Modified current collector, preparation method therefor, and lithium ion battery

Abstract

The present application provides a modified current collector, a preparation method therefor, and a lithium ion battery. The modified current collector comprises a first functionally modified coating layer, a first nano-carbon coating layer, a current collector, a second nano-carbon coating layer, and a second functionally modified coating layer sequentially arranged in a stacked configuration; the first nano-carbon coating layer and the second nano-carbon coating layer each independently comprise a nano-carbon coating material; and the first functionally modified coating layer and the second functionally modified coating layer each independently comprise a nano-carbon coating material and a functionalized modification material. The described modified current collector not only enhances the conductive network between an active material and the current collector, but also increases ion transport capacity, thereby reducing polarization resistance and inhibiting DCR increases in lithium-ion batteries during charging and discharging cycles, and thus improving rate performance and cycle life in lithium-ion batteries. In addition, the modified current collector having the above structure has high porosity, thereby helping to improve wettability of the modified current collector in an electrolyte.

Description

Modified current collector, preparation method thereof, and lithium ion battery

[0001] The present application claims priority to the Chinese patent application No. 202411527251.5, filed on October 29, 2024, to the Chinese Patent Office, the content of the above application being hereby incorporated by reference into the present application. TECHNICAL FIELD

[0002] The present application relates to the technical field of current collectors, in particular, relates to a modified current collector, a preparation method thereof, and a lithium ion battery, and more particularly relates to an application of the modified current collector and the preparation method thereof in the preparation of a lithium ion battery. BACKGROUND

[0003] With the rapid development of lithium ion battery technology, higher requirements are now placed on the power performance, rate performance, and cycle life of lithium ion batteries. Due to the low electrical conductivity and electronic conductivity of the material structure itself, phosphate system power batteries usually adopt carbon-coated methods for optimization and modification. However, the contact between the current collector and the active material of the lithium ion battery is also an important factor affecting the charge and discharge performance, and therefore, the modification of the current collector has become an effective method to improve the performance of lithium ion batteries. The commonly used modification method is to use a functional coating for surface treatment, for example, uniformly coating dispersed nanometer conductive graphite and carbon black particles on an aluminum foil or a copper foil to prepare a carbon-coated foil, thereby reducing the internal resistance of the battery and reducing polarization, and thus improving the rate performance and cycle life of the lithium ion battery. However, the functional coating with low porosity hinders the diffusion of Li + in the electrode, thereby reducing the rate performance and cycle life of the lithium ion battery. TECHNICAL PROBLEM

[0004] The functional coating with low porosity in the related art hinders the diffusion of Li + in the electrode, resulting in poor rate performance and cycle life of the lithium ion battery. SOLUTION

[0005] In a first aspect, embodiments of the present application provide a modified current collector, which comprises a first functional modification coating, a first nanometer carbon coating, a current collector, a second nanometer carbon coating, and a second functional modification coating which are sequentially stacked; the first nanometer carbon coating and the second nanometer carbon coating each independently comprise a nanometer carbon coating material; and the first functional modification coating and the second functional modification coating each independently comprise a nanometer carbon coating material and a functional modification material.

[0006] Secondly, embodiments of this application provide a method for preparing the modified current collector, characterized in that the preparation method includes: step S1, mixing raw materials including nano-carbon coating material, a first dispersant, a first organic solvent and a first binder to obtain a nano-carbon coating slurry; step S2, mixing raw materials including nano-carbon coating material, functionalized modified material, a second dispersant, a second organic solvent and a second binder to obtain a functional modified coating slurry; step S3, coating the nano-carbon coating slurry onto two opposite surfaces of the current collector to form a first nano-carbon coating and a second nano-carbon coating; step S4, coating the surfaces of the first nano-carbon coating and the second nano-carbon coating away from the current collector with a functional modified coating slurry to form a first functional modified coating and a second functional modified coating, thereby obtaining the modified current collector.

[0007] Thirdly, embodiments of this application provide a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode and / or the negative electrode includes the modified current collector described above. Beneficial effects

[0008] 1. The modified current collector using the above-described layered structure of this application, on the one hand, the first and second nano-carbon coatings can enhance the conductive network between the active material and the current collector; on the other hand, the combination of the nano-carbon coating material and the functionalized modified material in the first and second functional modified coatings can increase their porosity, thereby further improving the Li... + The diffusion rate in the electrode, thereby increasing the Li + The ion transport capability is enhanced by a gradient design that increases the electron diffusion channels from the first nano-carbon coating to the first functional modified coating (or from the second nano-carbon coating to the second functional modified coating), thereby improving interfacial contact impedance, increasing adhesion strength, and mitigating performance degradation caused by interfacial stress during long cycles. Through the synergistic effect of these two aspects, the conductive network between the active material and the current collector is strengthened, while simultaneously increasing ion transport capability. This reduces polarization resistance and suppresses the growth of DCR during charge-discharge cycles, thus improving the rate performance and cycle life of the lithium-ion battery. Furthermore, the modified current collector with the above structure has abundant porosity, which helps improve its wettability in the electrolyte.

