Composite current collector with automatic fire extinguishing function and preparation method thereof

Abstract

The application provides a composite current collector with automatic fire extinguishing function and a preparation method thereof. The composite current collector comprises a polymer film substrate and a metal layer plated on the upper surface and the lower surface of the polymer film substrate; wherein the polymer film substrate comprises a polymer and a fire extinguishing agent, and the mass of the fire extinguishing agent is 0.3% to 20% of the mass of the polymer film substrate. The composite current collector provided by the application can be released in time in the initial stage of battery thermal runaway due to the doping of the fire extinguishing agent with a lower melting boiling point in the polymer film substrate, and does not have to be released after the polymer substrate is melted, so that the composite current collector has better active fire extinguishing effect and the safety protection capability of the current collector in the battery is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology. Specifically, this invention relates to a composite current collector with automatic fire extinguishing function and its preparation method. Background Technology

[0002] With the rapid popularization of electric vehicles and the rapid development of new energy sources in recent years, the installed capacity of lithium-ion batteries has experienced explosive growth. As technology advances, the energy density, power density, and environmental adaptability of lithium-ion batteries have significantly improved. However, the increase in energy density inevitably increases the safety hazards of lithium-ion batteries. When subjected to mechanical or thermal stress, lithium-ion batteries may experience internal short circuits, leading to thermal runaway. Furthermore, when battery inconsistencies are amplified, a single cell subjected to electrical abuse is prone to catching fire or even exploding. Therefore, improving the safety of lithium-ion batteries is currently a hot research topic.

[0003] Lithium-ion battery cells typically consist of positive and negative electrode materials, a separator, current collectors, and an electrolyte. Current research focuses on adding flame retardants to the electrolyte to suppress battery fires and explosions. However, the electrolyte directly participates in the electrochemical reactions within the battery, and flame retardants, often organic molecules, are highly susceptible to redox side reactions at the electrode potentials, affecting normal battery operation. Current collectors, as auxiliary materials that do not directly participate in electrochemical reactions, serve as excellent fire extinguishing agents. Since current collectors do not directly contribute to capacity, their weight must be minimized to maximize the overall energy density of the battery. Traditional lithium-ion battery current collectors are metal current collectors, using aluminum foil for the positive electrode and copper foil for the negative electrode. Pure metal current collectors are not only heavy but also rigid and prone to breakage, easily generating burrs that can puncture the separator and cause short circuits.

[0004] Composite current collectors are used to improve the safety of lithium-ion batteries. These collectors utilize polymer materials as a substrate, with a metal layer deposited on the surface to achieve conductivity. The lightweight nature of polymers also increases battery energy density. However, regarding safety, polymers are often flammable and produce significant smoke. Existing technologies typically address this issue by adding flame retardants to the polymer substrate. However, this method focuses on flame retardancy of the current collector and does not provide active fire suppression. Furthermore, polymer substrates usually have high melting points, meaning current technologies only release the flame retardant after the polymer substrate melts, thus achieving a flame-retardant effect. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a composite current collector with automatic fire extinguishing function and its preparation method.

[0006] One embodiment of the present invention provides a composite current collector, comprising a polymer film substrate and a metal layer deposited on the upper and lower surfaces of the polymer film substrate;

[0007] The polymer film substrate comprises a polymer and a fire extinguishing agent; and the mass of the fire extinguishing agent is 0.3% to 20% of the mass of the polymer film substrate.

[0008] The composite current collector of this invention, by doping and modifying the current collector, allows the fire extinguishing agent to be directly incorporated into the gaps in the polymer molecular structure. This enables the fire extinguishing agent to spontaneously vaporize and escape from the current collector during thermal runaway, thereby achieving the effect of active fire extinguishing.

[0009] In some embodiments of the present invention, the mass of the extinguishing agent is preferably 10% to 15% of the mass of the polymer film substrate.

[0010] In some embodiments of the present invention, the fire extinguishing agent is selected from at least one of perfluorohexanone, heptafluoropropane, and haloalkanes, preferably perfluorohexanone.

