Electrolyte-resistant functional current collector and preparation method thereof, pole piece and battery

Abstract

The invention discloses an electrolyte-resistant functional current collector, a preparation method of the electrolyte-resistant functional current collector, a pole piece and a battery. The functional current collector comprises a macromolecular base membrane layer, a base coat, a fluorine ion trapping agent layer and a metal layer from inside to outside, the fluorine ion trapping agent layer contains a fluorine ion trapping agent, and the fluorine ion trapping agent is a chemical substance capable of adsorbing fluorine ions in the surrounding environment; the preparation method comprises the following steps: performing bottoming treatment on the surface of the macromolecular base membrane to form a bottoming layer; immersing the high-molecular base membrane subjected to the bottoming treatment into a solution containing a fluorine ion capturing agent; taking out the polymer-based membrane in the solution, and drying to obtain a semi-finished product of the electrolyte-resistant modified functional current collector containing the fluorine ion capturing agent layer; and preparing a metal layer on the surface of the electrolyte-resistant modified functional current collector semi-finished product to obtain the electrolyte-resistant functional current collector. According to the invention, deplating of a metal layer during use of the battery can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte-resistant functional current collector, a preparation method thereof, a pole piece and a battery. Background Art

[0002] As the application of functional current collectors in lithium batteries becomes increasingly widespread, some problems in their use have gradually become prominent. The bonding strength between the polymer layer in the middle of the functional current collector and the outer metal layer is affected by the material properties. The bonding is mainly maintained by intermolecular forces. The metal coating is not easy to fall off in the atmosphere. However, under the influence of the liquid electrolyte present in the lithium battery, the bonding strength of the coating will rapidly decay, causing the metal layer to peel off during the battery cycle, causing the battery internal resistance to increase rapidly and the cycle to drop. According to research and analysis, the main component in the electrolyte that affects the coating peeling strength is lithium salt. Trace moisture in the electrolyte can cause the lithium salt to decompose into strong oxidizing acids such as HF. Some side reactions during the use of the battery will also generate a small amount of highly corrosive fluoride. These fluorides can penetrate into the polymer-metal interface layer through the gaps between the metal layer grains, destroying the base layer and causing deplating.

[0003] To address these issues, various companies and research institutions have developed optimization methods to improve adhesion. These methods primarily include: 1) pre-treatment of the base film, such as increasing the polarity and surface roughness of the base film through ion sources, lasers, and physical friction; 2) replacing different types of base layers, such as silica or alumina; 3) optimizing the base layer process; and 4) adding a polar coating or anti-corrosion layer to the surface of the base film to strengthen adhesion with the coating and provide a barrier. While these methods have some effect, they do not significantly improve the electrolyte resistance of the functional current collector. Summary of the Invention

[0004] The purpose of the present invention is to provide an electrolyte-resistant functional current collector and a preparation method thereof, a pole piece and a battery in response to the above-mentioned situation.

[0005] The present invention is achieved through the following technical solutions:

[0006] The first aspect of the present application provides an electrolyte-resistant functional current collector, which includes, from the inside to the outside, a polymer base film layer, a base layer, a fluoride ion scavenger layer and a metal layer; the fluoride ion scavenger layer contains a fluoride ion scavenger, and the fluoride ion scavenger is a chemical substance that can adsorb fluoride ions in the surrounding environment.

[0007] To optimize the above technical solutions, specific measures taken also include:

[0008] The fluoride ion capture agent in the fluoride ion capture agent layer is selected from at least one of perfluorosulfonic acid resin, polystyrene anion exchange resin with fluorine-chelating functional groups, and quaternary ammonium salt fluoride ion exchange resin.

[0009] Furthermore, the perfluorosulfonic acid resin is Nafion D-520 dispersion; the anion exchange resin of polystyrene structure containing fluorine chelating functional groups is selected from CH-87 resin, CH-32 resin; the quaternary ammonium salt fluoride ion exchange resin is selected from polyquaternium-11 and PFA100 ion exchange resin.

[0010] Furthermore, the functional current collector is an aluminum functional current collector, the base layer is a composite of one or more materials selected from aluminum oxide, silicon dioxide, metal zinc or their oxides, and the base layer has a thickness of 1 to 50 nm.

