Binder, slurry, lithium battery positive electrode and lithium battery

Abstract

The invention relates to a binder, slurry, a lithium battery positive electrode and a lithium battery, the binder comprises a first polymer, a second polymer, a third polymer and a fourth polymer, the first polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polycarbonate and polyacrylic acid, and the second polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polycarbonate and polyacrylic acid. The second polymer is selected from at least one of sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated polyetheretherketone, sulfonated polyetheretherketone lithium, sulfonated polyethersulfone lithium and sulfonated polyetheretherketone lithium, the third polymer is a conductive polymer, and the fourth polymer is a copolymer of ethylene and acrylic acid. The binder disclosed by the invention has relatively good lithium ion conduction effect, electron conduction effect and binding performance.

Description

Technical Field

[0001] This application relates to the field of new energy, and particularly to lithium batteries. Background Art

[0002] A lithium battery consists of four parts: a lithium battery positive electrode, a lithium battery negative electrode, a separator, and an electrolyte. Among them, the materials of the lithium battery positive electrode include components such as a positive electrode active electrode material, a conductive medium, and a binder. During the charge and discharge process of the battery, lithium ions migrate between the positive and negative electrodes and react with the active electrode material of the positive electrode to achieve the storage and release of electrical energy. Since the active electrode material is an electrically insulating metal compound or sulfur element, its electrochemical activity is relatively low during the reaction process. By mixing a conductive medium in the positive electrode, the electron conduction rate of the positive electrode can be increased. The binder is used to bond the active electrode material and the conductive medium together to construct a continuous conductive network and maintain the structural stability of the positive electrode material. Currently, the most widely used binders are polyvinylidene fluoride, styrene-butadiene rubber, and carboxymethyl cellulose. The good binding effect of these binders can bond the active electrode material and the conductive medium to construct a continuous conductive network; however, their poor lithium ion conduction ability and electron conduction ability limit the ion conduction and electron conduction between the active electrode material and the electrolyte. Adding materials such as lithium-containing polymer electrolytes and conductive polymers to the binder is beneficial to improving the lithium ion conduction and electron conduction effects of the binder, but it will also affect the binding performance of the binder. Summary of the Invention

[0003] Embodiments of this application provide a binder, a slurry, a lithium battery positive electrode, and a lithium battery to solve the technical problem that it is difficult to balance the lithium ion conduction effect, electron conduction effect, and binding performance of existing binders.

[0004] In a first aspect, embodiments of this application provide a binder, which includes a first polymer, a second polymer, a third polymer, and a fourth polymer.

[0005] The first polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polycarbonate, and polyacrylic acid.

[0006] The second polymer is selected from at least one of sulfonated polyether ether ketone, sulfonated polyether sulfone, sulfonated polyether ketone ketone, sulfonated polyether ether ketone lithium, sulfonated polyether sulfone lithium, and sulfonated polyether ketone ketone lithium.

[0007] The third polymer is a conductive polymer.

[0008] The fourth polymer is a copolymer of ethylene and acrylic acid.

[0009] In some embodiments of this application, the weight average molecular weight of the first polymer is 1000 - 500000; and / or,

[0010] The weight-average molecular weight of the second polymer is 1,000 to 500,000; and / or,

[0011] The weight-average molecular weight of the third polymer is 1,000 to 500,000; and / or,

[0012] The weight-average molecular weight of the fourth polymer is 1,000 to 500,000.

[0013] In some embodiments of the present application, in the binder, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 8:1 to 2:1 to 2:70 to 90.

[0014] Second, embodiments of the present application provide a slurry, and the slurry includes:

[0015] An active electrode material for the positive electrode of a lithium battery;

[0016] A conductive agent;

[0017] A solvent;

[0018] The binder according to any one of the embodiments of the first aspect.

[0019] In some embodiments of the present application, the active electrode material includes at least one of elemental sulfur, lithium cobaltate, lithium manganate, lithium titanate, lithium iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

[0020] In some embodiments of the present application, the conductive agent is at least one of acetylene black, carbon black, graphite, carbon nanotubes, and carbon nanorods.

