CN113097493B - Preparation method of composite current collector and lithium ion battery - Google Patents
Preparation method of composite current collector and lithium ion battery Download PDFInfo
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- CN113097493B CN113097493B CN202110348292.8A CN202110348292A CN113097493B CN 113097493 B CN113097493 B CN 113097493B CN 202110348292 A CN202110348292 A CN 202110348292A CN 113097493 B CN113097493 B CN 113097493B
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- 239000002131 composite material Substances 0.000 title claims abstract description 246
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 229920000642 polymer Polymers 0.000 claims abstract description 133
- 238000013329 compounding Methods 0.000 claims abstract description 24
- 150000001875 compounds Chemical class 0.000 claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- 239000010410 layer Substances 0.000 claims description 372
- 229910052782 aluminium Inorganic materials 0.000 claims description 199
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 181
- 239000011888 foil Substances 0.000 claims description 112
- -1 polyethylene terephthalate Polymers 0.000 claims description 39
- 239000008367 deionised water Substances 0.000 claims description 37
- 229910021641 deionized water Inorganic materials 0.000 claims description 37
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 37
- 238000005266 casting Methods 0.000 claims description 36
- 239000004743 Polypropylene Substances 0.000 claims description 28
- 229920001155 polypropylene Polymers 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 19
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 13
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- 230000000052 comparative effect Effects 0.000 description 61
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- 230000007797 corrosion Effects 0.000 description 23
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- 238000007747 plating Methods 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
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- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 150000001845 chromium compounds Chemical class 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
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- 238000000861 blow drying Methods 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920006254 polymer film Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 2
- 238000010345 tape casting Methods 0.000 description 2
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 241001391944 Commicarpus scandens Species 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
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- 230000000996 additive effect Effects 0.000 description 1
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- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000005025 cast polypropylene Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- WYYQVWLEPYFFLP-UHFFFAOYSA-K chromium(3+);triacetate Chemical compound [Cr+3].CC([O-])=O.CC([O-])=O.CC([O-])=O WYYQVWLEPYFFLP-UHFFFAOYSA-K 0.000 description 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical class [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 1
- GRWVQDDAKZFPFI-UHFFFAOYSA-H chromium(III) sulfate Chemical compound [Cr+3].[Cr+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O GRWVQDDAKZFPFI-UHFFFAOYSA-H 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
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- 239000010439 graphite Substances 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/665—Composites
- H01M4/667—Composites in the form of layers, e.g. coatings
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Composite Materials (AREA)
- Cell Electrode Carriers And Collectors (AREA)
Abstract
The invention provides a preparation method of a composite current collector and a lithium ion battery. The preparation method of the composite current collector comprises the following steps: compounding a first polymer to one functional surface of the first conductive layer to obtain a first composite layer comprising the first polymer layer and the first conductive layer; compounding a second polymer to one functional surface of the second conductive layer to obtain a second composite layer comprising a second polymer layer and a second conductive layer; right first composite bed with first conducting layer and second conducting layer in the second composite bed carry out the attenuate processing after, it is right first polymer layer and second polymer layer carry out thermal compound processing, obtain the compound mass flow body, the compound mass flow body is including first attenuate conducting layer, polymer layer and the second attenuate conducting layer of range upon range of setting. The preparation method can be used for preparing the extremely thin current collector, and the current collector has the advantages of compact and uniform surface, small square resistance, low cost and high production efficiency.
Description
Technical Field
The invention belongs to the field of batteries, and relates to a preparation method of a composite current collector and a lithium ion battery.
Background
The current collector is one of indispensable constituent components in a lithium ion battery. The current collector plays an important role in the use of the lithium ion battery, on one hand, the current collector can bear positive and negative active substances, and on the other hand, electrons generated by electrochemical reaction can be collected and conducted to an external circuit, so that chemical energy is converted into electric energy. The ideal current collector should satisfy high conductivity, high stability, high strength, flexibility and lightness.
The single metal foil is poor in toughness, mechanical property and mechanical property when being used as a current collector of the lithium ion battery, and is easy to break or generate cracks in the processing and using processes of the lithium ion battery, so that the safety performance of the lithium ion battery is reduced.
The traditional single metal foil current collector is modified into the composite current collector comprising the polymer layer, so that the toughness of the current collector can be enhanced, the current collector has higher mechanical property and mechanical property, and the safety performance of the lithium ion battery is further improved. However, most current collectors including polymer layers are prepared by adopting expensive vacuum coating equipment through a vacuum evaporation method, the composite current collector prepared by the method has a loose surface structure and poor compactness and uniformity, so that the sheet resistance of the current collector is high, the internal resistance of a battery can be increased when the composite current collector is used in a lithium ion battery, and the electrochemical performance of the lithium ion battery is poor.