[0011] Furthermore, the functional current collector is a copper functional current collector, the base layer is a composite of one or more materials selected from metal nickel or its oxide, metal chromium or its oxide, metal titanium or its oxide, and the base layer thickness is 5 to 50 nm.

[0012] A second aspect of the present application provides a method for preparing an electrolyte-resistant functional current collector, comprising the following steps:

[0013] Perform primer treatment on the surface of the polymer base film to form a base layer;

[0014] Immersing the primed polymer base membrane in a solution containing a fluoride ion scavenger;

[0015] Taking out the polymer base film from the solution and drying it to obtain a semi-finished product of an electrolyte-resistant modified functional current collector containing a fluorine ion scavenger layer;

[0016] A metal layer is prepared on the surface of the electrolyte-resistant modified functional current collector semi-finished product to obtain the electrolyte-resistant functional current collector.

[0017] In order to optimize the above-mentioned preparation method and technical solution, the specific measures taken also include:

[0018] The concentration of the solution containing the fluoride ion scavenger is 2-10% w / w by mass percentage; the polymer base membrane after the primer treatment is immersed in the solution containing the fluoride ion scavenger for 15-60 seconds, and the thickness of the fluoride ion scavenger layer after drying is 1-10 nm.

[0019] Furthermore, the base layer is prepared by one or more methods including physical vapor deposition, chemical vapor deposition, in-situ forming, and coating; and the metal layer is prepared by one or more methods including chemical vapor deposition, magnetron sputtering, vacuum evaporation, or water electroplating.

[0020] The third aspect of the present application provides a pole piece comprising the above-mentioned electrolyte-resistant functional current collector.

[0021] A fourth aspect of the present application provides a battery comprising the above-mentioned electrode.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides an electrolyte-resistant modified functional current collector and a preparation method thereof. The functional current collector is provided with a fluoride ion scavenger layer outside the base layer. The fluoride ion scavenger layer contains a fluoride ion scavenger with functional groups such as quaternary ammonium salts, perfluorosulfonic acid groups, and fluorine-containing chelating functional groups. These functional groups can adsorb fluoride ions in the surrounding environment and have good chemical stability such as acid and alkali resistance and redox resistance. The reduction of fluoride ions in the environment can effectively protect the base layer, maintain a stable connection interface between the base layer and the polymer base film layer, and prevent the metal layer from being stripped during use. In addition, the polarity of these functional groups can also enhance the connectivity between the base layer and the metal interface layer, effectively ensuring the interface layer bonding strength of the functional current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Schematic diagram of the structure of the electrolyte-resistant modified functional current collector of the present invention.

[0025] In the figure: 1-polymer base film layer, 2-base layer, 3-fluoride ion capture agent layer, 4-metal layer. DETAILED DESCRIPTION

[0026] The above contents of the present invention are further described in detail below in the form of specific implementation methods, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0027] The experimental methods used in the following examples are conventional methods unless otherwise specified, and the reagents, methods and equipment used are conventional reagents, methods and equipment in the art unless otherwise specified.

[0028] For the sake of simplicity, this document only specifically discloses some numerical values ​​and optional ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range; the optional items in the optional range can also be combined arbitrarily.

[0029] Unless otherwise specified, the terms used in this application have the commonly known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0030] The present invention provides an electrolyte-resistant functional current collector, which comprises, from the inside to the outside, a polymer base film layer, a primer layer, a fluoride ion capture agent layer and a metal layer; the fluoride ion capture agent layer contains a fluoride ion capture agent, which is a chemical substance capable of adsorbing fluoride ions in the surrounding environment.

[0031] In this application, the polymer base film layer serves as a support layer, and the primer layer serves as a transition layer to enhance the bonding strength between the metal layer and the polymer base film layer; the fluoride ion scavenger layer is arranged on the outside of the primer layer to prevent the fluoride ions in the electrolyte from damaging the primer layer, and the metal layer is arranged on the outermost side to play the role of electronic conduction.

[0032] In some embodiments, the fluoride ion capture agent in the fluoride ion capture agent layer is selected from at least one of perfluorosulfonic acid resins, polystyrene anion exchange resins with fluorine-chelating functional groups, and quaternary ammonium salt fluoride ion exchange resins.

