A functional set fluid and its preparation method

Abstract

The present invention relates to the technical field of current collectors, and particularly relates to a functional current collector and a preparation method thereof. The preparation method of the functional current collector comprises the following steps: S1. depositing a metal layer on at least one surface of a base film by magnetron sputtering; S2. spraying an inorganic nanoparticle solution on the surface of the metal layer to obtain a semi-finished product; S3. drying the semi-finished product to obtain the functional current collector. In the preparation process of the functional current collector of the present invention, by spraying an inorganic nanoparticle solution on the surface of the metal layer, stress can be effectively released from aspects such as microstructure and interfacial properties, reducing the overall stress level of the functional current collector, thereby achieving the purpose of reducing the residual stress of the functional current collector and improving the stability and mechanical strength of the functional current collector.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors, and particularly relates to a functional current collector and a preparation method thereof. Background Art

[0002] With the rapid development of new energy and electronic technologies, higher requirements are put forward for the cycle life, safety performance, and energy density of batteries. As a very important part of the battery, the current collector is used to collect the current generated by the active substances in the battery to form a larger current for external output, and its performance directly affects the cycle life, energy density, safety performance, etc. of the battery.

[0003] At present, copper foils and aluminum foils are mostly used as current collectors for the positive and negative electrode plates in batteries. Such current collectors have high costs and weights, which are not conducive to the control of battery costs and the improvement of energy density. Compared with using traditional foil materials as current collectors, composite foil materials are significantly more advantageous. The composite foil current collector is usually a "sandwich" structure, with a polymer polymer layer in the inner layer and metal conductive layers on both sides. Due to the relatively thin metal layer on the surface and the relatively light polymer layer inside the functional current collector, it can well reduce the overall weight of the functional current collector, thereby improving the energy density of the battery. At the same time, the relatively thin metal layer on the surface of the functional current collector is more likely to break during thermal runaway of the battery than the traditional foil current collector, thereby isolating the connection between the active substances and the current collector and preventing the continuous progress of battery thermal runaway.

[0004] Although the functional current collector has the advantages of low cost and light weight, in the current process of manufacturing the functional current collector, especially during the process of preparing the metal layer by magnetron sputtering, residual stress is easily generated. The residual stress will cause stress deformation of the film after electroplating, increasing the risk of metal layer peeling off, thereby deteriorating the performance of the battery. Summary of the Invention

[0005] In order to solve the problem that residual stress is easily generated during the magnetron sputtering process of the existing functional current collector and reduce the residual stress of the functional current collector, the present invention provides a functional current collector and a preparation method thereof.

[0006] According to the first aspect of the present invention, a preparation method of a functional current collector is provided, and the method includes the following steps:

[0007] S1. Depositing a metal layer on at least one surface of a base film by magnetron sputtering;

[0008] S2. Spraying an inorganic nanoparticle solution on the surface of the metal layer to obtain a semi-finished product;

[0009] S3. Drying the semi-finished product to obtain a functional current collector.

[0010] In the method for preparing the functional current collector provided by the present invention, a metal layer is deposited on the surface of the base film by magnetron sputtering, and then an inorganic nanoparticle solution is sprayed on the surface of the metal layer and dried to obtain the functional current collector. Since the inorganic nanoparticles have a high specific surface area and surface activity, during the process of spraying the inorganic nanoparticle solution on the surface of the metal layer, the inorganic nanoparticles contained therein can form good contact and interaction with the surface of the metal layer and change the microstructure of the metal layer, increasing the number of defects and dislocations on the surface of the metal layer. These defects and dislocations can serve as stress concentration points, enabling the stress of the functional current collector to be dispersed and released at these positions, thereby reducing the overall stress level of the functional current collector. Moreover, the interfacial bonding force between the inorganic nanoparticles and the metal layer is weak, and during the spraying process or when subjected to other external stresses, the inorganic nanoparticles are prone to minor sliding and deformation at the interface between them and the metal layer, which is beneficial for absorbing or releasing stress and can play a good buffering role. In summary, in the process of preparing the functional current collector of the present invention, by spraying the inorganic nanoparticle solution on the surface of the metal layer, stress can be effectively released from aspects such as microstructure and interfacial properties, thereby achieving the purpose of reducing the residual stress of the functional current collector and improving the stability and mechanical strength of the functional current collector.

