Coated carbon current collector with controllable coating structure, preparation method thereof and secondary battery

Abstract

The application provides a carbon-coated current collector with controllable coating structure, a preparation method of the carbon-coated current collector and a secondary battery, and the preparation method comprises the following steps: adopting a laser to ablate a carbon coating of the carbon-coated current collector, so as to obtain the carbon-coated current collector with controllable structure. The carbon coating is ablated by the laser, so that nanoscale processing of the coating can be realized, the thickness and the surface density of the carbon coating can be reduced, the thinning processing and the structure design of the carbon coating can be realized, and the carbon coating can be used in a wide range.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a carbon-coated current collector with controllable coating structure, its preparation method, and a secondary battery. Background Technology

[0002] In traditional lithium-ion battery electrode manufacturing processes, active material slurry is directly coated onto the surface of a base foil current collector. After drying, an adhesive is used to fix the active material onto the base foil current collector surface, and then positive and negative electrodes are fabricated. However, conventional base foils have the following problems: ① The contact area between the conventional base foil metal current collector and the active material particles is limited, resulting in a relatively high interfacial resistance; ② The adhesive strength of the adhesive is limited, and during continuous charging and discharging, the active material is prone to expansion and detachment from the current collector, leading to a further increase in the battery's internal resistance and affecting the battery's cycle life and safety performance; ③ Due to the processing technology of the foil, the surface roughness of conventional base foil metal current collectors, especially aluminum foil current collectors, is limited. Residual oil from additives added during rolling results in high interfacial tension, making it difficult to wet the electrode material coating, leading to missed coatings, uneven coating, and high processing difficulty, which affects the battery's electrical performance.

[0003] To address the aforementioned problems, carbon-coated current collectors have been developed. Carbon-coated current collectors are produced by uniformly coating a conductive carbon slurry onto the surface of a base foil, then drying and winding it up. After coating with electrode materials, positive and negative electrodes can be fabricated. The existing process route for carbon-coated current collectors is basically as follows: slurry preparation (conductive agent slurry) – base foil coating and unwinding – corona treatment (or preheating oven) – traction mechanism – forward coating mechanism – first-layer oven – reverse coating mechanism – second-layer oven – traction mechanism – winding – slitting (rewinding) – packaging.

[0004] Currently, carbon coating mainly employs gravure coating technology, where a conductive agent slurry is coated onto the surface of a base foil, followed by drying and curing. However, existing carbon coating technologies still have the following shortcomings: ① The current coating level for carbon current collectors can only achieve a thickness of 0.5 μm and a basis weight of 0.2 g / m³. 2① Gravure coating technology is no longer sufficient to achieve the required precision coating structure; ② With the pursuit of thinner coating thickness, surface density, and conductivity without degradation, existing gravure coating technology will result in incomplete coating if the coating is to be thinned, leading to insufficient production difficulty and processing precision; ③ Gravure coating technology uses laser or electro-engraving processes to prepare gravure rollers. To achieve thinner coatings, the number of engraving lines will increase, and the depth of the engraved cells will be shallower. Higher line counts and shallower cells will reduce the lifespan of the printing roller, resulting in increased production costs; ④ As the coating thickness decreases, the microstructure of the gravure coating will be affected by the mesh walls, resulting in uneven coating, reducing the uniformity of contact with the battery electrodes, and reducing the conductivity of the coating; ⑤ The coating structure of gravure coating technology is mainly controlled by the mesh structure of the gravure roller and the self-leveling effect of the slurry during processing. The control capability is poor, making further fine processing impossible; ⑥ Due to inconsistent customer needs and the diversification of product types, the coating width of gravure coating technology requires printing rollers to be customized according to different product size requirements, making the printing rollers non-universal.

