Dry electrode and manufacturing method therefor, battery, and electric device

Abstract

The present application relates to a dry electrode and a manufacturing method therefor, a battery, and an electric device. The dry electrode comprises a self-supporting electrode film. The self-supporting electrode film comprises components, i.e., an active material, a conductive agent, and a binder. The binder includes modified polytetrafluoroethylene obtained by using a sodium naphthalene solution to treat polytetrafluoroethylene. The dry electrode improves the stability of the self-supporting electrode film, thereby improving the cycle stability of the dry electrode and a battery provided with the dry electrode.

Description

Dry-type electrode, preparation method thereof, battery and electric device

[0001] Cross-reference to related applications

[0002] The present application claims priority to the Chinese patent application No. CN2024110737395, filed on August 6, 2024, and entitled "Dry-type electrode, preparation method thereof, battery and electric device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of batteries, in particular to a dry-type electrode, a preparation method thereof, a battery and an electric device. BACKGROUND

[0004] With the development of electric vehicles, the requirements for energy storage systems such as lithium-ion batteries are becoming higher and higher. Dry-type electrode is a new electrode manufacturing technology that can effectively simplify the preparation process and improve battery performance compared to wet process. Dry-type electrode is a new electrode manufacturing technology that can effectively simplify the preparation process and improve battery performance. Among them, the polymer fibrillation method is a special dry-type electrode manufacturing technology that uses a fibrillatable binder to fibrillate into a network structure under external force to coat the active material and the conductive agent. Polytetrafluoroethylene (PTFE) is known as the "plastic king" and has excellent chemical resistance, thermal stability, dielectric properties, non-stickiness and wear resistance, and is a very important special engineering plastic. At the same time, PTFE has poor adhesion to other materials, which leads to the problem that when it is applied to dry-type electrodes, the active material is easy to fall off, resulting in an increase in the internal resistance of the battery, and PTFE reacts with lithium ions, affecting the capacity performance of the battery. Therefore, how to improve the cycle stability of the dry-type electrode and the battery provided with the same is a technical problem that needs to be solved urgently.

[0005] SUMMARY

[0006] Therefore, the purpose of the present application is to provide a dry-type electrode with high cycle stability, a preparation method thereof, a battery and an electric device.

[0007] In a first aspect, the present application provides a dry-type electrode, comprising a self-supporting electrode film, the components of the self-supporting electrode film comprising an active material, a conductive agent and a binder, the binder comprising modified polytetrafluoroethylene treated by using a naphthalene sodium solution on polytetrafluoroethylene.

[0008] In an alternative embodiment, at least one of the following conditions is met:

[0009] (1) the thickness of the self-supporting electrode film is 100 μm to 150 μm;

[0010] (2) the mass-volume ratio of the polytetrafluoroethylene to the naphthalene sodium solution is 1 g:(2-4) mL;

[0011] (3) the modified polytetrafluoroethylene surface has a carbonized layer with a thickness of 0.05 μm-1 μm;

[0012] (4) the dry electrode further comprises a current collector, and the self-supporting electrode film is arranged on at least one side of the current collector.

[0013] In an alternative embodiment, the naphthalene sodium solution comprises naphthalene, metallic sodium, and a diluent, and the diluent comprises at least one of tetrahydrofuran and toluene.

[0014] In an alternative embodiment, the naphthalene sodium solution is prepared by mixing a naphthalene sodium treatment solution and the diluent in a volume ratio of 1:(1-2).

[0015] In an alternative embodiment, at least one of the following conditions is satisfied:

[0016] (1) the conductive agent comprises at least one of Super P, CNTs, and conductive graphite;

[0017] (2) in the self-supporting electrode film, the mass content of the active material is 50%-96%;

[0018] (3) in the self-supporting electrode film, the mass content of the conductive agent is 2%-40%;

[0019] (4) in the self-supporting electrode film, the mass content of the binder is 2%-10%.

[0020] In an alternative embodiment, the active material is a positive electrode active material, and the positive electrode active material comprises at least one of lithium manganese nickel acid, lithium iron phosphate, lithium cobaltate, and a ternary material; or,

[0021] the active material is a negative electrode active material, and the negative electrode active material comprises at least one of graphite, activated carbon, hard carbon material, soft carbon material, silicon-based negative electrode material, and lithium titanate.