[0011] Preferably, in S2, the inorganic nanoparticles in the inorganic nanoparticle solution include at least one of nano-silica, nano-alumina, nano-iron powder, and nano-nickel powder.

[0012] Preferably, in S2, the inorganic nanoparticles in the inorganic nanoparticle solution include at least one of nano-silica and nano-alumina.

[0013] Compared with nano-iron powder and nano-nickel powder, the nano-silica and nano-alumina used as the inorganic nanoparticles in the inorganic nanoparticle solution have more chemically inert properties, which can reduce the situation of oxidation during use or unnecessary chemical reactions with the metal layer that affect the performance of the functional current collector. Moreover, the nano-silica and nano-alumina have a higher specific surface area and surface activity, which is beneficial for enhancing the contact and interaction between the nano-silica, nano-alumina and the metal layer, and further improving the stress dispersion and release effect of the functional current collector.

[0014] Preferably, the particle size of the inorganic nanoparticles is 10 - 20 nm.

[0015] Inorganic nanoparticles with particle sizes within the above ranges have good dispersibility, moderate surface activity, as well as good penetration and filling capabilities. During the preparation process of the functional current collector, controlling the particle size of the inorganic nanoparticles used in the inorganic nanoparticle solution within the above ranges, firstly, can ensure the uniform distribution of the inorganic nanoparticles on the surface of the metal layer; secondly, can not only ensure that the inorganic nanoparticles effectively interact with the surface of the metal layer of the functional current collector to play the function of stress release, but also reduce the risk of instability or excessive reaction of the inorganic nanoparticles caused by excessive surface activity of the inorganic nanoparticles; thirdly, can penetrate into the microstructure of the functional current collector to a certain extent, fill the tiny voids therein, and enhance the overall structural stability and mechanical strength of the functional current collector.

[0016] If the particle size of the inorganic nanoparticles used in the inorganic nanoparticle solution is too small, during the preparation process of the functional current collector, the surface energy of the inorganic nanoparticles with too small particle sizes is too high, their stability in the solvent decreases, and they are prone to agglomeration or precipitation. Moreover, the too small particle size will cause the penetration depth of the inorganic nanoparticles in the functional current collector to be too large, thereby making it difficult for the inorganic nanoparticles to play the role of stress release on the metal layer; if the particle size of the inorganic nanoparticles used in the inorganic nanoparticle solution is too large, during the preparation process of the functional current collector, the dispersion performance of the inorganic nanoparticles with too large particle sizes in the organic solvent becomes poor, and they are prone to agglomeration in the solvent, resulting in a decrease in the uniformity of the inorganic nanoparticles, thereby affecting the distribution uniformity of the inorganic nanoparticles on the surface of the metal layer of the functional current collector and the effect of stress release. Additionally, the inorganic nanoparticles with too large particle sizes will affect the uniformity of the microstructure of the functional current collector, thereby affecting its overall performance.

[0017] Preferably, the material of the base film is selected from at least one of polyethylene terephthalate (PET) film, polypropylene (PP) film, and polyimide (PI) film.

[0018] Preferably, in S2, the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution is 5 - 15%.

[0019] During the preparation process of the functional current collector, controlling the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution within the above ranges can not only provide sufficient stress concentration points and defect numbers on the surface of the metal layer, enabling the residual stress generated during the preparation process of the functional current collector to be well dispersed and released, but also make the inorganic nanoparticles uniformly dispersed in the solution, so that the inorganic nanoparticles can be uniformly attached to the surface of the metal layer during the process of spraying the inorganic nanoparticle solution on the surface of the metal layer, thereby improving the residual stress release effect of the functional current collector.

[0020] If the mass fraction of inorganic nanoparticles in the inorganic nanoparticle solution is too low, firstly, the number of stress concentration points and defects provided by the inorganic nanoparticles will be insufficient, making it difficult to effectively disperse and release the stress generated by the functional current collector during the preparation process, thereby making it difficult to achieve the ideal stress release effect. Secondly, too few inorganic nanoparticles will make it difficult to fully change the microstructure of the functional current collector, so that its hindering effect on the regular arrangement of metal atoms in the metal layer of the functional current collector is not obvious, and its effect on reducing the accumulation of internal stress is limited, which leads to an unsatisfactory residual stress reduction effect of the functional current collector. If the mass fraction of inorganic nanoparticles in the inorganic nanoparticle solution is too high, firstly, it is easy to cause the nanoparticles to agglomerate in the solution, making it difficult to disperse evenly. The agglomerated inorganic nanoparticles are difficult to evenly cover the surface of the metal layer of the functional current collector, affecting the stress release effect of the functional current collector finally obtained. Secondly, too many inorganic nanoparticles will increase the viscosity of the inorganic nanoparticle solution, making it difficult to evenly adhere to the surface of the metal layer of the functional current collector during the spraying process, thereby leading to uneven local stress release of the functional current collector finally obtained.