[0009] 2. This application combines nano-carbon coating materials and functionalized modified materials to obtain a first functional modified coating and a second functional modified coating, which can not only increase their porosity, thereby improving the Li... +The diffusion rate in the electrode can also reduce the polarization resistance. Through the coating methods in steps S3 and S4, a modified current collector consisting of the first functional modified coating, the first nano-carbon coating, the current collector, the second nano-carbon coating, and the second functional modified coating can be obtained. This not only enhances the conductive network between the active material and the current collector but also increases the ion transport capacity, thereby reducing the polarization resistance and suppressing the increase of DCR during the charge-discharge cycle of the lithium-ion battery, thus improving the rate performance and cycle life of the lithium-ion battery.

[0010] 3. Lithium-ion batteries using the above-mentioned modified current collector have higher rate performance and cycle life. Attached Figure Description

[0011] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0012] Figure 1 shows a schematic diagram of the modified current collector of this application;

[0013] The above figures include the following reference numerals:

[0014] 1. First functional modified coating; 2. First nano-carbon coating; 3. Current collector; 4. Second nano-carbon coating; 5. Second functional modified coating; 6. Nano-carbon coating material; 7. Transition metal oxide nanowires and transition metal oxide nanofibers; 8. Conductive polymer nanowires and conductive polymer nanofibers; 9. MXene; 10. MOFs.

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0016] In some embodiments of this application, the tortuosity ratio of the modified current collector is: ,in, The bending factor is the bending factor of the first or second nano-carbon coating. The bending factor is the first functional modified coating or the second functional modified coating; the bending factor ratio of the modified current collector is 5~90%, and in some embodiments of this application, the bending factor ratio of the modified current collector is 10~80%; and / or, the electronic conductivity ratio of the modified current collector is... ,in, The electronic conductivity of the first or second nano-carbon coating. The electronic conductivity of the first functional modified coating or the second functional modified coating; the electronic conductivity ratio of the modified current collector is 2~85%, and in some embodiments of this application, the electronic conductivity ratio of the modified current collector is 5~80%.

[0017] Controlling the torsional coefficient of the modified current collector within the aforementioned range is beneficial for fully leveraging the synergistic effect between the first nano-carbon coating and the first functional modified coating (or the second nano-carbon coating and the second functional modified coating). This allows the modified current collector to maintain good conductivity even under bending or deformation conditions. Controlling the electronic conductivity ratio of the modified current collector within the aforementioned range helps to effectively transmit current and reduce internal polarization of the battery, thereby contributing to improved rate performance and cycle life of lithium-ion batteries.

[0018] In some embodiments of this application, the mass content of the functionalized modified material in the first functional modified coating is 0.05-50%; and / or, the mass content of the functionalized modified material in the second functional modified coating is 0.05-50%; and / or, the nano-carbon coating material is selected from any one or more of conductive graphite, carbon black, graphene, carbon nanotubes, and VGCF; and / or, the functionalized modified material is selected from any one or more of transition metal oxide nanowires, transition metal oxide nanofibers, conductive polymer nanowires, conductive polymer nanofibers, MXene, and MOFs.

[0019] Controlling the mass content of the functionalized modifier in the first functional modified coating and the mass content of the functionalized modifier in the second functional modified coating within the above-mentioned range helps to increase the porosity of both the first and second functional modified coatings, thereby contributing to improving the Li... + Diffusion rate in the electrode. Controlling the types of nano-carbon coating materials and functionalized modified materials within the above range helps to achieve more effective composite of nano-carbon coating materials and functionalized modified materials, thereby helping to enhance the conductive network between the active material and the current collector and improve Li. + Ion transport capability, which in turn helps to improve the rate performance and cycle life of lithium-ion batteries.