[0022] In an alternative embodiment, the active material is a positive electrode active material, and the binder further comprises a positive electrode fluorine-based polymer; or,

[0023] the active material is a negative electrode active material, and the binder further comprises at least one of polyperfluoroethylene propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoro-propylene-vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer, sodium carboxymethyl cellulose, and styrene butadiene rubber.

[0024] In an alternative embodiment, at least one of the following conditions is satisfied:

[0025] (1) the positive electrode fluorine-based polymer comprises at least one of polyfluoroethylene propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer, and polyvinylidene fluoride;

[0026] (2) the positive electrode fluorine-based polymer has an elongation of 220% to 500%;

[0027] (3) the positive electrode fluorine-based polymer has a compression ratio of 300 to 4000;

[0028] (4) the positive electrode fluorine-based polymer has a melting point of 220 to 380℃.

[0029] In a second aspect, the application provides a preparation method of the dry electrode, comprising the following steps:

[0030] The active material, the conductive agent, and the binder containing the modified polytetrafluoroethylene are dispersed to form a mixture, and the mixture is fiberized to form the self-supporting electrode film under the action of a roller.

[0031] In a third aspect, the application provides a battery comprising oppositely arranged positive and negative electrode sheets, at least one of which is the dry electrode as described in any of the above.

[0032] In a fourth aspect, the application provides an electric device comprising the battery described above.

[0033] Advantages: The binder of the self-supporting electrode film of the dry electrode described above comprises modified polytetrafluoroethylene treated by a naphthalene sodium solution. The modified polytetrafluoroethylene has polar groups such as -OH, C=O, -COOH, and C=C introduced on the surface after being treated by the naphthalene sodium solution, so that the surface energy of the modified polytetrafluoroethylene is increased, the contact angle is reduced, and the wettability is improved. The shortcomings of polytetrafluoroethylene, such as large contact angle, small surface tension, and poor surface wettability, are improved, the adhesion between the active material and the conductive agent is improved, the stability of the self-supporting electrode film is improved, and the cycle stability of the dry electrode and the battery provided with the same is improved.

[0034] The preparation method of the dry electrode described above is simple, the modified PTFE can be fiberized under the action of shear force, and when applied as a binder of an electrode in a lithium ion battery or the like, the active material and the conductive additive can be connected and coated together to improve the stability of the structure of the dry electrode during the cycle operation. In the dry electrode described above, the modified PTFE is fiberized modified PTFE. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0036] FIG. 1 is an infrared spectrum of the modified polytetrafluoroethylene prepared in Example 1 of the present application.

[0037] FIG. 2 is a scanning electron microscope image of the self-supporting electrode film in the positive electrode sheet prepared in Example 3 of the present application.

[0038] FIG. 3 is a cycle performance test diagram of the half-cell assembled by the positive electrode sheet prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the present application are shown in the accompanying drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] "RANGES" disclosed herein can be defined with both a lower and an upper limit, and a given range is defined with a lower limit and an upper limit that defines the boundaries of the particular range. Ranges defined by these methods can be inclusive or exclusive of the endpoints, and any endpoint can be independently included or excluded, and can be arbitrarily combined with any other endpoint to define a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that a range of 60-110 and 80-120 is also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" indicates a shorthand way of describing each and every number that is an integer within the given range of a to b. For example, the numerical range "0-5" indicates that all real numbers between 0 and 5 have been listed herein, and "0-5" is merely a shorthand way of describing each and every number that is an integer within the given range of 0 to 5. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is stated to be an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0042] In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0043] In one aspect of the present application, a dry electrode and a preparation method thereof are provided, and the dry electrode will be described in detail below in combination with the preparation method.

[0044] In one embodiment of the present application, the dry electrode comprises a self-supporting electrode film. The components of the self-supporting electrode film comprise an active material, a conductive agent, and a binder, and the binder comprises modified polytetrafluoroethylene treated with a sodium naphthalene solution.

[0045] In another embodiment of the present application, a preparation method of the above dry electrode is provided, comprising the following steps: dispersing an active material, a conductive agent, and a binder containing modified polytetrafluoroethylene to form a mixture, and fiberizing the mixture to form a self-supporting electrode film under the action of a roller.