[0021] Preferably, in S2, the solvent in the inorganic nanoparticle solution includes at least one of ethanol and acetone.

[0022] Compared with water or other organic solvents such as ethyl acetate or xylene, the inorganic nanoparticle solution used in the preparation process of the functional current collector uses ethanol and / or acetone as solvent. Ethanol and acetone have certain volatility but do not evaporate too quickly. In the process of spraying the inorganic nanoparticle solution with ethanol and / or acetone as solvent on the surface of the metal layer, the volatilization of the solvent will cause the inorganic nanoparticles to be evenly distributed on the surface of the metal layer. These evenly distributed inorganic nanoparticles can effectively hinder the regular arrangement of metal atoms in the metal layer and reduce the accumulation of internal stress.

[0023] If water is used as a solvent to prepare an inorganic nanoparticle solution, due to the large surface tension of water, it is difficult for the inorganic nanoparticles to be evenly distributed on the surface of the metal layer during the preparation of the functional current collector, resulting in agglomeration of the inorganic nanoparticles, making it difficult to effectively penetrate and cover the surface of the metal layer. In addition, water is a non-volatile solvent, and its residue in the functional layer will affect the electrochemical properties of the functional current collector and subsequent processing technology.

[0024] If ethyl acetate is used as a solvent to prepare an inorganic nanoparticle solution, due to the high volatility of ethyl acetate, the inorganic nanoparticles will aggregate together too quickly before the solvent completely evaporates during the preparation of the functional current collector, making it difficult for the inorganic nanoparticles to be evenly distributed on the surface of the metal layer. This will cause the action range of the inorganic nanoparticles to be reduced and uneven, making it difficult to effectively reduce the overall stress level of the final functional current collector.

[0025] If xylene is used as a solvent for preparing an inorganic nanoparticle solution, due to the weak volatility of xylene, it is difficult for inorganic nanoparticles to be promptly compounded and fixed on the surface of the metal layer during the preparation of the functional current collector, which affects the stress release effect of the functional current collector. Moreover, excessive xylene residue will affect the electrochemical performance of the functional current collector and have an adverse impact on the subsequent processing process.

[0026] Preferably, in S3, after drying the semi-finished product, it further includes the step of cleaning the dried semi-finished product with a cleaning solution; the cleaning solution contains a surfactant, and the surfactant includes fatty alcohol polyoxyethylene ether.

[0027] After spraying the inorganic nanoparticle solution on the surface of the metal layer and drying, the solvent in the inorganic nanoparticle solution will volatilize. After the inorganic nanoparticles play a stress release role on the metal layer and its surface, the inorganic nanoparticles attached to the metal layer are not necessary for the subsequent application process of the functional current collector. Excessive residual inorganic nanoparticles may affect the product performance of the functional current collector during actual application. In this solution, the dried semi-finished product is cleaned with a cleaning solution containing the surfactant fatty alcohol polyoxyethylene ether. The hydrophilic polyoxyethylene ether chain and the hydrophobic fatty alcohol chain in fatty alcohol polyoxyethylene ether interact with the inorganic nanoparticles and the metal layer, which can reduce the interfacial tension between the metal layer and the inorganic nanoparticles, reduce the adhesion of the inorganic nanoparticles, make the inorganic nanoparticles easy to detach from the metal layer and stably disperse in the cleaning solution, thereby achieving the purpose of removing the inorganic nanoparticles on the metal layer and its surface and ensuring the product performance of the finally prepared functional current collector during actual application.

[0028] Preferably, the conditions for the cleaning operation are as follows: time 10 - 20 s, temperature 20 - 25 °C.

[0029] Preferably, in S1, in the direction away from the base film, the metal layer includes a nickel-chromium alloy layer and a copper layer sequentially compounded.

