High-specific-surface-area current collector and manufacturing method therefor, electrode sheet and battery

Abstract

A current collector and a manufacturing method therefor, an electrode sheet and a battery. The current collector comprises a metal foil, the metal foil being provided with a plurality of concave holes, and the diameter of each concave hole being ≤20 μm. The total area of the concave holes accounts for 25% or less of the total area of the metal foil, and the water contact angle of the metal foil is ≤5°. The adhesive force between the current collector and electrode materials is large, and the internal resistance of a battery is low.

Description

A high surface area current collector, a preparation method thereof, an electrode sheet and a battery Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a high-specific surface area current collector and a preparation method thereof, an electrode sheet and a battery. Background Art

[0002] Lithium-ion batteries generally include: active materials, separators, electrolytes and current collectors. Copper foil is generally used as the negative current collector of lithium-ion batteries, and aluminum foil is generally used as the positive current collector. Since the rolled surface of general metal foil is relatively smooth, some problems will arise when coating the active material, such as poor wettability, loose bonding, low bonding strength, small bonding area, and difficulty in adhesion, which will lead to large interface resistance between the active material and the current collector, easy to fall off, and difficult to coat. The above problems will lead to a decline in battery performance. For example, large interface resistance leads to severe polarization, which affects the lithium storage capacity, rate performance and cycle stability of the active material, making it difficult to meet the current demand for high rate, high energy density and long cycle life. Therefore, improving the surface state and properties of metal foil strips is of great significance for improving the compatibility between active materials and current collectors, improving bonding strength, increasing bonding area, and thus improving battery performance.

[0003] Existing Chinese patents such as CN111180741A, CN111180741A, and CN116742007A all employ a coating of carbon material on a metal foil to increase the surface area of ​​the current collector. However, the widely used carbon materials suffer from shortcomings such as poor conductivity, difficulty dispersing, weak bonding strength between the coating and the metal foil, and relatively thick coatings.

[0004] Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high specific surface area current collector with strong adhesion to electrode materials and low internal resistance.

[0006] The technical problem that the present invention also aims to solve is to provide a method for preparing a high specific surface area current collector, which has little effect on the tensile strength and elongation of the metal foil and can meet the requirements of the electrode sheet manufacturing process.

[0007] Another technical problem to be solved by the present invention is to provide an electrode sheet having good electro-liquid wettability and electron channels.

[0008] The technical problem that the present invention also aims to solve is to provide a battery with good coulombic efficiency, cycle stability and rate performance.

[0009] In order to solve the above problems, in the first aspect, the present invention provides a high specific surface area current collector, including a metal foil, wherein the metal foil is provided with a plurality of concave holes, the diameter of the concave holes is ≤20μm, the total area of ​​the concave holes accounts for 25% or less of the total area of ​​the metal foil, and the water drop angle of the metal foil is ≤5°.

[0010] As an improvement of the above solution, the surface energy of the metal foil is as follows: when 2 mol of deionized water is dropped on the metal foil, the diffusion speed of the water drop is ≥20 mm / 5 s.

[0011] As an improvement to the above solution, the diameter of the concave hole is ≤10 μm.

[0012] As an improvement to the above solution, the metal foil is copper foil or aluminum foil.

[0013] As an improvement to the above solution, the thickness of the metal foil is 10 to 30 μm. Preferably, the thickness of the metal foil is 12 to 20 μm.

[0014] As an improvement to the above solution, the method for preparing the metal foil includes: using two high-energy physical discharge processes to perform metal treatment on the smooth metal foil to form a plurality of concave holes on the smooth metal foil.

[0015] As an improvement to the above solution, laser is used to irradiate the smooth metal foil.

[0016] In a second aspect, the present invention provides an electrode sheet comprising a current collector and an electrode material, wherein the current collector is any one of the high surface area current collectors described above, and the electrode material is a positive electrode material or a negative electrode material.

[0017] As an improvement to the above solution, the resistivity of the electrode sheet is ≤30Ω·m;

[0018] And / or, the peel strength of the electrode sheet is ≥13N / 25mm.

