阅读说明：本技术 粘结剂、使用该粘结剂的电化学装置和电子设备 (Binder, electrochemical device using the same, and electronic apparatus ) 是由 李嘉文 石长川 张青文 于 2021-01-21 设计创作，主要内容包括：本申请涉及储能技术领域,具体讲,涉及一种粘结剂、使用该粘结剂的电化学装置和电子设备。该粘结剂包含聚合物,所述聚合物通过第一单体、第二单体、第三单体和第四单体聚合而得到；其中,所述第一单体、第二单体和第三单体各自独立地选自芳香族烯基化合物、烯属不饱和羧酸、烯属不饱和羧酸盐或烯属不饱和羧酸酯；所述第四单体选自取代或未取代的具有胺基和至少两个烯基的化合物。本申请通过第四单体的加入能提升粘结剂的提升耐电解液性能,提升粘结剂的导锂离子性能,从而提高电池的低温放电性能。(The application relates to the technical field of energy storage, in particular to a binder, an electrochemical device using the binder and electronic equipment. The binder comprises a polymer obtained by polymerizing a first monomer, a second monomer, a third monomer and a fourth monomer; wherein the first monomer, the second monomer and the third monomer are each independently selected from an aromatic alkenyl compound, an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated carboxylate salt or an ethylenically unsaturated carboxylic acid ester; the fourth monomer is selected from substituted or unsubstituted compounds having an amine group and at least two alkenyl groups. This application can promote the electrolyte resistance of promotion of binder through the addition of fourth monomer, promotes the lithium ion conduction performance of binder to improve the low temperature discharge performance of battery.)

1. An adhesive, comprising a polymer obtained by polymerizing a first monomer, a second monomer, a third monomer, and a fourth monomer;

wherein the first monomer, the second monomer and the third monomer are independently selected from aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid salts or ethylenically unsaturated carboxylic acid esters, and the first monomer, the second monomer and the third monomer are different from each other;

the fourth monomer includes a substituted or unsubstituted compound having an amine group and at least two alkenyl groups.

2. The binder of claim 1 wherein the fourth monomer comprises substituted or unsubstituted diallylamine;

when substituted, the substituent on the amino group and the substituent on the alkenyl group are respectively and independently selected from one of alkyl with 1-10 carbon atoms, alkoxy with 1-10 carbon atoms, aralkyl with 6-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkynyl with 2-10 carbon atoms.

3. The binder of claim 1 wherein the fourth monomer comprises at least one of diallylamine or N-alkyldiallylamine.

4. The binder of claim 3 wherein the N-alkyldiallylamine comprises at least one of N-methyldiallylamine or N-ethyldiallylamine.

5. The binder according to claim 1, wherein the fourth monomer accounts for 0.1 to 8% by mass of the polymer.

6. The binder of claim 1 wherein the first monomer comprises an aromatic alkenyl compound, the second monomer comprises an ethylenically unsaturated carboxylic acid or salt thereof, and the third monomer comprises an ethylenically unsaturated carboxylic acid ester.

7. The binder of claim 6 wherein the aromatic alkenyl compound comprises at least one of styrene, alpha-methylstyrene, divinylbenzene, t-butylstyrene, p-methylstyrene, p-ethylstyrene, 1-diphenylethylene, vinylnaphthalene, vinylanthracene, or vinylpyridine.

8. The binder of claim 6 wherein the ethylenically unsaturated carboxylic acid or salt comprises at least one of acrylic acid, methacrylic acid, lithium acrylate, potassium acrylate, sodium acrylate, lithium methacrylate, potassium methacrylate, or sodium methacrylate.

9. The binder of claim 6 wherein the ethylenically unsaturated carboxylic acid ester comprises at least one of methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, hexyl acrylate, heptyl acrylate, 2-isooctyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, or 2-isooctyl methacrylate.

10. The binder according to any one of claims 1 to 9, wherein the first monomer accounts for 5 to 46% by mass of the polymer; the mass ratio of the second monomer in the polymer is 0.5-89.9%; the third monomer accounts for 5 to 45.5 mass% of the polymer.

11. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein at least one of the positive electrode sheet, the negative electrode sheet and the separator contains the binder according to any one of claims 1 to 10.

12. The electrochemical device according to claim 11, wherein the negative electrode tab comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, a conductive agent, and the binder according to any one of claims 1 to 10; the binder is contained in the negative electrode active material layer in an amount of 0.5 to 8% by mass.

13. An electronic device comprising the electrochemical device according to any one of claims 11 to 12.

[ technical field ] A method for producing a semiconductor device

The present disclosure relates to the field of energy storage technologies, and more particularly, to a binder, an electrochemical device using the binder, and an electronic apparatus using the binder.

[ background of the invention ]

Electrochemical devices (such as lithium ion batteries) have the advantages of high energy density, long cycle life, small self-discharge, environmental protection, no public nuisance, and the like, and are widely applied to the fields of mobile phones, computers, electric bicycles, electric automobiles, and the like. In recent years, with the rapid development of various electronic devices and scientific technologies, people have made higher requirements on the electrochemical performance of lithium ion batteries, such as low-temperature performance and cycle performance of lithium ion batteries.

The poor temperature characteristics, especially low temperature performance, of the lithium ion battery restrict the further use of the lithium ion battery, especially the application of special equipment such as EV/HEV, aerospace and military at low temperature. The binder is used as a component of the battery and plays a certain role in improving the electrochemical performance of the battery. In recent years, how to improve the low-temperature performance of lithium ion batteries by means of preparing novel binders and the like has become one of the important research points in the related fields.

However, none of the existing binders such as styrene-acrylic emulsion, polyvinylidene fluoride, carboxymethyl cellulose, etc. can improve the low temperature performance of the battery well. Among them, the conventional styrene-acrylic emulsion is generally obtained by polymerizing styrene and acrylic ester, and has disadvantages in that: the affinity of the styrene-acrylic emulsion binder and the battery electrolyte is greatly different, so that the polar electrolyte cannot permeate into active material particles of the electrode, the interface resistance of the electrode is increased, the effect is more obvious at low temperature, and the low-temperature discharge performance of the battery is poor.

In view of this, the present application is particularly proposed for improving the low-temperature discharge performance of the battery.

[ summary of the invention ]

The primary application of the present application is directed to an adhesive.

A second application of the present application is directed to an electrochemical device and an electronic apparatus using the binder.