Disclosure of Invention
The invention provides a preparation method of a composite current collector, which prepares the composite current collector by adopting a combined process of casting a polymer film on a conducting layer, corroding and thinning the conducting layer and thermally compounding a polymer layer, can prepare an extremely thin current collector, and the prepared current collector has a compact and uniform surface structure and small sheet resistance.
The invention also provides a composite current collector which is prepared by the preparation method provided by the invention and has the advantages of compact and uniform surface structure and small sheet resistance.
The invention also provides a lithium ion battery, which comprises the composite current collector, on one hand, the lithium ion battery can have lower internal resistance due to lower sheet resistance of the current collector, and on the other hand, the thickness of the current collector can be controlled to be very thin, so that the lithium ion battery has higher energy density.
The invention provides a preparation method of a composite current collector, which comprises the following steps: compounding a first polymer to one functional surface of the first conductive layer to obtain a first composite layer comprising the first polymer layer and the first conductive layer; compounding a second polymer to one functional surface of the second conductive layer to obtain a second composite layer comprising a second polymer layer and a second conductive layer; and thinning the first conducting layer and the second conducting layer in the first composite layer and the second composite layer, and then carrying out thermal composite treatment on the first polymer layer and the second polymer layer to obtain a composite current collector, wherein the composite current collector comprises the first thinned conducting layer, the polymer layer and the second thinned conducting layer which are stacked.
According to the invention, the first conductive layer and the second conductive layer are used as substrates, and the first polymer and the second polymer are respectively compounded on one functional surface of the first conductive layer and one functional surface of the second conductive layer to respectively obtain the first composite layer and the second composite layer.
And thinning the first conducting layer and the second conducting layer in the first composite layer and the second composite layer, then pasting the first polymer layer and the second polymer layer in the first composite layer and the second composite layer together, and melting the polymer layers into a polymer layer through the thermal compounding effect, thereby obtaining the composite current collector with the first thinned conducting layer-the polymer layer-the second thinned conducting layer.
According to the preparation method of the composite current collector, the prepared current collector has a compact and uniform surface structure and smaller sheet resistance, and the preparation of the ultrathin composite current collector can be realized through thinning treatment and thermal recombination, so that a battery has higher energy density.
In a specific embodiment, the first conductive layer comprises a first functional surface and a second functional surface, wherein the first functional surface is provided with a first polymer layer, the second functional surface comprises a first area and a second area, and the second area is provided with a protective layer; and/or the second conductive layer comprises a first functional surface and a second functional surface, wherein the first functional surface is provided with a second polymer layer, the second functional surface comprises a first area and a second area, and the second area is provided with a protective layer. The protective layers are arranged in the second area of the first conductive layer and the second area of the second conductive layer for preventing the second area from being thinned.
Further, the compounding in the present invention may be carried out by a tape casting compounding process, and the temperature of the tape casting is maintained to melt the polymer and less than the decomposition temperature of the polymer.
Further, in the thinning treatment in the present invention, the first conductive layer and the second conductive layer may be etched by using an etching solution. The corrosion includes chemical corrosion or electrochemical corrosion. The pH of the etching solution can be controlled to 5-9 so that the etching solution does not react with the polymer layer in the composite layer.
When the thinning treatment is carried out by adopting a chemical corrosion method, in order to enable the surface structure of the thinned conducting layer to be more smooth and compact, a solution containing 1-15wt% of sulfuric acid, 0.1-2wt% of polyacrylic acid and 83-98.9wt% of deionized water can be selected as a corrosive solution.
In order to ensure that the prepared composite current collector has the lowest possible thickness, the thicknesses of the first and second thinning conductive layers can be controlled to be 0.1-5 mu m respectively by adjusting the formula of the corrosive liquid, the corrosion time and the like.
Accordingly, the thickness of the first and second polymer layers can be controlled to be 0.1-10 μm by setting the die lip gap of the casting machine. The greater the thickness of the polymer layer, the greater the total thickness and the lower the total weight of the current collector, the lower the energy density of the battery prepared using the current collector; the smaller the thickness of the polymer layer, the greater the total thickness and the lower the total weight of the current collector, and the lower the energy density of the battery prepared using the current collector. However, if the thickness of the polymer layer is too small, the mechanical properties and mechanical properties of the current collector are poor, which may result in the safety performance of the battery being reduced, and even the battery being unable to be processed normally subsequently, and finally unable to be prepared. The thickness range can enable the battery to have high manufacturability, ensure the safety performance and simultaneously have low internal resistance.
When the first polymer layer and the second polymer layer are subjected to the thermal compounding treatment, the temperature for thermal compounding is ensured to be capable of melting the first polymer and the second polymer without decomposing the two.
In a specific implementation process, the first conductive layer and the second conductive layer may be respectively and independently selected from one of an aluminum foil and a copper foil.