[0019] In a third aspect, the present invention provides a battery comprising the electrode sheet described in any one of the above items.

[0020] The implementation of the present invention has the following beneficial effects:

[0021] The high specific surface area current collector of the present invention has a higher specific surface area, and its adhesion to the electrode material is increased by more than 15%.

[0022] The high surface area current collector of the present invention has a high surface tension value, excellent electrolyte wettability and good electron channel, which helps to reduce the internal resistance of the lithium-ion battery (the internal resistance is reduced by more than 50%), thereby improving the coulombic efficiency, cycle stability and rate performance of the battery; in addition, it can also effectively disperse the heat in the battery, thereby reducing the temperature rise of the battery and extending the service life of the battery.

[0023] The high specific surface area current collector of the present invention has flexibility, which not only allows the elastomer in the electrode material to expand and contract repeatedly without falling off, but also reduces the contact internal resistance with the electrode material and reduces the transmission internal resistance.

[0024] Compared with smooth metal foil, the metal foil of the present invention has the same volume ratio, a larger specific surface area, an increased contact area with the electrode material, and can be embedded in the electrode material, with low cost. On the one hand, it can replace the current collector coated with carbon material; on the other hand, it can also be used in combination with carbon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a surface energy test result diagram of a high specific surface area current collector according to the present invention;

[0026] FIG2 is a surface energy test result diagram of an existing smooth aluminum foil;

[0027] FIG3 is an electron microscope image of a high surface area current collector according to the present invention;

[0028] FIG4 is an electron microscope image of an existing smooth aluminum foil;

[0029] FIG5 is a schematic diagram of an embodiment of laser irradiation of a metal foil according to the present invention;

[0030] FIG6 is a schematic diagram of another embodiment of laser irradiation of a metal foil according to the present invention;

[0031] FIG7 is an enlarged view of a concave hole formed by the preparation method of the present invention;

[0032] FIG8 is an enlarged view of a concave hole formed by a chemical etching method. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is hereby stated that any directional terms such as "up," "down," "left," "right," "front," "back," "inside," and "outside" that appear or will appear herein are based solely on the accompanying drawings and are not intended to limit the present invention.

[0034] The present invention provides a high specific surface area current collector, comprising a metal foil having a plurality of concave holes, wherein the diameter of the concave holes is ≤20 μm, the total area of ​​the concave holes accounts for 25% or less of the total area of ​​the metal foil, and the water drop angle of the metal foil is ≤1°.

[0035] Existing smooth foils undergo multiple rolling passes per sheet, resulting in a thicker passivation layer and a high oil content that is difficult to remove. This results in a higher contact resistance between the electrode material (such as LFP) and the metal foil. Existing methods for coating smooth metal foil with carbon materials only improve adhesion but do not reduce contact resistance. Furthermore, the use of high-power corona generators generates large amounts of aluminum powder or iron-containing aluminum powder (1100 alloy), which can lead to excessive battery self-discharge, especially at high rates.

[0036] The high specific surface area current collector of the present invention has a higher specific surface area, and its adhesion to the electrode material is increased by more than 15%.

[0037] The high surface area current collector of the present invention has a high surface tension value, excellent electrolyte wettability and good electron channel, which helps to reduce the internal resistance of the lithium-ion battery (the internal resistance is reduced by more than 50%), thereby improving the coulombic efficiency, cycle stability and rate performance of the battery; in addition, it can also effectively disperse the heat in the battery, thereby reducing the temperature rise of the battery and extending the service life of the battery.

[0038] The high specific surface area current collector of the present invention has flexibility, which not only allows the elastomer in the electrode material to expand and contract repeatedly without falling off, but also reduces the contact internal resistance with the electrode material and reduces the transmission internal resistance.

[0039] Compared with smooth metal foil, the metal foil of the present invention has the same volume ratio, a larger specific surface area, an increased contact area with the electrode material, and can be embedded in the electrode material, with low cost. On the one hand, it can replace the current collector coated with carbon material; on the other hand, it can also be used in combination with carbon material.