[0030] During the preparation of the functional current collector, a nickel-chromium alloy layer is first compounded on the surface of the base film, and then a copper layer is compounded on the nickel-chromium alloy layer. Both the nickel-chromium alloy layer and the copper layer serve as the metal layer. By setting the nickel-chromium alloy layer as a connection between the base film and the copper layer, the nickel-chromium alloy layer has a higher affinity with the base film and higher molecular bond binding ability, which can improve the binding force between the base film and the copper layer, and thus improve the mechanical strength of the functional current collector.

[0031] Preferably, the thickness of the nickel-chromium alloy layer is 5 - 15 nm.

[0032] During the preparation of the functional integrated fluid, controlling the thickness of the nickel-chromium alloy layer used to connect the base film and the copper layer within this range is beneficial to ensuring good bonding strength between the copper layer and the base film. If the thickness of the nickel-chromium alloy layer is too small, it will be difficult to provide sufficient bonding strength, and the copper layer and the base film are likely to separate, thereby affecting the stability and reliability of the functional integrated fluid. If the thickness of the nickel-chromium alloy layer is too large, it will increase the resistance of the functional integrated fluid, reduce its electrical conductivity, and thus affect the charge-discharge efficiency and energy density of the battery using this functional integrated fluid.

[0033] According to the second aspect of the present invention, there is provided a functional integrated fluid, which is prepared by the preparation method of the above-mentioned functional integrated fluid.

[0034] The functional integrated fluid prepared by using the method provided by the present invention has the characteristics of low residual stress, high stability, and mechanical strength. Specific Embodiments

[0035] The technical features in the technical solutions provided by the present invention will be further clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Example 1

[0037] A functional integrated fluid is prepared through the following steps:

[0038] (1) Equipment Preparation

[0039] Prepare a high-vacuum winding magnetron sputtering equipment to ensure its normal operation, and at the same time prepare a hydroelectroplating line to ensure its normal operation;

[0040] (2) Target Preparation

[0041] Select nickel-chromium alloy and copper with a flat surface and no impurities as targets;

[0042] (3) Base Film Preparation

[0043] Select a PP film with a thickness of 4 μm and a flat and impurity-free surface as Base Film 1;

[0044] (4) Magnetron Sputtering

[0045] Start the magnetron sputtering equipment, deposit a nickel-chromium alloy layer with a thickness of 10 nm on both surfaces of the base film using nickel-chromium alloy as the target, and then deposit a copper layer with a thickness of 50 nm on the surface of the nickel-chromium alloy layer using copper as the target. The nickel-chromium alloy layer and the metal layer are collectively referred to as the metal layer;

[0046] (5) Hydroelectroplating

[0047] After the base film with a metal layer plated on its surface is loaded onto the electroplating machine, a basic electroplating solution is added, and the copper layer with a thickness of 50 nm obtained by magnetron sputtering is thickened to 1 μm using the hydroelectroplating process;

[0048] Among them, the basic electroplating solution contains copper acid medicine water and additives A / B;

[0049] The copper acid medicine water is purchased from Dongyouyue (Suzhou) Electronic Technology New Materials Co., Ltd. The copper acid medicine water contains hydrochloric acid, copper sulfate solution and sulfuric acid solution. The concentration of hydrochloric acid is 40 - 70 g / L, the concentration of copper sulfate solution is 70 - 130 g / L, and the concentration of sulfuric acid solution is 100 - 140 g / L;

[0050] The additives A / B are purchased from Suzhou Jerry Chemical Co., Ltd. Additive A is a leveling agent, and its specific components include tetrahydrothiazole thione, polyethyleneimine alkyl compound, fatty amine ethoxysulfonate, and sodium mercaptoimidazole propanesulfonate; Additive B is a brightening agent, and its specific components include sodium polydithiopropane sulfonate (SPS), sodium phenyl dithiopropane sulfonate (BSP), sodium mercaptoalkyl propane sulfonate (HP), and sodium polydimethylamide sulfonate;

[0051] (6) Preparation of the functional current collector

[0052] An inorganic nanoparticle solution is sprayed on the surface of the thickened copper layer to obtain a semi-finished product. After the semi-finished product is dried, the dried semi-finished product is cleaned with a cleaning solution at 23°C for 15 s, and then dried to obtain the functional current collector of this example;

[0053] The solvent used in the inorganic nanoparticle solution is ethanol. The inorganic nanoparticles used in the inorganic nanoparticle solution are nano-silica with a particle size of 15 nm, and the mass fraction of nano-silica in the inorganic nanoparticle solution is 10%;

[0054] The cleaning solution is prepared from surfactant fatty alcohol polyoxyethylene ether and water according to a mass ratio of 1:10.