[0021] In some embodiments of the present application, the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0022] In some embodiments of the present application, in the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8 to 3:1 to 3:1 to 3:70 to 90.

[0023] Third, embodiments of the present application provide a positive electrode of a lithium battery, and the positive electrode of the lithium battery includes:

[0024] A current collector;

[0025] A positive electrode material disposed on the current collector, and the positive electrode material is formed from the slurry according to any one of the embodiments of the second aspect.

[0026] Fourth, embodiments of the present application provide a lithium battery, and the lithium battery includes the positive electrode of the lithium battery according to any one of the embodiments of the third aspect.

[0027] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0028] The binder provided by the embodiments of the present application includes a first polymer, a second polymer, a third polymer, and a fourth polymer. The first polymer is beneficial to improving the interfacial contact effect between the binder and the active electrode material and the lithium ion transmission rate. The second polymer and the third polymer are beneficial to improving the lithium ion transmission rate and the electron conduction ability of the binder itself. The fourth polymer can effectively bond the first polymer, the second polymer, and the third polymer, thereby enhancing the bonding ability of the binder. In summary, the binder of the present application has good lithium ion conduction effect, electron conduction effect, and bonding performance. Detailed implementation manners

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0030] Unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. In case of conflict, this specification shall prevail.

[0031] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through the market or can be prepared by existing methods.

[0032] There is a technical problem that it is difficult to balance the lithium ion conduction effect, electron conduction effect, and bonding performance of the existing binder.

[0033] The technical solutions provided by the embodiments of the present application to solve the above technical problems are generally as follows:

[0034] In a first aspect, the embodiments of the present application provide a binder, and the binder includes a first polymer, a second polymer, a third polymer, and a fourth polymer,

[0035] The first polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polycarbonate, and polyacrylic acid,

[0036] The second polymer is selected from at least one of sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated polyetherketoneketone, sulfonated polyetheretherketone lithium, sulfonated polyethersulfone lithium, and sulfonated polyetherketoneketone lithium.

[0037] The third polymer is a conductive polymer,

[0038] The fourth polymer is a copolymer of ethylene and acrylic acid.

[0039] It is easy to understand that the first polymer is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polycarbonate and polyacrylic acid, so that the first polymer can absorb more electrolyte by swelling, thereby improving the interface contact effect between the binder and the active electrode material and the lithium ion transmission rate.

[0040] It is easy to understand that the second polymer surface carries sulfonic acid groups, which will produce SO3 after dissociation. - group, SO3 - The groups can serve as lithium ion transport channels, increasing the lithium ion transfer rate and enhancing the rate performance of the lithium battery. Furthermore, when the second polymer comprises sulfonated polyetheretherketone lithium, sulfonated polyethersulfone lithium, or sulfonated polyetherketoneketone lithium, the partially lithiated polymer can partially ionize lithium ions, thereby increasing the lithium ion content in the electrolyte and, consequently, the charge and discharge capacity of the corresponding lithium battery.

[0041] It is easy to understand that the third polymer is a conductive polymer, which can improve the electronic conductivity of the binder and is beneficial to promoting electronic conduction between the active material, the binder and the conductive agent.

[0042] It is easy to understand that the fourth polymer is a copolymer of ethylene and acrylic acid. The copolymer of ethylene and acrylic acid has good compatibility with the first polymer, the second polymer and the third polymer. The copolymer of ethylene and acrylic acid also has good bonding ability, high strength and strong toughness, and can effectively bond the first polymer, the second polymer and the third polymer, thereby enhancing the bonding ability of the adhesive.