[0040] Specifically, the surface energy of metal foil is as follows: 2 mol of deionized water is dropped onto the metal foil, and the diffusion rate of the water droplet is ≥ 20 mm / 5 seconds. That is, after 5 seconds, a single drop of 2 mol of deionized water is dropped onto the metal foil, and the diameter of the water droplet is 20 mm, as shown in Figure 1. Figure 2 shows the surface energy test results of commercially available polished aluminum foil. As can be seen from Figures 1 and 2, the high-surface-weighted current collector of the present invention has excellent wettability, thus providing good electron conduction and reducing the internal resistance of the battery.

[0041] The metal foil of the present invention is copper foil or aluminum foil, wherein copper foil is generally used as the current collector of the negative electrode material, and aluminum foil is generally used as the current collector of the positive electrode material.

[0042] It should be noted that the thickness of the metal foil is of great importance to the energy density of the battery. The thinner the metal foil, the higher the energy density of the electrode. This is because the energy of the lithium battery is mainly concentrated in the positive electrode material, and if the thickness of the metal foil is too large, the internal resistance of the battery will increase, thereby reducing the energy density of the battery. In addition, the metal foil also needs to carry the active material and fix it on the electrode, which has certain requirements for its thickness. If the thickness of the metal foil is too thin, it will affect its carrying capacity and thus affect the stability of the electrode. Preferably, the thickness of the metal foil is 8 to 30 μm. More preferably, the thickness of the metal foil is 12 to 20 μm.

[0043] The specific thickness of the metal foil needs to be selected and optimized according to the specific usage scenario to achieve the best electrode performance.

[0044] It should be noted that during the production of lithium-ion batteries, processes such as coating, rolling, winding, and core shaping require that the metal foil current collector and the electrode sheet remain intact, and certain requirements are placed on the tensile strength, elongation, and bending performance of the metal foil current collector. In order to improve the energy density of lithium-ion batteries, the thickness of the metal foil current collector is preferably 10 to 15 μm. If the total area of ​​the concave holes accounts for more than 25% of the total area of ​​the metal foil, the mechanical properties of the metal foil will be reduced and the requirements of the electrode manufacturing process will not be met. Preferably, the total area of ​​the concave holes is 15% to 25% of the total area of ​​the metal foil. In addition, the diameter of the concave holes will also affect the mechanical properties of the metal foil and the adhesion between the metal foil and the active material. Therefore, the diameter of the concave holes is ≤20 μm. Preferably, the diameter of the concave holes is ≤10 μm.

[0045] Compared with smooth aluminum foil, the high surface area current collector of the present invention has the following advantages:

[0046] (1) It can load more electrode materials, improve the adhesion between the current collector foil and the electrode material, and is more conducive to thick electrodes, ultra-thin electrodes, and dry electrodes;

[0047] (2) It can alleviate the repeated deformation and stress of the elastomer during expansion and contraction, thereby improving the battery cycle life;

[0048] (3) It can reduce and delay the generation of dendrites at the positive and negative electrodes, change the direction of dendrite growth, and improve battery safety;

[0049] (4) It can reduce the problem of positive and negative electrode yin and yang surfaces, improve the penetration and wettability of electrolyte between active materials of high-rate batteries under high rolling, make lithium ion migration more free, reduce ohmic polarization and concentration polarization between active materials, and improve battery rate and cycle life;

[0050] (5) Reduce the proportion of foil in battery mass and improve battery energy density;

[0051] (6) Improve electrolyte wettability, improve battery production efficiency, consistency and yield rate.

[0052] In addition, during the production of lithium-ion batteries, processes such as coating, rolling, winding, and core forming require that the metal foil current collector and the electrode remain intact, and there are certain requirements for the tensile strength, elongation, and bending performance of the metal foil current collector.

[0053] In order to solve the above problems, the present invention provides a method for preparing a high specific surface area current collector, comprising the following steps:

[0054] S1. Provide smooth metal foil;

[0055] S2. Processing the smooth metal foil using two high-energy physical discharge processes to obtain a semi-finished metal foil;

[0056] S3. The semi-finished metal foil is subjected to heat acid treatment, cleaning, and drying in sequence to obtain a high specific surface area metal foil.