When an aluminum foil is selected as the first conductive layer and/or the second conductive layer, the aluminum foil needs to be surface-treated. In the manufacturing process of the aluminum foil, an oxidation film is inevitably formed on the surface of the metal aluminum in the high-temperature homogenizing process and the high-temperature annealing process aiming at improving the (100) crystal face occupancy rate, a distortion layer of the oxidation film is formed on the surface of the aluminum foil by rolling, and a pollution layer of aluminum, grease and the like is adhered on the rolled surface, so that the surface of the aluminum foil is uneven. Therefore, before use, the uneven oxide film on the surface of the aluminum foil needs to be removed, and a uniform and flat passivation film needs to be formed on the surface of the metal aluminum again to improve the corrosion resistance of the aluminum foil.
Specifically, the method for surface treatment of the aluminum foil in the invention comprises the following steps: firstly, cleaning an aluminum foil in an acetone solvent for 0.5-5min, drying the aluminum foil by cold air, cleaning the aluminum foil by using alkali liquor of 0.05-0.3mol/L for 0.5-5min, cleaning the aluminum foil by using deionized water for 0.5-10min, passivating the aluminum foil by using a passivation solution for 0.5-10min, cleaning the aluminum foil by using deionized water for 1-20min, drying the aluminum foil by cold air, and finally baking the aluminum foil at 50-100 ℃ for 10-60min.
Wherein the alkali solution can be potassium hydroxide solution or sodium hydroxide solution; the passivation solution is a solution comprising a chromium compound and an additive, wherein the mass fraction of the chromium compound can be 0.05-5%, and the chromium compound preferably comprises trivalent chromium and/or hexavalent chromium compounds.
In order to ensure that the polymer layer has good tensile strength and flexibility, the first polymer and the second polymer can be respectively and independently selected from at least one of polyethylene terephthalate, polybutylene terephthalate, nylon 66, ethylene-propylene copolymer and polypropylene.
Further, the polypropylene may be selected from at least one of cast polypropylene, biaxially oriented polypropylene, modified polypropylene.
Still further, the modified polypropylene may be selected from polypropylene grafted maleic anhydride.
A second aspect of the present invention provides a composite current collector, and fig. 1 is a schematic structural diagram of the composite current collector of the present invention, and as shown in fig. 1, the current collector includes a first thinned conductive layer 101, a polymer layer 102, and a second thinned conductive layer 103, which are sequentially stacked, and the current collector is obtained by using the above preparation method, and has the advantages of compact and uniform surface structure, and small sheet resistance.
The third aspect of the invention provides a lithium ion battery, which comprises the composite current collector obtained by the preparation method provided by the invention, and the lithium ion battery provided by the invention has the advantage of small internal resistance because the sheet resistance of the current collector is small.
Compared with the prior art, the invention at least has the following beneficial effects:
1. the preparation method of the composite current collector can control the process to prepare the composite current collector with the conducting layer and the polymer layer with extremely thin thickness, and is beneficial to improving the energy density of the battery.
2. The composite current collector prepared by the preparation method has a compact and uniform surface structure, so that the current collector has lower sheet resistance.
3. The composite current collector prepared by the preparation method is applied to the lithium ion battery, so that the lithium ion battery has lower internal resistance on the basis of excellent safety performance.
4. The preparation method of the composite current collector can avoid the use of vacuum coating equipment with high price and low production efficiency, thereby reducing the production cost and facilitating the industrial application.
Drawings
Fig. 1 is a schematic structural view of the composite current collector of the present invention.
Description of reference numerals:
101: a first thinned conductive layer;
102: a polymer layer;
103: and secondly, thinning the conducting layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present invention will be further illustrated by the following specific examples and comparative examples. The reagents, materials and instruments used in the following description are all conventional reagents, conventional materials and conventional instruments which are all commercially available if no specific description is made, and the reagents can also be synthesized by conventional synthesis methods.
Example 1
1) Cleaning an aluminum foil with the thickness of 8 mu m in an acetone solvent for 5min, drying the aluminum foil by using cold air, sequentially cleaning the aluminum foil by using 0.1mol/L sodium hydroxide alkali liquor for 5min, cleaning the aluminum foil by using deionized water for 10min, passivating the cleaned aluminum foil by using 5wt% chromic anhydride/0.5 wt% boric acid passivation solution for 0.5min, cleaning the passivated aluminum foil by using deionized water for 20min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 100 ℃ for 60min to obtain the surface-treated aluminum foil.
2) Adding polypropylene grafted maleic anhydride into a feeding port of a casting machine, setting the casting temperature to be 230 ℃, controlling the die lip gap of the casting machine to be 2 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil after surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 8 mu m, and the thickness of the polymer layer is 2 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 5wt% of sulfuric acid, 1wt% of polyacrylic acid and 94wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 1.5 mu m, and the thickness of the polymer layer is both 2 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 190 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 4 mu m), and marking the composite current collector as Z1.