[0043] The binder described in this application includes a first polymer, a second polymer, a third polymer, and a fourth polymer. The first polymer serves as the basis of the binder and is selected from at least one of poly(vinylidene fluoride - hexafluoropropylene) (PVDF - HFP), poly(vinyl alcohol) (PVA), poly(vinylidene fluoride) (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), and poly(acrylic acid) (PAA). These polymers provide good binding properties and certain chemical stability, which helps to firmly bind the cathode materials together while maintaining good compatibility with the electrolyte, facilitating the improvement of the interfacial contact effect between the binder and the active electrode material and the lithium - ion transport rate. The second polymer is selected from at least one of sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(ether sulfone) (SPES), sulfonated poly(ether ketone ketone) (SPEKK), lithium - sulfonated poly(ether ether ketone) (SPEEKLi), lithium - sulfonated poly(ether sulfone) (SPESLi), and lithium - sulfonated poly(ether ketone ketone) (SPEKKLi). These sulfonated polymers have excellent lithium - ion conduction performance due to the presence of sulfonic acid groups, which can effectively improve the ionic conductivity of lithium - ion batteries, thereby improving the battery performance. The third polymer is a conductive polymer, such as polyaniline, polypyrrole, or polythiophene, etc. Such polymers can not only provide additional electron conduction paths, reduce the internal resistance of the battery, but also enhance the electrochemical activity and cycle stability of the battery to a certain extent. In addition, the second polymer and the third polymer are beneficial to improving the lithium - ion transport rate and electron conduction ability of the binder itself. The fourth polymer is a copolymer of ethylene and acrylic acid (EAA). This copolymer not only has good adhesiveness but also can interact with lithium salts in the electrolyte to form a stable solid electrolyte interface (SEI), which helps to protect the cathode material and extend the service life of the battery. At the same time, the fourth polymer can effectively bond the first polymer, the second polymer, and the third polymer. By carefully selecting and combining these four polymers, the binder of this application exhibits excellent comprehensive performance: good lithium - ion conduction effect ensures the efficient charge - discharge of the battery; the improvement of the electron conduction effect helps to reduce the internal resistance, improve the energy density and power output of the battery; and the strong binding performance ensures the stability and cycle life of the cathode structure.

[0044] In summary, the binder provided by the embodiments of this application is ingeniously designed, taking into account the multiple requirements of lithium - ion batteries for ion conduction, electron conduction, and mechanical strength, and is expected to significantly improve the comprehensive performance of lithium - ion batteries, especially in terms of energy density, cycle stability, and safety.

[0045] In some embodiments of this application, the weight - average molecular weight of the first polymer is 1000 - 500000; and / or,

[0046] the weight - average molecular weight of the second polymer is 1000 - 500000; and / or,

[0047] The weight-average molecular weight of the third polymer is 1,000 to 500,000; and / or,

[0048] The weight-average molecular weight of the fourth polymer is 1,000 to 500,000.

[0049] As an example, the weight-average molecular weight of the first polymer can be 1,000, 3,000, 10,000, 30,000, 500,000.

[0050] As an example, the weight-average molecular weight of the second polymer can be 1,000, 3,000, 10,000, 30,000, 500,000.

[0051] As an example, the weight-average molecular weight of the third polymer can be 1,000, 3,000, 10,000, 30,000, 500,000.

[0052] As an example, the weight-average molecular weight of the fourth polymer can be 1,000, 3,000, 10,000, 30,000, 500,000.

[0053] The weight-average molecular weight is the molecular weight of all synthetic macromolecular compounds and most natural macromolecular compounds, and is a statistical average molecular weight of a mixture of homologues with different molecular weights. It is a statistical average molecular weight by mass, that is, the molecular weight averaged per unit weight, and is the statistical average molecular weight obtained by averaging the molecular weights of different molecular weights in a polymer, which is the sum of the products of the molecular weights of all molecules and their respective weight fractions.

[0054] In some embodiments of the present application, in the binder, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 8:1 to 2:1 to 2:70 to 90.

[0055] Second, the embodiments of the present application provide a slurry, and the slurry includes:

[0056] An active electrode material for the positive electrode of a lithium battery;

[0057] A conductive agent;

[0058] A solvent;

[0059] The binder according to any one of the first aspects.

[0060] The slurry is realized based on the binder according to any one of the first aspects. The specific implementation manner of the slurry can refer to the above embodiments and common general knowledge in the art. Since the slurry adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated herein one by one.