[0057] The high specific surface area of ​​the metal foil prepared by the present invention is 10% or more higher than that of the smooth metal foil, and the tensile strength of the high specific surface area of ​​the metal foil is 3% or less lower than that of the smooth metal foil.

[0058] Compared with smooth metal foil, since the specific surface area of ​​the high specific surface area metal foil of the present invention is increased by 10% or more, the adhesion between the high specific surface area metal foil of the present invention and the electrode material is increased by more than 15%.

[0059] In addition, the high-surface-weight metal foil of the present invention has a higher surface tension value, excellent electrolyte wettability and good electron channel, which helps to reduce the internal resistance of lithium-ion batteries (internal resistance is reduced by more than 50%), thereby improving the coulombic efficiency, cycle stability and rate performance of the battery; in addition, it can also effectively disperse the heat in the battery, thereby reducing the temperature rise of the battery and extending the service life of the battery.

[0060] Secondly, the high specific surface area metal foil of the present invention has better flexibility, which not only allows the elastomer in the electrode material to expand and contract repeatedly without falling off, but also reduces the contact internal resistance with the electrode material and reduces the transmission internal resistance.

[0061] Compared with smooth metal foil, the high specific surface area metal foil of the present invention has the same volume ratio, a larger specific surface area, an increased contact area with the electrode material, and can be embedded in the electrode material, with low cost. On the one hand, it can replace the current collector coated with carbon material; on the other hand, it can also be used in combination with carbon material.

[0062] Specifically, the present invention uses two high-energy physical discharge processes to treat the metal of the smooth metal foil to form a plurality of concave holes on the smooth metal foil. Referring to Figures 3 and 4, Figure 3 is an electron microscope image of the high-surface-ratio metal aluminum foil of the present invention, and Figure 4 is an electron microscope image of the commercially available smooth aluminum foil (the smooth aluminum foil in step S1). It can be seen from Figures 3 and 4 that the surface area of ​​the high-surface-ratio metal aluminum foil prepared by the preparation method of the present invention is significantly increased, wherein one high-energy physical discharge process forms concave holes with good size consistency and distribution on the metal aluminum foil, and the other high-energy physical discharge process further etches the metal aluminum foil around the concave holes, further increasing the specific surface area of ​​the metal aluminum foil without affecting the tensile strength of the metal aluminum foil. However, the surface of the smooth aluminum foil is smooth and cannot increase the surface area, so it is impossible to expand the contact area with the electrode material.

[0063] The present invention adopts two high-energy physical discharge processes to treat the metal of the smooth metal foil, including: using laser to irradiate the smooth metal foil to change the grain structure and orientation of the metal foil surface, and controlling the surface roughness of the metal foil to obtain concave holes of target number and aperture.

[0064] Due to the characteristics of laser beam such as high energy density, controllable direction and strong focusing ability, the laser interacts with pollutants such as oil stains and oxide layers attached to the smooth metal foil, and separates them from the smooth metal foil in the form of instantaneous thermal expansion, melting, gas volatilization, etc.

[0065] Specifically, a point laser is used to laser-drill a smooth metal foil to form concave holes, and a line laser is used to laser-ablate the smooth metal foil to remove oxide layers, oil stains, and debris generated by laser drilling. Point lasers have high energy and can impact concave holes on the surface of the metal foil. Line lasers have lower energy than point lasers, but they have a larger active area and can quickly vaporize oil stains, oxide layers, and other contaminants on the metal foil surface, as well as remove debris generated by laser drilling.

[0066] The present invention not only can obtain concave holes of target size through the mutual cooperation of the above two lasers, but also the concave holes are evenly distributed and have little effect on the tensile strength of the metal foil.