[0005] Therefore, there is an urgent need to provide a method to improve the processing accuracy and uniformity of carbon coatings, avoid missed coating, and be widely applicable without being limited by coating components such as gravure rollers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a carbon-coated current collector with controllable coating structure, its preparation method, and a secondary battery. This invention utilizes laser ablation to treat the carbon coating, achieving nanoscale coating processing. This improves the processing precision and uniformity of the carbon coating, effectively reducing its thickness and areal density, enabling thinning and structural design of the carbon coating. Simultaneously, the laser can completely ablate and peel off the coating at specific locations as needed, allowing for universal printing roller compatibility without altering the roller's structure and dimensions, preventing missed coating, and broadening its application range.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a carbon-coated current collector with controllable coating structure, the preparation method comprising:

[0009] A carbon coating on a carbon-coated current collector is ablated using a laser to obtain a carbon-coated current collector with controllable structure.

[0010] It should be noted that the carbon-coated current collector includes a base foil and a carbon coating applied to at least one surface of the base foil. "At least one side" can mean, for example, one side or both sides. The present invention does not limit the type of base foil; for example, it can be aluminum foil.

[0011] This invention provides a method for preparing a carbon-coated current collector with controllable coating structure, which has the following advantages:

[0012] (1) Using laser to ablate carbon coating can achieve nanoscale processing of the coating, which can improve the processing accuracy and uniformity of carbon coating, and can also effectively reduce the thickness and surface density of carbon coating, thereby achieving thinning treatment and structural design of carbon coating, which can improve the energy density and cycle life of battery.

[0013] (2) The carbon coating structure can be designed according to requirements, which can increase the contact area between the carbon coating and the electrode active material, improve the adhesion between the active material and the current collector, and reduce the manufacturing cost of the electrode sheet.

[0014] (3) The laser can completely ablate and peel off the coating at the corresponding position according to the requirements, realize the universality of the printing roller, without changing the structure and size of the printing roller, and there will be no missed coating. It has a wide range of applications.

[0015] (4) The carbon coating after laser ablation can protect the current collector from being corroded by the electrolyte;

[0016] (5) The carbon-coated current collector after laser ablation can reduce the internal resistance of the battery and significantly reduce the increase in dynamic internal resistance during cycling.

[0017] (6) Laser ablation technology can improve the consistency of carbon-coated current collectors and increase the cycle life of batteries;

[0018] (7) The carbon-coated current collector after laser ablation can suppress battery polarization, reduce thermal effects, and improve rate performance.

[0019] Preferably, the method for preparing the carbon-coated current collector includes: roughening the surface of the base foil using a laser, then coating the treated base foil surface with a carbon-containing slurry, and baking to obtain the carbon-coated current collector.

[0020] Current coating technologies mainly use methods such as corona treatment to treat residual oil in current collectors (such as aluminum foil). The corona process generates a large amount of ozone, and ozone at a certain concentration is harmful to humans and the environment.

[0021] This application preferably uses laser to roughen the surface of the base foil. During this process, the oil on the surface of the base foil is also removed, and no harmful components such as ozone are generated.

[0022] Preferably, the carbon coating comprises carbon and a polymeric binder.

[0023] In this invention, the mechanism of laser ablation of carbon coatings (including carbon and polymer binders) is as follows: When the laser sweeps across the carbon coating, the carbon itself remains unchanged. A portion of the polymer binder in the coating directly vaporizes, while another portion melts. The carbon at the vaporized binder moves towards the base foil and recombines with the melted binder, adhering to the surface near the foil. Simultaneously, when the laser sweeps across the carbon coating, both the binder and carbon absorb energy, resulting in a gradual decrease in laser energy along the direction closer to the foil surface. Combining these two factors, after the laser sweeps across the carbon coating, a groove wider at the top and narrower at the bottom is formed in the thickness direction of the carbon coating, achieving the purpose of thinning the carbon coating and controlling its structure. This facilitates close contact between the carbon-coated current collector and the electrode active material.

[0024] Preferably, the particle size D50 of the carbon is 30-500 nm.