[0061] In some embodiments of the present application, the active electrode material includes at least one of elemental sulfur, lithium cobalt oxide, lithium manganate, lithium titanate, lithium iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

[0062] It is easy to understand that elemental sulfur, lithium cobalt oxide, lithium manganate, lithium titanate, lithium iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate are all materials applicable to the positive electrode of a lithium battery and can undergo a chemical reaction with lithium ions to achieve energy storage and release. When the above materials are used for the positive electrode of a lithium battery, they are all solid particles, and the binders described in the present application are all chain-like polymers, which have good binding effects on the solid particles.

[0063] In some embodiments of the present application, the conductive agent is at least one of acetylene black, carbon black, graphite, carbon nanotubes, and carbon nanorods.

[0064] It is easy to understand that acetylene black, carbon black, graphite, carbon nanotubes, and carbon nanorods are all solid particles when used as conductive agents and can be well blended with the active electrode material.

[0065] In some embodiments of the present application, the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0066] In some embodiments of the present application, in the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8 - 3:1 - 3:1 - 3:70 - 90.

[0067] In a third aspect, an embodiment of the present application provides a positive electrode of a lithium battery, which includes:

[0068] A current collector;

[0069] A positive electrode material disposed on the current collector, and the positive electrode material is formed from the slurry according to any one of the embodiments in the second aspect.

[0070] The positive electrode of the lithium battery is realized based on the slurry according to any one of the embodiments in the second aspect. The specific implementation manners of the positive electrode of the lithium battery can refer to the above embodiments and the common general knowledge in the art. Since the positive electrode of the lithium battery adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated herein one by one.

[0071] In a fourth aspect, an embodiment of the present application provides a lithium battery, which includes the positive electrode of the lithium battery according to any one of the embodiments in the third aspect.

[0072] The lithium battery is implemented based on the positive electrode of the lithium battery described in any embodiment of the second aspect. For the specific implementation of the lithium battery, reference may be made to the above embodiments and common general knowledge in the art. Since the lithium battery adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0073] The following further elaborates the present application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions indicated in the following embodiments, they are generally determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0074] Example 1

[0075] This example provides an adhesive, and the adhesive includes a first polymer, a second polymer, a third polymer, and a fourth polymer.

[0076] The first polymer is polyvinylidene fluoride.

[0077] The second polymer is lithium sulfonated polyether ether ketone.

[0078] The third polymer is polyaniline.

[0079] The fourth polymer is a copolymer of ethylene and acrylic acid.

[0080] Among them, the weight-average molecular weight of the first polymer is 400,000.

[0081] The weight-average molecular weight of the second polymer is 500,000.

[0082] The weight-average molecular weight of the third polymer is 40,000.

[0083] The weight-average molecular weight of the fourth polymer is 200,000.

[0084] In the adhesive, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 10:5:15:20.

[0085] This example also provides a slurry, and the slurry includes:

[0086] Active electrode material, and the active electrode material is lithium iron phosphate.

[0087] Conductive agent, and the conductive agent is carbon black.

[0088] Solvent, and the solvent is N,N-dimethylformamide.

[0089] The binder described in this embodiment.

[0090] In the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8:1:1:90.

[0091] This embodiment also provides a positive electrode of a lithium battery, which is prepared by the following method:

[0092] Coat the slurry described in this embodiment onto a current collector, and the current collector is selected as aluminum foil;

[0093] Dry the slurry coated on the current collector to obtain the positive electrode of the lithium battery.

[0094] This embodiment also provides a lithium battery, which is prepared by the following method:

[0095] Mix graphite, styrene-butadiene rubber, acetylene black, and N-methylpyrrolidone according to a mass ratio of 9:1:0.3:90 to obtain a negative electrode slurry;

[0096] Coat the negative electrode slurry onto a copper foil, and dry the negative electrode slurry on the copper foil to obtain a negative electrode of the lithium battery;

[0097] Provide a separator, an electrolyte, and a button battery case, wherein the separator is a polyethylene separator and the electrolyte is a solution of lithium hexafluorophosphate in ethylene carbonate;

[0098] Assemble the positive electrode of the lithium battery, the negative electrode of the lithium battery, the separator, the electrolyte, and the button battery case into a button battery to obtain the lithium battery.