In order to accomplish the purpose of the application, the technical scheme is as follows:

the present application relates to a binder comprising a polymer obtained by polymerizing a first monomer, a second monomer, a third monomer, and a fourth monomer;

wherein the first monomer, the second monomer and the third monomer are independently selected from aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid salts or ethylenically unsaturated carboxylic acid esters, and the first monomer, the second monomer and the third monomer are different from each other;

the fourth monomer includes a substituted or unsubstituted compound having an amine group and at least two alkenyl groups.

Preferably, the fourth monomer comprises substituted or unsubstituted diallylamine;

when substituted, the substituent on the amino group and the substituent on the alkenyl group are respectively and independently selected from one of alkyl with 1-10 carbon atoms, alkoxy with 1-10 carbon atoms, aralkyl with 6-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkynyl with 2-10 carbon atoms.

Preferably, the fourth monomer comprises at least one of diallylamine or N-alkyldiallylamine.

Preferably, the N-alkyldiallylamine includes at least one of N-methyldiallylamine or N-ethyldiallylamine.

Preferably, the first monomer is selected from aromatic alkenyl compounds, the second monomer is selected from ethylenically unsaturated carboxylic acids or ethylenically unsaturated carboxylic acid salts, and the third monomer is selected from ethylenically unsaturated carboxylic acid esters.

Preferably, the aromatic alkenyl compound includes an aromatic vinyl compound.

Preferably, the aromatic alkenyl compound includes at least one of styrene, α -methylstyrene, divinylbenzene, t-butylstyrene, p-methylstyrene, p-ethylstyrene, 1-diphenylethylene, vinylnaphthalene, vinylanthracene, or vinylpyridine. More preferably, the aromatic alkenyl compound includes at least one of styrene, α -methylstyrene or divinylbenzene.

Preferably, the ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic acid salt comprises at least one of acrylic acid, methacrylic acid, lithium acrylate, potassium acrylate, sodium acrylate, lithium methacrylate, potassium methacrylate or sodium methacrylate.

Preferably, the ethylenically unsaturated carboxylic acid ester includes at least one of alkyl acrylate and alkyl methacrylate. More preferably, the ethylenically unsaturated carboxylic acid ester includes an alkyl group (C) having 1 to 10 carbon atoms₁To C₁₀Alkyl) acrylate or alkyl (C) having 1 to 10 carbon atoms₁To C₁₀Alkyl) methacrylates.

Preferably, the ethylenically unsaturated carboxylic acid ester includes at least one of methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, hexyl acrylate, heptyl acrylate, 2-isooctyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, or 2-isooctyl methacrylate.

Preferably, the mass ratio of the fourth monomer in the polymer is 0.1% to 8%, preferably 0.5% to 7%, and more preferably 1% to 6%.

Preferably, the mass ratio of the first monomer in the polymer is 5% to 46%, preferably 10% to 46%;

the third monomer accounts for 5 to 45.5 percent of the polymer by mass, and preferably accounts for 10 to 45.5 percent of the polymer by mass;

the second monomer accounts for 0.5 to 89.9 mass%, preferably 1.5 to 79.5 mass% of the polymer.

The binder polymer of the present application has a simple structure, and can be easily prepared by those skilled in the art according to its structure. The preparation process is simple, easy to control, high in feasibility, less in environmental pollution and suitable for industrial mass production.

Specifically, the binder described herein can be prepared by the following method:

mixing a part of emulsifier with the first monomer, the second monomer and the third monomer according to a certain proportion, and quickly emulsifying in a certain amount of water to obtain a pre-emulsion. Mixing and dissolving the initiator, the other part of the emulsifier and a certain amount of water uniformly, and adding the mixture into the first dropping liquid pipe to obtain initiator emulsion; pouring about 1/3 of the obtained pre-emulsion into a reaction kettle, heating and stirring, and adding about 2/3 of the pre-emulsion into a second dropping pipe; when the temperature rises to 60-80 ℃, slowly dropping the initiator emulsion in the first dropping tube into the reaction kettle, simultaneously dropping the fourth monomer by using the third dropping tube, controlling the temperature to be about 80 +/-10 ℃, then slowly dropping the pre-emulsion in the second dropping tube, keeping the solid content of the emulsion to be about 50% (bluing state), and keeping the temperature for 0.5-4 h. And after the reaction is finished, cooling to room temperature, and adjusting the pH value to be between 7 and 8 to obtain the binder.

Wherein, optionally, the emulsifier can be, for example, higher fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylates, carboxylates such as potassium laurate, sulfate salts such as sodium lauryl sulfate, sulfonates such as sodium dioctyl sulfosuccinate, and the like. In the process of preparing the binder, the mass of the part of the emulsifier added is 0.05% to 10%, preferably 0.1% to 8%, of the total mass of the first monomer, the second monomer, the third monomer and the fourth monomer.

Wherein, optionally, the mass ratio of the part of the emulsifier to the other part of the emulsifier is 2: 1 to 6: 1, preferably 3: 1 to 5: 1.

among them, the initiator may be, for example, azobisisobutyronitrile, azobisisoheptonitrile, azobiscyclohexylcarbonitrile, benzoyl peroxide, t-butyl hydroperoxide, ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride (V-50 initiator), azobisisobutylimidazoline hydrochloride (VA-044 initiator), azobisisobutylimidazoline (VA061 initiator), or the like, as an alternative. In the process of preparing the binder, the initiator is added in an amount of 0.01 to 1% by mass, preferably 0.05 to 0.6% by mass, based on the sum of the masses of the first, second, third and fourth monomers.

The adhesive is prepared by adopting the solvent system or the monomer system, the preferable emulsifier and the preferable initiator within the range of the proportion and in the preferable polymerization atmosphere, temperature and time, the types and the proportion of the emulsifier and the initiator are proper, the reaction condition is mild, and the obtained adhesive has good stabilizer and adhesive property.

The binder of the present application may be used as a binder in a positive electrode sheet, a negative electrode sheet or a separator for an electrochemical device such as a secondary battery. The binder of the present application is particularly preferable as a binder of a negative electrode tab of a secondary battery, because problems caused by the binding of the negative electrode tab in the secondary battery are more significant.

Therefore, the present application also relates to an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein at least one of the positive electrode sheet, the negative electrode sheet and the separator comprises the binder of the present application.