[0011] In some embodiments of the present invention, the thickness of the polymer film substrate is 4 to 20 μm; the thickness of the metal layer is 1 to 3 μm.

[0012] In some embodiments of the present invention, the polymer is selected from at least one of polyethylene terephthalate, polyurethane, polycarbonate, polyamide, polyimide, polyvinylidene fluoride, polypropylene, polymethyl methacrylate, epoxy resin, and carboxymethyl cellulose, preferably polyethylene terephthalate or polyimide.

[0013] In some embodiments of the present invention, the metal layer is made of any one of copper, aluminum, silver or gold.

[0014] In some embodiments of the present invention, the polymer film substrate is prepared by one of the following steps (1), (2), and (3):

[0015] (1) After cleaning and vacuum drying, the polymer is mixed evenly with the fire extinguishing agent and then melted at 245-275°C for 30-60 minutes to obtain a composite slurry; the composite slurry is then extruded, stretched and cooled to obtain the polymer film substrate.

[0016] (2) After cleaning and vacuum drying, the polymer is dissolved in a solvent, and then fire extinguishing agent is added and mixed evenly to obtain a composite slurry; then the polymer film substrate is prepared by casting molding process; wherein, the solvent is any one of hexafluoroisopropanol, hexafluoroacetic acid, tetrafluoroacetic acid, trifluoroacetic acid, or a mixture of phenol and tetrachloroethane.

[0017] (3) Mix the corresponding monomer molecules of the polymer in proportion and carry out the polymerization reaction to obtain the polymer; then add the fire extinguishing agent and mix evenly to obtain the composite slurry, and then use the coating process to obtain the polymer film substrate.

[0018] Another aspect of this invention provides a method for preparing the aforementioned composite current collector, comprising the following steps:

[0019] S1, Preparation of polymer thin film substrate;

[0020] S2, at 25-35℃, the upper and lower surfaces of the polymer film substrate are subjected to plasma treatment respectively;

[0021] S3. First, a metal layer is deposited on the upper and lower surfaces of the treated polymer film substrate by magnetron sputtering. Then, the thickness of the metal layer is increased by vacuum evaporation to achieve a thickness of 1-3 μm, thus obtaining the composite current collector.

[0022] In some embodiments of the present invention, in step S2, the plasma treatment time is 5 to 20 minutes.

[0023] The features and advantages described above for composite current collectors also apply to the preparation method of composite current collectors, and will not be repeated here.

[0024] In another aspect, the present invention provides an electrode comprising the aforementioned composite current collector, wherein the electrode is a positive electrode or a negative electrode.

[0025] This invention also proposes a lithium-ion battery comprising the aforementioned composite current collector.

[0026] The advantages and beneficial effects of this invention are as follows: The composite current collector of this invention, by directly doping the fire extinguishing agent into the gaps in the polymer molecular structure, does not have any additional coating material, and has the characteristics of low release threshold and fast speed; moreover, the selected fire extinguishing agent has a low melting and boiling point, and can be released in time in the early stage of battery thermal runaway, without having to wait for the polymer film substrate to melt before it can be released, thus having a better active fire extinguishing effect and significantly improving the safety protection capability of the current collector in the battery cell. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the process of releasing the extinguishing agent using a composite current collector according to an embodiment of the present invention.

[0028] Figure label:

[0029] 1-Polymer film substrate; 2-Metal layer; 3-Extinguishing agent; 3'-Extinguishing agent after being heated and vaporized. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0031] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0032] One embodiment of the present invention provides a composite current collector, comprising a polymer thin film substrate and a metal layer deposited on the upper and lower surfaces of the polymer thin film substrate;

[0033] The polymer film substrate comprises a polymer and a fire extinguishing agent; and the mass of the fire extinguishing agent is 0.3% to 20% of the mass of the polymer film substrate.

[0034] The composite current collector of this invention, by doping and modifying the current collector, allows the fire extinguishing agent to be directly incorporated into the gaps in the polymer molecular structure. This enables the fire extinguishing agent to spontaneously vaporize and escape from the current collector during thermal runaway, thereby achieving the effect of active fire extinguishing.