[0099] Example 2

[0100] This embodiment provides a binder, which includes a first polymer, a second polymer, a third polymer, and a fourth polymer,

[0101] The first polymer is polyvinyl alcohol,

[0102] The second polymer is at least one of lithium sulfonated polyether ketone ketone,

[0103] The third polymer is polypyrrole,

[0104] The fourth polymer is a copolymer of ethylene and acrylic acid.

[0105] Among them, the weight-average molecular weight of the first polymer is 200,000,

[0106] The weight-average molecular weight of the second polymer is 500,000,

[0107] The weight-average molecular weight of the third polymer is 60,000,

[0108] The weight-average molecular weight of the fourth polymer is 200,000.

[0109] In the binder, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 30:50:10:10.

[0110] This embodiment also provides a slurry, which includes:

[0111] Active electrode material, the active electrode material is lithium nickel cobalt aluminate, specifically LiNi 0.815 Co 0.15 Al 0.035 O2;

[0112] Conductive agent, the conductive agent is carbon black;

[0113] Solvent, the solvent is N,N-dimethylformamide;

[0114] The binder described in this embodiment.

[0115] In the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8:2:2:90.

[0116] This embodiment also provides a positive electrode of a lithium battery, which is prepared by the following method:

[0117] Coat the slurry described in this embodiment on a current collector, and the current collector is made of aluminum foil;

[0118] Dry the slurry coated on the current collector to obtain the positive electrode of the lithium battery.

[0119] This embodiment also provides a lithium battery, which is prepared by the following method:

[0120] Mix graphite, styrene-butadiene rubber, acetylene black, and N-methylpyrrolidone in a mass ratio of 9:1:0.3:90 to obtain a negative electrode slurry;

[0121] Coat the negative electrode slurry on a copper foil, and dry the negative electrode slurry on the copper foil to obtain a negative electrode of a lithium battery;

[0122] Provide a separator, an electrolyte, and a button battery case, where the separator is a polyethylene separator and the electrolyte is a solution of lithium hexafluorophosphate in ethylene carbonate;

[0123] Assemble the positive electrode of the lithium battery, the negative electrode of the lithium battery, the separator, the electrolyte, and the button battery case into a button battery to obtain the lithium battery.

[0124] Example 3

[0125] This embodiment provides an adhesive, which includes a first polymer, a second polymer, a third polymer, and a fourth polymer.

[0126] The first polymer is polyacrylic acid.

[0127] The second polymer is lithium sulfonated polyethersulfone.

[0128] The third polymer is polythiophene.

[0129] The fourth polymer is a copolymer of ethylene and acrylic acid.

[0130] Among them, the weight-average molecular weight of the first polymer is 500,000.

[0131] The weight-average molecular weight of the second polymer is 140,000.

[0132] The weight-average molecular weight of the third polymer is 20,000.

[0133] The weight-average molecular weight of the fourth polymer is 200,000.

[0134] In the adhesive, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 20:25:10:15.

[0135] This embodiment also provides a slurry, which includes:

[0136] Active electrode material, and the active electrode material is elemental sulfur.

[0137] Conductive agent, and the conductive agent is carbon black.

[0138] Solvent, and the solvent is N,N-dimethylformamide.

[0139] The adhesive described in this embodiment.

[0140] In the slurry, the mass ratio of the active electrode material, the conductive agent, the adhesive, and the solvent is 8:2:1:70.

[0141] This embodiment also provides a positive electrode of a lithium battery, which is prepared by the following method:

[0142] Coat the slurry described in this embodiment onto a current collector, and the current collector is made of aluminum foil.

[0143] Dry the slurry coated on the current collector to obtain the positive electrode of the lithium battery.

[0144] Comparative Example 1

[0145] The difference between this comparative example and Example 1 is only that: the binder described in this comparative example does not contain the copolymer of ethylene and acrylic acid.

[0146] Specifically as follows:

[0147] This comparative example provides a binder, and the binder includes a first polymer, a second polymer, and a third polymer.

[0148] The first polymer is polyvinylidene fluoride.

[0149] The second polymer is lithium sulfonated poly(ether ether ketone).

[0150] The third polymer is polyaniline.

[0151] Among them, the weight-average molecular weight of the first polymer is 400,000.