[0046] The binder used in the self-supporting electrode film of the dry electrode described above includes modified polytetrafluoroethylene treated with a sodium naphthalene solution, which introduces polar groups such as -OH, C=O, -COOH, C=C on the surface of the modified polytetrafluoroethylene after treatment with the sodium naphthalene treatment solution, increases the surface energy of the modified polytetrafluoroethylene, reduces the contact angle, and improves the wettability, thereby improving the shortcomings of polytetrafluoroethylene such as large contact angle, small surface tension, and poor surface wetting performance, improving the adhesion between the active material and the conductive agent, and thus improving the stability of the self-supporting electrode film, and further improving the cycle stability of the dry electrode and the battery provided with the same.

[0047] The preparation method of the dry electrode described above is simple, and the modified PTFE can be fiberized under the action of shear force. When applied as a binder for electrodes in batteries such as lithium ion batteries, the active material and the conductive additive can be connected and coated together to improve the stability of the structure of the dry electrode during the cycle operation. In the dry electrode described above, the modified PTFE is fiberized modified PTFE.

[0048] The modified PTFE described above can be used to prepare a positive electrode sheet, and can also be used to prepare a negative electrode sheet. That is, the dry electrode described above can be a positive electrode sheet, or a negative electrode sheet.

[0049] In some embodiments, the thickness of the self-supporting electrode film is 100 μm to 150 μm. For example, the thickness can be 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or a range formed by any two of the above values as end values, for example, 120 μm to 150 μm, and the like hereinafter. The thickness of the self-supporting electrode film in this range can further improve the cycle performance of the battery.

[0050] In some embodiments, the mass-to-volume ratio of polytetrafluoroethylene to sodium naphthalene solution is 1 g:(2-4) mL. For example, it can be 1 g:2 mL, 1 g:3 mL, or 1 g:4 mL. Controlling the mass-to-volume ratio can further improve the adhesion of the modified PTFE prepared, and thus improve the stability of the electrode and the cycle stability of the battery.

[0051] In some embodiments, the naphthalene sodium solution includes naphthalene, metallic sodium, and a diluent, the diluent including at least one of tetrahydrofuran and toluene. Further, the naphthalene sodium solution is prepared by mixing the naphthalene sodium treatment solution and the diluent in a volume ratio of 1:(1-2), for example, the volume ratio can be 1:1, 1:1.5, 1:2. Further, the naphthalene sodium treatment solution includes naphthalene and metallic sodium, and further, the mass ratio of the metallic sodium and the naphthalene in the naphthalene sodium treatment solution is 1:(1-10), for example, the mass ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10. Further, the diluent is tetrahydrofuran.

[0052] Further, the step of treating the polytetrafluoroethylene with the naphthalene sodium solution to obtain the modified polytetrafluoroethylene includes mixing and stirring the polytetrafluoroethylene with the naphthalene sodium solution for 2-60 minutes, then filtering, washing the solid with tetrahydrofuran, water, and acetone in sequence, filtering to obtain the solid, and drying the solid by vacuum or other methods to obtain the modified PTFE particles.

[0053] Further, the temperature for fiberizing the mixture can be 20-25°C. After fiberizing, the mixture can be converted into a flocculent or soft mass under the action of shearing force before being rolled.

[0054] Further, the step of rolling the fiberized mixture to form the self-supporting electrode film can be performed in a fibrillation film forming machine. The fiberizing step can also be performed by manual or mechanical grinding.

[0055] In some embodiments, the modified polytetrafluoroethylene has a carbonized layer on the surface with a thickness of 0.05-1 μm. The carbonized layer is dark brown. For example, the thickness of the carbonized layer can be 0.05 μm, 0.1 μm, 0.2 μm, 0.5 μm, or 1 μm.

[0056] In some embodiments, the dry electrode further includes a current collector, and the self-supporting electrode film is arranged on at least one side of the current collector. Further, the self-supporting electrode film can be arranged on one or both sides of the current collector by hot pressing.

[0057] In an example, the dry electrode is a positive electrode sheet, and the current collector can be a metal foil or a composite current collector. For example, the aluminum foil can be used as the metal foil. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.