[0055] Example 2

[0056] This example provides a functional current collector. Compared with Example 1, the difference in composition is that: in step (4) of the preparation of the functional current collector, the thickness of the nickel-chromium alloy layer is 5 nm; in step (6) of the preparation of the functional current collector, the particle size of the inorganic nanoparticles nano-silica used in the inorganic nanoparticle solution is 10 nm, and the mass fraction of nano-silica in the inorganic nanoparticle solution is 5%. Except for the above differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0057] Example 3

[0058] This example provides a functional current collector. Compared with Example 1, the difference in composition is as follows: in the preparation step (4) of the functional current collector, the thickness of the nickel-chromium alloy layer is 15 nm; in the preparation step (6) of the functional current collector, the inorganic nanoparticles used in the inorganic nanoparticle solution are nano-silica with a particle size of 20 nm, and the mass fraction of nano-silica in the inorganic nanoparticle solution is 15%. Except for the above differences, the materials, formulation ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0059] Example 4

[0060] This example provides a functional current collector. Compared with Example 1, the difference in composition is as follows: in the preparation step (6) of the functional current collector, the inorganic nanoparticles used in the inorganic nanoparticle solution are nano-aluminum oxide with a particle size of 15 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0061] Example 5

[0062] This example provides a functional current collector. Compared with Example 1, the difference in composition is as follows: in the preparation step (6) of the functional current collector, the inorganic nanoparticles used in the inorganic nanoparticle solution are nano-iron powder with a particle size of 15 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0063] Example 6

[0064] This example provides a functional current collector. Compared with Example 1, the difference in composition is as follows: in the preparation step (6) of the functional current collector, the inorganic nanoparticles used in the inorganic nanoparticle solution are nano-nickel powder with a particle size of 15 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0065] Example 7

[0066] This example provides a functional current collector. Compared with Example 1, the difference in composition is as follows: in the preparation step (6) of the functional current collector, the solvent used in the inorganic nanoparticle solution is acetone. Except for the above differences, the materials, formulation ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0067] Example 8

[0068] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the solvent used in the inorganic nanoparticle solution is water. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0069] Embodiment 9

[0070] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the solvent used in the inorganic nanoparticle solution is ethyl acetate. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0071] Embodiment 10

[0072] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the solvent used in the inorganic nanoparticle solution is xylene. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0073] Embodiment 11

[0074] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the mass fraction of nano-silica in the inorganic nanoparticle solution is 3%. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0075] Embodiment 12

[0076] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the mass fraction of nano-silica in the inorganic nanoparticle solution is 18%. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0077] Embodiment 13

[0078] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the particle size of the nano-silica used in the inorganic nanoparticle solution is 5 nm. Except for the above difference, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0079] Embodiment 14

[0080] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the particle size of the nano-silica used in the inorganic nanoparticle solution is 30 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0081] Example 15

[0082] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (4) of the functional current collector, the thickness of the nickel-chromium alloy layer is 3 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0083] Example 16

[0084] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (4) of the functional current collector, the thickness of the nickel-chromium alloy layer is 18 nm. Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0085] Example 17

[0086] This embodiment provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (4) of the functional current collector, the metal layer prepared by magnetron sputtering does not contain a nickel-chromium alloy layer. Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0087] Comparative Example 1

[0088] This comparative example provides a functional current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step (6) of the functional current collector, the operation of spraying the inorganic nanoparticle solution on the surface of the thickened copper layer is omitted. Except for the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly the same as those in Embodiment 1.

[0089] Test Example

[0090] 1. Test Subjects

[0091] In this test example, the functional current collectors prepared in Examples 1 to 17 and Comparative Example 1 were used as test subjects for relevant performance tests.

[0092] 2. Test Contents

[0093] (1) Tensile Strength, Elongation

[0094] a. Detection Equipment: Universal Material Testing Machine

[0095] b. Specimen preparation: Cut the functional current collector to obtain specimens, ensuring that the specimen surface is flat, without obvious oxidation and contamination.

[0096] c. Testing procedure: Install the specimen on the fixture of a universal material testing machine, ensuring that the fixture clamps the specimen and the specimen is in a vertical state without slipping or twisting during the test. Set the parameters of the testing machine; start the testing machine and conduct a tensile test on the specimen; the testing machine will record the force and displacement data during the tensile process in real time; as the tensile test progresses, the specimen will gradually elongate until it breaks, and record the maximum force value and the corresponding displacement at the time of fracture.