Example 2
1) Cleaning an aluminum foil with the thickness of 8 mu m in an acetone solvent for 5min, drying the aluminum foil by using cold air, sequentially cleaning the aluminum foil by using 0.1mol/L sodium hydroxide alkali liquor for 5min, cleaning the aluminum foil by using deionized water for 10min, passivating the cleaned aluminum foil by using 5wt% chromic anhydride/0.5 wt% boric acid passivation solution for 0.5min, cleaning the passivated aluminum foil by using deionized water for 20min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 100 ℃ for 60min to obtain the surface-treated aluminum foil.
2) Adding polyethylene terephthalate into a feeding port of a casting machine, setting the casting temperature to be 320 ℃, controlling the gap between die lips of the casting machine to be 2 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil after surface treatment to obtain a first composite layer comprising an aluminum layer-polymer layer, wherein the thickness of the aluminum layer is 8 mu m, and the thickness of the polymer layer is 2 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 5wt% of sulfuric acid, 1wt% of polyacrylic acid and 94wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 1.5 mu m, and the thickness of the polymer layer is both 2 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 280 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 4 mu m), and marking the composite current collector as Z2.
Example 3
1) Cleaning an aluminum foil with the thickness of 8 mu m in an acetone solvent for 5min, drying the aluminum foil by using cold air, sequentially cleaning the aluminum foil by using 0.1mol/L sodium hydroxide alkali liquor for 5min, cleaning the aluminum foil by using deionized water for 10min, passivating the cleaned aluminum foil by using 5wt% chromic anhydride/0.5 wt% boric acid passivation solution for 0.5min, cleaning the passivated aluminum foil by using deionized water for 20min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 100 ℃ for 60min to obtain the surface-treated aluminum foil.
2) Adding nylon 66 into a feeding port of a casting machine, setting the casting temperature to be 300 ℃, controlling the die lip gap of the casting machine to be 2 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil subjected to surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 8 mu m, and the thickness of the polymer layer is 2 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 5wt% of sulfuric acid, 1wt% of polyacrylic acid and 94wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 1.5 mu m, and the thickness of the polymer layer is both 2 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 260 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 4 mu m), and marking the composite current collector as Z3.
Example 4
1) Cleaning an aluminum foil with the thickness of 20 mu m in an acetone solvent for 5min, drying the aluminum foil by using cold air, sequentially cleaning the aluminum foil by using 0.3mol/L sodium hydroxide alkali liquor for 0.5min and deionized water for 10min, passivating the cleaned aluminum foil by using 5wt% chromic anhydride/0.5 wt% boric acid passivation solution for 0.5min, cleaning the passivated aluminum foil by using deionized water for 20min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 100 ℃ for 60min to obtain the surface-treated aluminum foil.
2) Adding polyethylene terephthalate into a feeding port of a casting machine, setting the casting temperature to be 330 ℃, controlling the gap between die lips of the casting machine to be 2 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil after surface treatment to obtain a first composite layer comprising an aluminum layer-polymer layer, wherein the thickness of the aluminum layer is 20 mu m, and the thickness of the polymer layer is 2 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 5wt% of sulfuric acid, 1wt% of polyacrylic acid and 94wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 1 mu m, and the polymer layers are both 2 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 290 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 4 mu m), and marking the composite current collector as Z4.
Example 5
1) Cleaning an aluminum foil with the thickness of 6 mu m in an acetone solvent for 0.5min, drying by using cold air, sequentially cleaning by using 0.05mol/L sodium hydroxide alkali liquor for 3min, cleaning by using deionized water for 0.5min, passivating the cleaned aluminum foil by using 0.05wt% potassium dichromate/0.1 wt% citric acid passivation solution for 5min, cleaning the passivated aluminum foil by using deionized water for 1min, drying by using cold air, and finally baking at 80 ℃ for 20min to obtain the surface-treated aluminum foil.
2) Adding polypropylene grafted maleic anhydride into a feeding port of a casting machine, setting the casting temperature to be 250 ℃, controlling the die lip gap of the casting machine to be 1 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil subjected to surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 6 mu m, and the thickness of the polymer layer is 1 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) The method comprises the steps of respectively soaking a first composite layer and a second composite layer in corrosive liquid consisting of 1wt% sulfuric acid, 0.1wt% polyacrylic acid and 98.9wt% deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and blow-drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 2 mu m, and the polymer layers are both 1 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 195 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 2 mu m), and marking the composite current collector as Z5.
Example 6
1) Firstly cleaning an aluminum foil with the thickness of 100 mu m in an ethanol solvent for 2min, drying the aluminum foil by using cold air, then sequentially cleaning the aluminum foil by using 0.1mol/L sodium hydroxide alkali liquor for 3min and deionized water for 8min, passivating the cleaned aluminum foil by using 2wt% of chromium sulfate/0.5 wt% of tartaric acid passivation solution for 5min, cleaning the passivated aluminum foil by using deionized water for 5min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 50 ℃ for 10min to obtain the surface-treated aluminum foil.
