High-safety current collector, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and particularly relates to a high-safety current collector as well as a preparation method and application thereof.The high-safety current collector comprises a current collector layer and a heat-conducting and flame-retardant polymer layer arranged on the current collector layer, and the heat-conducting and flame-retardant polymer layer is provided with a hollow structure, so as to achieve the purpose of differentiating and isolating the current collector layer.The high-safety current collector can effectively separate the active material slurry, thereby effectively differentiating the electrode sheet, controlling the local overheating or short-circuit risk of the electrode sheet in the working process within a certain range, and avoiding the diffusion of single-point overheating and short circuit to the entire electrode sheet.The heat-conducting and flame-retardant polymer layer of the high-safety current collector also has the functions of flame retardation and heat dissipation, further preventing the thermal runaway of the battery, and improving the safety of the battery.In addition, the preparation method has the advantages of simple operation, low cost and the like, is suitable for large-scale production and application, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a high-safety current collector, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used as power supply devices in mobile phones, computers, electric vehicles, and other fields. With continuous technological development, the market is placing higher demands on the energy density and safety performance of lithium-ion batteries.

[0003] Current collectors are an important component of lithium-ion battery electrodes. On one hand, they carry the positive and negative electrode active materials, ensuring the integrity and stability of the battery structure. On the other hand, they collect electrons generated by the electrochemical reaction and conduct them to the external circuit, thus achieving conductivity. In conventional lithium-ion battery manufacturing processes, the active material slurry is directly coated onto the smooth surface of the current collector, and after drying, an adhesive is used to fix the active material to the surface of the current collector.

[0004] However, the above technologies often have the following defects or shortcomings: 1. Due to the uneven distribution of active material thickness on the current collector, one or more hot spots may be generated during battery operation. The electrode itself has limited heat dissipation capacity, resulting in excessively high battery temperature and affecting performance; 2. At one or more hot spots or due to the battery itself, short circuits are prone to occur during cycling. In severe cases, fire may occur. Single-point short circuits and combustion are propagating and may spread to affect the entire electrode, greatly affecting battery cycle life and safety performance. Summary of the Invention

[0005] To address the problems existing in the prior art, one of the objectives of this invention is to provide a high-safety current collector, comprising a current collector layer and a thermally conductive and flame-retardant polymer layer. Compared to ordinary current collectors, the composite current collector of this invention, covered with a thermally conductive and flame-retardant polymer layer, not only serves to address the issues of differential electrode plates, flame retardancy, and prevention of the spread of short circuits caused by single-point overheating during battery operation, but also, due to the excellent thermal conductivity of the polymer layer itself, accelerates battery heat dissipation, reduces the impact of temperature on battery performance, and further improves battery safety.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A high-safety current collector includes a current collector layer and a thermally conductive and flame-retardant polymer layer disposed on the current collector layer. The thermally conductive and flame-retardant polymer layer has perforations, which serves to micro-divide the current collector layer. The thermally conductive and flame-retardant polymer layer is prepared from a thermally conductive and flame-retardant polymer including a high-melting-point polymer. By adopting the above technical solution, using a thermally conductive and flame-retardant polymer layer with perforations, the current collector layer can be micro-divided into several small block structures, thereby effectively improving battery safety performance after the current collector layer comes into contact with other substances such as active materials.

[0008] Preferably, the thermally conductive and flame-retardant polymer layer is disposed on all surfaces of the current collector layer, including the upper and lower surfaces.

[0009] Preferably, the thermally conductive and flame-retardant polymer layer is disposed on the current collector layer in a preset shape. The thermally conductive and flame-retardant polymer layer consists of protrusions on the upper and lower surfaces of the current collector, forming the preset shape. The preset shape can be customized and includes various common shapes, such as cartoon shapes, array shapes, text shapes, and creative shapes. More preferably, on any surface of the current collector layer, the total area of ​​the thermally conductive and flame-retardant polymer layer does not exceed 10% of the total area of ​​the corresponding surface of the current collector layer. Even more preferably, the laying method and area of ​​the thermally conductive and flame-retardant polymer layer on the upper and lower surfaces are matched.