[0067] It should be noted that laser wavelength, laser power, pulse width, and pulse frequency have a significant impact on the formation of concave holes, but are specifically limited by the number and size of the concave holes, as well as the thickness of the smooth metal foil. In the present invention, the laser parameters are set based on the following conditions: the smooth metal foil thickness is 10-30 μm, the concave hole diameter is ≤ 20 μm, and the total area of ​​the concave holes is 15%-25% of the total area of ​​the smooth metal foil.

[0068] Point laser, laser wavelength is 520-540nm, laser power is 8-10W, pulse width is 5-8ns, pulse frequency is 60-100MHz;

[0069] Linear laser, laser wavelength is 1000~1100nm, laser power is 3~5W, pulse width is 1~3ns, and pulse frequency is 20~50MHz.

[0070] 5 , the laser light source 2 can be disposed on one side of the smooth metal foil 1 to form concave holes on one side of the smooth metal foil 1. Alternatively, as shown in FIG6 , the laser light source 2 can be disposed on both sides of the smooth metal foil 1 to form concave holes on both sides of the smooth metal foil 1.

[0071] Specifically, the method of performing a thermal acid treatment on the semi-finished metal foil in step S3 includes: immersing the semi-finished metal foil in a pickling tank, wherein the pickling solution in the pickling tank includes HF and H2SO4, and the temperature of the pickling solution is 40-50°C. The thermal acid treatment can not only further remove impurities such as debris and oil stains on the metal foil, but also remove iron ions, magnesium ions, etc., further improving the wettability of the metal foil and allowing lithium ions to migrate more freely. More importantly, since the edges of the concave holes produced by laser drilling are uneven, an oxidation reaction will occur around the concave holes, forming a layer of oxide film. The thermal acid treatment of the present invention can expand the concave holes, make the edges of the concave holes smooth, and remove the oxide film.

[0072] Compared to conventional pickling solutions, the concentration of the pickling solution of the present invention cannot be too high, otherwise it will affect the aperture of the concave holes and the tensile strength of the metal foil. Preferably, the total mass of HF and H2SO4 is 2% to 3% of the total mass of the pickling solution, and the mass ratio of HF to H2SO4 is 1:(2.5-5). More preferably, the total mass of HF and H2SO4 is 2.2% to 2.8% of the total mass of the pickling solution, and the mass ratio of HF to H2SO4 is 1:(3-4).

[0073] It should be noted that after the metal foil passes through the pickling tank, it also needs to be cleaned in a cleaning tank. The cleaning tank contains deionized water, which mainly removes the residual pickling solution and decomposition products generated during the pickling process on the metal foil, effectively improving the cleanliness and surface wetting tension of the metal foil. Without a cleaning tank, the pickling solution and pickling decomposition products remaining on the metal foil will affect the conductivity and electrochemical properties of the conductive coating or electrode active material subsequently applied to the metal foil, thereby affecting the lifespan, number of cycles, and power consumption of the lithium battery.

[0074] Preferably, the temperature of the deionized water is 50-70°C. More preferably, the temperature of the deionized water is 55-60°C.

[0075] Referring to Figures 7 and 8, Figure 7 is an enlarged view of the concave holes formed by the preparation method of the present invention, and Figure 8 is an enlarged view of the concave holes formed by the chemical etching method. It can be seen from Figures 7 and 8 that the method of opening holes by using two high-energy physical discharge processes in the present invention has high production efficiency. Compared with the existing method of opening holes by chemical etching of metal foils, the aperture consistency of the concave holes formed by laser irradiation of the polished aluminum foil by the present invention is high, while the concave holes formed by the chemical etching method are unevenly distributed and the aperture sizes of the concave holes are different.

[0076] The preparation method of the present invention is simple. Two high-energy physical discharge processes are used to treat the smooth metal foil, which can not only remove oil stains, oxide layers, impurities, etc. on the surface of the metal foil, but also change the grain structure and orientation of the metal foil surface, and control the surface roughness of the metal foil to obtain concave holes with a target number and aperture. Ultimately, without affecting the tensile strength of the metal foil, a high-specific surface area metal foil with high specific surface area, high adhesion, good wettability and low internal resistance is obtained.