[0058] In some embodiments, the dry electrode is a cathode sheet, and the active material in the dry electrode is a cathode active material. The cathode active material includes, but is not limited to, at least one of lithium manganese nickel acid, lithium iron phosphate (LiFeP04), lithium cobalt oxide (LiCo02), and ternary materials.

[0059] Further, the ternary material includes, but is not limited to, at least one of nickel cobalt manganese ternary material (NCM) and nickel cobalt aluminum ternary material (NCA). As an example, the nickel cobalt manganese ternary material (NCM) includes, but is not limited to, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2. The nickel cobalt aluminum ternary material (NCA) can include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0060] In some embodiments, the dry electrode is a cathode sheet, and the active material in the dry electrode is a cathode active material. The binder further includes a cathode fluorine-based polymer. Further, in the binder, the mass content of the cathode fluorine-based polymer is 0-50%, such as 0, 1%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%.

[0061] It can be understood that, in some examples, the binder is the modified PTFE described above.

[0062] Further, the cathode fluorine-based polymer includes at least one of polyperfluoroethylene propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoro-propylene-vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer, and polyvinylidene fluoride.

[0063] Further, the elongation of the cathode fluorine-based polymer is 220%-500%, such as 220%, 250%, 300%, 400%, or 500%. A larger elongation means that the polymer has better mechanical properties, which is conducive to the stability of the structure of the electrode during the cycle process.

[0064] Further, the compression ratio of the cathode fluorine-based polymer is 300-4000; such as 300, 500, 1000, 2000, 3000, or 4000. A larger compression ratio is conducive to the processing of the binder in the battery system.

[0065] Further, the melting point of the positive electrode fluorine-based polymer is 220-380℃; as examples, it can be 220℃, 250℃, 280℃, 300℃, 350℃ or 380℃. Good thermal stability is conducive to the stability of the binder when the temperature inside the electrode environment rises.

[0066] In an example, the dry electrode is a negative electrode sheet, and the current collector can be a metal foil or a composite current collector. As a metal foil, copper foil can be used.

[0067] In some embodiments, the dry electrode is a negative electrode sheet, and the active material in the dry electrode is a negative electrode active material, which includes at least one of graphite, activated carbon, hard carbon material, soft carbon material, silicon-based negative electrode material and lithium titanate.

[0068] In some embodiments, the dry electrode is a negative electrode sheet, and the active material is a negative electrode active material, and the binder further includes at least one of polyfluoroethylene-propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoro-propylene-vinyl fluoride copolymer, ethylene-tetrafluoroethylene copolymer, sodium carboxymethyl cellulose and butadiene-styrene rubber.

[0069] In some embodiments, the conductive agent includes, but is not limited to, at least one of Super P, CNTs and conductive graphite.

[0070] In some embodiments, in the self-supporting electrode film, the mass content of the active material is 50%-96%, as examples, it can be 50%, 60%, 70%, 80%, 85%, 90%, 92%, 95%, 96%.

[0071] In some embodiments, in the self-supporting electrode film, the mass content of the conductive agent is 2%-40%, as examples, it can be 2%, 4%, 5%, 6%, 8%, 10%, 20%, 30%, 40%.

[0072] In some embodiments, in the self-supporting electrode film, the mass content of the binder is 2%-10%. As examples, it can be 2%, 4%, 5%, 6%, 8%, 10%.

[0073] In another aspect of the present application, a battery is provided, which includes oppositely arranged positive and negative electrode sheets, and at least one of the positive and negative electrode sheets is the dry electrode of any of the above.

[0074] The above battery, in which at least one of the positive and negative electrode sheets is the dry electrode of any of the above, has improved stability of the electrode, thereby improving the cycle stability of the battery.

[0075] The battery further includes an electrolyte solution impregnated in the positive electrode sheet and the negative electrode sheet. The electrolyte solution includes an electrolyte salt and a solvent. The electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0076] In some embodiments, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, butyrolactone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0077] The battery further includes a separator disposed between the positive electrode sheet and the negative electrode sheet, which mainly functions to prevent short circuiting of the positive and negative electrodes while allowing ions to pass through. In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0078] The battery can be, but is not limited to, a lithium ion battery, a lithium metal battery, a sodium ion battery.

