm. The cut pole piece sample with fixed size is stuck on a double-sided adhesive tape with the test surface facing upwards, then a low-viscosity green tape MD-XTG-620-2335L with the width of 20mm and the length of more than 140mm is flatly stuck on the surface of the test surface, and then the pole piece sample is rolled three times along the same direction on the surface of the pole piece by a 3kg press roller. Then fixing the sample on a testing machine, fixing one end of a steel plate, which is not attached with a pole piece, by using a lower clamp, turning up a green tape, fixing the green tape by using an upper clamp, loading the testing machine at a stripping speed of 10mm/min until the pole piece breaks, stopping testing, recording the maximum loading force as F (unit N), ensuring that the pole piece width L=20 mm, and calculating the stripping strength F1 (unit N/m) according to f1=F/L.

[ test for folding the Positive electrode film ]

And after the positive electrode diaphragm is folded in half, rolling the positive electrode diaphragm back and forth for 3 times by using a compression roller with the weight of 2kg, then paving the positive electrode diaphragm, repeating the operation until light leakage occurs at the folded position, and recording the folding times. Each group was tested 5 times and averaged.

[ resistance test of Positive electrode Membrane ]

And testing the resistance of the positive electrode diaphragm by using a CRM-01 pole piece resistance tester. Each group was tested 5 times and averaged.

[ Battery Capacity Retention Rate ]

The secondary battery prepared as described below was charged to 3.65V at a constant current of 1/3C, charged to 0.05C at a constant voltage of 3.65V, left for 5min, discharged to 2.7V at 1/3C, and the resulting capacity was designated as initial capacity C ₀ . Repeating the above steps for the same battery, and simultaneously recording the discharge capacity C of the battery after the nth cycle _n Battery capacity retention rate P after each cycle _n ＝C _n /C ₀ *100%. In this test procedure, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and … … the 100 th cycle corresponds to n=100. The battery capacity retention rate data corresponding to example 13 in table 2 is data measured after cycling 800 times under the above-described test conditions, i.e., the value of P800.

Example 1

200g of poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) (available from Shanghai Ala Biochemical technologies Co., ltd., wherein the polymerization monomer lithium acrylate: methyl acrylate: hydroxymethyl acrylate=5:2:3 (molar ratio), number average molecular weight 20 ten thousand) was added to a flask, 500 ml of anhydrous toluene was added to stir and dissolve, 0.53g (0.0219 mol) of sodium hydride was added, stirring was performed at room temperature under nitrogen protection for 4 hours, and 2.03g (0.0219 mol) of epichlorohydrin was further added thereto, and stirring was performed at room temperature for 12 hours to obtain poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) having an epoxy group. The resulting poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) having an epoxy group was evaporated by rotary evaporation and dried, and then added to 500 ml of deionized water, 59.5g (0.219 mol) of sodium dodecyl sulfonate was added, 3.92g (0.0219 mol) of 3-aminopropyl trimethoxysilane was added, and stirred at 50℃for 24 hours. A silicone-functionalized aqueous adhesive emulsion of poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) was obtained with a viscosity of 1500 mPas and a solids content of 34.7% and an infrared spectrum as shown in FIG. 7.

Example 2

The preparation was essentially the same as in example 1, except that poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) was used, wherein lithium acrylate: methyl acrylate: molar ratio of hydroxymethyl acrylate = 4:3:3.

example 3

The preparation was essentially the same as in example 1, except that poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) was used, wherein lithium acrylate: methyl acrylate: molar ratio of hydroxymethyl acrylate = 3:4:3.

example 4

The preparation process was substantially the same as in example 1 except that 1.06g of sodium hydride, 4.06g of epichlorohydrin and 7.84g of 3-aminopropyl trimethoxysilane were added.

Example 5

The preparation was carried out in the same manner as in example 1 except that 1.59g of sodium hydride, 6.09g of epichlorohydrin and 11.76g of 3-aminopropyl trimethoxysilane were added.

Example 6

The preparation was essentially the same as in example 1, except that the copolymer used was poly (lithium acrylate-propyl acrylate-hydroxymethyl acrylate) and the number average molecular weight was 20 ten thousand.

Example 7

The preparation was essentially the same as in example 1, except that a copolymer of poly (lithium acrylate-amyl acrylate-hydroxymethyl acrylate) was used having a number average molecular weight of 20 ten thousand.

Example 8

The preparation was essentially the same as in example 1, except that the copolymer used was poly (lithium acrylate-acrylamide-hydroxymethyl acrylate) having a number average molecular weight of 20 ten thousand.