Preferably, the negative electrode plate comprises the binder of the application. The negative pole piece comprises a negative pole current collector and a negative pole active substance layer coated on the surface of the negative pole current collector, wherein the negative pole active substance layer contains the binder.

Preferably, the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder containing the polymer. The mass percentage of the binder in the negative electrode diaphragm is 0.5-8%, preferably 1-4%.

Preferably, the negative electrode active material is not limited and includes at least one of a graphite-based material or a silicon-based material.

Preferably, the conductive agent is not limited and includes at least one of conductive carbon black, lamellar graphite, carbon fiber, graphene, ketjen black, single-walled carbon nanotubes or multi-walled carbon nanotubes.

Methods of preparing negative electrode sheets using binders are well known to those skilled in the art. Optionally, one method for preparing the negative electrode plate by using the binder of the present application is as follows: the binder, the conductive agent and the negative active material are mixed in deionized water, and the obtained slurry is coated on a current collector to prepare a negative pole piece.

Another method for preparing a negative electrode plate by using the binder of the present application is as follows: the binder of the present application is directly coated on the current collector to form a coating. In some embodiments, the negative electrode plate contains the binder of the present application, specifically, the negative electrode plate comprises a negative electrode current collector, a coating and a negative electrode active material layer, wherein the coating is arranged between the negative electrode current collector and the negative electrode active material layer, and the coating contains the binder described in the present application.

The application also relates to an electronic device comprising said electrochemical device.

The technical scheme of the application has at least the following beneficial effects:

the binder, the electrochemical device using the binder and the electronic equipment provided by the application, wherein the binder comprises a polymer, the polymer is obtained by polymerizing a monomer mixture containing a first monomer, a second monomer, a third monomer and a fourth monomer, and particularly, the fourth monomer containing a substituted or unsubstituted compound with amino and at least two alkenyl is added, so that a high molecular polymer can be changed into a polymer with a certain network structure from a linear structure, the electrolyte resistance of the binder is improved, and the physical properties of an adhesive film are favorably improved; moreover, the nitrogen atom in the amino group has a pair of lone-pair electrons, does not participate in conjugation, has certain electronegativity, and can be combined with lithium ions, so that the permeability of the film to the lithium ions is good, the impedance increase caused by film formation can be effectively reduced, the lithium ion conduction can be improved, and the lithium ion conduction performance of the binder is improved.

Therefore, in the low-temperature discharge process of an electrochemical device such as a lithium ion battery containing the binder, lithium ions can be quickly conducted into electrolyte from a negative electrode plate, and the low-temperature discharge performance is good. Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.

The present application is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. The formulation, ratio, etc. in the examples can be selected according to local conditions without substantially affecting the results.

[ detailed description ] embodiments

The binder, the electrochemical device, and the electronic apparatus according to the present application are explained in detail below.

[ Binders ]

According to one aspect of the present application, the present application relates to a binder comprising a polymer obtained by polymerizing a first monomer, a second monomer, a third monomer, and a fourth monomer; wherein the first monomer, the second monomer and the third monomer are independently selected from aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid salts or ethylenically unsaturated carboxylic acid esters, and the first monomer, the second monomer and the third monomer are different from each other; the fourth monomer is selected from substituted or unsubstituted compounds having an amine group and at least two alkenyl groups. The binder can improve electrolyte resistance, improve physical properties of adhesive films, improve lithium ion conductivity, improve low-temperature discharge performance of the battery, and improve high-temperature storage performance of the battery.

The binder contains a copolymer mainly obtained by copolymerizing a first monomer, a second monomer, a third monomer and a fourth monomer, particularly wherein the fourth monomer is selected from substituted or unsubstituted compounds having an amine group and at least two alkenyl groups. Through reasonable structural design, in the synthesis process of the adhesive, a substituted or unsubstituted compound monomer with amido and at least two alkenyl groups is added, so that the prepared high molecular polymer is changed into a network structure from a linear structure, and the adhesive obtained by polymerization has more excellent electrolyte resistance, is beneficial to improving the physical property of an adhesive film and has better low-temperature discharge performance. And the nitrogen atom in the amino group has a pair of lone-pair electrons, does not participate in conjugation, has certain electronegativity, and can be combined with lithium ions, so that the permeability of the film to the lithium ions is good, the impedance increase caused by film formation can be effectively reduced, the lithium ion conduction can be improved, and the lithium ion conduction performance of the binder is improved. Therefore, the electrode plate and the electrochemical device such as a secondary battery using the adhesive have good low-temperature discharge performance and good high-temperature storage performance in the low-temperature discharge process.

As an improvement to the binder of the present application, the fourth monomer is selected from the group consisting of substituted or unsubstituted diallylamine; when substituted, the substituent on the amino group and the substituent on the alkenyl group are respectively and independently selected from one of alkyl with 1-10 carbon atoms, alkoxy with 1-10 carbon atoms, aralkyl with 6-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkynyl with 2-10 carbon atoms. Preferably, when substituted, the substituent on the amino group is selected from one of an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms.

Unless otherwise specified, compounds or functional groups used herein may be substituted or unsubstituted. Wherein, the term "substituted" is used to mean that at least one hydrogen atom contained in the compound or functional group is replaced by at least one substituent selected from the group consisting of: c₁～C₁₀Alkyl of (C)₁～C₁₀Alkoxy group of (C)₁～C₁₀Aralkyl of (2), C₂～C₁₀Alkenyl of, C₂～C₁₀Alkynyl of (A), C₁～C₁₀And derivatives thereof.

As used herein, the term "alkyl" has the meaning commonly understood in the art and refers to a saturated hydrocarbon consisting of only two elements, C and H, that is a radical formed after any carbon atom has lost one hydrogen atom. Alkyl includes straight chain alkyl and branched chain alkyl. The alkyl group may be unsubstituted or substituted, but is preferably unsubstituted. When the alkyl group is substituted, the number of the substituents may be, for example, 1 to 3. Examples of alkyl groups described herein include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, heptyl, octyl, chloromethyl, fluoroethyl, trifluoromethyl, or 1,1, 1-trifluoroethyl, and the like.

Similarly, the terms "alkenyl", "alkynyl", "amine", "alkoxy", "aralkyl", and the like are used with their commonly understood meaning in the art and will not be described in detail herein. Illustratively, the term "alkenyl" includes straight-chain and branched alkenyl groups having 2 to 10 carbon atoms, and examples of alkenyl groups include, but are not limited to, vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl and the like.