[0020] In some embodiments of this application, transition metal oxide nanowires and transition metal oxide nanofibers are each independently selected from any one or more of RuO2, MnO2, V2O5, NiO2 and their corresponding derivatives; and / or, conductive polymer nanowires and conductive polymer nanofibers are each independently selected from any one or more of polyaniline, polypyrrole, polythiophene and their corresponding derivatives; and / or, MXene is selected from the chemical formula […]. Two-dimensional layered materials derived from transition metal carbides, with the general chemical formula: Two-dimensional layered materials derived from transition metal nitrides, with the general chemical formula: The material can be any one or more of two-dimensional layered materials derived from transition metal carbonitrides, wherein M is a transition metal element selected from any one or more of Ti, V, Cr, Zr, and Nb; and X is carbon and / or nitrogen. The surface group is selected from any one or more of hydroxyl, fluorine, and carbonyl groups, where 1 ≤ n ≤ 4; and / or, the MOFs are porous materials composed of metals and organic ligands, where the metal is a metal ion and / or a metal cluster, and the MOFs are selected from any one or more of network metal-organic framework materials (IRMOFs), zeolite-like imidazole ester framework materials (ZIFs), Levasil framework materials (MILs), and pore-channel framework materials (PCNs).

[0021] The types of transition metal oxide nanowires / fibers, conductive polymer nanowires / fibers, MXenes, and MOFs fall within the aforementioned range, which helps to combine them with nano-carbon coating materials to form gradient-designed electron diffusion channels, thereby improving interfacial contact resistance, increasing bonding strength, and mitigating performance degradation caused by interfacial stress during long cycles.

[0022] In some embodiments of this application, the thickness of the first nano-carbon coating and the second nano-carbon coating are each independently 0.5~80 μm; and / or, the width of the first nano-carbon coating and the second nano-carbon coating are each independently 50~1000 mm; and / or, the thickness of the first functionally modified coating and the second functionally modified coating are each independently 0.5~80 μm; and / or, the width of the first functionally modified coating and the second functionally modified coating are each independently 50~1000 mm; and / or, the first functionally modified coating, the first nano-carbon coating, and the current collector... The thickness ratio of the body is 10~60:10~60:10~15; and / or, the thickness ratio of the second functional modified coating, the second nano-carbon coating, and the current collector is 10~60:10~60:10~15; and / or, the thickness of the current collector is 6~16μm; the current collector is copper foil or aluminum foil; and / or, the thickness of the aluminum foil is 12~16μm; and / or, the thickness of the copper foil is 6~12μm; and / or, the porosity of the modified current collector is 20~80%, and in some other embodiments of this application, the porosity of the modified current collector is 40~80%.

[0023] Controlling the thicknesses of the first and second nano-carbon coatings, as well as the thicknesses of the first and second functionally modified coatings, within the aforementioned ranges helps reduce polarization resistance and further facilitates the regulation of Li. + The effective transport path; controlling the thickness ratio of the first functional modified coating, the first nano-carbon coating, and the current collector within the above range helps to further improve the Li +An effective transmission path. Controlling the type of current collector and the thickness of the aluminum and copper foils within the above ranges helps maintain the conductivity and mechanical strength of the modified current collector, thereby contributing to improving the cycle life of lithium-ion batteries.

[0024] In some embodiments of this application, step S1 further includes: step S11, dispersing the nano-carbon coating material, the first dispersant, and the first organic solvent to obtain a first conductive slurry; step S12, mixing the first conductive slurry and the first adhesive to obtain a nano-carbon coating slurry; wherein the mass ratio of the nano-carbon coating material, the first dispersant, and the first organic solvent is 1:0.01~0.5:2~50; and / or, the viscosity of the nano-carbon coating slurry is 800~10000 mPa·s, and in other embodiments of this application, the viscosity of the nano-carbon coating slurry is 850~9000 mPa·s; and / or, the rotation speed of the first dispersion is 20~100 The first dispersion time is 0.00 rpm, and / or the first dispersion time is 0.5~1.5 h, and / or the first mixing time is 0.5~24 h; and / or the first dispersant is selected from any one or more of anionic dispersants, cationic dispersants, nonionic dispersants and electrically neutral dispersants; and / or the first organic solvent is selected from any one or more of N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and dimethylformamide (DMF); and / or the first binder is selected from any one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and polyacrylonitrile (PAN).

[0025] Controlling the mass ratio of the nano-carbon coating material, the first dispersant, and the first organic solvent, the first dispersion rotation speed and time, and the types of the first dispersant and the first organic solvent within the aforementioned ranges helps to better disperse the nano-carbon coating material in the first organic solvent, thereby obtaining a first conductive slurry. Controlling the first mixing time and the type of the first binder within the aforementioned ranges helps to obtain a nano-carbon coating slurry with a viscosity within the aforementioned range, thereby facilitating coating onto the current collector. Controlling the anionic dispersant to be sodium acetate or sodium benzenesulfonate, the cationic dispersant to be polyethyleneimine, and the nonionic dispersant to be polyvinylpyrrolidone or polyethylene glycol helps to improve the dispersibility of the nano-carbon coating material.