[0077] In addition, the preparation method of the present invention only needs to be processed in a low-concentration pickling tank, which is more environmentally friendly.

[0078] The present invention also provides an electrode sheet, comprising a current collector and an electrode material, wherein the current collector is the high specific surface area current collector mentioned above.

[0079] The electrode sheet of the present invention can be a positive electrode sheet or a negative electrode sheet. If the metal foil of the current collector is aluminum foil and the electrode material is a positive electrode material, the electrode sheet is a positive electrode sheet. If the metal foil of the current collector is copper foil and the electrode material is a negative electrode material, the electrode sheet is a negative electrode sheet.

[0080] Since the current collector of the present invention has a high specific surface area, its contact area with the electrode material is large, so the electrode sheet of the present invention has low resistivity and high peel strength.

[0081] The electrode sheet of the present invention can be a semi-solid electrode sheet, a solid electrode sheet or a dry electrode sheet.

[0082] Correspondingly, the present invention further provides a battery comprising the above-mentioned electrode sheet. Specifically, the battery of the present invention is a lithium iron battery.

[0083] The present invention will be further described below with reference to specific embodiments.

[0084] Example 1

[0085] A method for preparing a high-surface-weight current collector comprises the following steps:

[0086] S1. Provide a smooth aluminum foil with a thickness of 15 μm;

[0087] S2, using a point laser and a line laser to sequentially irradiate both sides of the smooth aluminum foil to obtain a semi-finished aluminum foil;

[0088] The parameters of the point laser are as follows: laser wavelength 525 nm, laser power 8 W, pulse width 6 ns, pulse frequency 70 MHz;

[0089] The parameters of the linear laser are as follows: laser wavelength 1040 nm, laser power 3 W, pulse width 2 ns, and pulse frequency 30 MHz;

[0090] S3, sequentially subjecting the semi-finished aluminum foil to thermal acid treatment, cleaning, and drying to obtain a high specific surface area aluminum foil having concave pores;

[0091] The hot acid treatment method includes: immersing the semi-finished aluminum foil in a pickling tank, wherein the pickling solution in the pickling tank includes HF and H2SO4 in a mass ratio of 1:3, the temperature of the pickling solution is 45°C, and the total mass of HF and H2SO4 is 2% of the total mass of the pickling solution;

[0092] The high surface area current collector prepared in this embodiment has a total area of ​​concave holes that accounts for 25% of the total area of ​​the smooth aluminum foil, a diameter of the concave holes ≤ 10 μm, and a water drop angle of the high surface area aluminum foil ≤ 5°.

[0093] Example 2

[0094] A method for preparing a high-surface-weight current collector comprises the following steps:

[0095] S1, providing a smooth aluminum foil with a thickness of 15 μm;

[0096] S2, using a point laser and a line laser to sequentially irradiate both sides of the smooth aluminum foil to obtain a semi-finished aluminum foil;

[0097] The parameters of the point laser are as follows: laser wavelength 525 nm, laser power 9 W, pulse width 7 ns, pulse frequency 80 MHz;

[0098] The parameters of the linear laser are as follows: laser wavelength 1040 nm, laser power 4 W, pulse width 2 ns, and pulse frequency 40 MHz;

[0099] S3, sequentially subjecting the semi-finished aluminum foil to thermal acid treatment, cleaning, and drying to obtain a high specific surface area aluminum foil;

[0100] Among them, the hot acid treatment method includes: soaking the semi-finished aluminum foil in a pickling tank, the pickling solution in the pickling tank includes HF and H2SO4 in a mass ratio of 1:4, the temperature of the pickling solution is 50°C, and the total mass of HF and H2SO4 is 2.5% of the total mass of the pickling solution.

[0101] The high surface area current collector prepared in this embodiment has a total area of ​​concave holes that accounts for 23% of the total area of ​​the smooth aluminum foil, a diameter of the concave holes ≤ 10 μm, and a water drop angle of the high surface area aluminum foil ≤ 5°.

[0102] Comparative Example 1

[0103] The commercially available smooth aluminum foil has a thickness of 15 μm and a water drop angle of 110°.