[0025] In this invention, the carbon particles are contained across the entire size range of 30-500nm. The relatively concentrated particle size distribution makes them difficult to densely pack together, hindering laser ablation and structural control. This leads to the accumulation of voids and, during ablation, large-area breakage and detachment. This is due to the principle of close-packed microparticles; the more dispersed the particle size, the denser the packing. Compared to single-size particles, gaps form between particles, creating cavities during ablation and causing collapse.

[0026] Preferably, the carbon includes at least one of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers.

[0027] Preferably, the polymeric binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylic acid.

[0028] Preferably, the polymeric binder has a mass fraction of 4-80% based on the total mass of the carbon coating (100%), for example, it can be 4%, 8%, 15%, 30%, 45%, 50%, or 70%.

[0029] Preferably, the thickness of the carbon coating is 0.5-2μm, for example, it can be 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.6μm or 1.8μm.

[0030] Preferably, the surface density of the carbon coating is 0.3-0.4 g / m². 2 For example, it could be 0.3g / m 2 0.32 g / m², 0.34 g / m² 2 0.35g / m 2 0.38g / m 2 or 0.4g / m 2 wait.

[0031] Preferably, the laser includes a picosecond laser.

[0032] Preferably, the power of the picosecond laser is 300-450W, for example, it can be 300W, 320W, 350W, 380W, 400W, 420W or 450W, etc., preferably 380W.

[0033] In this invention, if the power of the femtosecond laser is too low, the ablation ability is insufficient, and it is impossible to accurately control the structure of the coating and reduce its thickness through ablation; if the power of the femtosecond laser is too high, the ablation ability is uncontrollable, which can easily cause excessive ablation of the coating, damage the foil, and form pinholes.

[0034] Preferably, the wavelength of the picosecond laser is 800-1200nm, for example, it can be 800nm, 900nm, 1000nm, 1100nm or 1200nm.

[0035] Preferably, the pulse frequency of the picosecond laser is 100-150MHz, for example, it can be 100MHz, 110MHz, 120MHz, 130MHz, 140MHz or 150MHz, etc., preferably 120MHz.

[0036] Preferably, the laser scanning speed of the picosecond laser is 200-400 mm / s, for example, it can be 200 mm / s, 220 mm / s, 250 mm / s, 280 mm / s, 300 mm / s, 350 mm / s or 380 mm / s, etc., and preferably 320 mm / s.

[0037] As a preferred technical solution of the present invention, the method for preparing the carbon-coated current collector with controllable coating structure specifically includes the following steps:

[0038] A1. Unwind;

[0039] A2. Laser surface treatment: The surface of the base foil is roughened using a laser, and then the thickness of the base foil after treatment is measured using a thickness measuring laser device; the thickness measurement data of the base foil is then transmitted to the CNC host system.

[0040] A3. Front coating: Applying carbon-containing paste to the front side of the treated base foil;

[0041] A4. Baking of the front coating: Baking the current collector that has been coated on the front side;

[0042] A5. Laser ablation thinning / structural design (front coating): The CNC host system performs a thinning closed loop based on the thickness measurement feedback data, and controls the laser to perform thinning and / or structural design on the front coating of the baked current collector according to the CNC programming structural design.

[0043] A6. Reverse coating: Applying carbon-containing slurry to the reverse side of the current collector that has already been coated on the front side;

[0044] A7. Baking the reverse-coated surface: Baking the current collector that has been coated on the reverse side;

[0045] A8. Laser ablation thinning / structural design (reverse coating): The CNC host system performs a thinning closed loop based on the thickness measurement feedback data, and controls the laser to perform thinning and / or structural design on the reverse coating of the baked current collector according to the CNC programming structural design.

[0046] A9. Collect the roll.

[0047] Optionally, the present invention provides the device components required for the above preferred technical solution, as shown below:

[0048] Unwinding: includes a frame and a three-phase braked geared motor, an air shaft, a coating substrate, a roller, a tension detection device, an unwinding correction device, and a control circuit mounted on the frame;

[0049] Thickness measurement laser module: includes laser thickness measurement photoelectric probe, laser ablation treatment device, data acquisition encoder, control circuit and data acquisition line;

[0050] CNC host system: The program instructions input to the control part by a dedicated control computer are recorded on an information carrier and received by a program reading device, or can be directly manually input by the keyboard of the control part. It can realize data input decoding and analysis, coating structure design model establishment or coating thinning depth control instructions.