[0152] The weight-average molecular weight of the second polymer is 500,000.

[0153] The weight-average molecular weight of the third polymer is 40,000.

[0154] In the binder, the mass ratio of the first polymer, the second polymer, and the third polymer is 10:5:15.

[0155] This comparative example also provides a slurry, and the slurry includes:

[0156] Active electrode material, and the active electrode material is lithium iron phosphate.

[0157] Conductive agent, and the conductive agent is carbon black.

[0158] Solvent, and the solvent is N,N-dimethylformamide.

[0159] The binder described in this comparative example.

[0160] In the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8:1:1:90.

[0161] This comparative example also provides a positive electrode of a lithium battery, and the positive electrode of the lithium battery is prepared by the following method:

[0162] Coat the slurry described in this comparative example onto a current collector, and the current collector is selected as aluminum foil.

[0163] Dry the slurry coated on the current collector to obtain the positive electrode of the lithium battery.

[0164] This comparative example also provides a lithium battery, and the lithium battery is prepared by the following method:

[0165] Graphite, styrene-butadiene rubber, acetylene black, and N-methylpyrrolidone are mixed in a mass ratio of 9:1:0.3:90 to obtain a negative electrode slurry;

[0166] The negative electrode slurry is coated on a copper foil, and the negative electrode slurry on the copper foil is dried to obtain a negative electrode of a lithium battery;

[0167] A separator, an electrolyte, and a button battery case are provided. The separator is a polyethylene separator, and the electrolyte is a solution of lithium hexafluorophosphate in ethylene carbonate;

[0168] The positive electrode of the lithium battery, the negative electrode of the lithium battery, the separator, the electrolyte, and the button battery case are assembled into a button battery to obtain the lithium battery.

[0169] Comparative Example 2

[0170] The difference between this comparative example and Example 1 is only that: the binder in this comparative example only contains polyvinylidene fluoride.

[0171] Specifically as follows:

[0172] This comparative example provides a binder, and the binder is polyvinylidene fluoride.

[0173] Among them, the weight-average molecular weight of the polyvinylidene fluoride is 400,000.

[0174] This comparative example also provides a slurry, and the slurry includes:

[0175] Active electrode material, and the active electrode material is lithium iron phosphate;

[0176] Conductive agent, and the conductive agent is carbon black;

[0177] Solvent, and the solvent is N,N-dimethylformamide;

[0178] The binder described in this comparative example.

[0179] In the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8:1:1:90.

[0180] This comparative example also provides a positive electrode of a lithium battery, and the positive electrode of the lithium battery is prepared by the following method:

[0181] The slurry described in this comparative example is coated on a current collector, and the current collector is an aluminum foil;

[0182] The slurry coated on the current collector is dried to obtain the positive electrode of the lithium battery.

[0183] This comparative example also provides a lithium battery, and the lithium battery is prepared by the following method:

[0184] Graphite, styrene-butadiene rubber, acetylene black, and N-methylpyrrolidone were mixed in a mass ratio of 9:1:0.3:90 to obtain the negative electrode slurry;

[0185] The negative electrode slurry was coated on a copper foil, and the negative electrode slurry on the copper foil was dried to obtain the negative electrode of the lithium battery;

[0186] A separator, an electrolyte, and a button battery case were provided. The separator was a polyethylene separator, and the electrolyte was a solution of lithium hexafluorophosphate in ethylene carbonate;

[0187] The positive electrode of the lithium battery, the negative electrode of the lithium battery, the separator, the electrolyte, and the button battery case were assembled into a button battery to obtain the lithium battery.

[0188] Related experiments and effect data:

[0189] Related experiments and effect data:

[0190] The lithium batteries of Examples 1-2 and Comparative Examples 1-2 were electrochemically tested at a current density of 1C. The initial capacity and the capacity after 100 charge-discharge cycles were measured, and the capacity retention rate was calculated. The above electrochemical test results are shown in Table 1.