[0010] Preferably, the thermally conductive and flame-retardant polymer layer is uniformly distributed in an array shape on the surface of the current collector layer. The array shape includes common array patterns with a certain spacing, such as striped array, grid array, and concentric ring array. The spacing corresponds to the hollow structure part set in the thermally conductive and flame-retardant polymer layer. The smaller the spacing of the array pattern, the higher the degree of micro-differentiation of this high-safety current collector and the higher the safety.

[0011] Preferably, the high-melting-point polymer is a polymer with a melting point of not less than 300°C, more preferably at least one of polyphthalamide (PPA), polyimide (PI), poly(m-phenylene isophthalamide) (PMIA), polybenzimidazole (PBI), and polytetrafluoroethylene (PTFE). More preferably, the high-melting-point polymer has a particle size range of 10-30 μm. This particle size allows for easier and more uniform mixing of the high-melting-point polymer with other substances, further improving the uniformity of the thermally conductive and flame-retardant polymer layer, but is not limited to this particle size range.

[0012] Preferably, the thermally conductive and flame-retardant polymer also includes flame-retardant inorganic materials. By adding flame-retardant inorganic materials as fillers for the thermally conductive and flame-retardant polymer, the flame-retardant properties of the thermally conductive and flame-retardant polymer layer can be further enhanced.

[0013] More preferably, the flame-retardant inorganic material is at least one of silicon dioxide (SiO2), antimony trioxide (Sb2O3), aluminum hydroxide (Al(OH)3), and magnesium hydroxide (Mg(OH)2), and more preferably, the particle size range of the flame-retardant inorganic material is 10nm to 100nm.

[0014] Preferably, the thermally conductive and flame-retardant polymer further includes a solvent; the solvent is any one or more combinations of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and acetonitrile.

[0015] More preferably, the high-melting-point polymer accounts for 80%-95% of the total mass of the high-melting-point polymer and the flame-retardant inorganic material; and the solvent accounts for 60-75% of the total mass of the mixture of the high-melting-point polymer, the flame-retardant inorganic material and the solvent.

[0016] Preferably, the thickness of the thermally conductive and flame-retardant polymer layer is 100-200 μm; more preferably, the thickness of the thermally conductive and flame-retardant polymer layer is not less than the thickness of the active material layer coated during the subsequent electrode fabrication; "not less than" means that the thickness of the thermally conductive and flame-retardant polymer layer is preferably equal to that of the active material layer during coating, or it can be slightly larger than that of the active material layer during coating. Regardless of whether the two thicknesses are equal or the polymer layer thickness is slightly larger, the active material layer only fills the gaps in the thermally conductive and flame-retardant polymer layer.

[0017] Preferably, the current collector of the current collector layer is at least one of conventional conductive current collectors such as aluminum foil, copper foil, titanium foil, and nickel foil.

[0018] Preferably, the high-safety current collector is prepared by the following method:

[0019] S1: Preparation of thermally conductive and flame-retardant polymer slurry: Add high-melting-point polymer and flame-retardant inorganic material to solvent, stir to mix and dissolve them fully to form thermally conductive and flame-retardant polymer slurry;

[0020] S2: The thermally conductive and flame-retardant polymer slurry prepared in step S1 is coated onto the current collector layer in a preset shape, and after curing, a thermally conductive and flame-retardant polymer layer is formed, thus obtaining the high-safety current collector with the thermally conductive and flame-retardant polymer layer.

[0021] More preferably, in step S2, the total area of ​​the thermally conductive and flame-retardant polymer layer does not exceed 10% of the total area of ​​the current collector layer, the curing temperature range is preferably 60-300℃, and curing is carried out until all solvent is removed. The general curing time is to continue curing at the curing temperature for a certain period of time after the slurry is laid and there is no flow at the curing temperature, preferably 8-14h, until the solvent is removed.

[0022] Another object of the present invention is to provide a method for preparing any of the above-mentioned high-safety current collectors, comprising the following steps:

[0023] S1: Preparation of thermally conductive and flame-retardant polymer slurry: High-melting-point polymer and flame-retardant inorganic material are added to a solvent and mixed to form a thermally conductive and flame-retardant polymer slurry;

[0024] S2: The thermally conductive and flame-retardant polymer slurry prepared in step S1 is coated onto the current collector layer, and after curing, a high-safety current collector with a thermally conductive and flame-retardant polymer layer is obtained.