[0051] Front coating: includes material box, feeding system, glue roller, gravure roller, high-precision servo motor, doctor blade device and pressure sensor;

[0052] Baking of the front coating: including heating pack, fresh air control system, exhaust air control system, return air control system, waste heat recovery system, transmission rollers, oven cavity and temperature and air frequency control circuit;

[0053] Frontal laser ablation device module: including data transmission lines, picosecond laser ablation device, drive motor, multi-track motion module, heat dissipation system and carbon powder negative pressure adsorption device;

[0054] Reverse coating: Same as front coating;

[0055] Baking of the reverse coating side: Same as baking of the front coating side;

[0056] Reverse laser ablation device module: Same as the front laser ablation device module;

[0057] Rewinding: includes a frame and a three-phase braked geared motor, an air shaft, a coating substrate, a roller, a tension detection device, a winding roll correction micro-oscillation device, and a control circuit mounted on the frame.

[0058] In a second aspect, the present invention provides a carbon-coated current collector with controllable coating structure, wherein the carbon-coated current collector with controllable coating structure is prepared by the preparation method described in the first aspect.

[0059] In this invention, the carbon coating structure of the carbon-coated current collector can be, for example, equidistant tetrahedrons, equidistant hexahedrons, equidistant octahedrons, or closely arranged horizontal and vertical lines.

[0060] Thirdly, the present invention provides a secondary battery, wherein the electrodes of the secondary battery include a carbon-coated current collector with a controllable coating structure as described in the second aspect.

[0061] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0062] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0063] This invention provides a method for preparing a carbon-coated current collector with controllable coating structure, which has the following advantages:

[0064] (1) Using laser to ablate carbon coating can achieve nanoscale processing of the coating, which can improve the processing accuracy and uniformity of carbon coating, and can also effectively reduce the thickness and surface density of carbon coating, thereby achieving thinning treatment and structural design of carbon coating, which can improve the energy density and cycle life of battery.

[0065] (2) The carbon coating structure can be designed according to requirements, which can increase the contact area between the carbon coating and the electrode active material, improve the adhesion between the active material and the current collector, and reduce the manufacturing cost of the electrode sheet.

[0066] (3) The laser can completely ablate and peel off the coating at the corresponding position according to the requirements, realize the universality of the printing roller, without changing the structure and size of the printing roller, and there will be no missed coating. It has a wide range of applications.

[0067] (4) The carbon coating after laser ablation can protect the current collector from being corroded by the electrolyte;

[0068] (5) The carbon-coated current collector after laser ablation can reduce the internal resistance of the battery and significantly reduce the increase in dynamic internal resistance during cycling.

[0069] (6) Laser ablation technology can improve the consistency of carbon-coated current collectors and increase the cycle life of batteries;

[0070] (7) The carbon-coated current collector after laser ablation can suppress battery polarization, reduce thermal effects, and improve rate performance. Attached Figure Description

[0071] Figure 1 A schematic flowchart illustrating the preparation method of carbon-coated current collectors provided for a specific embodiment of the present invention.

[0072] Figure 2 This is a microstructure diagram of the carbon-coated current collector after ablation and thinning provided in Embodiment 1 of the present invention.

[0073] Figure 3 This is a microstructure diagram of the carbon-coated current collector provided in Comparative Example 1 of the present invention.

[0074] Figure 4 This is a top view schematic diagram of a carbon coating with a tetrahedral structure provided in Embodiment 6 of the present invention.

[0075] Figure 5 This is a schematic cross-sectional view of the carbon-coated current collector after ablation provided in Embodiment 6 of the present invention.

[0076] Figure 6 This is a top view schematic diagram of the carbon coating of the carbon current collector provided in Comparative Example 3 of the present invention.