[0033] In the present application, non-limiting examples of perfluorosulfonic acid resins are selected from Nafion D-520 dispersion; non-limiting examples of anion exchange resins with polystyrene structures containing fluorine chelating functional groups are selected from CH-87 resin, CH-32 resin; non-limiting examples of quaternary ammonium salt fluoride ion exchange resins are selected from polyquaternium-11 and PFA100 ion exchange resins.

[0034] The polymer base film layer of the present application can be made of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), polyimide (PI) and the like.

[0035] The thickness of the polymer base film layer may be 2 to 15 μm, preferably 4 to 8 μm.

[0036] The base layer of the present application is not limited to the examples in this article, and various types of base layers available in the art can be used. In some embodiments, the more commonly used functional current collectors, such as aluminum functional current collectors and copper functional current collectors, are used as examples:

[0037] When the functional current collector is an aluminum functional current collector, the base layer is selected from a composite of one or more materials selected from aluminum oxide, silicon dioxide, metal zinc or oxides thereof. Preferably, the base layer has a thickness of 1 to 50 nm.

[0038] When the functional current collector is copper, the base layer is selected from a composite of one or more materials selected from metal nickel or its oxide, metal chromium or its oxide, metal titanium or its oxide. Preferably, the base layer has a thickness of 5 to 50 nm.

[0039] The present invention also provides a method for preparing an electrolyte-resistant functional current collector, comprising the following steps:

[0040] Perform primer treatment on the surface of the polymer base film to form a base layer;

[0041] Immersing the primed polymer base membrane in a solution containing a fluoride ion scavenger;

[0042] Taking out the polymer base film from the solution and drying it to obtain a semi-finished product of an electrolyte-resistant modified functional current collector containing a fluorine ion scavenger layer;

[0043] A metal layer is prepared on the surface of the electrolyte-resistant modified functional current collector semi-finished product to obtain the electrolyte-resistant functional current collector.

[0044] The concentration of the solution containing the fluoride ion scavenger is 2 to 10% w / w.

[0045] The polymer base film after primer treatment is immersed in a solution containing a fluoride ion scavenger for 15 to 60 seconds. The thickness of the fluoride ion scavenger layer after drying is 1 to 10 nm. Within this range, the fluoride ion scavenger layer can not only play a barrier role for fluoride ions, but also minimize the impact on the primer layer. Specifically, the thickness of the fluoride ion scavenger layer is very thin, and the impact on the surface roughness and morphology of the primer layer is very small, which can reduce the impact on the bonding between the metal layer and the primer layer.

[0046] The preparation method of the primer layer of the present application can adopt one or more methods such as physical vapor deposition, chemical vapor deposition, and in-situ forming; physical vapor deposition methods include vacuum evaporation and magnetron sputtering; chemical vapor deposition includes atmospheric pressure chemical vapor deposition and plasma enhanced chemical vapor deposition; in-situ forming includes a method of forming a metal oxide passivation layer in situ on the metal surface; coating methods include die coating, blade coating, and extrusion coating;

[0047] In some preferred embodiments, the primer layer can be prepared by vacuum evaporation or magnetron sputtering.

[0048] The metal layer of the present application can be prepared by one or more methods including chemical vapor deposition, magnetron sputtering, vacuum evaporation or water electroplating;

[0049] In some preferred embodiments, the metal layer can be prepared by vacuum evaporation or water electroplating, such as:

[0050] For aluminum functional current collectors: the aluminum metal layer is thickened to a thickness of 0.5-2μm mainly through physical deposition methods such as vacuum evaporation;

[0051] For copper functional current collectors: the copper metal layer is thickened to a thickness of 0.5-2μm mainly through processes such as water electroplating.

[0052] The present invention also provides a pole piece comprising the above-mentioned electrolyte-resistant functional current collector.

[0053] The present invention also provides a battery comprising the above-mentioned electrode piece.

[0054] The technical solution of the present invention is further described in detail below with reference to specific embodiments:

[0055] Comparative Example 1:

[0056] A 6-micron-thick PET film was placed in a vacuum evaporation chamber, and a 5-nm-thick aluminum oxide base layer was deposited by evaporation with oxygen. Subsequently, a 1-μm-thick metal aluminum layer was deposited on the outside of the base layer by vacuum evaporation to obtain an aluminum functional current collector.