[0025] Preferably, in step S1, the high-melting-point polymer and the flame-retardant inorganic material can be added to the solvent separately and then mixed and dispersed. Alternatively, the high-melting-point polymer and the flame-retardant inorganic material can be mixed first and then the mixture can be added to the solvent for further mixing and dispersion. Mixing the two first, for example by ball milling, can further ensure the uniformity of the subsequent slurry.

[0026] Preferably, the mixing in step S1 can be assisted by stirring, ultrasonication, or other steps to achieve sufficient mixing and dispersion, forming a fully mixed and dispersed slurry. More preferably, the stirring rate is 150-500 rpm and the time is 2-20 h, but the stirring rate and time are not limited, as long as the corresponding substances are fully mixed and dispersed in the solvent.

[0027] Preferably, in step S2, the total area of ​​the thermally conductive and flame-retardant polymer layer does not exceed 10% of the total area of ​​the current collector layer.

[0028] Preferably, the curing temperature range in step S2 is 60-300℃, and curing continues until all solvent is removed. The general curing time is to continue curing at the curing temperature for a certain period of time after the slurry is laid and no longer flows at the curing temperature, preferably 8-14 hours, until the solvent is removed.

[0029] Another object of this invention is to provide an application of any of the above-mentioned high-safety current collectors or the high-safety current collectors prepared by any of the preparation methods in the field of lithium-ion battery electrodes. By using the high-safety current collectors described in this invention to prepare lithium-ion battery electrodes, the safety of lithium-ion batteries can be effectively improved.

[0030] Preferably, when preparing lithium-ion battery electrodes, the thickness of the thermally conductive and flame-retardant polymer layer is not less than the thickness of the active material layer coated when making lithium-ion battery electrodes.

[0031] In this invention, a perforated thermally conductive and flame-retardant polymer layer is formed on the surface of the current collector. This allows the high-safety current collector to effectively separate the active material slurry, thereby effectively micro-dispersing the electrode sheet. This controls the risk of localized overheating or short circuits during operation within a certain range, preventing single-point overheating and short circuits from spreading to the entire electrode sheet. The thermally conductive and flame-retardant polymer layer of this high-safety current collector also has flame-retardant and heat-dissipating properties, further preventing battery thermal runaway and effectively improving battery safety. Furthermore, the preparation method provided by this invention has advantages such as simple operation and low cost, making it suitable for large-scale production and application, and possessing broad application and market prospects.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] (1) In this invention, by providing a thermally conductive and flame-retardant polymer layer on the current collector, the risk of battery overheating and combustion is greatly reduced, thereby improving the safety performance of the battery.

[0034] (2) In this invention, because the polymer layer is provided with hollows, for example, it is solidified and generated according to a specific shape, which can effectively micronize the electrode sheet, control the single-point short circuit of the electrode to the minimum range, and further improve the battery safety performance.

[0035] (3) The preparation process of this invention is simple, low cost, highly reliable, and widely applicable, and is applicable to the field of battery positive and negative electrode sheet manufacturing. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the high-safety current collector structure of Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the cross-sectional structure of the high-safety current collector in Embodiment 1 of the present invention;

[0038] Figure 3 This is a schematic diagram of the high-safety current collector structure of Embodiment 2 of the present invention;

[0039] Figure 4 This is a schematic diagram of the high-safety current collector structure in Embodiment 3 of the present invention;

[0040] In the diagram: 1. Current collector layer; 2. Thermally conductive and flame-retardant polymer layer. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings, but the scope of protection of the present invention is not limited thereto. In the present invention, the electrode sheet and the flame-retardant inorganic material are common knowledge in the art and can be obtained by those skilled in the art through self-production or purchase according to actual needs, and are not limited to the materials used in the present invention.