Example 9

The preparation was substantially the same as in example 1, except that a copolymer of poly (acrylonitrile-methyl acrylate-hydroxymethyl acrylate) was used, and the number average molecular weight was 20 ten thousand.

Example 10

The preparation was essentially the same as in example 1, except that the copolymer used was poly (sodium acrylate-acrylonitrile-hydroxymethyl acrylate) having a number average molecular weight of 20 ten thousand.

Example 11

The preparation was substantially the same as in example 1, except that 3-aminopropyl triethoxysilane (0.0219 mol) was used as the siloxane compound.

Example 12

The preparation was substantially the same as in example 1, except that 3-aminopropyl tripropoxy silane (0.0219 mol) was used as the siloxane compound.

Comparative example 1

The preparation was essentially the same as in example 1, except that grafting was not performed using 3-aminopropyl tripropoxy silane.

Table 1: properties of the raw materials used in examples and the adhesive films obtained therefrom

As can be seen from Table 1, the copolymer grafted with the silicone compound of the present invention can achieve better film properties than the copolymer not subjected to grafting (see comparative example 1).

Example 13

Preparation of positive electrode plate and secondary battery

Preparing a positive electrode plate: 95 parts by weight of lithium iron phosphate, 2 parts by weight of conductive carbon black Super P and 1 part by weight of carboxymethyl cellulose are taken, added into a stirring tank, kneaded for 1 hour by adding 30 parts by weight of deionized water, continuously added with 70 parts by weight of deionized water, stirred for 1.5 hours, then added with 2 parts by weight of the aqueous binder emulsion synthesized in example 1, and continuously stirred for 1 hour, thus obtaining aqueous positive electrode slurry. The obtained slurry was coated on the surface of an aluminum foil (thickness: 12 μm) by extrusion coating, and dried at 120℃for 5 minutes to obtain a water-based positive electrode sheet.

Preparing a negative electrode plate: dissolving negative electrode active material artificial graphite, conductive agent acetylene black, binder Styrene Butadiene Rubber (SBR) and thickener sodium carboxymethylcellulose (CMC-Na) in deionized water according to the weight ratio of 95:1:3:1, and fully stirring and uniformly mixing to prepare negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector copper foil, and then drying, cold pressing and cutting to obtain a negative electrode plate.

Isolation film: a polypropylene film is used.

Preparation of electrolyte: mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1, and then mixing LiPF ₆ Uniformly dissolving in the solution to obtain an electrolyte. In the electrolyte, liPF ₆ The concentration of (C) was 1mol/L.

Preparation of secondary battery: sequentially stacking and winding the positive electrode plate, the isolating film and the negative electrode plate to obtain an electrode assembly; and placing the electrode assembly into an outer package, adding the prepared electrolyte, and obtaining the secondary battery after the procedures of packaging, standing, formation, aging and the like.

Example 14

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 2.

Example 15

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 3.

Example 16

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 4.

Example 17

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 5.

Example 18

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 6.

Example 19

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 7.

Example 20

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 8.

Example 21

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 9.

Example 22

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 10.

Example 23

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 11.

Example 24

The preparation method was substantially the same as in example 13, except that the adhesive used in the preparation of the positive electrode sheet was the adhesive synthesized in example 12.

Comparative example 2

In preparing the positive electrode sheet, the other portions were the same as in example 13 except that the adhesive used was poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate) of comparative example 1, which was not grafted with silicone.

Table 2: performance test results of the prepared positive electrode plate

As can be seen from table 2, the adhesive of the present invention has better adhesive properties. Unexpectedly, secondary batteries using the binders of the present invention also have improved battery capacity retention.

Claims

A binder comprising a graft polymer comprising as a backbone a copolymer of formula I and grafted to the backbone a siloxane of formula II:

wherein R is ₁ 、R ₂ And R is ₃ Each independently selected from at least one of hydrogen and C1-C6 alkyl, optionally each independently selected from at least one of hydrogen and methyl;

R ₄ selected from C (=O) OLi, C (=O) ONa, CN, C (=O) NH ₂ And at least one of carbonyloxy C1-C6 alkyl, optionally at least one selected from C (=o) OLi, C (=o) ONa and CN;

R ₅ selected from C (=O) OLi, C (=O) ONa, CN, C (=O) NH ₂ And at least one of carbonyloxy C1-C6 alkyl, optionally selected from C (=O) NH ₂ And at least one of a carbonyloxy C1-C6 alkyl group;