[0035] like Figure 1 The diagram shown illustrates the process of the composite current collector releasing the extinguishing agent according to an embodiment of the present invention. Figure 1 As can be seen, under normal circumstances, the extinguishing agent is sealed in the polymer film matrix. However, when the battery experiences thermal runaway and the temperature rises, the extinguishing agent molecules begin to vaporize, accompanied by an increase in pressure. When the continuous thermal runaway causes the temperature to rise further, the vaporization of the extinguishing agent intensifies, the internal pressure increases further, and the agent breaks through the polymer film matrix and metal layer to be released, thus achieving active fire extinguishing.

[0036] In some embodiments of the present invention, the mass of the extinguishing agent is preferably 10% to 15% of the mass of the polymer film substrate, and non-limiting examples include 10%, 12%, 15%, etc.

[0037] In some embodiments of the present invention, the fire extinguishing agent is selected from at least one of perfluorohexanone, heptafluoropropane, and haloalkanes, preferably perfluorohexanone; the selected fire extinguishing agent has a low melting and boiling point, and can be released in time at the initial stage of battery thermal runaway, without having to wait for the polymer film substrate to melt before it can be released, thus having a better active fire extinguishing effect.

[0038] Furthermore, haloalkanes are organic compounds formed by replacing one or more hydrogen atoms in a C1-C3 alkane molecule (methane, ethane, or propane) with halogen atoms; wherein the halogen is fluorine, chlorine, bromine, or iodine.

[0039] In some embodiments of the present invention, the thickness of the polymer film substrate is 4 to 20 μm, and non-limiting examples include: 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, etc.

[0040] In some embodiments of the present invention, the thickness of the metal layer is 1 to 3 μm, and non-limiting examples include 1 μm, 1.5 μm, 2 μm, 3 μm, etc. If the metal layer is too thick, it will lead to a longer preparation time and increased cost. In addition, it will also cause a decrease in the stability of the metal layer, thereby affecting the cycle durability of the composite current collector. If the metal layer is too thin, it will cause insufficient conductivity and reduced strength of the metal layer, thereby affecting the electronic conductivity and strength of the composite current collector.

[0041] In some embodiments of the present invention, the polymer is selected from at least one of polyethylene terephthalate (PET), polyurethane (PU), polycarbonate (PC), polyamide (PA), polyimide (PI), polyvinylidene fluoride (PVDF), polypropylene (PP), polymethyl methacrylate (PMMA), epoxy resin (EP), and carboxymethyl cellulose (CMC), preferably polyethylene terephthalate (PET) or polyimide (PI).

[0042] In some embodiments of the present invention, the metal layer is made of any one of copper, aluminum, silver or gold;

[0043] Furthermore, the metal layers on the upper and lower surfaces of the polymer film substrate have the same composition and thickness.

[0044] In some embodiments of the present invention, the polymer film substrate is prepared by one of the following steps (1), (2), and (3):

[0045] (1) After cleaning and vacuum drying, the polymer is mixed evenly with the fire extinguishing agent and then melted at 245-275℃ for 30-60 minutes to obtain a composite slurry; the composite slurry is then extruded, stretched and cooled to obtain a polymer film substrate.

[0046] (2) After cleaning and vacuum drying, the polymer is dissolved in a solvent and then fire extinguishing agent is added and mixed evenly to obtain a composite slurry; then a polymer film substrate is prepared by casting molding process; wherein the solvent is any one of hexafluoroisopropanol, hexafluoroacetic acid, tetrafluoroacetic acid, trifluoroacetic acid, or a mixture of phenol and tetrachloroethane.

[0047] (3) Mix the corresponding monomer molecules of the polymer in proportion and carry out the polymerization reaction to obtain the polymer; then add the fire extinguishing agent and mix evenly to obtain the composite slurry, and then use the coating process to obtain the polymer film substrate.