[0042] This invention provides a high-safety current collector, comprising a current collector layer and a thermally conductive and flame-retardant polymer layer disposed on the current collector layer. The thermally conductive and flame-retardant polymer layer has perforations, which micro-divide the current collector layer into several small block structures. When in contact with subsequent active materials or other substances, the substances come into contact with the current collector through the perforations. The thermally conductive and flame-retardant polymer layer is prepared from a thermally conductive and flame-retardant polymer including a high-melting-point polymer. By micro-dividing the current collector layer into several small block structures, the battery safety performance can be effectively improved.

[0043] In one embodiment of the present invention, the thermally conductive and flame-retardant polymer layer is disposed on the upper and lower surfaces of the current collector layer.

[0044] In one embodiment of the present invention, the thermally conductive and flame-retardant polymer layer is disposed on the current collector layer in a preset shape. The thermally conductive and flame-retardant polymer layer consists of protrusions on the upper and lower surfaces of the current collector, forming the preset shape. The preset shape can be customized and includes various common shapes, such as cartoon shapes, array shapes, text shapes, creative shapes, etc. More preferably, on any surface of the current collector layer, the total area of ​​the thermally conductive and flame-retardant polymer layer is no more than 10% of the total area of ​​the corresponding surface of the current collector layer. Even more preferably, the laying method and area of ​​the thermally conductive and flame-retardant polymer layer on the upper and lower surfaces are consistent.

[0045] In one embodiment of the present invention, the thermally conductive and flame-retardant polymer layer is uniformly distributed in an array shape on the surface of the current collector layer. The array shape includes common array patterns with a certain spacing, such as striped array, grid array, and concentric ring array. The spacing corresponds to the hollow structure part set in the thermally conductive and flame-retardant polymer layer. The smaller the spacing of the array pattern, the higher the degree of micro-differentiation of this high-safety current collector and the higher the safety.

[0046] In one embodiment of the present invention, the high-melting-point polymer is a polymer with a melting point of not less than 300°C, more preferably at least one selected from polyphthalamide (PPA), polyimide (PI), poly(m-phenylene isophthalamide) (PMIA), polybenzimidazole (PBI), and polytetrafluoroethylene (PTFE). More preferably, the particle size range of the high-melting-point polymer is 10-30 μm. This particle size allows for easier and more uniform mixing of the high-melting-point polymer with other substances, further improving the uniformity of the thermally conductive and flame-retardant polymer layer, but is not limited to this particle size range.

[0047] In one embodiment of the present invention, the thermally conductive and flame-retardant polymer further includes a flame-retardant inorganic material. By adding the flame-retardant inorganic material as a filler for the thermally conductive and flame-retardant polymer, the flame-retardant performance of the thermally conductive and flame-retardant polymer layer can be further enhanced. More preferably, the flame-retardant inorganic material is at least one of silicon dioxide (SiO2), antimony trioxide (Sb2O3), aluminum hydroxide (Al(OH)3), and magnesium hydroxide (Mg(OH)2), and more preferably, the particle size range of the flame-retardant inorganic material is 10 nm to 100 nm.

[0048] In one embodiment of the present invention, the thermally conductive and flame-retardant polymer further includes a solvent; the solvent is any one or more combinations of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and acetonitrile. The presence of the solvent allows the thermally conductive and flame-retardant polymer to form a slurry, which is then coated onto the current collector layer to form a thermally conductive and flame-retardant polymer layer. Furthermore, the slurry form allows for more thorough mixing of solid materials and further improves the uniformity of the thermally conductive and flame-retardant polymer layer.

[0049] In one embodiment of the present invention, the high-melting-point polymer accounts for 80%-95% of the total mass of the high-melting-point polymer and the flame-retardant inorganic material. At this proportion, the flame-retardant performance can be guaranteed and the flame-retardant performance can be further improved in a coordinated manner. The solvent accounts for 60%-75% of the total mass of the mixture of the high-melting-point polymer, the flame-retardant inorganic material and the solvent. At this proportion, the solid substances in the slurry can be more easily and fully mixed and dispersed, and a thermally conductive flame-retardant polymer layer can be formed in a shorter time during subsequent coating without affecting properties such as uniformity.