As used herein, any expression relating to a range of numerical values of the number of carbon atoms, such as "the number of carbon atoms is 1 to 10" or "C₂～C₁₀"can be represented as" C_1～10"or" C_2～10"etc., all refer to the enumeration of all positive integers within their upper and lower limits. For example, "C_1～10"represents" C₁、C₂、C₃、C₄、C₅、C₆、C₇、C₈、C₉、C₁₀". Similarly, where a numerical range refers to the number of substituents, that range also refers to the enumeration of all positive integers within its upper and lower limits.

As an improvement of the binder of the present application, the substituted or unsubstituted diallylamine has 6 to 20, preferably 6 to 15, and more preferably 6 to 10 carbon atoms.

Specifically, as an improvement of the binder of the present application, the fourth monomer is at least one selected from the group consisting of diallylamine and N-alkyldiallylamine. Wherein the N-alkyldiallylamine comprises at least one of N-methyldiallylamine and N-ethyldiallylamine.

Wherein the diallylamine and the N-methyldiallylamine are represented by the following formulae 1 and 2, respectively.

In the above-mentioned polymerizationIn the compound, the diallylamine, N-methyldiallylamine or N-ethyldiallylamine is used as the fourth monomer, the raw material is easily available, and the lone pair of electrons on the N atom of the monomer can effectively promote Li⁺And (4) conducting.

As an improvement of the binder of the present application, the fourth monomer is present in the polymer in a mass ratio of 0.1% to 8%, that is, in a mass percentage of 0.1% to 8%, preferably 0.5% to 7%, and more preferably 1% to 6%, based on the mass of the polymer. When the mass percentage of the fourth monomer is less than 0.1%, particularly less than 0.5%, the monomer cannot effectively exert the function of ion conduction, and when the mass percentage of the fourth monomer is more than 8%, the synthesis reaction is severe and the implosion is easy to occur.

As an improvement of the binder herein, in the above polymer, the first monomer is selected from aromatic alkenyl compounds, the second monomer is selected from ethylenically unsaturated carboxylic acids or ethylenically unsaturated carboxylic acid salts, and the third monomer is selected from ethylenically unsaturated carboxylic acid esters.

Wherein the aromatic alkenyl compound comprises an aromatic vinyl compound. The aromatic vinyl compound monomer unit is not particularly limited, and examples thereof include: any one or more of styrene, alpha-methylstyrene, divinylbenzene, tert-butylstyrene, p-methylstyrene, p-ethylstyrene, 1-diphenylethylene, vinylnaphthalene, vinylanthracene or vinylpyridine. Preferably, the aromatic vinyl compound includes at least one of styrene, α -methylstyrene or divinylbenzene. More preferably, the aromatic vinyl compound is selected from styrene. Among the aromatic vinyl monomer units, a styrene unit is preferred because of easy availability of raw materials.

When the first monomer used in the polymer is two or more of the above aromatic vinyl compounds, the ratio of styrene, α -methylstyrene, divinylbenzene, t-butylstyrene, p-methylstyrene, p-ethylstyrene, 1-diphenylethylene, vinylnaphthalene, vinylanthracene, and vinylpyridine is not limited, and the total mass of the monomers in the polymer may be in the content range defined in the present application.

The ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic acid salt monomer unit is not particularly limited, and examples thereof include: any one or more of acrylic acid, methacrylic acid, lithium acrylate, potassium acrylate, sodium acrylate, lithium methacrylate, potassium methacrylate or sodium methacrylate. More preferably, the ethylenically unsaturated carboxylic acid is selected from acrylic acid. Among the ethylenically unsaturated carboxylic acid monomer units, acrylic acid is preferred because of the ready availability of raw materials.

When the second monomer used in the polymer is two or more of the above-mentioned ethylenically unsaturated carboxylic acids or ethylenically unsaturated carboxylic acid salts, the ratio of the acrylic acid, methacrylic acid, lithium acrylate, potassium acrylate, sodium acrylate, lithium methacrylate, potassium methacrylate, and sodium methacrylate is not limited, and the total mass of the second monomer in the polymer may be within the content range defined in the present application.

As an improvement of the binder of the present application, the ethylenically unsaturated carboxylic acid ester comprises an alkyl acrylate or an alkyl methacrylate. More preferably, the ethylenically unsaturated carboxylic acid ester includes an alkyl group (C) having 1 to 10 carbon atoms₁To C₁₀Alkyl) acrylate or alkyl (C) having 1 to 10 carbon atoms₁To C₁₀Alkyl) methacrylates. Specifically, the ethylenically unsaturated carboxylic acid ester monomer unit is not particularly limited, and examples thereof include: any one or more of methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, hexyl acrylate, heptyl acrylate, 2-isooctyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, or 2-isooctyl methacrylate.

When the third monomer used in the polymer is two or more of the above ethylenically unsaturated carboxylic acid ester salts, the ratio of methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, hexyl acrylate, heptyl acrylate, 2-isooctyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, and 2-isooctyl methacrylate is not limited, and the total weight of the monomers in the polymer may be within the content range defined in the present application.

As a modification of the binder of the present application, the mass ratio of the first monomer, the second monomer and the third monomer is preferably within a suitable range. The mass ratio of the first monomer in the polymer is 5% to 46%, preferably 10% to 46%, based on the mass of the polymer; the third monomer accounts for 5 to 45.5 percent of the polymer by mass, and preferably accounts for 10 to 45.5 percent of the polymer by mass; the second monomer accounts for 0.5 to 89.9 mass%, preferably 1.5 to 79.5 mass% of the polymer.

The mass contents of the first monomer, the second monomer and the third monomer are within the ranges, so that the problems of low adhesive force of the adhesive, abnormal slurry processing, poor compatibility with electrolyte and the like caused by too high mass ratio can be avoided, and the effect of inhibiting the expansion of the pole piece caused by too low mass ratio can be relatively poor.