[0077] Figure 7 This is a schematic cross-sectional view of the carbon-coated current collector provided in Comparative Example 3 of the present invention. Detailed Implementation

[0078] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0079] In one embodiment, the present invention provides a method for preparing a carbon-coated current collector with controllable coating structure, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0080] A1. Unwind;

[0081] A2. Laser surface treatment: The surface of the base foil is roughened using a laser, and then the thickness of the base foil after treatment is measured using a thickness measuring laser device; the thickness measurement data of the base foil is then transmitted to the CNC host system.

[0082] A3. Front coating: Applying carbon-containing paste to the front side of the treated base foil;

[0083] A4. Baking of the front coating: Baking the current collector that has been coated on the front side;

[0084] A5. Laser ablation thinning / structural design (front coating): The CNC host system performs a thinning closed loop based on the thickness measurement feedback data, and controls the laser to perform thinning and / or structural design on the front coating of the baked current collector according to the CNC programming structural design.

[0085] A6. Reverse coating: Applying carbon-containing slurry to the reverse side of the current collector that has already been coated on the front side;

[0086] A7. Baking the reverse-coated surface: Baking the current collector that has been coated on the reverse side;

[0087] A8. Laser ablation thinning / structural design (reverse coating): The CNC host system performs a thinning closed loop based on the thickness measurement feedback data, and controls the laser to perform thinning and / or structural design on the reverse coating of the baked current collector according to the CNC programming structural design.

[0088] A9. Collect the roll.

[0089] Example 1

[0090] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0091] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing slurry is then coated onto the surface of the aluminum foil, and after baking, a carbon-coated current collector is obtained. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyvinylidene fluoride (polyvinylidene fluoride) (a polymeric binder). The particle size D50 of the carbon is 50 nm, and the mass fraction of polyvinylidene fluoride is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5 μm, and the surface density of the carbon coating on one side is 0.3 g / m². 2 ;

[0092] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 420W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 320mm / s. The microstructure of the thinned carbon-coated current collector is shown below. Figure 2 As shown.

[0093] Example 2

[0094] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0095] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing slurry is then coated onto the surface of the aluminum foil, and after baking, a carbon-coated current collector is obtained. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyvinylidene fluoride (polyvinylidene fluoride) (a polymeric binder). The particle size D50 of the carbon is 50 nm, and the mass fraction of polyvinylidene fluoride is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5 μm, and the surface density of the carbon coating on one side is 0.3 g / m². 2 ;

[0096] (2) The carbon coatings on both sides are ablated and thinned by picosecond laser. The power of the picosecond laser is 400W, the wavelength of the picosecond laser is 800-1200nm, the pulse frequency of the picosecond laser is 120MHz, and the laser scanning speed of the picosecond laser is 320mm / s.

[0097] Example 3

[0098] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0099] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing slurry is then coated onto the surface of the aluminum foil, and after baking, a carbon-coated current collector is obtained. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyvinylidene fluoride (polyvinylidene fluoride) (a polymeric binder). The particle size D50 of the carbon is 50 nm, and the mass fraction of polyvinylidene fluoride is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5 μm, and the surface density of the carbon coating on one side is 0.3 g / m². 2 ;

[0100] (2) The carbon coatings on both sides are ablated and thinned by picosecond laser. The power of the picosecond laser is 380W, the wavelength of the picosecond laser is 800-1200nm, the pulse frequency of the picosecond laser is 120MHz, and the laser scanning speed of the picosecond laser is 320mm / s.

[0101] Example 4

[0102] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0103] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing slurry is then coated onto the surface of the aluminum foil, and after baking, a carbon-coated current collector is obtained. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyvinylidene fluoride (polyvinylidene fluoride) (a polymeric binder). The particle size D50 of the carbon is 50 nm, and the mass fraction of polyvinylidene fluoride is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5 μm, and the surface density of the carbon coating on one side is 0.3 g / m². 2 ;

[0104] (2) The carbon coatings on both sides are ablated and thinned by picosecond laser. The power of the picosecond laser is 360W, the wavelength of the picosecond laser is 800-1200nm, the pulse frequency of the picosecond laser is 120MHz, and the laser scanning speed of the picosecond laser is 320mm / s.