[0026] In some embodiments of this application, step S2 further includes: step S21, dispersing the nano-carbon coating material, the functionalized modified material, the second dispersant, and the second organic solvent to obtain a second conductive slurry; and step S22, mixing the second conductive slurry and the second adhesive to obtain a functionalized coating slurry; wherein the mass ratio of the nano-carbon coating material, the functionalized modified material, the second dispersant, and the second organic solvent is 1:0.01~0.95:0.01~0.5:2~50; and / or, the viscosity of the functionalized coating slurry is 1200~10000 mPa·s. In some embodiments of this application, the functionalized coating slurry... The viscosity of the material is 1500~9500 mPa·s; and / or, the rotation speed of the second dispersion is 50~8000 rpm; and / or, the second dispersion time is 0.5~1.5 h; and / or, the second mixing time is 0.5~24 h; and / or, the second dispersant is selected from any one or more of anionic dispersants, cationic dispersants, nonionic dispersants, and electrically neutral dispersants; and / or, the second organic solvent is selected from any one or more of N-methylpyrrolidone, γ-butyrolactone, and dimethylformamide; and / or, the second binder is selected from any one or more of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

[0027] Controlling the mass ratio of the nano-carbon coating material, the functionalized modified material, the second dispersant, and the second organic solvent, as well as the rotation speed and time of the second dispersion, and the types of the second dispersant and the second organic solvent, within the aforementioned ranges, not only helps the nano-carbon coating material and the functionalized modified material to be better dispersed in the second organic solvent, but also helps the nano-carbon coating material and the functionalized modified material to be better composited, thereby obtaining a second conductive slurry. Controlling the second mixing time and the type of the second binder within the aforementioned ranges helps to obtain a functionalized modified coating slurry with a viscosity within the aforementioned ranges, thereby helping to coat the first nano-carbon coating and the second nano-carbon coating to obtain a modified current collector.

[0028] In some embodiments of this application, step S3 further includes cleaning the current collector before coating. The cleaning agent used for cleaning is an acid solution, which is selected from any one or more of 0.5-50 wt% acetic acid solution, 0.5-37 wt% hydrochloric acid solution, and 0.5-45 wt% phosphoric acid solution; and / or, the pH value of the acid solution is 1-6.

[0029] Using the aforementioned types of acid solutions as cleaning agents to clean the surface current collector helps to remove surface impurities more thoroughly, thereby helping to ensure the quality of subsequent coating.

[0030] The beneficial effects of this application will be further illustrated below with reference to the embodiments. Example

[0031] The conductive graphite nano-carbon coating material, the first dispersant polyethyleneimine, and the first organic solvent DMF are first dispersed at a mass ratio of 1:0.01:2 to obtain a first conductive slurry. The first dispersion speed is 20 rpm and the first dispersion time is 0.5 h. The first conductive slurry and the first binder PVDF are first mixed to obtain a nano-carbon coating slurry with a viscosity of 800 mPa·s. The first mixing time is 0.5 h.

[0032] The conductive graphite nano-carbon coating material, the functionalized modified material RuO2, the second dispersant polyethyleneimine, and the second organic solvent DMF were dispersed in a mass ratio of 1:0.01:0.01:2 to obtain a second conductive slurry. The second dispersion speed was 50 rpm and the second dispersion time was 0.5 h. The second conductive slurry and the second binder PVDF were then mixed in a second mixture for 0.5 h to obtain a functionalized modified coating slurry with a viscosity of 1200 mPa·s.

[0033] Before coating, a copper foil current collector with a thickness of 6 μm and a weight of 1.5 g was cleaned with a 50 wt% acetic acid solution to remove surface impurities. The pH value of the acetic acid solution was 1. Nano-carbon coating slurry was coated on both sides of the copper foil current collector to form a first nano-carbon coating and a second nano-carbon coating. The first nano-carbon coating had a thickness of 0.5 μm and a width of 50 mm, and the second nano-carbon coating had a thickness of 0.5 μm and a width of 50 mm. Functional modification coating slurry was then coated on the surfaces of the first and second nano-carbon coatings away from the copper foil current collector to form a first functional modification coating and a second functional modification coating. The first functional modification coating had a thickness of 0.5 μm and a width of 50 mm, and the second functional modification coating had a thickness of 0.5 μm and a width of 50 mm, resulting in a modified current collector, the structure of which is shown in Figure 1. Example

[0034] The conductive graphite nano-carbon coating material, the first dispersant polyethyleneimine, and the first organic solvent NMP are first dispersed at a mass ratio of 1:0.2:30 to obtain a first conductive slurry. The first dispersion speed is 5000 rpm and the first dispersion time is 1 h. The first conductive slurry and the first binder SBR are first mixed to obtain a nano-carbon coating slurry with a viscosity of 5000 mPa·s. The first mixing time is 12 h.