In the specific embodiment of the application, the type of the binder is modified styrene-acrylic emulsion, and the polymerization mode can adopt emulsion polymerization. Specifically, the binder can be prepared by the following method:

mixing a part of emulsifier with the first monomer, the second monomer and the third monomer according to a certain proportion, and quickly emulsifying in a certain amount of water to obtain a pre-emulsion. Mixing and dissolving the initiator, the other part of the emulsifier and a certain amount of water uniformly, and adding the mixture into the first dropping liquid pipe to obtain initiator emulsion; pouring about 1/3 of the obtained pre-emulsion into a reaction kettle, heating and stirring, and adding about 2/3 of the pre-emulsion into a second dropping pipe; when the temperature rises to 60-80 ℃, slowly dripping initiator emulsion in the first dripping pipe into the reaction kettle, simultaneously dripping a certain proportion of fourth monomer by using the third dripping pipe, controlling the temperature to be about 80 +/-10 ℃, then slowly dripping pre-emulsion in the second dripping pipe, keeping the solid content of the emulsion to be about 50% (bluing state), and keeping the temperature for 0.5-4 h. And after the reaction is finished, cooling to room temperature, and adjusting the pH value to be between 7 and 8 to obtain the binder.

The preparation process of the adhesive is simple, easy to control, high in feasibility, less in environmental pollution and suitable for industrial mass production.

Wherein, optionally, the emulsifier can be, for example, higher fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylates, carboxylates such as potassium laurate, sulfate salts such as sodium lauryl sulfate, sulfonates such as sodium dioctyl sulfosuccinate, and the like. In the process of preparing the binder, the mass of the part of the emulsifier added is 0.05% to 10%, preferably 0.1% to 8%, of the total mass of the first monomer, the second monomer, the third monomer and the fourth monomer.

Wherein, optionally, the mass ratio of the part of the emulsifier to the other part of the emulsifier is 2: 1 to 6: 1, preferably 3: 1 to 5: 1.

among them, the initiator may be, for example, azobisisobutyronitrile, azobisisoheptonitrile, azobiscyclohexylcarbonitrile, benzoyl peroxide, t-butyl hydroperoxide, ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride (V-50 initiator), azobisisobutylimidazoline hydrochloride (VA-044 initiator), azobisisobutylimidazoline (VA061 initiator), or the like, as an alternative. In the process of preparing the binder, the initiator is added in an amount of 0.01 to 1% by mass, preferably 0.05 to 0.6% by mass, based on the sum of the masses of the first, second, third and fourth monomers.

Wherein, optionally, the mass ratio of the first monomer in the polymer is 5% to 46%, preferably 10% to 46%; the second monomer accounts for 0.5 to 89.9 percent of the mass ratio of the polymer, and preferably 1.5 to 79.5 percent of the mass ratio of the second monomer; the third monomer accounts for 5 to 45.5 percent of the polymer by mass, and preferably accounts for 10 to 45.5 percent of the polymer by mass; the mass ratio of the fourth monomer in the polymer is 0.1% to 8%, preferably 0.5% to 7%, and more preferably 1% to 6%.

The adhesive is prepared by adopting the solvent system or the monomer system, the preferable emulsifier and the preferable initiator within the range of the proportion and in the preferable polymerization atmosphere, temperature and time, the types and the proportion of the emulsifier and the initiator are proper, the reaction condition is mild, and the obtained adhesive has good stabilizer and adhesive property.

In the preparation process of the adhesive, a fourth monomer of a compound with amino and at least two alkenyl groups is simultaneously dripped along with an initiator azo or organic peroxide compound, and the fourth monomer is added at the stage, so that the function of the fourth monomer can be fully exerted, and the low-temperature discharge performance of the battery is improved. Particularly, the nitrogen atom of the diallylamine monomer has a pair of lone-pair electrons and does not participate in conjugation, so that the diallylamine monomer has certain electronegativity and can be combined with lithium ions, and therefore, the membrane has good permeability to the lithium ions, can effectively reduce impedance increase caused by membrane formation, and improves lithium ion conduction. And the addition of the diene structure monomer enables the linear structure of the high molecular polymer to be changed into a network structure, thereby improving the electrolyte resistance of the binder and being beneficial to improving the physical properties of the adhesive film.

[ electrochemical device ]

According to yet another aspect of the present application, the present application relates to an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, at least one of the positive electrode sheet, the negative electrode sheet, and the separator comprising the binder of the present application.

The adhesive is prepared by adding the fourth monomer of the compound with amino and at least two alkenyl dropwise along with an initiator azo or organic peroxide compound in a synthesis stage, wherein the fourth monomer can enable a high polymer to have a certain network structure, improve the electrolyte resistance of the adhesive, facilitate the improvement of the physical property of an adhesive film and improve the lithium ion conductivity of the adhesive. Therefore, in the low-temperature discharge process of an electrochemical device such as a lithium ion battery made of the binder, lithium ions can be quickly conducted into electrolyte from a negative pole piece, so that the low-temperature discharge performance of the battery can be improved.

The binder can be used for preparing the positive pole piece/the negative pole piece, a mixture containing the positive pole active substance/the negative pole active substance and the binder is prepared into slurry to be coated on a current collector, and the positive pole piece/the negative pole piece is obtained through drying. Alternatively, the binder can be coated on a separation film to bond a positive electrode plate and the separation film, or to bond a negative electrode plate and the separation film. Among them, the binder of the present application is particularly preferable as a binder of a negative electrode tab of a secondary battery, because problems caused by the binding of the negative electrode tab in the secondary battery are more significant.

As an improvement of the negative pole piece of the application, the negative pole piece comprises a negative pole current collector and a negative pole active substance layer coated on the surface of the negative pole current collector. The adhesive can be used as an adhesive for a positive pole piece, a negative pole piece or an isolating membrane. The binder of the present application is particularly preferable as a binder of a negative electrode tab because problems caused by the binding of the negative electrode tab in a secondary battery are more significant.

As an improvement of the negative pole piece of the application, the negative active material layer comprises a negative active material, a conductive agent and a binder, wherein the binder contains the polymer.

As an improvement of the negative electrode plate of the present application, the mass percentage content of the binder in the negative electrode active material layer is 0.5% to 8%, preferably 1% to 4%, and more preferably 1% to 2%. In the negative electrode active material layer, when the content of the binder is less than 0.5%, particularly less than 1%, the effect of improving suppression of swelling of the negative electrode sheet is not satisfactory, and when the content of the binder is too high, for example, more than 8%, the internal resistance of the battery becomes high, the cycle performance deteriorates, and the energy density of the battery may be impaired.

Alternatively, the negative active material includes, but is not limited to, at least one of a graphite-based material or a silicon-based material. Specific examples of the negative electrode active material include one or more of artificial graphite, natural graphite, silicon, a silicon oxide compound, a silicon-carbon composite material, soft carbon, and hard carbon.