[0097] d. Calculation: Calculate the tensile strength and elongation rate according to the following formulas. Tensile strength = maximum force value / original cross-sectional area of the specimen; Elongation rate = (displacement at fracture - initial gauge length) / initial gauge length × 100%.

[0098] (2) Resistivity

[0099] a. Testing equipment: Four-probe resistivity tester

[0100] b. Specimen preparation: Cut the functional current collector to obtain specimens, ensuring that the specimen surface is flat, without obvious oxidation and contamination.

[0101] c. Testing procedure: Place the specimen on the test platform of the four-probe resistivity tester, ensuring good contact between the probes and the specimen; set the parameters of the tester and start the tester. The instrument will apply current to the specimen through four probes and measure the corresponding voltage value; according to the measured current and voltage values, as well as parameters such as the probe spacing, the instrument will automatically calculate the resistivity of the specimen.

[0102] (3) Residual stress

[0103] The residual stress of the functional current collector was detected by X-ray diffraction (XRD). The specific detection principle is as follows: The residual stress is calculated by measuring the strain of the crystal lattice. When X-rays irradiate a crystal, specific diffraction phenomena will occur. In a stress-free state, the lattice spacing of the crystal is fixed, and the diffraction peaks appear at specific positions. When there is residual stress in the material, the lattice will undergo strain, resulting in a change in the lattice spacing. This change in the lattice spacing will cause a displacement of the diffraction peaks. Therefore, by measuring the displacement of the diffraction peaks and combining parameters such as the elastic constant of the material, the strain of the lattice can be calculated. Then, according to the theory of elasticity, the lattice strain is converted into residual stress. Specifically, the residual stress will cause a change in the spacing of certain crystal planes of the crystal, thus changing the diffraction angle. According to Bragg's law: nλ = 2d×sinθ (where n is the diffraction order, λ is the X-ray wavelength, d is the crystal plane spacing, and θ is the diffraction angle), when d changes, θ will also change accordingly. By accurately measuring the change in the diffraction angle, the magnitude and direction of the residual stress can be calculated.

[0104] 3. Experimental Results

[0105] Table 1 Test Results of Related Properties of the Functional Current Collector

[0106]

[0107] The test results of the related properties of the functional current collectors prepared in Examples 1 to 17 and Comparative Example 1 are shown in Table 1.

[0108] Through comparison, it is found that the residual stresses of the functional current collectors prepared in Examples 1 to 17 are all lower than that in Comparative Example 1. The reason for the above phenomenon is that in the preparation process of the functional current collector in Comparative Example 1, the inorganic nanoparticle solution was not sprayed on the surface of the thickened copper layer, while in the preparation process of the functional current collectors in Examples 1 to 17, the inorganic nanoparticle solution was sprayed on the surface of the thickened copper layer. The inorganic nanoparticles contained in the inorganic nanoparticle solution have a high specific surface area and surface activity. During the process of spraying the inorganic nanoparticle solution on the surface of the metal layer, the inorganic nanoparticles contained therein can form good contact and interaction with the surface of the metal layer and change the microstructure of the metal layer, increasing the number of defects and dislocations on the surface of the metal layer. These defects and dislocations can serve as stress concentration points, enabling the stress of the functional current collector to be dispersed and released at these positions, thereby reducing the overall stress level of the functional current collector. Moreover, the interfacial bonding force between the inorganic nanoparticles and the metal layer is weak. During the spraying process or when subjected to other external stress effects, the inorganic nanoparticles are prone to undergo slight sliding and deformation at the interface between them and the metal layer, which is beneficial for absorbing or releasing stress and can play a good buffering role. Therefore, by spraying the inorganic nanoparticle solution on the surface of the metal layer (copper layer) during the preparation process of the functional current collector, stress can be effectively released from aspects such as microstructure and interfacial properties, thereby achieving the purpose of reducing the residual stress of the functional current collector, improving the stability, mechanical strength, and electrochemical performance of the functional current collector.