[0079] In another aspect of the present application, a power consuming device is provided, which includes the battery described above.

[0080] The power consuming device can include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc. The mobile device can be, for example, a mobile phone, a laptop, etc.; the electric vehicle can be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0081] In order to make the purpose, technical scheme and advantages of the present application more concise and clear, the present application is described by the following specific examples, but the present application is not limited to these examples. The examples described below are only good examples of the present application, which can be used to describe the present application, and should not be understood as limiting the scope of the present application. It should be noted that any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

[0082] In order to better illustrate the present application, the content of the present application is further described below in combination with examples. The following are specific examples.

[0083] Example 1: Preparation of PTFE treated by naphthalene sodium solution

[0084] About 10g of PTFE was taken in a beaker, 10mL of FS-004 naphthalene sodium treatment solution was added, 10mL of tetrahydrofuran solution was added for dilution, and the PTFE was treated with the naphthalene sodium treatment solution and tetrahydrofuran in a volume ratio of 1:1. After stirring for about 2-4min, the surface of the PTFE turned into a dark brown carbonized layer, and the stirring was continued for 10-30min. The above operation was repeated until the required amount of PTFE was obtained, which was poured into a sieve and washed with tetrahydrofuran, water and acetone three times respectively, and then filtered for 2h and vacuum dried for 8h to obtain modified polytetrafluoroethylene particles.

[0085] Example 2: Preparation of PTFE treated by naphthalene sodium solution

[0086] About 5g of PTFE was taken in a beaker, 10mL of FS-004 naphthalene sodium treatment solution was added, 10mL of tetrahydrofuran solution was added for dilution, and the PTFE was treated with the naphthalene sodium treatment solution and tetrahydrofuran in a volume ratio of 1:1. After stirring for about 2-4min, the surface of the PTFE turned into a dark brown carbonized layer, and the stirring was continued for 10-30min. The above operation was repeated until the required amount of PTFE was obtained, which was poured into a sieve and washed with tetrahydrofuran, water and acetone three times respectively, and then filtered for 2h and vacuum dried for 8h to obtain modified polytetrafluoroethylene particles.

[0087] Example 3: Preparation of battery

[0088] LiNi 0.8 Co 0.1 Mn 0.1O2 as active material, 3% by mass of conductive agent Super P, mixed at room temperature for 1 hour, 2% by mass of modified polytetrafluoroethylene particles prepared in Example 1, mixed at -10°C for 2 hours, to make a binder non-deformable multi-component mixture, ground at 20°C to be fibrous, and then mixed for 20 minutes to make a granular coating; the obtained granular coating was calendered at 100°C to make a continuous positive electrode self-supporting electrode film with a thickness of 150 μm. The positive electrode self-supporting electrode film was attached to a positive electrode current collector aluminum foil by hot pressing to make a positive electrode sheet.

[0089] An electrolyte of 1 mol / L LiPF6was prepared by using DEC (diethyl carbonate) and EC (ethylene carbonate) as solvents in a volume ratio of 1:1 and adding LiPF6. A battery was assembled by using Celgard 2500 as a separator and a metal Li sheet as a negative electrode.

[0090] Example 4: Preparation of a battery

[0091] LiNi 0.6 Co 0.2 Mn 0.2 O2 as active material, 3% by mass of conductive agent Super P, mixed at room temperature for 1 hour, 2% by mass of modified polytetrafluoroethylene particles prepared in Example 1, mixed at -10°C for 2 hours, to make a binder non-deformable multi-component mixture, ground at 20°C to be fibrous, and then mixed for 20 minutes to make a granular coating; the obtained granular coating was calendered at 100°C to make a continuous positive electrode self-supporting electrode film with a thickness of 150 μm. The positive electrode self-supporting electrode film was attached to a positive electrode current collector aluminum foil by hot pressing to make a positive electrode sheet.

[0092] An electrolyte of 1 mol / L LiPF6was prepared by using DEC (diethyl carbonate) and EC (ethylene carbonate) as solvents in a volume ratio of 1:1 and adding LiPF6. A battery was assembled by using Celgard 2500 as a separator and a metal Li sheet as a negative electrode.