Optionally, the conductive agent includes, but is not limited to, one or more of conductive carbon black, lamellar graphite, carbon fiber, graphene, ketjen black, single-walled carbon nanotubes, or multi-walled carbon nanotubes.

Optionally, the negative electrode active material layer further contains a thickener or a dispersant. The thickener or dispersant may be any known thickener or dispersant used in the preparation of negative electrode sheets in the art.

As the negative electrode current collector holding the negative electrode active material, any known current collector may be used. Examples of the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like. In some embodiments, the negative current collector is a copper foil.

Methods of preparing negative electrode sheets using binders are well known to those skilled in the art. Optionally, one method for preparing the negative electrode plate by using the binder of the present application is as follows: mixing the binder, the conductive agent, the negative active material and the optional thickener or dispersant in deionized water to obtain slurry; and coating the obtained slurry on a negative current collector, and drying and cold-pressing to form a negative diaphragm on the negative current collector, thereby obtaining the negative pole piece.

The slurry-making apparatus for preparing the slurry is not particularly limited, and examples thereof include a double planetary mixer, a horizontal mixer, and a screw kneader.

The specific form of applying the slurry to the negative electrode current collector is not particularly limited, and examples thereof include applying the slurry to the surface of the negative electrode current collector by extrusion, transfer, gravure coating, spray coating, and the like.

The solvent of the slurry is also not particularly limited, and for example, usual water or other organic solvents including, but not limited to, N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide and the like can be used.

In addition, the negative pole piece prepared by using the binder can also adopt another method: the binder of the present application is directly coated on the current collector to form a coating. Contain the binder of this application in this negative pole piece, specifically, negative pole piece includes negative current collector, coating and negative active material layer, be provided with between negative current collector and the negative active material layer the coating, the coating contains this application the binder.

As an improvement of the positive pole piece, the positive pole piece comprises a positive pole current collector and a positive pole active substance layer coated on the surface of the positive pole current collector. Further, the positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder.

As an improvement of the binder in the positive electrode sheet, it includes, but is not limited to, at least one of polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethylcellulose, water-based acrylic resin, ethylene-vinyl acetate copolymer, styrene-butadiene rubber, fluorinated rubber, and polyurethane.

As an improvement of the positive electrode active material, a lithium transition metal complex compound or a lithium transition metal phosphate compound may be mentioned. Examples of the positive active material may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

As an improvement of the conductive agent, it includes, but is not limited to, a carbon material, for example, at least one selected from graphite, carbon black, graphene, carbon nanotube conductive fiber. Commonly used conductive agents include Ketjen black (ultra fine conductive carbon black, particle size 30-40nm), SP (Super P, small particle conductive carbon black, particle size 30-40 μm), S-O (ultra fine graphite powder, particle size 3-4 μm), KS-6 (large particle graphite powder, particle size 6.5 μm), acetylene black, VGCF (vapor grown carbon fiber, particle size 3-20 μm). The optional conductive agent also includes metal powder, conductive whisker, conductive metal compound, conductive polymer, etc.

As an improvement of the positive electrode active material layer, in the positive electrode active material layer, the mass percentage of the positive electrode active material is 80-98%, the mass percentage of the binder is 1-10%, and the mass percentage of the conductive agent is 1-10%.

As an improvement of the electrolyte, it comprises an organic solvent, a lithium salt and an additive.

As an improvement of the organic solvent, the organic solvent is one or more selected from conventional organic solvents such as cyclic carbonate, linear carbonate, carboxylic ester and the like. The organic solvent which can be specifically selected from the following is not limited thereto: one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), Vinylene Carbonate (VC), propylene carbonate, dipropyl carbonate, methyl formate, Ethyl Propionate (EP), propyl propionate, methyl butyrate, and ethyl acetate.

As an improvement of the lithium salt, at least one selected from inorganic lithium salts and organic lithium salts. The inorganic lithium salt is selected from lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium hexafluoroarsenate (LiAsF)₆) Lithium perchlorate (LiClO)₄) At least one of (1). The organic lithium salt is selected from lithium bis (oxalato) borate (LiB (C)₂O₄)₂Abbreviated as LiBOB), lithium bis (fluorosulfonyl) imide (LiFSI), and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI).

As an improvement of the additive, the additive is one or more of fluorine-containing compounds, sulfur-containing compounds and unsaturated double bond-containing compounds. The following substances can be selected in particular and are not limited thereto: one or more of fluoroethylene carbonate, ethylene sulfite, propane sultone, N-methyl pyrrolidone, N-methyl formamide, N-methyl acetamide, acetonitrile, acrylonitrile, gamma-butyrolactone and methyl sulfide.

In order to prevent short-circuiting, a separator is generally provided between the positive electrode and the negative electrode. In this case, the electrolyte is generally used by penetrating the separator.

The material and shape of the separator are not particularly limited in the present application as long as the effects of the present application are not significantly impaired. The separator may be a resin formed of a material stable to the electrolytic solution, glass fiber, inorganic substance, or the like.

In the electrochemical device of the present application, the material of the separator includes, but is not limited to, a polymer separator, for example, one selected from the group consisting of polyethylene, polypropylene, and ethylene-propylene copolymer.

The electrochemical device of the present application includes any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

In some embodiments of the present application, taking a lithium ion secondary battery as an example, a positive electrode plate, a separator, and a negative electrode plate are sequentially wound or stacked to form an electrode member, and then, the electrode member is placed in, for example, an aluminum plastic film for packaging, and an electrolyte is injected into the electrode member, so as to form and package the electrode member, thereby forming the lithium ion secondary battery. Then, the prepared lithium ion secondary battery was subjected to a performance test and a cycle test. Those skilled in the art will appreciate that the above-described methods of making electrochemical devices (e.g., lithium ion batteries) are merely examples. Other methods commonly used in the art may be employed without departing from the disclosure herein.

Optionally, the lithium ion secondary battery may be a wound or stacked or multi-tab structure lithium ion battery.

The shape of the outer package of the lithium ion secondary battery is also arbitrary, and may be any of a cylindrical shape, a rectangular shape, a laminated shape, a button shape, a large size, and the like.

[ electronic apparatus ]

According to yet another aspect of the present application, the present application relates to an electronic device comprising the aforementioned electrochemical device.

The use of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic apparatus known in the art.

In some embodiments, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.