[0109] Compared with Example 1, the inorganic nanoparticles in the inorganic nanoparticle solutions used in Examples 5 and 6 during the preparation process of the functional current collector are nano iron powder and nano nickel powder respectively. The test results show that the residual stresses and resistivities of the functional current collectors provided by Examples 5 and 6 are higher than those in Example 1, and the tensile strengths and elongation rates are lower than those in Example 1. This is mainly because the chemical properties of nano iron powder and nano nickel powder are relatively active and are prone to oxidation or unnecessary chemical reactions with the metal layer during use, thus affecting the mechanical strength and electrochemical performance of the functional current collector. Moreover, the specific surface areas and surface activities of nano iron powder and nano nickel powder are not as good as those of nano silica and nano alumina, and the contact and interaction effects with the surface of the metal layer are poor, and the effect of stress dispersion and release is not obvious.

[0110] Compared with Examples 1 and 7, in the preparation of the functional current collector in Examples 8, 9, and 10, water, ethyl acetate, and xylene were used as solvents for the inorganic nanoparticle solution respectively. The test results showed that the residual stress and resistivity of the functional current collectors prepared in Examples 8, 9, and 10 were higher than those in Examples 1 and 7, while the tensile strength and elongation were lower than those in Examples 1 and 7. This was mainly because in the preparation of the functional current collector in Examples 1 and 7, ethanol or acetone was used as the solvent for the inorganic nanoparticle solution. Ethanol and acetone have certain volatility but not too fast. During the spraying process of the inorganic nanoparticle solution with ethanol or acetone as the solvent on the surface of the metal layer, ethanol and / or acetone can be evenly distributed on the surface of the metal layer. This evenly distributed inorganic nanoparticle can effectively hinder the regular arrangement of metal atoms in the metal layer and reduce the accumulation of internal stress. In the preparation of the functional current collector in Example 8, water was used as the solvent for the inorganic nanoparticle solution. Due to the large surface tension of water, it was difficult for the inorganic nanoparticles to be evenly distributed on the surface of the metal layer during the preparation of the functional current collector, resulting in the aggregation of inorganic nanoparticles, making it difficult to effectively penetrate and cover the surface of the metal layer, and thus leading to a higher residual stress in the finally prepared functional current collector than in Examples 1 and 7. In the preparation of the functional current collector in Example 9, ethyl acetate was used as the solvent for the inorganic nanoparticle solution. Due to the too strong volatility of ethyl acetate, the inorganic nanoparticles aggregated too quickly before the solvent completely volatilized during the preparation of the functional current collector, making it difficult for the inorganic nanoparticles to be evenly distributed on the surface of the metal layer. This would result in a reduced and uneven action range of the inorganic nanoparticles, making it difficult to effectively reduce the overall stress level of the finally prepared functional current collector. In the preparation of the functional current collector in Example 10, xylene was used as the solvent for the inorganic nanoparticle solution. Due to the weak volatility of xylene, it was difficult for the inorganic nanoparticles to be timely compounded and fixed on the surface of the metal layer during the preparation of the functional current collector, affecting the stress release effect of the functional current collector.

[0111] Compared with Example 1, in the preparation of the functional current collector in Examples 11 and 12, the mass fractions of nano-silica in the inorganic nanoparticle solution are 3% and 18% respectively. The test results show that the residual stress and resistivity of the functional current collectors provided by Examples 11 and 12 are higher than those of Example 1, while the tensile strength and elongation are lower than those of Example 1. This is mainly because in the preparation of the functional current collector in Example 1, the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution sprayed on the surface of the metal layer is controlled within the range of 5-15%. This can not only provide sufficient stress concentration points and defect numbers on the surface of the metal layer, so that the residual stress generated during the preparation of the functional current collector can be well dispersed and released, but also make the inorganic nanoparticles evenly dispersed in the solution, so that the inorganic nanoparticles can be evenly attached to the surface of the metal layer during the spraying process of the inorganic nanoparticle solution on the surface of the metal layer, thereby improving the residual stress release effect of the functional current collector. In Example 11, the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution used in the preparation of the functional current collector is too low. First, it will lead to insufficient stress concentration points and defect numbers provided by the inorganic nanoparticles, making it difficult to effectively disperse and release the stress generated during the preparation of the functional current collector, and thus it is difficult to achieve an ideal stress release effect. Second, too few inorganic nanoparticles are difficult to sufficiently change the microstructure of the functional current collector, making the hindering effect of the inorganic nanoparticles on the regular arrangement of metal atoms in the metal layer of the functional current collector not obvious, and the role of reducing the internal stress accumulation is limited, thereby resulting in an unsatisfactory reduction effect of the residual stress of the functional current collector. In Example 12, the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution used in the preparation of the functional current collector is too high. First, it is easy to cause agglomeration of the nanoparticles in the solution and difficult to disperse evenly. The agglomerated inorganic nanoparticles are difficult to evenly cover the surface of the metal layer of the functional current collector, affecting the stress release effect of the finally prepared functional current collector. Second, too many inorganic nanoparticles will increase the viscosity of the inorganic nanoparticle solution, making it difficult to evenly adhere to the surface of the metal layer of the functional current collector during the spraying process, resulting in uneven local stress release of the finally prepared functional current collector.