[0057] Example 1:

[0058] A 6-micron-thick PET film was placed in a vacuum evaporation chamber, and a 5-nm-thick aluminum oxide base layer was deposited by evaporation with oxygen. The primed base film was then immersed in a fluoride ion scavenger polyquaternium-11 dispersion (from the Sinopharm Reagent Network, the solvent was water, and the concentration was 5% w / w). After 30 seconds, it was taken out and dried. After drying, the thickness of the fluoride ion scavenger layer was 2 nm. A 1-μm-thick metal aluminum layer was deposited on the outside of the dried fluoride ion scavenger layer by vacuum evaporation to obtain an aluminum functional current collector.

[0059] Example 2:

[0060] A 6-micron-thick PET film was placed in a vacuum evaporation chamber, and a 5-nm-thick aluminum oxide base layer was deposited by evaporation with oxygen. The primed base film was then immersed in a fluoride ion scavenger Nafion D-520 dispersion (the solvent was isopropyl alcohol: water = 1:1, and the concentration was 5% w / w). After 30 seconds, it was taken out and dried. After drying, the thickness of the fluoride ion scavenger layer was 2 nm. A 1-μm-thick metal aluminum layer was deposited on the outside of the dried fluoride ion scavenger layer by vacuum evaporation to obtain an aluminum functional current collector.

[0061] Comparative Example 2:

[0062] A 4.5μm thick PET base film is placed in a magnetron device, and a 30nm nickel-chromium base layer is deposited on the surface of the base film by magnetron method. Then it enters the water electroplating process, and a 1μm thick copper layer is deposited outside the base layer to obtain a copper functional current collector.

[0063] Example 3:

[0064] A PET base film with a thickness of 4.5 μm was placed in a magnetron device, and a 30 nm nickel-chromium primer layer was deposited on the surface of the base film by magnetron method. The primed base film was then immersed in a fluoride ion scavenger Nafion D-520 dispersion (the solvent was isopropyl alcohol: water = 1:1, and the concentration mass percentage was 5% w / w). After 30 seconds, it was taken out and dried. After drying, the thickness of the fluoride ion scavenger layer was 1.5 nm. The dried base film entered the water electroplating process, and a 1 μm thick copper layer was deposited outside the fluoride ion scavenger layer to obtain a copper functional current collector.

[0065] Example 4:

[0066] A 6-micron thick PET film was placed in a vacuum evaporation chamber, and a 5-nm thick aluminum oxide base layer was deposited by evaporation with oxygen. 0.1% w / w of cross-linking agent was added to the dichloromethane dispersion of CH-87 polymer (concentration mass percentage is 10% w / w), and the mixture was taken out after 30 seconds and dried at 85°C. After drying, the thickness of the fluoride ion scavenger layer was about 2.5 nm. A 1 μm thick metal aluminum layer was deposited on the outside of the dried fluoride ion scavenger layer by vacuum evaporation to obtain an aluminum functional current collector.

[0067] Experimental testing:

[0068] The test method is as follows:

[0069] (1) Adhesion: A layer of Permacel P-94 double-sided tape was adhered to a 1 mm thick aluminum foil, and a functional current collector was adhered on top of the double-sided tape. A layer of ethylene acrylic acid copolymer film (DuPont Nurcel 0903, 50 μm thick) was covered on top of the sample. The sample was then hot-pressed at 1.3 × 105 N / m2 and 120°C for 10 seconds, cooled to room temperature, and cut into 150 mm × 15 mm strips. Finally, the ethylene acrylic acid copolymer film of the sample strip was fixed to the upper fixture of the tensile testing machine, and the rest of the sample was fixed to the lower fixture. After fixing, the two were peeled off at an angle of 180° and a speed of 100 mm / min to test the peeling force, that is, the adhesion between the middle layer of the current collector and the outer metal layer.

[0070] (2) Electrolyte immersion peel test: Three 50*150mm functional current collector samples were packaged in a 60*170mm aluminum-plastic film bag in a glove box (ambient water content ≤1ppm). 20mL of electrolyte was injected using a syringe and sealed. After standing at room temperature for 3 days, the metal layer adhesion was tested. The electrolyte was a commercially available conventional ternary power battery electrolyte from Tianci Materials.