2) Adding polypropylene grafted maleic anhydride into a feeding port of a casting machine, setting the casting temperature to be 250 ℃, controlling the die lip gap of the casting machine to be 0.1 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil subjected to surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 100 mu m, and the thickness of the polymer layer is 0.05 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 15wt% of sulfuric acid, 2wt% of polyacrylic acid and 83wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 5 mu m, and the thicknesses of the polymer layers are both 0.1 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layer to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 185 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 0.2 mu m), and marking the composite current collector as Z6.
Example 7
1) Cleaning an aluminum foil with the thickness of 9 mu m in an acetone solvent for 2min, drying the aluminum foil by using cold air, sequentially cleaning the aluminum foil by using 0.2mol/L sodium hydroxide alkali liquor for 2min, cleaning the aluminum foil by using deionized water for 10min, passivating the cleaned aluminum foil by using 3wt% of chromium nitrate/1 wt% of oxalic acid passivation solution for 5min, cleaning the passivated aluminum foil by using deionized water for 5min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 70 ℃ for 20min to obtain the surface-treated aluminum foil.
2) Adding polypropylene grafted maleic anhydride into a feeding port of a casting machine, setting the casting temperature to be 250 ℃, controlling the die lip gap of the casting machine to be 10 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil after surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 9 mu m, and the thickness of the polymer layer is 10 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) The method comprises the steps of respectively soaking a first composite layer and a second composite layer in corrosive liquid consisting of 5wt% of sodium hydroxide, 2wt% of sodium acetate and 93wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and blow-drying the first composite layer and the second composite layer by using cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 0.1 mu m, and the polymer layers are both 10 mu m.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 185 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 20 mu m), and marking the composite current collector as Z7.
Example 8
1) Firstly cleaning an aluminum foil with the thickness of 10 mu m in an acetone solvent for 4min, drying the aluminum foil by using cold air, then sequentially cleaning the aluminum foil by using 0.15mol/L sodium hydroxide alkali liquor for 3min and deionized water for 10min, passivating the cleaned aluminum foil by using a 4wt% chromium acetate/2 wt% itaconic acid passivation solution for 5min, cleaning the passivated aluminum foil by using deionized water for 5min, drying the aluminum foil by using cold air, and finally baking the aluminum foil at 80 ℃ for 10min to obtain the surface-treated aluminum foil.
2) Adding polypropylene grafted maleic anhydride into a feeding port of a casting machine, setting the casting temperature to be 250 ℃, controlling the die lip gap of the casting machine to be 4 mu m, casting and compounding the molten polypropylene grafted maleic anhydride to one functional surface of the aluminum foil after surface treatment to obtain a first composite layer comprising an aluminum layer and a polymer layer, wherein the thickness of the aluminum layer is 10 mu m, and the thickness of the polymer layer is 4 mu m.
3) And repeating the step 2) to obtain a second composite layer, wherein the second composite layer is the same as the first composite layer.
4) Respectively soaking the first composite layer and the second composite layer in corrosive liquid consisting of 4wt% of sulfuric acid, 0.5wt% of polyacrylic acid and 95.5wt% of deionized water, thinning aluminum layers in the first composite layer and the second composite layer through chemical corrosion, taking out the thinned first composite layer and the thinned second composite layer, cleaning the first composite layer and the thinned second composite layer with deionized water for three times, and drying the first composite layer and the second composite layer through cold air, wherein the thicknesses of the aluminum layers in the thinned first composite layer and the thinned second composite layer are both 5 micrometers, and the polymer layers are both 4 micrometers.
5) And (3) attaching the polymer layers in the thinned first composite layer and the second composite layer together, enabling the aluminum layers to face outwards, fusing the polymers in the two polymer layers together through a thermal compound machine, setting the temperature of the thermal compound machine to be 185 ℃, obtaining a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure (the total thickness of the polymer layers is 8 mu m), and marking the composite current collector as Z8.
Comparative example 1
Selecting a polypropylene grafted maleic anhydride film with the thickness of 4 mu m, respectively evaporating and plating aluminum layers with the thickness of 1.5 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, and marking the composite current collector as Z9.
Comparative example 2
Selecting a polyethylene terephthalate film with the thickness of 4 mu m, and respectively evaporating aluminum layers with the thickness of 1.5 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, wherein the composite current collector is marked as Z10.
Comparative example 3
Selecting a nylon 66 film with the thickness of 4 microns, and respectively evaporating and plating aluminum layers with the thickness of 1.5 microns on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, wherein the composite current collector is marked as Z11.