[0112] Compared with Example 1, the particle sizes of the inorganic nanoparticles in the inorganic nanoparticle solution used in Examples 13 and 14 during the preparation of the functional current collector are 5 nm and 30 nm respectively. The test results show that the residual stress and resistivity of the functional current collectors provided by Examples 13 and 14 are higher than those of Example 1, and the tensile strength and elongation are lower than those of Example 1. This is mainly because the particle size of the inorganic nanoparticles in the inorganic nanoparticle solution used in Example 1 during the preparation of the functional current collector satisfies 10-20 nm. Inorganic nanoparticles within the above range have good dispersibility, moderate surface activity, and good penetration and filling capabilities, which can ensure the uniform distribution of the inorganic nanoparticles on the surface of the metal layer, enable the inorganic nanoparticles to effectively interact with the surface of the metal layer of the functional current collector, and can also reduce the risk of instability or excessive reaction of the inorganic nanoparticles caused by excessive surface activity of the inorganic nanoparticles. To a certain extent, they can penetrate into the microstructure of the functional current collector, fill the tiny voids therein, enhance the overall structural stability and performance of the functional current collector, and play the function of stress release. In Example 13, the particle size of the inorganic nanoparticles in the inorganic nanoparticle solution used during the preparation of the functional current collector is too small. Inorganic nanoparticles with too small particle sizes have too high surface energy, their stability in the solvent decreases, and they are prone to agglomeration or precipitation. Moreover, the too small particle size will cause the penetration depth of the inorganic nanoparticles in the functional current collector to be too large, resulting in difficulty for the inorganic nanoparticles to play the role of stress release in the metal layer. In Example 14, the particle size of the inorganic nanoparticles in the inorganic nanoparticle solution used during the preparation of the functional current collector is too large. Inorganic nanoparticles with too large particle sizes have poor dispersion performance in the solvent and are prone to agglomeration in the solvent, resulting in reduced uniformity of the inorganic nanoparticles, which in turn affects the distribution uniformity of the inorganic nanoparticles on the surface of the metal layer of the functional current collector and the effect of stress release. In addition, inorganic nanoparticles with too large particle sizes will affect the uniformity of the microstructure of the functional current collector, thereby affecting its overall mechanical properties.

[0113] The above examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A method for preparing a functional current collector, characterized in that: The following steps are involved: S1. Plating a metal layer on at least one surface of the base film by magnetron sputtering; S2. spraying an inorganic nanoparticle solution on the surface of the metal layer to obtain a semi-finished product; S3. Drying the semi-finished product to obtain the functional current collector; In S1, along the direction away from the base film, the metal layer includes a nickel-chromium alloy layer and a copper layer which are compounded in sequence; In S2, the inorganic nanoparticles in the inorganic nanoparticle solution include at least one of nano-silicon dioxide, nano-aluminum oxide, nano-iron powder, and nano-nickel powder, the particle size of the inorganic nanoparticles in the inorganic nanoparticle solution is 10-20 nm, and the mass fraction of the inorganic nanoparticles in the inorganic nanoparticle solution is 5-15%.

2. The method for preparing the functional fluid collector according to claim 1, characterized in that: In S2, the solvent in the inorganic nanoparticle solution includes at least one of ethanol and acetone.

3. The method for preparing the functional fluid collector according to claim 1, characterized in that: In S3, after the semi-finished product is dried, the step of washing the semi-finished product after drying with a washing liquid is also included; The cleaning solution contains a surfactant, and the surfactant includes fatty alcohol polyoxyethylene ether.

4. The method for preparing the functional fluid collector according to claim 3, characterized in that: The cleaning conditions are as follows: time 10-20 s, temperature 20-25°C.

5. A functional fluid collector, characterized in that: The functional current collector is prepared by the preparation method of the functional current collector according to any one of claims 1 to 4.

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