[0191] Table 1

[0192]

[0193]

[0194] It should be noted that the only difference between Comparative Examples 1-2 and Example 1 is the binder. From the electrochemical test results, the initial capacities of Example 1 and Comparative Example 1 were basically at the same level, while the initial capacity of Comparative Example 2 was slightly lower than that of Examples 1-2. This may be because both the binders of Example 1 and Comparative Example 1 contain lithium sulfonated polyether ether ketone and polyaniline. Lithium sulfonated polyether ether ketone can add extra lithium ions to the lithium battery, while polyaniline can effectively increase the electronic conductivity of the binder, which is beneficial to the increase of the capacity of the lithium battery. From the perspective of the capacity retention rate, different active materials were used to prepare the positive electrode of the lithium battery in Examples 1 and 2, but the capacity retention rates both reached a high level of more than 92%; while the capacity retention rates of Comparative Examples 1-2 were both 89%. This may be because the binders of Examples 1-2 contain a copolymer of ethylene and acrylic acid, which increases the adhesion ability of the binder, and thus makes the positive electrode of the lithium battery more stable, and thus shows a higher capacity retention rate.

[0195] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0196] In addition, in the description of the present application specification, the terms "include", "comprise", etc. mean "including but not limited to". Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements. In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone. For the association relationship of more than three associated objects described with "and / or", it means that these three associated objects can exist alone, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist simultaneously, or three of them exist simultaneously. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "at least one of the following (individuals)" or similar expressions refer to any combination of these items, including any combination of single item (individuals) or plural items (individuals). For example, "at least one of a, b, or c (individuals)," or "at least one of a, b, and c (individuals)", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple respectively. "Number representation" involved in this application, such as parts by weight, parts by mass, etc., represents the proportional relationship between each component. In the proportional relationship involved in this application, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0197] The above description is only the specific implementation manners of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather should be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An adhesive, characterized in that, The binder includes a first polymer, a second polymer, a third polymer, and a fourth polymer. The first polymer is selected from at least one of poly(vinylidene fluoride - hexafluoropropylene), poly(vinyl alcohol), poly(vinylidene fluoride), polyacrylonitrile, polycarbonate, and polyacrylic acid. The second polymer is selected from at least one of sulfonated poly(ether ether ketone), sulfonated poly(ether sulfone), sulfonated poly(ether ketone ketone), lithium sulfonated poly(ether ether ketone), lithium sulfonated poly(ether sulfone), and lithium sulfonated poly(ether ketone ketone). The third polymer is a conductive polymer.

2. The binder according to claim 1, wherein The weight - average molecular weight of the first polymer is 1000 - 500000; and / or, The weight - average molecular weight of the second polymer is 1000 - 500000; and / or, The weight - average molecular weight of the third polymer is 1000 - 500000; and / or, The weight - average molecular weight of the fourth polymer is 1000 - 500000.

3. The binder according to claim 1, characterized in that, In the binder, the mass ratio of the first polymer, the second polymer, the third polymer, and the fourth polymer is 8:1 - 2:1 - 2:70 - 90.

4. A slurry, characterized in that, The slurry includes: Active electrode material, which is used for the positive electrode of a lithium - ion battery. Conductive agent. Solvent. The binder according to any one of claims 1 - 3.

5. The paste according to claim 4, characterized in that, The active electrode material includes at least one of elemental sulfur, lithium cobaltate, lithium manganate, lithium titanate, lithium iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

6. The slurry according to claim 4, wherein The conductive agent is at least one of acetylene black, carbon black, graphite, carbon nanotubes, and carbon nanorods.

7. The slurry according to claim 4, wherein The solvent is at least one of N,N - dimethylformamide, dimethyl sulfoxide, and N - methylpyrrolidone.

8. The paste according to claim 4, characterized in that, In the slurry, the mass ratio of the active electrode material, the conductive agent, the binder, and the solvent is 8 - 3:1 - 3:1 - 3:70 - 90.

9. A lithium battery cathode, characterized in that, The positive electrode of the lithium - ion battery includes: Current collector. Positive electrode material disposed on the current collector, and the positive electrode material is formed from the slurry according to any one of claims 4 - 8.

10. A lithium battery, characterized in that, The lithium - ion battery includes the positive electrode of the lithium - ion battery according to claim 9.

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