[0093] Example 5: Preparation of a battery

[0094] LiFePO4 as active material, 3% by mass of conductive agent Super P, mixed at room temperature for 1 hour, 2% by mass of modified polytetrafluoroethylene particles prepared in Example 1, mixed at -10°C for 2 hours, to make a binder non-deformable multi-component mixture, ground at 20°C to be fibrous, and then mixed for 20 minutes to make a granular coating; the obtained granular coating was calendered at 100°C to make a continuous positive electrode self-supporting electrode film with a thickness of 120 μm. The positive electrode self-supporting electrode film was attached to a positive electrode current collector aluminum foil by hot pressing to make a positive electrode sheet.

[0095] The electrolyte of 1 mol / L LiPF6was prepared by using DEC (diethyl carbonate) and EC (ethylene carbonate) as solvent with volume ratio of 1:1 and adding LiPF6. The battery was assembled by using Celgard 2500 as separator and metal Li sheet as anode.

[0096] Example 6: Preparation of battery

[0097] The active material of LiCoO2with mass fraction of 95% was mixed with conductive agent Super P with mass fraction of 3% at room temperature for 1 h, 2% modified polytetrafluoroethylene particles prepared in Example 1 was added and mixed at -10 ℃ for 2 h to prepare a multi-component mixture with no deformation of binder, and the mixture was grinded to be fibrous at 20 ℃ and then mixed for 20 min to prepare a granular coated material; the obtained granular coated material was calendered at 100 ℃ to form a continuous positive electrode self-supporting electrode film with thickness of 120 μm. The positive electrode self-supporting electrode film was attached to the positive electrode current collector aluminum foil by hot pressing to prepare a positive electrode sheet.

[0098] The electrolyte of 1 mol / L LiPF6was prepared by using DEC (diethyl carbonate) and EC (ethylene carbonate) as solvent with volume ratio of 1:1 and adding LiPF6. The battery was assembled by using Celgard 2500 as separator and metal Li sheet as anode.

[0099] Example 7: Preparation of battery

[0100] The preparation was basically the same as that in Example 3, except that the conductive agent was replaced by equal mass of conductive agent CNTs.

[0101] Example 8: Preparation of battery

[0102] The preparation was basically the same as that in Example 4, except that the conductive agent was replaced by equal mass of conductive agent CNTs.

[0103] Example 9: Preparation of battery

[0104] The preparation was basically the same as that in Example 5, except that the conductive agent was replaced by equal mass of conductive agent CNTs.

[0105] Example 10: Preparation of battery

[0106] The preparation was basically the same as that in Example 6, except that the conductive agent was replaced by equal mass of conductive agent CNTs.

[0107] Example 11: Preparation of battery

[0108] The preparation was basically the same as that in Example 7, except that the formula of the positive electrode self-supporting film was different, specifically, LiNi 0.8 Co 0.1 Mn 0.1O2as active material, 2% by mass of the conductive agent Super P, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0109] Example 12: Preparation of a battery

[0110] The same as Example 8, except that the formulation of the positive electrode self-supporting film is different, specifically, LiFePO4with a mass fraction of 96% is used as the active material, 2% by mass of the conductive agent Super P, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1. 0.6 Co 0.2 Mn 0.2 O2as active material, 2% by mass of the conductive agent Super P, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0111] Example 13: Preparation of a battery

[0112] The same as Example 5, except that the formulation of the positive electrode self-supporting film is different, specifically, LiFePO4with a mass fraction of 96% is used as the active material, 2% by mass of the conductive agent Super P, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0113] Example 14: Preparation of a battery

[0114] The same as Example 6, except that the formulation of the positive electrode self-supporting film is different, specifically, LiCoO2with a mass fraction of 96% is used as the active material, 2% by mass of the conductive agent Super P, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0115] Example 15: Preparation of a battery

[0116] The same as Example 7, except that the formulation of the positive electrode self-supporting film is different, specifically, LiNi 0.8 Co 0.1 Mn 0.1 O2as active material, 2% by mass of the conductive agent CNTs, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0117] Example 16: Preparation of a battery

[0118] The same as Example 8, except that the formulation of the positive electrode self-supporting film is different, specifically, LiNi 0.6 Co 0.2 Mn 0.2 O2as active material, 2% by mass of the conductive agent CNTs, and 2% by mass of the modified polytetrafluoroethylene particles prepared in Example 1.