[0050] In one embodiment of the present invention, the thickness of the thermally conductive and flame-retardant polymer layer is 100-200 μm; more preferably, the thickness of the thermally conductive and flame-retardant polymer layer is not less than the thickness of the active material layer coated during subsequent electrode fabrication; "not less than" means that the thickness of the thermally conductive and flame-retardant polymer layer is preferably equal to that of the active material layer during coating, or it can be slightly larger than that of the active material layer during coating. Regardless of whether the two thicknesses are equal or the polymer layer thickness is slightly larger, the active material layer only fills the gaps in the thermally conductive and flame-retardant polymer layer.

[0051] In one embodiment of the present invention, the current collector of the current collector layer is at least one of conventional conductive current collectors such as aluminum foil, copper foil, titanium foil, and nickel foil.

[0052] In one embodiment of the present invention, the high-safety current collector is prepared by the following method:

[0053] S1: Preparation of thermally conductive and flame-retardant polymer slurry: Add high-melting-point polymer and flame-retardant inorganic material to solvent, stir to mix and dissolve them fully to form thermally conductive and flame-retardant polymer slurry;

[0054] S2: The thermally conductive and flame-retardant polymer slurry prepared in step S1 is coated onto the current collector layer in a preset shape, and after curing, a thermally conductive and flame-retardant polymer layer is formed, thus obtaining the high-safety current collector with the thermally conductive and flame-retardant polymer layer.

[0055] More preferably, in step S2, the total area of ​​the thermally conductive and flame-retardant polymer layer does not exceed 10% of the total area of ​​the current collector layer, the curing temperature range is preferably 60-300℃, and curing is carried out until all solvent is removed. The general curing time is to continue curing at the curing temperature for a certain period of time after the slurry is laid and there is no flow at the curing temperature, preferably 8-14h, until the solvent is removed.

[0056] Another object of the present invention is to provide a method for preparing any of the above-mentioned high-safety current collectors, comprising the following steps:

[0057] S1: Preparation of thermally conductive and flame-retardant polymer slurry: High-melting-point polymer and flame-retardant inorganic material are added to a solvent and mixed to form a thermally conductive and flame-retardant polymer slurry;

[0058] S2: The thermally conductive and flame-retardant polymer slurry prepared in step S1 is coated onto the current collector layer, and after curing, a high-safety current collector with a thermally conductive and flame-retardant polymer layer is obtained.

[0059] In one embodiment of the present invention, in step S1, the high-melting-point polymer and the flame-retardant inorganic material can be added to the solvent separately and then mixed and dispersed. Alternatively, the high-melting-point polymer and the flame-retardant inorganic material can be mixed first and then the mixture can be added to the solvent for further mixing and dispersion. Mixing the two first, for example by ball milling, can further ensure the uniformity of the subsequent slurry.

[0060] In one embodiment of the present invention, the mixing in step S1 can be assisted by stirring, ultrasonication and other steps to achieve sufficient mixing and dispersion, forming a fully mixed and dispersed slurry. More preferably, the stirring rate is 150-500 r / min and the time is 2-20 h, but the stirring rate and time are not limited, as long as the corresponding substances are fully mixed and dispersed in the solvent.

[0061] In one embodiment of the present invention, the total area of ​​the thermally conductive and flame-retardant polymer layer laid in step S2 does not exceed 10% of the total area of ​​the current collector layer.

[0062] In one embodiment of the present invention, the curing temperature range in step S2 is 60-300°C, and curing is carried out until all solvent is removed. The general curing time is to continue curing at the curing temperature for a certain period of time after the slurry is laid and no longer flows at the curing temperature, preferably 8-14 hours, until the solvent is removed.

[0063] Another object of this invention is to provide an application of any of the above-mentioned high-safety current collectors or the high-safety current collectors prepared by any of the preparation methods in the field of lithium-ion battery electrodes. By using the high-safety current collectors described in this invention to prepare lithium-ion battery electrodes, the safety of lithium-ion batteries can be effectively improved.

[0064] In one embodiment of the present invention, when preparing a lithium-ion battery electrode, the thickness of the thermally conductive and flame-retardant polymer layer is not less than the thickness of the active material layer coated when preparing the lithium-ion battery electrode.

[0065] The technical solutions and effects of the present invention will be further illustrated in detail below through specific embodiments. However, it should be noted that the following embodiments do not constitute a limitation on the technical solutions of the present invention.