[0035] The nano-carbon coating material carbon black, the functionalized modified material polyaniline, the second dispersant polyethyleneimine, and the second organic solvent NMP were dispersed in a mass ratio of 1:0.5:0.3:25 to obtain a second conductive slurry. The second dispersion speed was 4000 rpm and the second dispersion time was 1 h. The second conductive slurry and the second binder SBR were mixed in a second mixture for 12 h to obtain a functional modified coating slurry with a viscosity of 4500 mPa·s.

[0036] Before coating, a copper foil current collector with a thickness of 9 μm and a weight of 3 g was cleaned with a 25 wt% acetic acid solution to remove surface impurities. The pH value of the acetic acid solution was 3. Nano-carbon coating slurry was coated on both sides of the copper foil current collector to form a first nano-carbon coating and a second nano-carbon coating. The first nano-carbon coating had a thickness of 50 μm and a width of 300 mm, and the second nano-carbon coating had a thickness of 50 μm and a width of 300 mm. Functional modified coating slurry was then coated on the surfaces of the first and second nano-carbon coatings away from the copper foil current collector to form a first functional modified coating and a second functional modified coating. The first functional modified coating had a thickness of 50 μm and a width of 300 mm, and the second functional modified coating had a thickness of 50 μm and a width of 300 mm, resulting in a modified current collector, the structure of which is shown in Figure 1. Example

[0037] The nano-carbon coating material graphene, the first dispersant polyethyleneimine, and the first organic solvent GBL are first dispersed at a mass ratio of 1:0.5:50 to obtain a first conductive slurry. The first dispersion speed is 9000 rpm and the first dispersion time is 1.5 h. The first conductive slurry and the first binder PAN are first mixed to obtain a nano-carbon coating slurry with a viscosity of 10000 mPa·s. The first mixing time is 24 h.

[0038] The nano-carbon coating material carbon nanotubes, the functionalized modified material zeolite imidazole ester framework material, the second dispersant polyethyleneimine, and the second organic solvent GBL were dispersed in a mass ratio of 1:0.95:0.5:50 to obtain a second conductive slurry. The second dispersion speed was 8000 rpm and the second dispersion time was 1.5 h. The second conductive slurry and the second binder PAN were mixed in a second mixture for 24 h to obtain a functionalized modified coating slurry with a viscosity of 10000 mPa·s.

[0039] Before coating, a copper foil current collector with a thickness of 9 μm and a weight of 3 g was cleaned with a 0.5 wt% acetic acid solution to remove surface impurities. The pH value of the acetic acid solution was 6. Nano-carbon coating slurry was coated on both sides of the copper foil current collector to form a first nano-carbon coating and a second nano-carbon coating. The first nano-carbon coating had a thickness of 80 μm and a width of 1000 mm, and the second nano-carbon coating had a thickness of 80 μm and a width of 1000 mm. Functional modified coating slurry was then coated on the surfaces of the first and second nano-carbon coatings away from the copper foil current collector to form a first functional modified coating and a second functional modified coating. The first functional modified coating had a thickness of 80 μm and a width of 1000 mm, and the second functional modified coating had a thickness of 80 μm and a width of 1000 mm, resulting in a modified current collector, the structure of which is shown in Figure 1. Example

[0040] The difference from Example 1 is that the tortuosity factor of the modified current collector is 5%. Example

[0041] The difference from Example 1 is that the tortuosity factor of the modified current collector is 90%. Example

[0042] The difference from Example 1 is that the tortuosity ratio of the modified current collector is 95%. Example

[0043] The difference from Example 1 is that the electronic conductivity ratio of the modified current collector is 2%. Example

[0044] The difference from Example 1 is that the electronic conductivity ratio of the modified current collector is 85%. Example

[0045] The difference from Example 1 is that the electronic conductivity ratio of the modified current collector is 90%. Example

[0046] The difference from Example 1 is that the mass content of the functionalized modified material in the first functional modified coating is 0.05%, and the mass content of the functionalized modified material in the second functional modified coating is 0.05%, ultimately resulting in a modified current collector. Example

[0047] The difference from Example 1 is that the mass content of the functionalized modified material in the first functional modified coating is 50%, and the mass content of the functionalized modified material in the second functional modified coating is 50%, ultimately resulting in a modified current collector. Example

[0048] The difference from Example 1 is that the mass content of the functionalized modified material in the first functional modified coating is 60%, and the mass content of the functionalized modified material in the second functional modified coating is 60%, ultimately resulting in a modified current collector. Example

[0049] The difference from Example 1 is that the thickness ratio of the first functional modified coating, the first nano-carbon coating and the current collector in the modified current collector is 60:60:15. Example