R ₆ at least one selected from COOH, OH, CN and carbonyloxy C1-C6 alkyl hydroxy groupsOptionally at least one selected from OH and carbonyloxy C1-C6 alkyl hydroxy;

wherein x, y are each independently an integer from 0 to 5000, optionally an integer from 500 to 1500; x and y are not both 0;

z is an integer from 100 to 3000, optionally from 200 to 1500;

wherein R is ₇ At least one selected from the group consisting of C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 alkylazide, C1-C6 alkylamino, C1-C6 alkylcarboxy, C1-C6 alkylhydroxy, C1-C6 alkylepoxy and C1-C6 alkylmercapto, optionally at least one selected from the group consisting of C1-C6 alkylamino, C1-C6 alkylcarboxy and C1-C6 alkylepoxy;

R ₈ and R is ₉ Each independently selected from at least one of C1-C6 alkyl and C1-C6 alkyloxy;

R ₁₀ is a C1-C6 alkyl group.
The adhesive of claim 1 wherein the weight percent of the copolymer of formula I in the graft polymer is from 90% to 99.9%.
The adhesive according to claim 1 or 2, wherein the siloxane of formula II has a grafting ratio in the graft polymer of 0.1% to 5%.
A binder according to any one of claims 1 to 3, the copolymer of formula I being a terpolymer formed by copolymerization of three monomers, wherein the first monomer is lithium (meth) acrylate, sodium (meth) acrylate or acrylonitrile; the second monomer is C1-C6 alkyl (meth) acrylate, acrylamide or acrylonitrile; the third monomer is hydroxy C1-C6 alkyl (meth) acrylate.
The binder of any one of claims 1 to 4, wherein the molar ratio of the first monomer, the second monomer, and the third monomer is (0.5-3): (0.5-2): 1, optionally (0.8-2.5): (0.6-1.5): 1.
the adhesive according to any one of claims 1 to 5, wherein the terpolymer is selected from at least one of poly (lithium acrylate-methyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-propyl acrylate-hydroxymethyl acrylate), poly (lithium acrylate-acrylamide-hydroxymethyl acrylate), poly (acrylonitrile-methyl acrylate-hydroxymethyl acrylate), and poly (sodium acrylate-acrylonitrile-hydroxymethyl acrylate).
The adhesive according to any one of claims 1 to 6, wherein the siloxane of formula II is selected from at least one of 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and 3-aminopropyl tripropoxysilane.
The binder of any one of claims 1 to 7, wherein the binder is in the form of an aqueous emulsion, wherein the weight percent of the graft polymer in the aqueous emulsion is from 5% to 50%, alternatively from 10% to 40%.
The adhesive according to any one of claims 1 to 8, wherein the adhesive has a viscosity of 100 to 20000 mPa-s, optionally 500 to 2000 mPa-s.
A method of preparing the adhesive of claims 1 to 9, wherein the method comprises the steps of:

step (1): reacting a copolymer of formula I with a halogenated C1-C6 alkyl epoxy compound in the presence of a base, the reaction being carried out in the presence of a solvent;

step (2): after optional removal of the solvent and addition of water, the siloxane of formula II and optionally the surfactant are then added and stirred.
The process according to claim 10, wherein the weight ratio of copolymer of formula I to halogenated C1-C6 alkyl epoxy compound is 1 (0.005-0.1), optionally 1 (0.01-0.05).
The method of claim 10 or 11, wherein the molar ratio of the halogenated C1-C6 alkyl epoxy compound to the siloxane of formula II is 1 (0.5-2), alternatively 1 (0.8-1.5), further alternatively 1 (0.9-1.2);

optionally, the halogenated C1-C6 alkyl epoxy compound is epichlorohydrin;

optionally, the base is selected from at least one of sodium hydride and sodium hydroxide, optionally sodium hydride;

alternatively, the molar ratio of the halogenated C1-C6 alkyl epoxy compound to the base is 1 (0.5-2), alternatively 1 (0.8-1.5), and still alternatively 1 (0.9-1.2) 1.
A slurry comprising the binder of any one of claims 1 to 9 or the binder prepared according to the method of any one of claims 10 to 12.
The slurry of claim 13, wherein the slurry comprises 0.5 to 5 weight percent of the binder.
An electrode sheet comprising a current collector and a film layer formed of the slurry of claim 13 or 14 disposed on at least one surface of the current collector.
A secondary battery comprising the electrode tab of claim 15.
A battery module comprising the secondary battery according to claim 16.
A battery pack comprising the battery module of claim 17.
An electric device comprising at least one selected from the secondary battery of claim 16, the battery module of claim 17, or the battery pack of claim 18.