Taking a lithium ion battery as an example and describing the preparation of the lithium ion battery with reference to specific examples, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application. In the following examples and comparative examples, reagents, materials and instruments used therefor were commercially available unless otherwise specified.

Examples and comparative examples

Preparation of the Binder

(1) Preparation of Binder 1

According to the mass portion, 2 portions of fatty alcohol-polyoxyethylene ether, 25 portions of styrene, 24 portions of butyl acrylate and 1.5 portions of acrylic acid are mixed and quickly emulsified in 40.45 portions of water, so as to obtain the pre-emulsion.

And then 0.05 part of azodiisobutyronitrile, 0.5 part of fatty alcohol-polyoxyethylene ether and 6 parts of water are mixed and dissolved uniformly, and the mixture is added into the first dropping liquid pipe to obtain the initiator emulsion.

1/3 of the obtained pre-emulsion is poured into a reaction kettle to be heated and stirred, and the other 2/3 of the pre-emulsion is added into a second dropping liquid pipe; when the temperature rises to 80 ℃, slowly dripping initiator emulsion by using a first dripping pipe, simultaneously dripping 0.5 part of diallylamine monomer by using a third dripping pipe, controlling the temperature to be 80 ℃, slowly dripping the remaining 2/3 emulsion in the second dripping pipe, keeping the emulsion in a blue light state, and preserving the heat for 4 hours. And after the reaction is finished, cooling to room temperature, and adjusting the pH value to 7-8 to obtain the binder emulsion.

(2) Preparation of Binder 2-7

The preparation process of the adhesive 2 is the same as that of the adhesive 1, and the adhesive 2 is different from the adhesive 1 in that: 1 part of diallylamine monomer was used.

The preparation process of the adhesive 3 is the same as that of the adhesive 1, and the adhesive 3 is different from the adhesive 1 in that: 3 parts of diallylamine monomer were used.

The preparation process of the adhesive 4 is the same as that of the adhesive 1, and the adhesive 4 is different from the adhesive 1 in that: 5 parts of diallylamine monomer were used.

The preparation process of the adhesive 5 is the same as that of the adhesive 1, and the adhesive 5 is different from the adhesive 1 in that: 8 parts of diallylamine monomer were used.

The preparation process of the adhesive 6 is the same as that of the adhesive 1, and the adhesive 6 is different from the adhesive 1 in that: 5 parts of N-methyldiallylamine monomer are used.

(3) Preparation of Binder No. 1

The adhesive 1# adopts the existing styrene-acrylic emulsion.

The preparation method of the existing styrene-acrylic emulsion comprises the following steps: 2 parts of fatty alcohol-polyoxyethylene ether, 25 parts of styrene, 24 parts of butyl acrylate and 1.5 parts of acrylic acid are mixed according to a certain proportion and are quickly emulsified in 40.95 parts of water to obtain the pre-emulsion. And then 0.05 part of potassium persulfate, 0.5 part of fatty alcohol-polyoxyethylene ether and 6 parts of water are mixed and dissolved uniformly, the mixture is added into a first dropping tube to obtain initiator emulsion, 1/3 of the obtained pre-emulsion is poured into a reaction kettle to be heated and stirred, the other 2/3 pre-emulsion is added into a second dropping tube, when the temperature of the reaction kettle rises to 80 ℃, the initiator emulsion is slowly dropped into the first dropping tube, the temperature is controlled to be 80 ℃, the rest 2/3 emulsion is slowly dropped, the blue light state of the emulsion is kept, and the temperature is kept for 4 hours. And after the reaction is finished, cooling to room temperature, and adjusting the pH value to 7-8 to obtain the binder emulsion.

In the binders 1-6 and the binder 1#, the specific types and mass percentages of the monomers are shown in the following table 1.

TABLE 1

Note: "-" indicates that the substance was not added.

Preparation of lithium ion battery

(1) Preparation of negative pole piece

The negative electrode active material artificial graphite, conductive carbon black (Super P) as a conductive agent, sodium carboxymethylcellulose (cisolus 2200) as a thickening agent, and the negative electrode binder prepared as described above were mixed in an amount of 97.3%: 0.5%: 1.2%: 1.0% by mass of the slurry was added to solvent water, and a ROSS double planetary mixer was used to prepare a negative electrode slurry. The negative electrode slurry was coated on the surface of a 6 μm copper foil as a negative electrode current collector using an extrusion coater at a coating speed of 18 m/min. And then, baking in an oven until the pole piece is dried to obtain the negative pole piece.

(2) Preparation of positive pole piece

Mixing the positive active material lithium cobaltate, the conductive agent acetylene black, the binder polyvinylidene fluoride and the NMP solvent, and stirring to prepare the positive slurry. And coating the positive electrode slurry on the surface of a 6-micron aluminum foil serving as a positive electrode current collector, and drying to obtain the positive electrode piece.

(3) Preparation of the electrolyte

In the electrolyte, the concentration of lithium hexafluorophosphate is 1mol/L, and the organic solvent consists of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, fluoroethylene carbonate and 1, 3-propane sultone.

(4) Isolation film

The single-side coating ceramic and the double-side coating water-based vinylidene fluoride-hexafluoropropylene copolymer are used as the isolating membrane.

(5) Preparation of lithium ion battery

And welding the positive pole piece and the negative pole piece with lugs, winding the positive pole piece and the negative pole piece with an isolating film into a battery core, packaging the battery core by adopting an aluminum plastic film, baking the battery core for 24 hours in a vacuum state to remove moisture, injecting the electrolyte, standing the battery core at a high temperature, and forming and sorting the battery to obtain the square soft package lithium ion battery with the thickness, the width and the height of 3.8mm, 64mm and 82mm respectively.

In the embodiments 1 to 6, the binders 1 to 6 are respectively adopted in the process of preparing the negative electrode plate, and the corresponding lithium ion batteries B1 to B7 are obtained by adopting the manner.

In the comparative example 1, the binder # 1 is adopted in the process of preparing the negative pole piece, and the corresponding lithium ion battery D1 is obtained by adopting the manner.

Example 7, the above binder 3 was used in the preparation of the negative electrode sheet, and the difference between the preparation of the negative electrode sheet of example 7 and that of example 3 was: the mass ratio of the negative electrode active material artificial graphite, the conductive agent conductive carbon black, the sodium carboxymethyl cellulose and the binder is 96.5%: 1.3%: 1.2%: 1.0 percent.