[0119] Example 17: Preparation of a battery

[0120] The same as example 5, except that the formulation of the positive electrode self-supporting film is different, specifically, 96% by mass of LiFePO4 is used as the active material, 2% by mass of conductive agent CNTs, and 2% by mass of the modified polytetrafluoroethylene particles prepared in example 1.

[0121] Example 18: battery preparation

[0122] The same as example 6, except that the formulation of the positive electrode self-supporting film is different, specifically, 96% by mass of LiCoO2 is used as the active material, 2% by mass of conductive agent CNTs, and 2% by mass of the modified polytetrafluoroethylene particles prepared in example 1.

[0123] Example 19: battery preparation

[0124] The same as example 3, except that the formulation of the positive electrode self-supporting film is different, specifically, 90% by mass of LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the active material, 5% by mass of conductive agent Super P, and 5% by mass of the modified polytetrafluoroethylene particles prepared in example 1 are used as the binder to prepare a dry positive electrode sheet, and a lithium sheet is used as the counter electrode to assemble a half battery for testing.

[0125] Example 20: battery preparation

[0126] The same as example 3, except that the formulation of the positive electrode self-supporting film is different, specifically, 85% by mass of LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the active material, 7% by mass of conductive agent Super P, and 8% by mass of the modified polytetrafluoroethylene particles prepared in example 1 are used as the binder to prepare a dry positive electrode sheet, and a lithium sheet is used as the counter electrode to assemble a half battery for testing.

[0127] Comparative example 1

[0128] The same as example 3, except that it uses equal mass of toluene-modified modified polytetrafluoroethylene particles instead of the modified polytetrafluoroethylene particles prepared in example 1.

[0129] The preparation steps of the toluene-modified modified polytetrafluoroethylene particles are as follows:

[0130] About 10 g of PTFE was taken in a beaker, 10 mL of toluene was added, and 10 mL of tetrahydrofuran solution was added for dilution, and the PTFE was treated. After stirring for about 2-4 min, the surface of the PTFE turned into a dark carbonized layer, and the stirring was continued for 10-30 min. The above operation was repeated until the required amount of PTFE was obtained, which was poured into a sieve and washed with tetrahydrofuran, water, and acetone three times, respectively, and was allowed to stand for 2 h and was vacuum dried for 8 h to obtain modified polytetrafluoroethylene particles.

[0131] The following are performance tests.

[0132] (1) The modified polytetrafluoroethylene obtained in the above Example 1 was subjected to infrared detection analysis, and the obtained infrared spectrum is shown in Figure 1. Among them, the absorption peak at 1425 cm -1 corresponds to the bending vibration of C-H; the absorption peak at 1639 cm -1 corresponds to the stretching vibration of C=C. The absorption peak in the range of 3650 cm -1 -3610 cm -1 corresponds to the absorption peak of free -OH. It is proved that the surface of the modified polytetrafluoroethylene is introduced with -OH, C=C and other polar groups. The surface energy of the modified polytetrafluoroethylene is increased, the contact angle is reduced, and the wettability is improved. The difficult-to-stick polytetrafluoroethylene is improved to be stickable to plastics.

[0133] (2) The morphology of the self-supporting electrode film in the positive electrode sheet obtained in the above Example 3 was analyzed, and the obtained scanning electron microscope image is shown in Figure 2. From the figure, it can be seen that there are obvious filaments, which are formed under the action of shear force of PTFE, proving that the modified PTFE can normally produce fiberization behavior.

[0134] (3) The cycle performance tests of Examples 3-6, Examples 19-20, and Comparative Example 1 were carried out, and the specific conditions of the cycle performance test were as follows: a new battery test system was used, and the test voltage range was 3-4.2 V; the cycle performance test was carried out at a current of 0.1 C, and the time recording condition was 30 s.

[0135] The test results of Example 3 are shown in Figure 3. The initial specific discharge capacity was 190.88 mAh / g, the specific discharge capacity after 100 cycles was 146.49 mAh / g, the capacity retention rate was 76.7%, and excellent cycle performance was exhibited.