[0066] Example 1:

[0067] Add 2.70g of polyimide (PI) (particle size 18-25μm) and 0.30g of antimony trioxide (Sb2O3) powder (particle size 20-30nm) to 4.50g of N-methylpyrrolidone (NMP). Stir the mixture mechanically at 500r / min for 6h. Ultrasonic mixing can be used to further mix and disperse the slurry, forming a thermally conductive and flame-retardant polymer slurry. A homogenizer can be used to remove bubbles.

[0068] The thermally conductive and flame-retardant polymer slurry prepared above is coated in a striped array pattern onto the upper and lower surfaces of the current collector layer. In this embodiment, the current collector is aluminum foil or copper foil. The current collector layer is 30 cm long and 20 cm wide. The stripe width is controlled to be 0.5 mm, the length to be 20 cm, and the stripe gap to be 5 mm. At this point, the total area of ​​the thermally conductive and flame-retardant polymer layer is approximately 9.00% of the total area of ​​the current collector. After coating, it is cured at 120°C for about 10 hours to form a thermally conductive and flame-retardant polymer layer with a thickness of about 150 μm, thus obtaining a composite high-safety micro-current collector. (Appendix) Figure 1 This is a schematic diagram of the high-security current collector striped array structure in this embodiment. Figure 2 This is a schematic diagram of the cross-sectional structure of the high-safety current collector in this embodiment.

[0069] In this embodiment, a positive electrode (LiFePO4) was coated onto an aluminum foil composite current collector, and a negative electrode graphite slurry was coated onto a copper foil composite current collector. The coating thickness was 150 μm. Electrodes were then prepared, batteries were assembled, and needle penetration tests were performed. Thermal imaging was used to record changes in the battery surface temperature to observe for any combustion or explosion. Specific results are shown in Table 1.

[0070] Example 2:

[0071] 2.40g of polyphthalamide (PPA) and 0.60g of silica (SiO2) powder (particle size 30-40nm) were added to 9.00g of dimethylacetamide (DMAc). The slurry was mechanically stirred and then ultrasonically mixed. Finally, a homogenizer was used to remove bubbles to form a thermally conductive and flame-retardant polymer slurry.

[0072] The thermally conductive and flame-retardant polymer slurry prepared above was coated onto the surface of the current collector layer (aluminum foil, copper foil) in a grid array shape. The current collector was 30cm long and 20cm wide, with the grid width controlled at 0.4mm and the grid being a square with a side length of 8mm. At this point, the total area of ​​the thermally conductive and flame-retardant polymer layer was approximately 8.73% of the total area of ​​the current collector. After curing at 100℃, a 100μm thick thermally conductive and flame-retardant polymer layer was obtained, thus obtaining a high-safety micro-current collector. (Appendix) Figure 3 This is a schematic diagram of the high-security current collector grid array structure in this embodiment.

[0073] In this embodiment, positive electrode (LiFePO4) was coated on the composite current collector aluminum foil, and negative electrode graphite paste was coated on the composite current collector copper foil to prepare electrode sheets. The battery was then assembled and subjected to a needle penetration test. Thermal imaging was used to record changes in the battery surface temperature to observe for any combustion or explosion. Specific results are shown in Table 1.

[0074] Example 3:

[0075] Add 2.75g of appropriate amount of polybenzimidazole (PBI) and 0.15g of nano antimony trioxide (Sb2O3) powder (particle size of 20-30nm) to 7.00g of N-methylpyrrolidone (NMP). After mechanical stirring, the slurry is ultrasonically mixed and finally defoamed using a homogenizer to form a thermally conductive and flame-retardant polymer slurry.

[0076] The thermally conductive and flame-retardant polymer slurry prepared above was coated onto the surface of the current collector layer (aluminum foil, copper foil) in a concentric circle array. The current collector was 30cm long and 20cm wide. The diameters of the large and small concentric circles were controlled to be 10mm and 5mm respectively, with adjacent large circles in contact with each other. The thickness of the concentric circle layer was 0.2mm. At this point, the total area of ​​the thermally conductive and flame-retardant polymer was approximately 9.42% of the total area of ​​the current collector. After curing at 300℃, a 200µm thick thermally conductive and flame-retardant polymer layer was obtained, thus obtaining a high-safety micro-current collector. (Appendix) Figure 4 This is a schematic diagram of the high-security current collector concentric circle array structure in this embodiment.