[0105] Example 5

[0106] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0107] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing slurry is then coated onto the surface of the aluminum foil, and after baking, a carbon-coated current collector is obtained. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyvinylidene fluoride (polyvinylidene fluoride) (a polymeric binder). The particle size D50 of the carbon is 50 nm, and the mass fraction of polyvinylidene fluoride is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5 μm, and the surface density of the carbon coating on one side is 0.3 g / m². 2 ;

[0108] (2) The carbon coatings on both sides are ablated and thinned by picosecond laser. The power of the picosecond laser is 340W, the wavelength of the picosecond laser is 800-1200nm, the pulse frequency of the picosecond laser is 120MHz, and the laser scanning speed of the picosecond laser is 320mm / s.

[0109] Comparative Example 1

[0110] This comparative example provides a carbon-coated current collector, which is exactly the same as that of Example 1.

[0111] The microstructure of the carbon-coated current collector in Comparative Example 1 is as follows: Figure 3 As shown, the microstructure of the carbon-coated current collector after thinning in Comparative Example 1 is ( Figure 2 It can be seen that the method of the present invention can make the coating uniform and regular, while the carbon coating that has not undergone ablation treatment has poor uniformity.

[0112] Comparative Example 2

[0113] This comparative example provides a current collector, namely aluminum foil, which is exactly the same as the aluminum foil provided in Example 1.

[0114] test

[0115] The current collectors obtained in Examples 1-5 and Comparative Examples 1-2 were tested, specifically including:

[0116] (1) Thickness test:

[0117] The thickness of the carbon coating on one side was measured using a Malcolm thickness gauge.

[0118] (2) Single-sided surface density test

[0119] The surface density of a single surface is calculated by weighing with an electronic analytical balance and dividing the mass by the area per unit area.

[0120] (3) Carbon coating coverage test

[0121] The coating coverage is detected by taking pictures using a CCD (charge-coupled device) camera.

[0122] (4) Surface roughness test of carbon coating

[0123] The surface height difference was scanned using a scanning electron microscope (SEM), and the maximum height difference between the two sides of the coating was used as the value characterizing the surface roughness.

[0124] The test results are shown in Table 1.

[0125] Table 1

[0126]

[0127] Example 6

[0128] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0129] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0130] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 380W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 320mm / s. After ablation, the structure of the carbon coating on each side consisted of 10nm equidistant tetrahedrons (1 / 2), as shown below. Figure 4 and Figure 5 As shown.

[0131] Example 7

[0132] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0133] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0134] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 380W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 360mm / s. After ablation, the structure of the carbon coating on each side was a 10nm equidistant hexahedron (1 / 2).

[0135] Example 8

[0136] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0137] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0138] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 380W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 400mm / s. After ablation, the structure of the carbon coating on each side consisted of 10nm equidistant octahedrons (1 / 2).

[0139] Example 9

[0140] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0141] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0142] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 420W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 320mm / s. After ablation, the carbon coating on each side had a structure of closely spaced horizontal and vertical lines with a spacing of 15nm and an ablation depth of 20nm.

[0143] Example 10

[0144] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0145] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0146] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 420W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 350mm / s. After ablation, the carbon coating on each side had a structure of closely spaced horizontal and vertical lines with a spacing of 10nm and an ablation depth of 20nm.

[0147] Example 11

[0148] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0149] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0150] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 380W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 350mm / s. After ablation, the carbon coating on each side had a structure of closely spaced horizontal and vertical lines with a spacing of 10nm and an ablation depth of 10nm.