Comparative example 4
Selecting a polyethylene terephthalate film with the thickness of 4 mu m, and respectively evaporating aluminum layers with the thickness of 1 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, wherein the composite current collector is marked as Z12.
Comparative example 5
Selecting a polypropylene grafted maleic anhydride film with the thickness of 2 mu m, respectively evaporating and coating aluminum layers with the thickness of 2 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, and marking the composite current collector as Z13.
Comparative example 6
Selecting a polypropylene grafted maleic anhydride film with the thickness of 0.2 mu m, and respectively evaporating an aluminum layer with the thickness of 5 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment.
Comparative example 7
Selecting a polypropylene grafted maleic anhydride film with the thickness of 20 microns, and respectively evaporating and plating aluminum layers with the thickness of 0.1 micron on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, wherein the composite current collector is marked as Z14.
Comparative example 8
Selecting a polypropylene grafted maleic anhydride film with the thickness of 8 mu m, respectively evaporating and plating an aluminum layer with the thickness of 5 mu m on two functional surfaces of the film by adopting continuous vacuum coating equipment to obtain a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure, and marking the composite current collector as Z15.
Comparative example 9
Since no commercial aluminum foil with the thickness less than or equal to 5 μm exists at the present stage, the most common aluminum foil with the thickness of 9 μm on the market is subjected to corrosion thinning by using the corrosion solution in the embodiment 1, and the corrosion time is controlled so that the thickness of the aluminum foil after final corrosion is 5 μm. And (3) laminating an aluminum foil with the thickness of 5 microns, a polypropylene grafted maleic anhydride film with the thickness of 4 microns and an aluminum foil with the thickness of 5 microns, preparing a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure by adopting a hot-pressing compounding mode (the temperature is set to 249 ℃, the pressure is set to 0.2MPa, and the gap of a hot-pressing die is controlled to be 14 microns), and marking the current collector as Z16.
Comparative example 10
Since no commercial aluminum foil with the thickness less than or equal to 5 μm exists at the present stage, the most common aluminum foil with the thickness of 9 μm on the market is subjected to corrosion thinning by using the corrosion solution in the embodiment 1, and the corrosion time is controlled so that the thickness of the aluminum foil after final corrosion is 0.1 μm. And (3) laminating the obtained aluminum foil with the thickness of 0.1 mu m, the polypropylene grafted maleic anhydride film with the thickness of 20 mu m and the aluminum foil with the thickness of 0.1 mu m, preparing a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure by adopting a hot-pressing compounding mode (the temperature is set to 245 ℃, the pressure is set to 0.15MPa, and the gap of a hot-pressing die is controlled to be 20.2 mu m), and marking the current collector as Z17. Because the mechanical strength of the aluminum foil with the thickness of 0.1 mu m is extremely low, the aluminum foil is cracked in the hot pressing process, and the finally obtained current collector Z17 completely does not meet the basic use requirements of the current collector and belongs to unqualified products.
Comparative example 11
As no commercial aluminum foil with the thickness less than or equal to 5 mu m exists at the present stage, the most common aluminum foil with the thickness of 9 mu m on the market is directly adopted without corrosion thinning treatment. And (3) laminating the aluminum foil with the thickness of 9 microns, the polypropylene grafted maleic anhydride film with the thickness of 4 microns and the aluminum foil with the thickness of 9 microns, preparing a composite current collector with an aluminum layer-polymer layer-aluminum layer sandwich structure by adopting a hot-pressing compounding mode (the temperature is set to 245 ℃, the pressure is set to 0.15MPa, and the gap of a hot-pressing die is controlled to be 22 microns), and marking the current collector as Z18.
Examples 9 to 16
Examples 9 to 16 are similar to examples 1 to 8, wherein example 9 is comparative example 1, example 10 is comparative example 2, example 11 is comparative example 3, example 12 is comparative example 4, example 13 is comparative example 5, example 14 is comparative example 6, example 15 is comparative example 7, and example 16 is comparative example 8, except that the aluminum foil is replaced by a copper foil, and the obtained current collectors are designated as Z19 to Z26.