[0048] Another aspect of this invention provides a method for preparing the aforementioned composite current collector, comprising the following steps:

[0049] S1, Preparation of polymer thin film substrate;

[0050] S2, at 25-35℃, the upper and lower surfaces of the polymer film substrate are subjected to plasma treatment respectively;

[0051] S3. First, a metal layer is deposited on the upper and lower surfaces of the treated polymer film substrate by magnetron sputtering. Then, the thickness of the metal layer is increased by vacuum evaporation to achieve a thickness of 1-3 μm, thus obtaining the composite current collector.

[0052] The features and advantages described above for composite current collectors also apply to the preparation method of composite current collectors, and will not be repeated here.

[0053] In some embodiments of the present invention, the plasma treatment time in step S2 is 5 to 20 minutes;

[0054] Furthermore, the plasma is at least one of non-polymerizable gases such as O2, H2, N2, NH3, and Ar. Plasma treatment of the polymer film substrate before coating with the metal layer can graft hydrophilic functional groups such as -OH, -OH, and -NH3 onto the surface of the polymer film substrate, thereby solving the problem of low adhesion between the metal layer and the polymer film substrate and improving the stability and electronic conductivity of the metal layer.

[0055] In another aspect, the present invention provides an electrode comprising the aforementioned composite current collector, wherein the electrode is a positive electrode or a negative electrode.

[0056] This invention also proposes a lithium-ion battery comprising the aforementioned composite current collector.

[0057] The following are non-limiting embodiments and comparative examples of the present invention. It should be noted that the schemes of the comparative examples are not prior art, but are only set up for comparison with the schemes of the embodiments, and are not intended to limit the present invention. The experimental methods in the embodiments and comparative examples that do not specify specific conditions are conventional methods and conventional conditions well known in the art.

[0058] Example 1

[0059] A method for preparing a composite current collector includes the following steps:

[0060] (1) After cleaning and vacuum drying, 85 parts of polyethylene terephthalate (PET) were cut into small fragments and then mixed with 15 parts of perfluorohexanone. The mixture was melted at 245°C for 30 min to obtain a composite slurry. The composite slurry was then extruded, stretched, and cooled to obtain a PET film substrate with a thickness of 20 μm.

[0061] (2) At 25°C, the upper and lower surfaces of the PET film substrate were subjected to plasma treatment for 10 min respectively;

[0062] (3) First, a 500nm thick copper metal layer is deposited on the upper and lower surfaces of the treated PET film substrate by magnetron sputtering. Then, the thickness of the copper metal layer is increased by vacuum evaporation so that the thickness of the copper metal layer reaches 2μm, thus obtaining the composite current collector.

[0063] Following the conventional lithium-ion battery anode preparation process, 97 parts of graphite anode material, 1 part of acetylene black conductive agent, 1 part of sodium carboxymethyl cellulose (CMC), and 1 part of styrene-butadiene rubber (SBR) binder are mixed evenly to form a slurry, which is then coated onto the above-mentioned composite current collector. After drying, it is slit into anode sheet A.

[0064] Example 2

[0065] A method for preparing a composite current collector includes the following steps:

[0066] (1) After cleaning and vacuum drying, 85 parts of polyethylene terephthalate (PET) were cut into small fragments and then mixed with 15 parts of perfluorohexanone. The mixture was melted at 245°C for 30 min to obtain a composite slurry. The composite slurry was then extruded, stretched, and cooled to obtain a PET film substrate with a thickness of 20 μm.

[0067] (2) At 25°C, the upper and lower surfaces of the PET film substrate were subjected to plasma treatment for 10 min respectively;

[0068] (3) First, a 500nm thick aluminum metal layer is deposited on the upper and lower surfaces of the treated PET film substrate by magnetron sputtering. Then, the thickness of the aluminum metal layer is increased by vacuum evaporation so that the thickness of the aluminum metal layer reaches 2μm, thus obtaining the composite current collector.

[0069] Following the conventional lithium-ion battery cathode preparation process, 97 parts of lithium iron phosphate cathode material, 1.5 parts of acetylene black conductive agent, and 1.5 parts of PVDF binder are mixed evenly to form a slurry, which is then coated onto the above-mentioned composite current collector. After drying, it is slit into cathode sheet B.