[0151] Example 12

[0152] This embodiment provides a method for preparing a carbon-coated current collector with controllable coating structure, including the following steps:

[0153] (1) The surface of the aluminum foil is roughened using a 1000W laser. A carbon-containing paste is then coated onto the surface of the aluminum foil and baked to obtain a carbon-coated current collector. The carbon-coated current collector includes an aluminum foil and carbon coatings applied to both sides of the aluminum foil. The carbon coatings on both sides have the same parameters. The carbon coating contains carbon and polyacrylic acid (a polymeric binder). The particle size D50 of the carbon is 60nm, and the mass fraction of the polyacrylic acid is 30% (based on the total mass of the carbon coating being 100%). The thickness of the carbon coating on one side is 0.5μm, and the surface density of the carbon coating on one side is 0.3g / m³. 2 ;

[0154] (2) Picosecond lasers were used to ablate and thin the carbon coatings on both sides. The picosecond laser had a power of 380W, a wavelength of 800-1200nm, a pulse frequency of 120MHz, and a laser scanning speed of 380mm / s. After ablation, the structure of the carbon coating on each side consisted of closely spaced horizontal and vertical lines with a spacing of 5nm and an ablation depth of 10nm.

[0155] Example 13

[0156] The difference between this embodiment and embodiment 10 is that the power of the picosecond laser is adjusted to 280W, while the other parameters are completely the same as those in embodiment 10.

[0157] Example 14

[0158] The difference between this embodiment and embodiment 10 is that the power of the picosecond laser is adjusted to 480W, while the other parameters are completely the same as those in embodiment 10.

[0159] Comparative Example 3

[0160] This comparative example provides a carbon-coated current collector, which is exactly the same as that of Example 6.

[0161] The carbon coating structure of the carbon-coated current collector in Comparative Example 3 is as follows: Figure 6 and Figure 7 As shown, the carbon coating structure of the carbon-coated current collector in Comparative Example 6 is shown. Figure 4 and Figure 5 It can be seen that the method of the present invention can control the coating structure and thickness, and can precisely control the coating, while the carbon coating that has not undergone ablation treatment is irregular.

[0162] Comparative Example 4

[0163] This comparative example provides a current collector, namely aluminum foil, which is exactly the same as the aluminum foil provided in Example 6.

[0164] test

[0165] The current collectors obtained in Examples 6-12 and Comparative Examples 3-4 were tested, specifically including:

[0166] (1) Adhesion test between current collector and active material layer:

[0167] The coating adhesion was tested according to the test method for peel strength of adhesive tape in GB / T 2792-2014.

[0168] (2) Interface resistivity test:

[0169] Resistance was tested using a HPS2523 four-probe sheet resistance tester.

[0170] The test results are shown in Table 2.

[0171] Table 2

[0172]

[0173] Performance testing

[0174] The positive electrode slurry was coated onto the current collectors provided in Examples 1-14 and Comparative Examples 1-4, respectively. After baking, the positive electrode sheet was obtained and then assembled with a separator and a graphite negative electrode to form a lithium-ion battery. The positive electrode slurry included lithium iron phosphate, acetylene black, polyvinylidene fluoride, and N-methylpyrrolidone. The electrolyte used was commercial LiPF6 electrolyte. The performance of the assembled lithium-ion battery was tested.

[0175] (1) Cyclic performance test

[0176] Record the battery capacity retention rate after 500 cycles of 1C / 1C charge / discharge.

[0177] (2) Ratio Performance Test

[0178] a. Charge the lithium-ion battery at a constant current of 1C until the lithium battery charging termination voltage, then switch to constant voltage charging until the charging current drops to 0.05C, at which point charging stops.

[0179] b. At room temperature, the lithium battery is discharged at a current of 10C until the battery discharges to the discharge termination voltage, and the discharge capacity is recorded; calculate the ratio of the above discharge capacity to the discharge capacity at the rated 1C.

[0180] The test results are shown in Table 3.