[0071] Each embodiment and comparative example was tested and measured respectively, and the results are shown in Table 1:

[0072] Table 1 Comparison of test results of each embodiment and comparative example

[0073] sample Initial bonding strength (N / m) Adhesion strength after electrolyte immersion (N / m) Comparative Example 1 859.3 ＜100 Example 1 884.1 593.4 Example 2 793.9 785.3 Comparative Example 2 693.0 318.1 Example 3 652.6 598.0 Example 4 794.3 785.2

[0074] According to the test results, when not immersed in the electrolyte, the fluoride ion scavenger layer has no clear effect on the peeling force of the metal layer. However, after being immersed in the electrolyte, the peeling force of the modified functional current collector in the embodiment is significantly improved, proving that the fluoride ion scavenger layer plays a significant role in blocking fluoride ions.

[0075] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement and improvement made by any technician familiar with the profession to the above embodiment without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An electrolyte-resistant functional current collector, characterized by: The functional current collector comprises a polymer base film layer, a primer layer, a fluoride ion capture agent layer and a metal layer from the inside to the outside; the fluoride ion capture agent layer contains a fluoride ion capture agent, which is a chemical substance capable of adsorbing fluoride ions in the surrounding environment.

2. The electrolyte-resistant functional current collector according to claim 1, wherein: The fluoride ion capture agent in the fluoride ion capture agent layer is selected from at least one of perfluorosulfonic acid resin, polystyrene anion exchange resin with fluorine-chelating functional groups, and quaternary ammonium salt fluoride ion exchange resin.

3. The electrolyte-resistant functional current collector according to claim 2, wherein: The perfluorosulfonic acid resin is Nafion D-520 dispersion; the anion exchange resin of polystyrene structure containing fluorine chelating functional groups is selected from Tulsimer CH-87 resin, Tulsimer CH-32 resin; the quaternary ammonium salt fluoride ion exchange resin is selected from polyquaternium-11 and PFA100 ion exchange resin.

4. The electrolyte-resistant functional current collector according to claim 1, wherein: The functional current collector is an aluminum functional current collector, the bottom layer is a composite of one or more materials selected from aluminum oxide, silicon dioxide, metal zinc or their oxides, and the thickness of the bottom layer is 1 to 50 nm.

5. The electrolyte-resistant functional current collector according to claim 1, wherein: The functional current collector is a copper functional current collector, the bottom layer is a composite of one or more materials selected from metal nickel or its oxide, metal chromium or its oxide, metal titanium or its oxide, and the thickness of the bottom layer is 5 to 50 nm.

6. A method for preparing an electrolyte-resistant functional current collector, characterized in that: The following steps are involved: Perform primer treatment on the surface of the polymer base film to form a primer layer; Immersing the primed polymer base membrane in a solution containing a fluoride ion scavenger; Taking out the polymer base film from the solution and drying it to obtain a semi-finished product of an electrolyte-resistant modified functional current collector containing a fluorine ion scavenger layer; A metal layer is prepared on the surface of the electrolyte-resistant modified functional current collector semi-finished product to obtain the electrolyte-resistant functional current collector.

7. The electrolyte-resistant functional current collector according to claim 6, characterized in that: The concentration of the solution containing the fluoride ion scavenger is 2-10% w / w by mass percentage; the polymer base membrane after the primer treatment is immersed in the solution containing the fluoride ion scavenger for 15-60 seconds, and the thickness of the fluoride ion scavenger layer after drying is 1-10 nm.

8. The electrolyte-resistant functional current collector according to claim 7, characterized in that: The base layer is prepared by one or more methods including physical vapor deposition, chemical vapor deposition, in-situ forming, and coating; the metal layer is prepared by one or more methods including chemical vapor deposition, magnetron sputtering, vacuum evaporation, or water electroplating.

9. A pole piece, characterized in that: The invention relates to an electrolyte-resistant functional current collector prepared by the method described in any one of claims 1 to 5 or any one of claims 6 to 8.

10. A battery, characterized in that: Comprising the pole piece according to claim 9.

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