[0070] Example 3

[0071] A method for preparing a composite current collector includes the following steps:

[0072] (1) Using N,N-dimethylacetamide as a solvent, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4'-diaminodiphenyl ether (ODA) were added to the solvent at a molar ratio of 1:1 and stirred until homogeneous. Then, pyromellitic dianhydride was added, and the mixture was heated to 180°C for 2 hours to obtain polyamic acid. Acetic anhydride dehydrating agent and ethylenediamine catalyst were added, along with 15 wt% perfluorohexanone. The mixture was stirred until homogeneous and chemically dehydrated and cyclized at 35°C to obtain a composite slurry of polyimide (PI) and perfluorohexanone fire extinguishing agent. The composite slurry was then coated onto a glass plate, scraped to a thickness of 20 μm, and allowed to air dry naturally to obtain a PI film substrate.

[0073] (2) At 25°C, the upper and lower surfaces of the PI film substrate were subjected to plasma treatment for 10 min respectively;

[0074] (3) First, a 500 nm thick copper metal layer is deposited on the upper and lower surfaces of the treated PI thin film substrate by magnetron sputtering. Then, the thickness of the copper metal layer is increased by vacuum evaporation so that the thickness of the copper metal layer reaches 2 μm, thus obtaining the composite current collector.

[0075] Following the conventional lithium-ion battery anode preparation process, 97 parts of graphite anode material, 1 part of acetylene black conductive agent, 1 part of sodium carboxymethyl cellulose (CMC), and 1 part of styrene-butadiene rubber (SBR) binder were mixed evenly to form a slurry, which was then coated onto the above composite current collector. After drying, the slurry was cut into anode sheets C.

[0076] Example 4

[0077] A method for preparing a composite current collector includes the following steps:

[0078] (1) Using N,N-dimethylacetamide as a solvent, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4'-diaminodiphenyl ether (ODA) were added to the solvent at a molar ratio of 1:1 and stirred until homogeneous. Then, pyromellitic dianhydride was added, and the mixture was heated to 180°C for 2 hours to obtain polyamic acid. Acetic anhydride dehydrating agent and ethylenediamine catalyst were added, along with 15 wt% perfluorohexanone. The mixture was stirred until homogeneous and chemically dehydrated and cyclized at 35°C to obtain a composite slurry of polyimide (PI) and perfluorohexanone fire extinguishing agent. The composite slurry was then coated onto a glass plate, scraped to a thickness of 20 μm, and allowed to air dry naturally to obtain a PI film substrate.

[0079] (2) At 25°C, the upper and lower surfaces of the PI film substrate were subjected to plasma treatment for 10 min respectively;

[0080] (3) First, a 500 nm thick aluminum metal layer is deposited on the upper and lower surfaces of the treated PI thin film substrate by magnetron sputtering. Then, the thickness of the aluminum metal layer is increased by vacuum evaporation so that the thickness of the aluminum metal layer reaches 2 μm, thus obtaining the composite current collector.

[0081] Following the conventional lithium-ion battery cathode preparation process, 97 parts of lithium iron phosphate cathode material, 1.5 parts of acetylene black conductive agent, and 1.5 parts of PVDF binder are mixed evenly to form a slurry, which is then coated onto the above-mentioned composite current collector. After drying, it is slit into cathode sheet D.

[0082] Comparative Example 1

[0083] A method for preparing a current collector includes the following steps:

[0084] (1) After cleaning and vacuum drying, polyethylene terephthalate (PET) is cut into small fragments and then melted at 245°C for 30 min to obtain a slurry; the slurry is then extruded, stretched, and cooled to obtain a PET film substrate with a thickness of 20 μm;

[0085] (2) At 25°C, the upper and lower surfaces of the PET film substrate were subjected to plasma treatment for 10 min respectively;

[0086] (3) First, a 500nm thick copper metal layer is deposited on the upper and lower surfaces of the treated PET film substrate by magnetron sputtering. Then, the thickness of the copper metal layer is increased by vacuum evaporation so that the thickness of the copper metal layer reaches 2μm, thus obtaining the current collector.