[0181] Table 3

[0182]

[0183]

[0184] analyze:

[0185] Based on the data in Table 1, it can be seen from Examples 1-5 that laser ablation and thinning of the carbon coating can achieve nanoscale processing of the coating, effectively reducing the thickness and areal density of the carbon coating. Furthermore, the thinned carbon coating still achieves 100% coverage, and its higher roughness facilitates close contact with the active material layer. Compared to Comparative Example 1, the conventional carbon-coated current collector is thicker, has a higher areal density on one side, which affects the energy density of the battery, and cannot achieve 100% carbon coating coverage (only 98%), with lower carbon coating roughness. Compared to Comparative Example 2, the current collector without a carbon coating has lower surface roughness.

[0186] Based on the data in Table 2, as can be seen from Examples 6-12, laser ablation of the carbon coating allows for the design of various structures, achieving nanoscale processing of the carbon coating with high processing precision. It can increase the contact area between the carbon coating and the electrode active material, resulting in higher adhesion between the carbon-coated current collector and the active material layer, reducing electrode manufacturing costs, and lowering interfacial resistance. Examples 10 and 13-14 show that if the femtosecond laser power is too low, the ablation ability is insufficient, making precise control of the coating structure and thickness reduction impossible; if the femtosecond laser power is too high, the ablation ability is uncontrollable, easily causing excessive coating ablation, damaging the foil and forming pinholes. Examples 6 and Comparative Examples 3-4 show that using conventional carbon-coated current collectors or simple aluminum foil leads to a decrease in adhesion between the current collector and the active material layer, and an increase in interfacial resistivity.

[0187] Based on the data in Table 3, it can be seen from Examples 1-12 that laser ablation of the carbon coating allows for thinning and various structural designs, exhibiting excellent cycle performance and rate performance when applied to lithium batteries. Examples 10 and 13-14 show that both excessively low and excessively high femtosecond laser power lead to a decrease in battery cycle performance and rate performance. Examples 1, 6, and Comparative Examples 1-4 demonstrate that using conventional carbon-coated current collectors or simple aluminum foil results in poor battery cycle performance and rate performance.

[0188] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a carbon-coated current collector with controllable coating structure, characterized in that, The preparation method includes: The surface of the base foil is roughened by laser treatment, and then a carbon-containing slurry is coated on the treated base foil surface. After baking, a carbon coating is formed on the base foil surface to obtain the carbon-coated current collector; the carbon coating includes carbon and a polymer binder. A laser is used to ablate the carbon coating of the carbon-coated current collector. When the laser sweeps across the carbon coating, a groove that is wider at the top and narrower at the bottom is formed in the thickness direction of the carbon coating, resulting in a carbon-coated current collector with controllable structure. This increases the contact area between the carbon coating and the electrode active material, and improves the adhesion between the active material and the current collector.

2. The preparation method according to claim 1, characterized in that, The particle size D50 of the carbon is 30-500 nm.

3. The preparation method according to claim 1, characterized in that, The polymeric binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylic acid.

4. The preparation method according to claim 1, characterized in that, With the total mass of the carbon coating being 100%, the mass fraction of the polymer binder is 4-80%.

5. The preparation method according to claim 1, characterized in that, The thickness of the carbon coating is 0.5-2 mm. m.

6. The preparation method according to claim 1, characterized in that, The surface density of the carbon coating is 0.3-0.4 g / m³. 2 .

7. The preparation method according to claim 1, characterized in that, The laser includes a picosecond laser.

8. The preparation method according to claim 7, characterized in that, The power of the picosecond laser is 300-450W.

9. The preparation method according to claim 7, characterized in that, The wavelength of the picosecond laser is 800-1200nm.

10. The preparation method according to claim 7, characterized in that, The picosecond laser has a pulse frequency of 100-150MHz.

11. The preparation method according to claim 7, characterized in that, The scanning speed of the picosecond laser is 200-400 mm / s.

12. A carbon-coated current collector with controllable coating structure, characterized in that, The carbon-coated current collector with controllable coating structure is prepared by the preparation method according to any one of claims 1-11.

13. A secondary battery, characterized in that, The electrodes of the secondary battery include a carbon-coated current collector with a controllable coating structure as described in claim 12.

Images