[0050] The difference from Example 1 is that the thickness ratio of the first functional modified coating, the first nano-carbon coating and the current collector in the modified current collector is 60:60:16. Example

[0051] The difference from Example 1 is that the mass ratio of the nano-carbon coating material conductive graphite, the first dispersant polyethyleneimine, and the first organic solvent DMF is 1:0.5:50, and the modified current collector is finally obtained. Example

[0052] The difference from Example 1 is that the mass ratio of the nano-carbon coating material conductive graphite, the first dispersant polyethyleneimine, and the first organic solvent DMF is 1:1:50, and the modified current collector is finally obtained. Example

[0053] The difference from Example 1 is that the mass ratio of the nano-carbon coating material conductive graphite, the functionalized modified material RuO2, the second dispersant polyethyleneimine, and the second organic solvent DMF is 1:0.95:0.5:50, and the modified current collector is finally obtained. Example

[0054] The difference from Example 1 is that the mass ratio of the nano-carbon coating material conductive graphite, the functionalized modified material RuO2, the second dispersant polyethyleneimine, and the second organic solvent DMF is 1:1:1:50, and the modified current collector is finally obtained. Example

[0055] The difference from Example 1 is that the first dispersion speed is 10,000 rpm and the first dispersion time is 1.5 h, the second dispersion speed is 8,000 rpm and the second dispersion time is 1.5 h, and finally the modified current collector is obtained. Example

[0056] The difference from Example 1 is that the first dispersion speed is 11,000 rpm and the first dispersion time is 1.5 h, the second dispersion speed is 9,000 rpm and the second dispersion time is 1.5 h, and finally the modified current collector is obtained.

[0057] The difference from Example 1 is that the current collector is not coated on both sides, resulting in a modified current collector.

[0058] The difference from Example 1 is that a nano-carbon coating slurry is coated on both sides of the current collector to form a first nano-carbon coating and a second nano-carbon coating, thus obtaining a modified current collector.

[0059] Porosity testing method: The porosity was determined by nitrogen adsorption method. The isotherms from low pressure (0.00001 Torr) to saturation pressure (760 Torr) were recorded. The amount of condensed gas in the sample under different pressure conditions was measured, and its isothermal adsorption and desorption curves were plotted to obtain its pore volume and pore size distribution curves. The porosity was then calculated.

[0060] The test method for DCR growth rate is as follows: Charge the test battery with a constant current and constant voltage of 0.33C to 3.70V, cut off at 0.05C, then discharge at 0.33C for 90 minutes, let it rest for 10 minutes, and record the voltage V1 at the end of the rest period; then discharge at 2C (current I) for 10 seconds, and record the voltage V2 at the end of the discharge period. Calculate the DC impedance of the battery according to the following formula: .

[0061] Test method for bending factor ratio: Bending factor ratio of modified current collector = ,in, The bending factor is the bending factor of the first or second nano-carbon coating. The bending factor is the bending factor of the first or second functional modified coating. The testing method for the bending factor of the above coating is as follows: 3D imaging of the sample is performed using focused ion beam scanning electron microscopy (FIB-SEM). The bending factor of the three-dimensional structure is calculated using a geometric method. First, all initial plane phases are marked at unit distances. Then, the effective distances of adjacent voxels are marked. The effective length of the channel is repeatedly measured through a phase network orientation. The square of the ratio of the effective length to the actual length of the sample is calculated, which is the bending factor of the coating.

[0062] Electronic conductivity ratio: Electronic conductivity ratio of modified current collector = ,in, The electronic conductivity of the first or second nano-carbon coating. The electronic conductivity of the first functional modified coating or the second functional modified coating is given. The test method for the electronic conductivity of the above coating is as follows: the electronic conductivity of the coating is calculated by the four-probe method, the resistance R of the conductor is calculated by measuring the current through the conductor and the voltage drop through the conductor, and the length and cross-sectional area ratio K of the sample to be tested is measured. K*(1 / R) is the electronic conductivity of the above coating.

[0063] The modified current collector was applied to a LiFePO4 / graphite system soft-pack battery cell and subjected to 1000 high-temperature cycles.

[0064] The performance of the modified current collectors in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0065]

[0066] Figure 1 is a schematic diagram of the modified current collector of this application. As can be seen from Figure 1, the modified current collector includes a first functional modified coating 1, a first nano-carbon coating 2, a current collector 3, a second nano-carbon coating 4, and a second functional modified coating 5 stacked sequentially. The first nano-carbon coating 1 and the second nano-carbon coating 2 each independently include nano-carbon coating material 6. The first functional modified coating 4 and the second functional modified coating 5 each independently include nano-carbon coating material 6 and functionalized modified material. The functionalized modified material may include transition metal oxide nanowires and transition metal oxide nanofibers 7, conductive polymer nanowires and conductive polymer nanofibers 8, MXene 9, and MOFs 10.