[0087] Following the conventional lithium-ion battery anode preparation process, 97 parts of graphite anode material, 1 part of acetylene black conductive agent, 1 part of sodium carboxymethyl cellulose (CMC), and 1 part of styrene-butadiene rubber (SBR) binder are mixed evenly to form a slurry, which is then coated onto the aforementioned current collector. After drying, the slurry is cut into anode sheets A'.

[0088] Comparative Example 2

[0089] A method for preparing a current collector includes the following steps:

[0090] (1) After cleaning and vacuum drying, polyethylene terephthalate (PET) is cut into small fragments and then melted at 245°C for 30 min to obtain a slurry; the slurry is then extruded, stretched, and cooled to obtain a PET film substrate with a thickness of 20 μm;

[0091] (2) At 25°C, the upper and lower surfaces of the PET film substrate were subjected to plasma treatment for 10 min respectively;

[0092] (3) First, a 500nm thick aluminum metal layer is deposited on the upper and lower surfaces of the treated PET film substrate by magnetron sputtering. Then, the thickness of the aluminum metal layer is increased by vacuum evaporation so that the thickness of the aluminum metal layer reaches 2μm, thus obtaining the current collector.

[0093] Following the conventional lithium-ion battery cathode preparation process, 97 parts of lithium iron phosphate cathode material, 1.5 parts of acetylene black conductive agent, and 1.5 parts of PVDF binder are mixed evenly to form a slurry, which is then coated onto the aforementioned current collector. After drying, the slurry is cut into cathode sheets B'.

[0094] Comparative Example 3

[0095] A method for preparing a current collector includes the following steps:

[0096] (1) Using N,N-dimethylacetamide as a solvent, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4'-diaminodiphenyl ether (ODA) were added to the solvent at a molar ratio of 1:1 and stirred until homogeneous. Then, pyromellitic dianhydride was added and heated to 180°C for 2 hours to obtain polyamic acid. Acetic anhydride dehydrating agent and ethylenediamine catalyst were added and stirred until homogeneous. Chemical dehydration and cyclization were carried out at 35°C to obtain polyimide (PI) slurry. The slurry was then coated onto a glass plate and scraped to a thickness of 20 μm with a doctor blade. After air drying, PI film substrate was obtained.

[0097] (2) At 25°C, the upper and lower surfaces of the PI film substrate were subjected to plasma treatment for 10 min respectively;

[0098] (3) First, a 500 nm thick copper metal layer is deposited on the upper and lower surfaces of the treated PI thin film substrate by magnetron sputtering. Then, the thickness of the copper metal layer is increased by vacuum evaporation so that the thickness of the copper metal layer reaches 2 μm, thus obtaining the current collector.

[0099] Following the conventional lithium-ion battery anode preparation process, 97 parts of graphite anode material, 1 part of acetylene black conductive agent, 1 part of sodium carboxymethyl cellulose (CMC), and 1 part of styrene-butadiene rubber (SBR) binder are mixed evenly to form a slurry, which is then coated onto the aforementioned current collector. After drying, the slurry is cut into anode sheets C'.

[0100] Comparative Example 4

[0101] A method for preparing a current collector includes the following steps:

[0102] (1) Using N,N-dimethylacetamide as a solvent, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4'-diaminodiphenyl ether (ODA) were added to the solvent at a molar ratio of 1:1 and stirred until homogeneous. Then, pyromellitic dianhydride was added and heated to 180°C for 2 hours to obtain polyamic acid. Acetic anhydride dehydrating agent and ethylenediamine catalyst were added and stirred until homogeneous. Chemical dehydration and cyclization were carried out at 35°C to obtain polyimide (PI) slurry. The slurry was then coated onto a glass plate and scraped to a thickness of 20 μm with a doctor blade. After air drying, PI film substrate was obtained.

[0103] (2) At 25°C, the upper and lower surfaces of the PI film substrate were subjected to plasma treatment for 10 min respectively;

[0104] (3) First, a 500nm thick aluminum metal layer is deposited on the upper and lower surfaces of the treated PI thin film substrate by magnetron sputtering. Then, the thickness of the aluminum metal layer is increased by vacuum evaporation so that the thickness of the aluminum metal layer reaches 2μm, thus obtaining the current collector.