[0104] Comparative Example 2

[0105] A method for preparing a high-surface-weight current collector comprises the following steps:

[0106] S1. Provide a smooth aluminum foil with a thickness of 15 μm;

[0107] S2, irradiating both sides of the smooth aluminum foil with a point laser to obtain a semi-finished aluminum foil;

[0108] The parameters of the point laser are as follows: laser wavelength 525 nm, laser power 8 W, pulse width 6 ns, pulse frequency 70 MHz;

[0109] S3, sequentially subjecting the semi-finished aluminum foil to thermal acid treatment, cleaning, and drying to obtain a high specific surface area aluminum foil;

[0110] Among them, the hot acid treatment method includes: soaking the semi-finished aluminum foil in a pickling tank, the pickling solution in the pickling tank includes HF and H2SO4 in a mass ratio of 1:3, the temperature of the pickling solution is 45°C, and the total mass of HF and H2SO4 is 2% of the total mass of the pickling solution.

[0111] The high surface area current collector prepared in this embodiment has a total area of ​​concave holes that accounts for 11% of the total area of ​​the smooth aluminum foil, a diameter of the concave holes ≤ 30 μm, and a water drop angle of the high surface area aluminum foil ≤ 10°.

[0112] Comparative Example 3

[0113] A method for preparing a high-surface-weight current collector comprises the following steps:

[0114] S1. Provide a smooth aluminum foil with a thickness of 15 μm;

[0115] S2, irradiating both sides of the smooth aluminum foil with a linear laser to obtain a semi-finished aluminum foil;

[0116] The parameters of the linear laser are as follows: laser wavelength 1040 nm, laser power 3 W, pulse width 2 ns, pulse frequency 30 MHz;

[0117] S3, sequentially subjecting the semi-finished aluminum foil to thermal acid treatment, cleaning, and drying to obtain a high specific surface area aluminum foil;

[0118] Among them, the hot acid treatment method includes: soaking the semi-finished aluminum foil in a pickling tank, the pickling solution in the pickling tank includes HF and H2SO4 in a mass ratio of 1:3, the temperature of the pickling solution is 45°C, and the total mass of HF and H2SO4 is 2% of the total mass of the pickling solution.

[0119] The high surface area current collector prepared in this embodiment has a total area of ​​concave holes accounting for 8% of the total area of ​​the smooth aluminum foil, a diameter of the concave holes ≥30 μm, and a water drop angle of the high surface area aluminum foil ≤10°.

[0120] The current collectors of Example 1, Example 2, and Comparative Examples 1 to 3 were made into electrode sheets and batteries. The resistance and peel strength of each electrode sheet, as well as the gram capacity of the electrode were tested, and the results are shown in Table 1.

[0121] It should be noted that the smooth aluminum foils of Examples 1 to 2 and Comparative Examples 1 to 3 are from the same supplier and belong to the same batch. The high specific surface area aluminum foils prepared in Comparative Example 1 (smooth aluminum foil), Examples 1 to 2, and Comparative Examples 2 to 3 were tested to form 5 test groups. Three samples were taken from each test group for testing, and the results were averaged. The test items included tensile strength, specific surface area, and electrical resistance. The tensile strength decrease rate and specific surface area increase rate of the aluminum foil were calculated. The tensile strength decrease rate (%) = (tensile strength of the blank group - tensile strength of the aluminum foil of the experimental group) / tensile strength of the blank group * 100%, and the specific surface area increase rate (%) = (specific surface area of ​​the experimental group - specific surface area of ​​the blank group) / specific surface area of ​​the blank group * 100%;