Example 8, in the process of preparing the negative electrode plate, the above binder 3 is used, and the difference between the preparation of the negative electrode plate of example 8 and that of example 3 is that: the mass ratio of the negative electrode active material artificial graphite, the conductive agent conductive carbon black, the sodium carboxymethyl cellulose and the binder is 95.3%: 2.5%: 1.2%: 1.0 percent.

Example 9, the above binder 3 was used in the preparation of the negative electrode tab, and the difference between the preparation of the negative electrode tab of example 9 and that of example 3 was: the mass ratio of the negative electrode active material artificial graphite, the conductive agent conductive carbon black, the sodium carboxymethyl cellulose and the binder is 97.5%: 0.5%: 0.5%: 1.5 percent.

Performance testing

The measurement methods of the performance parameters of examples and comparative examples are as follows.

1) Peel force of pole piece

Taking a pole piece to be tested, and cutting a sample with the width of 30mm multiplied by the length of 100mm-160mm by a blade. The special double-sided adhesive tape is adhered to a steel plate, and the width of the adhesive tape is 20mm, and the length of the adhesive tape is 90mm-150 mm. And (4) pasting the pole piece sample intercepted in the last step on a double-faced adhesive tape, wherein the test surface faces downwards. Inserting a paper tape with the width equal to that of the pole piece and the length larger than the length of the sample by 80-200 mm below the pole piece, and fixing the paper tape by using wrinkle glue. And opening a power supply of the tensile machine, lighting an indicator light, and adjusting the limiting block to a proper position. And fixing one end of the steel plate, which is not attached with the pole piece, by using a lower clamp. The paper tape is turned upwards and fixed by an upper clamp, and the position of the upper clamp is adjusted by utilizing an 'up' button and a 'down' button on a manual controller attached to a tensile machine. And recording the data.

2) Wet film peel force

And (2) soaking the pole piece to be tested in the electrolyte for 24h, taking out, drying surface moisture by using absorbent paper, and testing the stripping force of the pole piece according to the same step of the stripping force of the pole piece 1).

3) Slurry stability

Taking a cup of slurry, placing the cup of slurry in a normal temperature environment, scraping the bottom slurry by using an iron sheet or a scraper after 24 hours (or 48 hours), and then vertically arranging the iron sheet or the scraper to enable the slurry on the cup of slurry to flow naturally, wherein if the agglomerated slurry is remained on the iron sheet or the scraper and cannot be normally left, the slurry is settled, otherwise, the slurry is not settled.

4) Full charge rebound of pole piece

Spreading the electrode plate after coating and drying, and measuring the thickness of the electrode plate by a ten-thousandth micrometer and recording the thickness as h₁. Charging the delivered battery to full charge, disassembling the battery, taking the pole piece out, spreading the pole piece smoothly, and measuring the thickness of the pole piece by a ten-thousandth micrometer and recording the thickness as h₂. And (3) calculating the full charge rebound rate of the pole piece according to the following formula:

full charge rebound rate of pole piece (h)₁-h₂)/h₁×100％。

5)60 ℃ full charge storage

The thickness of the initial cell measured by a micrometer is recorded as h₃. Fully charging the battery, storing the battery in a high-temperature box at 60 ℃ for 30d, taking out the battery, testing the thickness of the battery by using a micrometer and recording the thickness as h₄. The rebound rate of the full-electricity storage at 60 ℃ is calculated according to the following formula:

the full electricity storage rebound rate at 60 ℃ (30d) ═ h₃-h₄)/h₃×100％。

6)85 ℃ full charge storage

The thickness of the initial cell measured by a micrometer is recorded as h₅. Fully charging the battery, storing the battery in a high-temperature box at 85 ℃ for 7h, taking out the battery, testing the thickness of the battery by using a micrometer and recording the thickness as h₆. The rebound rate of the full-electricity storage at 85 ℃ is calculated according to the following formula:

rebound rate (7h) of full-electricity storage at 85 ℃ ═ h₅-h₆)/h₅×100％。

7)1.5C @12 ℃ discharge

The temperature of the test box is adjusted to 12 ℃, the battery is charged and discharged for 1 time at 1.5 ℃, and the initial capacity is recorded as q₁₂. Charging and discharging are continued for 10 times under the multiplying power, and the capacity is q after 10 times of recording_12-10。

8)1.0C @0 ℃ discharge

Adjusting the temperature of the test box to 0 ℃, charging and discharging the battery for 1 time at 1.0 ℃, and recording the initial capacity as q₀. Charging and discharging are continued for 10 times under the multiplying power, and the capacity is q after 10 times of recording_0-10。

9) Capacity retention rate of 500 cycles at 25 DEG C

Charging and discharging the initial battery for 1 time, and recording the initial capacity as q₁. Charging and discharging are continued for 500 times, and the capacity is recorded for q for 500 times₂. The capacity retention rate of the resin at 25 ℃ after 500 cycles is calculated according to the following formula:

capacity retention rate (q) after 500 cycles at 25 ℃₁-q₂)/q₁×100％。

10) Battery expansion rate of 500 times of 25 ℃ circulation

The thickness of the initial cell measured by a micrometer is recorded as h₇. Fully charging the battery, putting the battery into a thermostat for charging and discharging 500 times, taking out the battery, testing the thickness of the battery by using a micrometer and recording the thickness as h₈. The cell expansion rate was calculated for 500 cycles at 25 ℃ according to the following formula:

battery swelling rate (h) after 500 cycles at 25 ℃₇-h₈)/h₈×100％。

Test results

Table 2 shows the performance test results of the corresponding lithium ion batteries of examples 1-9 and comparative example 1.

Table 2:

as shown in the data in table 2 above, when the binder in the present application is applied to a negative electrode plate of a lithium ion battery, the peeling force of the electrode plate and the peeling force of a wet film can be significantly improved; the higher adhesive force enables the structural integrity of the pole piece to be maintained in the battery cycle process, so that the capacity retention rate of the lithium ion battery provided in the embodiments 1 to 9 is higher and the battery expansion rate is lower after the lithium ion battery provided in the comparative example 1 is cycled for 500 times. In particular, the lithium ion batteries provided in examples 1 to 9 of the present application have improved conductivity to lithium ions during low-temperature discharge compared to the severe lithium evolution during low-temperature discharge of comparative example 1, and thus substantially no or only slight lithium evolution occurs, improving the low-temperature discharge performance of the lithium ion batteries.

Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.