[0105] Following the conventional lithium-ion battery cathode preparation process, 97 parts of lithium iron phosphate cathode material, 1.5 parts of acetylene black conductive agent, and 1.5 parts of PVDF binder are mixed evenly to form a slurry, which is then coated onto the aforementioned current collector. After drying, the slurry is cut into cathode sheets D'.

[0106] The electrodes obtained in Examples 1-4 and Comparative Examples 1-4 were subjected to ignition and fire extinguishing tests. The test results are shown in Table 1.

[0107] Table 1. Performance test results of the electrodes in Examples 1-4 and Comparative Examples 1-4

[0108] Example 1 Negative electrode plate A It smokes but doesn't catch fire. Fire extinguished successfully 77～98℃ Example 2 Positive electrode plate B It smokes but doesn't catch fire. Fire extinguished successfully 74～84℃ Example 3 Negative electrode plate C No smoke, no fire Fire extinguished successfully 93～108℃ Example 4 Positive electrode plate D No smoke, no fire Fire extinguished successfully 89～103℃ Comparative Example 1 Negative electrode plate A' fire Unable to extinguish the fire / Comparative Example 2 Positive electrode plate B' fire Unable to extinguish the fire / Comparative Example 3 Negative electrode plate C' fire Unable to extinguish the fire / Comparative Example 4 Positive electrode plate D' fire Unable to extinguish the fire /

[0109] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0110] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A composite current collector, characterized in that, The invention includes a polymer film substrate and a metal layer deposited on the upper and lower surfaces of the polymer film substrate; wherein the polymer film substrate comprises a polymer and a fire extinguishing agent, and the mass of the fire extinguishing agent is 0.3% to 20% of the mass of the polymer film substrate, and the fire extinguishing agent is perfluorohexanone; the thickness of the polymer film substrate is 4 to 20 μm; and the thickness of the metal layer is 1 to 3 μm. The composite current collector is prepared by a method comprising the following steps: S1, Preparation of polymer thin film substrate; S2, at 25-35℃, the upper and lower surfaces of the polymer film substrate are subjected to plasma treatment respectively; S3. First, a metal layer is deposited on the upper and lower surfaces of the treated polymer film substrate by magnetron sputtering. Then, the thickness of the metal layer is increased by vacuum evaporation to achieve a thickness of 1-3 μm, thus obtaining the composite current collector.

2. The composite current collector according to claim 1, characterized in that, The mass of the extinguishing agent is 10% to 15% of the mass of the polymer film substrate.

3. The composite current collector according to claim 1, characterized in that, The polymer is selected from at least one of polyethylene terephthalate, polyurethane, polycarbonate, polyamide, polyimide, polyvinylidene fluoride, polypropylene, polymethyl methacrylate, epoxy resin, and carboxymethyl cellulose.

4. The composite current collector according to claim 1, characterized in that, The metal layer is made of any one of copper, aluminum, silver or gold.

5. The composite current collector according to claim 1, characterized in that, The polymer film substrate is prepared by one of the following steps (1) or (2): (1) After cleaning and vacuum drying, the polymer is dissolved in a solvent, and then fire extinguishing agent is added and mixed evenly to obtain a composite slurry; then the polymer film substrate is prepared by casting molding process; wherein, the solvent is any one of hexafluoroisopropanol, hexafluoroacetic acid, tetrafluoroacetic acid, trifluoroacetic acid, or a mixture of phenol and tetrachloroethane; (2) Mix the corresponding monomer molecules of the polymer in proportion and carry out the polymerization reaction to obtain the polymer; then add the fire extinguishing agent and mix evenly to obtain the composite slurry, and then use the coating process to obtain the polymer film substrate.

6. The composite current collector according to claim 1, characterized in that, In step S2, the plasma treatment time is 5 to 20 minutes.

7. An electrode comprising the composite current collector according to any one of claims 1-6.

8. A lithium-ion battery comprising the composite current collector according to any one of claims 1-6.

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