[0122] The high-surface-weight ratio aluminum foils prepared in Examples 1-2 and Comparative Examples 2-3, as well as the smooth aluminum foil of Comparative Example 1, were made into electrode sheets and batteries. Specifically, an electrode slurry was coated on the high-surface-weight ratio aluminum foil and the smooth aluminum foil to form an electrode layer with a thickness of 170 μm. The electrode slurry consisted of 95% by mass of lithium nickel cobalt manganese oxide and 5% by mass of a PVDF binder. The resistance and peel strength of each electrode sheet were tested, as well as the gram capacity of the electrode. The electrode sheets of Examples 1-2 and Comparative Examples 1-3 were subjected to an aging test and divided into five groups, each with five samples. The results were averaged. Specifically, the electrodes were placed in an aging chamber at 200°C for 96 hours. The area of ​​detachment between the electrode layer and the aluminum foil of the electrode sheet was observed and counted, and the detachment area ratio of the electrode sheet was calculated. The detachment area ratio = detachment area of ​​each electrode sheet / area of ​​each electrode sheet * 100%. The results are shown in Table 1.

[0123] Table 1 Test results of various embodiments and comparative examples

[0124] From the results in Table 1, it can be seen that compared with Comparative Examples 1 to 3, the high specific surface area current collectors of Examples 1 and 2 increase the specific surface area of ​​the metal foil by setting a target number and target size of recessed holes on the metal foil. When the volume ratio of the metal foil remains unchanged, more electrode materials can be embedded, thereby increasing the electrode gram capacity. In addition, the high specific surface area current collectors of Examples 1 and 2 have high adhesion to the electrode material, so the peel strength of the electrode sheet is significantly higher than that of Comparative Examples 1 to 3. Furthermore, the high specific surface area current collectors of Examples 1 and 2 have good wettability and electron channels, so their electrode sheet resistance is also significantly lower than that of Comparative Examples 1 to 3.

[0125] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high specific surface area fluid collector, characterized in that, It includes a metal foil, and multiple concave holes are provided on the metal foil. The diameter of the concave holes is ≤20 μm, the total area of the concave holes accounts for 25% or less of the total area of the metal foil, and the water contact angle of the metal foil is ≤5°.

2. The high specific surface area current collector according to claim 1, characterized in that, The surface energy of the metal foil is as follows: When 2 mol of deionized water drops on the metal foil, the diffusion speed of the water drops is ≥20 mm / 5S.

3. The high specific surface area current collector according to claim 1, characterized in that The diameter of the concave holes is ≤10 μm.

4. The high specific surface area current collector according to claim 1, wherein, The metal foil is copper foil or aluminum foil; And / or, the thickness of the metal foil is 10 - 30 μm.

5. A preparation method of a high specific surface area current collector according to any one of claims 1 to 4, characterized in that, It includes the following steps: S1. Provide a smooth metal foil. S2. Treat the smooth metal foil by using two high-energy physical discharge processes to obtain a semi-finished metal foil. S3. Sequentially perform hot acid treatment, cleaning, and drying on the semi-finished metal foil to obtain a high specific surface area metal foil. The specific surface area of the high specific surface area metal foil is 10% or more larger than that of the smooth metal foil, and the tensile strength of the high specific surface area metal foil is 3% or less less than that of the smooth metal foil.

6. The preparation method of the high specific surface area current collector according to claim 5, wherein In step S2, the method of treating the smooth metal foil by using two high-energy physical discharge processes includes: Using two lasers to irradiate the smooth metal foil to form multiple concave holes on the smooth metal foil.

7. The preparation method of the high specific surface area current collector according to claim 6, characterized in that, The method of using two lasers to irradiate the smooth metal foil includes: Performing laser drilling on the smooth metal foil by using a dot laser to form the concave holes; Performing laser ablation on the smooth metal foil by using a line laser to remove the oxide layer, oil stain, and debris generated by laser drilling on the smooth metal foil.

8. The preparation method of the high specific surface area current collector according to claim 5, characterized in that, In step S3, the method of performing hot acid treatment on the semi-finished metal foil includes: Immersing the semi-finished metal foil in a pickling tank. The pickling solution in the pickling tank includes HF and H2SO4, and the temperature of the pickling solution is 40 - 50 °C.

9. An electrode sheet, characterized in that, It includes a current collector and an electrode material, and the current collector is the high specific surface area current collector according to any one of claims 1 - 4.

10. A battery, characterized in that, It includes the electrode sheet according to claim 9.

Images