[0077] In this embodiment, positive electrode (NCM) was coated onto the composite current collector aluminum foil, and negative electrode graphite slurry was coated onto the composite current collector copper foil to prepare electrode sheets with a thickness of 150 μm. The battery was then assembled and subjected to a needle penetration test. Thermal imaging was used to record changes in the battery surface temperature to observe for any signs of combustion or explosion. Specific results are shown in Table 1.

[0078] The above three embodiments were compared with batteries using ordinary current collectors, and the results are shown in Appendix Table 1. Ordinary current collectors are those without a flame-retardant and thermally conductive polymer layer. Comparative Example 1 is a battery prepared using a current collector without a thermally conductive and flame-retardant polymer layer, based on Example 1; the battery preparation method is the same as in Example 1. Comparative Example 2 is a battery prepared using a current collector without a thermally conductive and flame-retardant polymer layer, based on Example 3; the battery preparation method is the same as in Example 3.

[0079] Table 1. Performance Comparison of High-Safety Current Collectors and Ordinary Current Collectors in Lithium-ion Battery Applications (Examples 1-3)

[0080]

[0081] As can be seen from the above results, by using the high-safety composite current collector described in this invention, and by setting a thermally conductive and flame-retardant polymer layer on the current collector, the function of the differential electrode sheet can be realized, thereby significantly improving the flame-retardant effect of the battery, significantly improving the heat dissipation effect of the battery, reducing the impact of temperature on battery performance, and significantly improving the safety performance of the battery.

[0082] It should be noted that the above-described embodiments are only some preferred solutions of the present invention and are not intended to limit the present invention in any way. There are other variations and modifications without departing from the technical solutions described in the claims.

Claims

1. A high-safety current collector, characterized in that, The device includes a current collector layer and a thermally conductive and flame-retardant polymer layer disposed on the current collector layer, wherein the thermally conductive and flame-retardant polymer layer has perforations; the total area of ​​the thermally conductive and flame-retardant polymer layer is not greater than 10% of the total area of ​​the current collector layer; the thermally conductive and flame-retardant polymer layer is prepared from a thermally conductive and flame-retardant polymer including a high-melting-point polymer; the high-melting-point polymer is a polymer with a melting point not lower than 300°C; the thermally conductive and flame-retardant polymer also includes a flame-retardant inorganic material, wherein the flame-retardant inorganic material is at least one of silicon dioxide, antimony trioxide, aluminum hydroxide, and magnesium hydroxide, and the particle size is 10nm to 100nm; the high-melting-point polymer is at least one of polyphthalamide, polyimide, polyisophthalamide, polybenzimidazole, and polytetrafluoroethylene, wherein the high-melting-point polymer accounts for 80%-95% of the total mass of the high-melting-point polymer and the flame-retardant inorganic material.

2. The high-safety current collector according to claim 1, characterized in that, The thickness of the thermally conductive and flame-retardant polymer layer is 100–200 μm.

3. The high-safety current collector according to claim 2, characterized in that, The thickness of the thermally conductive and flame-retardant polymer layer is not less than the thickness of the active material layer coated during the subsequent fabrication of the electrode sheet.

4. The high-safety current collector according to claim 1, characterized in that, The thermally conductive and flame-retardant polymer also includes a solvent, which is at least one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, and acetonitrile.

5. A method for preparing the high-safety current collector according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Preparation of thermally conductive and flame-retardant polymer slurry: High-melting-point polymer and flame-retardant inorganic material are added to a solvent and mixed to form a thermally conductive and flame-retardant polymer slurry; S2: The thermally conductive and flame-retardant polymer slurry prepared in step S1 is coated onto the current collector layer, and after curing, a high-safety current collector with a thermally conductive and flame-retardant polymer layer is obtained.

6. The method for preparing a high-safety current collector according to claim 5, characterized in that, The curing temperature range in step S2 is 60–300℃.

7. The application of the high-safety current collector according to any one of claims 1-4 in the field of lithium-ion batteries.

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