[0067] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0068] The modified current collector using the above-described layered structure of this application, on the one hand, enhances the conductive network between the active material and the current collector by combining the first and second nano-carbon coatings; on the other hand, the composite of the nano-carbon coating material and the functionalized modified material in the first and second functional modified coatings increases their porosity, thereby further improving the Li... + The diffusion rate in the electrode, thereby increasing the Li + The ion transport capability is enhanced by a gradient design that increases the electron diffusion channels from the first nano-carbon coating to the first functional modified coating (or from the second nano-carbon coating to the second functional modified coating), thereby improving interfacial contact impedance, increasing adhesion strength, and mitigating performance degradation caused by interfacial stress during long cycles. Through the synergistic effect of these two aspects, the conductive network between the active material and the current collector is strengthened, while simultaneously increasing ion transport capability. This reduces polarization resistance and suppresses the growth of DCR during charge-discharge cycles, thus improving the rate performance and cycle life of the lithium-ion battery. Furthermore, the modified current collector with the above structure has abundant porosity, which helps improve its wettability in the electrolyte.

[0069] The above are merely embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A modified current collector, characterized in that, The modified current collector includes a first functional modified coating, a first nano-carbon coating, a current collector, a second nano-carbon coating, and a second functional modified coating, which are sequentially stacked. The first nano-carbon coating and the second nano-carbon coating each independently comprise nano-carbon coating materials; The first functional modified coating and the second functional modified coating each independently comprise a nano-carbon coating material and a functionalized modified material.

2. The modified current collector according to claim 1, characterized in that, The tortuosity ratio of the modified current collector is: , in, The bending factor of the first or second nano-carbon coating. The bending factor of the first functionally modified coating or the second functionally modified coating; The tortuosity factor of the modified current collector is 5-90%; And / or, the electronic conductivity ratio of the modified current collector is ， in, The electronic conductivity of the first or second nano-carbon coating is given. The electronic conductivity of the first functionally modified coating or the second functionally modified coating; The electronic conductivity ratio of the modified current collector is 2-85%.

3. The modified current collector according to claim 2, characterized in that, The tortuosity ratio of the modified current collector is 10~80%.

4. The modified current collector according to claim 2, characterized in that, The electronic conductivity ratio of the modified current collector is 5-80%.

5. The modified current collector according to any one of claims 1 to 4, characterized in that, The mass content of the functionalized modified material in the first functionalized modified coating is 0.05~50%; and / or, the functionalized modified material is selected from any one or more of transition metal oxide nanowires, transition metal oxide nanofibers, conductive polymer nanowires, conductive polymer nanofibers, MXene and MOFs.

6. The modified current collector according to any one of claims 1 to 4, characterized in that, The mass content of the functionalized modified material in the second functional modified coating is 0.05~50%.

7. The modified current collector according to any one of claims 1 to 4, characterized in that, The nano-carbon coating material is selected from any one or more of conductive graphite, carbon black, graphene, carbon nanotubes, and VGCF.

8. The modified current collector according to claim 5, characterized in that, The transition metal oxide nanowires and the transition metal oxide nanofibers are each independently selected from any one or more of RuO2, MnO2, V2O5, NiO2 and their corresponding derivatives.

9. The modified current collector according to claim 5, characterized in that, The conductive polymer nanowires and the conductive polymer nanofibers are each independently selected from any one or more of polyaniline, polypyrrole, polythiophene and their corresponding derivatives.

10. The modified current collector according to claim 5, characterized in that, The MXene is selected from the chemical formula […]. Two-dimensional layered materials derived from transition metal carbides, with the general chemical formula: Two-dimensional layered materials derived from transition metal nitrides, with the general chemical formula: The material is selected from any one or more two-dimensional layered materials derived from transition metal carbonitrides, wherein M is a transition metal element selected from any one or more of Ti, V, Cr, Zr, and Nb; and X is carbon and / or nitrogen. The surface group is selected from any one or more of hydroxyl, fluorine, and carbonyl groups, where 1 ≤ n ≤ 4.

11. The modified current collector according to claim 5, characterized in that, The MOFs are porous materials composed of metals and organic ligands, wherein the metal is a metal ion and / or a metal cluster, and the MOFs are selected from any one or more of network metal-organic framework materials, zeolite-like imidazolium ester framework materials, Levasil framework materials, and pore-channel framework materials.