[0136] The capacity retention rate after 100 cycles = the capacity after 100 cycles / the capacity after the first cycle.

[0137] The results are shown in Table 1 below.

[0138] Table 1

[0139] From the above table, it can be seen that the battery prepared by the embodiment of the present application has high cycle stability.

[0140] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0141] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims. Industrial applicability

[0142] The binder used in the self-supporting electrode film of the dry electrode provided by the present application includes modified polytetrafluoroethylene treated by a sodium naphthalene solution, and the modified polytetrafluoroethylene has polar groups such as -OH, C=O, -COOH and C=C introduced on the surface after being treated by the sodium naphthalene treatment solution, so that the surface energy of the modified polytetrafluoroethylene is increased, the contact angle is reduced, and the wettability is improved. The shortcomings of polytetrafluoroethylene, such as large contact angle, small surface tension and poor surface wetting performance, are improved, the adhesion between the polytetrafluoroethylene and the active material and the conductive agent is improved, the stability of the self-supporting electrode film is improved, and the cycle stability of the dry electrode and the battery provided with the same is improved.

Claims

1. A dry electrode, characterized by, The self-supporting electrode film includes components including an active material, a conductive agent, and a binder including modified polytetrafluoroethylene treated with a naphthalene sodium solution.

2. The dry electrode of claim 1, wherein At least one of the following conditions is satisfied: (1) the thickness of the self-supporting electrode film is 100-150 μm; (2) the mass-volume ratio of the polytetrafluoroethylene to the naphthalene sodium solution is 1 g:(2-4) mL; (3) the modified polytetrafluoroethylene has a carbonized layer with a thickness of 0.05-1 μm on the surface thereof; (4) the dry electrode further includes a current collector, and the self-supporting electrode film is arranged on at least one side of the current collector.

3. The dry electrode of claim 1, wherein The naphthalene sodium solution includes naphthalene, metallic sodium, and a diluent including at least one of tetrahydrofuran and toluene.

4. The dry electrode of claim 3, wherein The naphthalene sodium solution is prepared by mixing a naphthalene sodium treatment solution and the diluent in a volume ratio of 1:(1-2).

5. The dry electrode of claim 1, wherein At least one of the following conditions is satisfied: (1) the conductive agent includes at least one of Super P, CNTs, and conductive graphite; (2) in the self-supporting electrode film, the mass content of the active material is 50-96%; (3) in the self-supporting electrode film, the mass content of the conductive agent is 2-40%; (4) in the self-supporting electrode film, the mass content of the binder is 2-10%.

6. The dry electrode of claim 1, wherein The active material is a positive electrode active material including at least one of lithium manganese nickel acid, lithium iron phosphate, lithium cobalt acid, and a ternary material; or The active material is a negative electrode active material including at least one of graphite, activated carbon, hard carbon material, soft carbon material, silicon-based negative electrode material, and lithium titanate.

7. The dry electrode according to any of claims 1 to 6, wherein The active material is a positive electrode active material, and the binder further includes a positive electrode fluorine-based polymer; or The active material is a negative electrode active material, and the binder further includes at least one of polyperfluoroethylene propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoro-propylene-vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer, sodium carboxymethyl cellulose, and styrene butadiene rubber.

8. The dry electrode of claim 7, wherein At least one of the following conditions is satisfied: (1) the positive electrode fluorine-based polymer includes at least one of polyperfluoroethylene propylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoro-propylene-vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer, and polyvinylidene fluoride; (2) the positive electrode fluorine-based polymer has an elongation of 220-500%; (3) the positive electrode fluorine-based polymer has a compression ratio of 300-4000; (4) the positive electrode fluorine-based polymer has a melting point of 220-380℃.

9. The method of producing a dry electrode according to any one of claims 1 to 8, wherein The method includes the following steps: The active material, the conductive agent, and the binder containing the modified polytetrafluoroethylene are dispersed to form a mixture, and the mixture is fiberized and rolled to form the self-supporting electrode film.

10. A battery, characterized by The battery includes oppositely arranged positive electrode sheets and negative electrode sheets, at least one of which is the dry electrode according to any one of claims 1-8.

11. An electrical device, characterized by The battery includes the battery according to claim 10.

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