Comparative examples 12 to 21
Comparative examples 12 to 21 are similar to comparative examples 1 to 11, respectively, wherein comparative example 12 is comparative example 1, comparative example 13 is comparative example 2, comparative example 14 is comparative example 3, comparative example 15 is comparative example 4, comparative example 16 is comparative example 5, comparative example 17 is comparative example 6, comparative example 18 is comparative example 7, comparative example 19 is comparative example 8, comparative example 20 is comparative example 9, comparative example 21 is comparative example 10, and comparative example 22 is comparative example 11, except that copper foil is substituted for aluminum foil, and comparative example 17 is similar to comparative example 6, and the current collectors obtained in comparative examples 12 to 16 are designated as Z27 to Z31, and the current collectors obtained in comparative examples 18 to 19 are designated as Z32 to Z33, because no polypropylene-grafted maleic anhydride film having a thickness of 0.1 μm is used as an intermediate layer. Comparative example 20 referring to comparative example 9, since there is a copper foil having a thickness of 5 μm at the present stage, a commercial copper foil of 5 μm was directly used to perform hot press lamination with a polymer film, and the resulting current collector was designated as Z34. Comparative example 21 referring to comparative example 10, since there is no commercial copper foil with a thickness of 2 μm or less at the present stage, only commercial copper foils with a thickness of 5 μm can be respectively etched to 0.1 μm, and finally, the ultra-thin copper foil after etching is broken in the hot pressing process due to low mechanical strength, the finally obtained current collector Z35 cannot meet the basic requirements of the current collector, and is a non-conforming product, and cannot be used for subsequent battery preparation. Comparative example 22 referring to comparative example 11, a 6 μm copper foil was used without performing etching thinning treatment, and the obtained current collector was designated as Z36.
Preparation of lithium ion battery
S1: 97 parts of lithium cobaltate positive electrode material (Beijing Dangshi materials science and technology Co., ltd., 4.40)V lithium cobalt oxide with specific capacity of 174 mAh/g), 1.5 parts of acetylene black conductive agent, 1.5 parts of polyvinylidene fluoride (PVDF) binder and 60 parts of N-methylpyrrolidone (NMP) are stirred for 4 hours under vacuum by a double-planet stirrer under the conditions of revolution of 30r/min and rotation of 1500r/min, the mixture is dispersed into uniform slurry, then the slurry is coated on a current collector and baked for 30 minutes at 130 ℃ to be dried, and rolled and cut under the rolling pressure of 40 tons to obtain a positive plate, wherein the surface density of the positive plate is 18mg/cm 2 The compacted density of the pole piece is 4.15g/cm 3 。
S2: 97 parts of graphite negative electrode (artificial graphite LKP-G5 of China Shanghai fir, inc., with specific capacity of 355mAh/G and primary coulombic efficiency of 92%), 1 part of acetylene black conductive agent, 1 part of sodium carboxymethylcellulose (CMC), 1 part of Styrene Butadiene Rubber (SBR) binder and 100 parts of deionized water are stirred for 4 hours under the conditions of revolution of 30r/min and autorotation of 1500r/min in vacuum by a double-planet stirrer to be dispersed into uniform slurry, then the slurry is coated on a current collector, is baked for 30 minutes at 100 ℃ to be dried, is rolled under 40 tons of rolling pressure and is cut to obtain a negative plate, wherein the surface density of the negative plate is 10mg/cm 2 The compacted density of the pole piece is 1.74g/cm 3 。
S3: the lithium ion battery is prepared by matching the positive plate with the negative plate respectively with a Polyethylene (PE) porous diaphragm (a wet diaphragm ND12 produced by Shanghai Enjie New Material science and technology Co., ltd., thickness of 12 μm), an electrolyte (an LBC445B33 type electrolyte of Shenzhen New Zealand science and technology Co., ltd.), and other necessary lithium ions Chi Fucai through a conventional preparation process of the lithium ion battery.
Test examples
1. Current collector sheet resistance test
The test method comprises the following steps: the collectors Z1-Z36 were tested for sheet resistance at 25 ℃ using a digital four-probe test, model ST2253, suzhou crystal lattice electronics, with the test results shown in table 1, with reference to ASTM F390-2011.
2. Internal resistance test of battery
The test method comprises the following steps: an internal resistance tester is adopted to apply 1KHz alternating current signals to the lithium ion batteries D1-D34, the internal resistance of the batteries is obtained by measuring the alternating current voltage drop, and the test result is shown in Table 1.
3. Energy density test
The test method comprises the following steps: charging the formed lithium ion battery to 4.25V at a constant current of 0.33C at 25 ℃ by using a battery charge-discharge tester, then charging the battery at a constant voltage until the current is reduced to 0.02C, discharging the battery to 2.5V at a constant current of 0.33C after standing for 5min, recording the first discharge capacity Qdischarge and the first discharge energy Edischarge of the battery, weighing the battery weight as W, and calculating the energy density ED = Edischarge/W.
TABLE 1
Note that the values of the sheet resistance of the current collector in table 1 refer to sheet resistances of Z1 to Z36, and not the sheet resistances of the 6 μm copper foil and the 9 μm copper foil listed in table 1.
1. As can be seen from table 1, in the case that the aluminum layer and the polymer layer have the same material and thickness, the composite current collector obtained by the preparation method of the present invention has lower sheet resistance than the composite current collector prepared by the vacuum evaporation method, and accordingly, the lithium ion battery including the composite current collector prepared by the preparation method of the present invention has lower internal resistance than the lithium ion battery including the composite current collector prepared by the vacuum evaporation method.