12. The modified current collector according to any one of claims 1 to 11, characterized in that, The thickness of the first nano-carbon coating and the second nano-carbon coating are each independently 0.5~80μm; and / or, the width of the first nano-carbon coating and the second nano-carbon coating are each independently 50~1000mm; and / or, the thickness of the first functional modified coating and the second functional modified coating are each independently 0.5~80μm; and / or, the width of the first functional modified coating and the second functional modified coating are each independently 50~1000mm. And / or, the thickness ratio of the first functional modified coating, the first nano-carbon coating, and the current collector is 10~60:10~60:10~15; And / or, the thickness ratio of the second functional modified coating, the second nano-carbon coating, and the current collector is 10~60:10~60:10~15; And / or, the thickness of the current collector is 6~16μm; The current collector is a copper foil or an aluminum foil; and / or, the aluminum foil has a thickness of 12-16 μm; and / or, the copper foil has a thickness of 6-12 μm; and / or, the modified current collector has a porosity of 20-80%.

13. The modified current collector according to claim 12, characterized in that, The porosity of the modified current collector is 40-80%.

14. A method for preparing the modified current collector according to any one of claims 1 to 13, characterized in that, The preparation method includes: Step S1: The raw materials including nano-carbon coating material, first dispersant, first organic solvent and first binder are first mixed to obtain nano-carbon coating slurry; Step S2 involves mixing the raw materials, including nano-carbon coating material, functionalized modified material, second dispersant, second organic solvent, and second binder, to obtain a functionalized modified coating slurry. Step S3: Coat the two opposite surfaces of the current collector with the nano-carbon coating slurry to form a first nano-carbon coating and a second nano-carbon coating. Step S4: The functionally modified coating slurry is coated on the surfaces of the first nano-carbon coating and the second nano-carbon coating away from the current collector, respectively, to form the first functionally modified coating and the second functionally modified coating, thus obtaining the modified current collector.

15. The preparation method according to claim 14, characterized in that, Step S1 further includes: Step S11: The nano-carbon coating material, the first dispersant, and the first organic solvent are first dispersed to obtain a first conductive slurry; Step S12: Mix the first conductive paste and the first adhesive to obtain the nano-carbon coating paste. Wherein, the mass ratio of the nano-carbon coating material, the first dispersant and the first organic solvent is 1:0.01~0.5:2~50; and / or, the viscosity of the nano-carbon coating slurry is 800~10000 mPa·s; And / or, the first dispersion rotation speed is 20~10000 rpm, and / or, the first dispersion time is 0.5~1.5 h, and / or, the first mixing time is 0.5~24 h; And / or, the first dispersant is selected from any one or more of anionic dispersants, cationic dispersants, nonionic dispersants, and electrically neutral dispersants; And / or, the first organic solvent is selected from any one or more of N-methylpyrrolidone, γ-butyrolactone, and dimethylformamide; And / or, the first adhesive is selected from any one or more of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

16. The preparation method according to claim 15, characterized in that, The viscosity of the nano-carbon coating slurry is 850~9000 mPa·s.

17. The preparation method according to claim 15 or 16, characterized in that, Step S2 further includes: Step S21: The nano-carbon coating material, the functionalized modified material, the second dispersant, and the second organic solvent are dispersed in a second manner to obtain a second conductive slurry; Step S22: The second conductive paste and the second adhesive are mixed in the second way to obtain the functional modified coating paste; Wherein, the mass ratio of the nano-carbon coating material, the functionalized modified material, the second dispersant and the second organic solvent is 1:0.01~0.95:0.01~0.5:2~50; and / or, the viscosity of the functionalized modified coating slurry is 1200~10000 mPa·s; And / or, the second dispersion rotation speed is 50~8000 rpm, and / or, the second dispersion time is 0.5~1.5 h, and / or, the second mixing time is 0.5~24 h; And / or, the second dispersant is selected from any one or more of anionic dispersants, cationic dispersants, nonionic dispersants, and electrically neutral dispersants; And / or, the second organic solvent is selected from any one or more of N-methylpyrrolidone, γ-butyrolactone, and dimethylformamide; And / or, the second adhesive is selected from any one or more of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

18. The preparation method according to claim 17, characterized in that, The viscosity of the functional modified coating slurry is 1500~9500 mPa·s.

19. The preparation method according to any one of claims 14 to 18, characterized in that, Step S3 further includes cleaning the current collector before coating, wherein the cleaning agent used for cleaning is an acid solution, and the acid solution is selected from any one or more of 0.5-50 wt% acetic acid solution, 0.5-37 wt% hydrochloric acid solution and 0.5-45 wt% phosphoric acid solution; and / or, the pH value of the acid solution is 1-6.

20. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode and / or the negative electrode comprises the modified current collector as described in any one of claims 1 to 13.

Images