2. Comparing example 6 with comparative example 6, it can be seen that the preparation method of the present invention has stronger universality, and can prepare a composite current collector with a thickness of 0.2 μm of an ultrathin polymer layer, and the preparation of the composite current collector is difficult to realize by using the current coating equipment and coating technology by using a vacuum evaporation method.
3. As can be seen from comparison between example 8 and comparative example 9, the sheet resistance of the composite current collector and the lithium ion battery prepared by the preparation method of the present invention is lower and the internal resistance of the battery is lower than that of the composite current collector and the lithium ion battery prepared by a simple hot-pressing composite method.
4. Comparing example 7 with comparative example 10, it can be seen that the preparation method of the present invention can prepare a composite current collector with an ultra-thin conductive layer compared to a simple hot press composite method.
5. As can be seen from comparative examples 1 to 3, the sheet resistance and the internal resistance of the current collector of the composite current collector prepared from different polymers and the lithium ion battery including the composite current collector have no significant difference.
6. Compared with current collectors prepared by other methods, the current collector has lower sheet resistance under the conditions of the same conductive material and the same conductive layer thickness. However, for the current collector of the present invention, the kind of the conductive material and the thickness of the conductive layer are changed, and the sheet resistance of the current collector is also changed, and the specific rule is as follows: the larger the thickness of the conducting layer is, the lower the sheet resistance is, and the thickness and the sheet resistance are approximately in an inverse proportion relation. For example: comparing examples 1 and 4, the sheet resistance and the internal cell resistance of the current collector of example 1 are slightly lower than those of example 4, since the thickness of the aluminum layer after etching of example 1 is 1.5 μm, and the thickness of the aluminum layer after etching of example 4 is 1 μm.
7. If the current collector is directly prepared by using commercial metal foil thermal compounding without adopting corrosion thinning treatment, the obtained current collector has thicker metal layer and heavier current collector, which directly results in lower energy density of the battery, and the energy density of the batteries of comparative example 11 and comparative example 22 is obviously lower than that of other batteries.
In practical application, the thickness of the conductive layer can be selected according to specific battery product characteristics, and for high-power product application, lower internal resistance is required, so that a current collector with a thicker conductive layer can be prepared consciously; for high energy density product applications, lighter and thinner current collectors are needed to reduce battery weight and thickness in order to achieve higher energy density, and therefore current collectors with thinner conductive layers can be intentionally prepared.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (5)
1. A preparation method of a composite current collector is characterized by comprising the following steps: the first polymer is compounded to one functional surface of the first conducting layer in a casting mode, and a first compound layer consisting of the first polymer layer and the first conducting layer is obtained; casting and compounding a second polymer to one functional surface of the second conductive layer to obtain a second composite layer consisting of the second polymer layer and the second conductive layer; thinning a first conducting layer in the first composite layer and a second conducting layer in the second composite layer, and then performing thermal compounding treatment on the first polymer layer and the second polymer layer to obtain the composite current collector;
the thinning treatment comprises the step of corroding the second conductive layers in the first composite layer and the second composite layer by using corrosive liquid; the corrosive liquid comprises the following components in percentage by mass: 1-15% of sulfuric acid, 0.1-2% of polyacrylic acid and 83-98.9% of deionized water;
the composite current collector consists of a first thinning conducting layer, a polymer layer and a second thinning conducting layer which are stacked;
the thickness of the first thinning conducting layer is 0.1-5 mu m, and the thickness of the second thinning conducting layer is 0.1-5 mu m;
the thickness of the first polymer layer is 0.1-10 μm, and the thickness of the second polymer layer is 0.1-10 μm;
the first conducting layer is selected from one of aluminum foil and copper foil, and the second conducting layer is selected from one of aluminum foil and copper foil.
2. The method of preparing a composite current collector of claim 1, wherein the first conductive layer comprises a first functional surface and a second functional surface, the first functional surface being provided with a first polymer layer; the second functional surface comprises a first area and a second area, and a protective layer is arranged on the second area; and/or the presence of a gas in the gas,
the second conductive layer comprises a first functional surface and a second functional surface, and the first functional surface is provided with a second polymer layer; the second functional surface includes a first region and a second region, and a protective layer is disposed on the second region.
3. The method for preparing a composite current collector according to claim 1, wherein the first polymer is at least one selected from polyethylene terephthalate, polybutylene terephthalate, nylon 66, ethylene-propylene copolymer, polypropylene; and/or the presence of a gas in the gas,
the second polymer is at least one selected from polyethylene terephthalate, polybutylene terephthalate, nylon, ethylene-propylene copolymer and polypropylene.
4. A composite current collector, characterized in that it is obtained by the manufacturing process according to any one of claims 1 to 3.
5. A lithium ion battery comprising the composite current collector of claim 4.
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