Copper foil and preparation method thereof, current collector, pole piece and energy storage device

Abstract

The invention relates to the technical field of batteries, in particular to a copper foil and a preparation method thereof, a current collector, a pole piece and an energy storage device. A connection degree gamma exists between the surface density of the copper foil and the size and arrangement of the through holes, the formula of the connection degree gamma is # imgabs0 #, and the value range of gamma is 1 + / -0.1; the copper foil is prepared through an electrolytic method, and an insulating acid-resistant coating is dispensed on the surface of a cathode of the electrolytic method to form an insulating acid-resistant layer; according to the electrolytic method, an active layer is formed on the surface of an anode by coating a mixed active substance solution and sintering, an inert substance is coated on the surface of the active layer opposite to a point coating position of a cathode to form an inert layer, and the range of the inert layer is smaller than 70% of the area of a pore region. The porous copper foil prepared by the method has a porous structure, the pore size distribution is more uniform, the size is consistent, meanwhile, the parts except the pores are dense copper layers, and the mechanical property of the material is good.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a copper foil and a preparation method thereof, a current collector, a pole piece, and an energy storage device. Background Art

[0002] In recent years, with the acceleration of global energy transformation, the energy storage industry, as a core pillar of the new energy system, has ushered in unprecedented development opportunities. Energy storage technology not only effectively addresses the intermittent and unstable nature of renewable energy, but also plays a vital role in grid frequency and peak regulation, distributed energy management, and other areas. Currently, the most widely used media in the energy storage industry are lithium batteries and supercapacitors.

[0003] Copper foil is often used as a carrier when using negative electrode active materials such as graphite in energy storage devices due to its good conductivity, flexibility, moderate potential, resistance to winding and rolling, mature manufacturing technology, and relatively low price. It also serves as a negative electrode current collector, collecting the current generated by the battery active material to produce a higher output current. Among them, the mass and cost of lithium battery copper foil account for 13% and 8% of the total mass and total cost of lithium batteries, respectively, second only to the positive and negative electrode materials and electrolyte. According to the lithium battery energy density calculation formula: mass energy density = battery capacity / battery mass, energy density can be increased by reducing battery mass while maintaining a constant battery capacity, or by increasing battery capacity while maintaining the same battery mass. The development of high-energy-density energy storage devices places high demands on high-energy-density active materials and lightweight current collectors.

[0004] As the energy density of graphite, a typical negative electrode material for energy storage, has been pushed to its limits, the high energy density of lithium-sulfur and lithium-oxygen batteries has become increasingly popular. Therefore, lithium metal anodes, using metallic lithium as the negative electrode active material, have enormous potential for application. However, when lithium metal is used as a negative electrode material in batteries, it is prone to the formation of lithium dendrites during cyclic charge and discharge. The presence of lithium dendrites not only easily pierces the separator, causing a short circuit in the battery, reducing its service life, and in severe cases, causing thermal runaway; the growth of lithium dendrites also leads to a decrease in coulombic efficiency, forming so-called "dead lithium," resulting in low initial charge and discharge efficiency and a reduced number of cycles. As our understanding of the nucleation and deposition models of metallic lithium continues to deepen, more and more methods have been developed to inhibit the growth of lithium dendrites. Among them, the use of porous copper foil as the negative electrode current collector is one method to inhibit the growth of lithium dendrites.

[0005] On the one hand, the porous current collector and the active material can form an "anchoring effect", effectively improving the adhesion of the electrode material and reducing the glue content in the negative electrode material. At the same time, the presence of its through-hole structure also reduces the weight of some copper foils and improves the energy density of the battery. On the other hand, the porous copper foil can not only load more negative electrode materials, but also adjust the distribution of lithium ions during the deposition process to make them evenly distributed. For example, the porous copper foil prepared by patents CN108011108A, CN114686961B and CN116288543A can effectively reduce the glue content in the negative electrode material and improve the energy density of the battery. In addition, while the porous copper foil inhibits the growth of lithium dendrites, it can also alleviate the volume expansion problem during the charge and discharge process, thereby maintaining good dimensional and mechanical stability during the lithium insertion process. Furthermore, the liquid electrolyte can improve the wetting effect on both sides of the substrate through the pore structure and reduce the polarization of the battery cell.

[0006] At present, the preparation methods of porous copper foil include mechanical processing, laser processing, electrochemical method, etc. The mechanical processing method is suitable for thicker (≥30μm) metal foils, and the precision is low. After punching and drilling, there are burrs around the holes, which can easily pierce the diaphragm and cause battery short circuits. The laser processing method has high precision, but the equipment is expensive and the production efficiency is low, and it cannot be mass-produced. The electrochemical method includes electrochemical etching and dealloying. The pore structure formed by electrochemical etching is diverse and cannot be precisely controlled. At the same time, waste liquid needs to be treated, which puts environmental pressure on it. The dealloying method selectively dissolves the active metal in the alloy to leave a porous structure, but for current collectors with high conductivity, the impurity content will seriously reduce the conductive performance of the electrode, which will have a significant impact on the internal resistance, rate and cycle of the battery. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a copper foil and its preparation method, current collector, electrode, and energy storage device, which are used to solve the problem that the porosity of porous copper foil in the prior art cannot be accurately controlled.

[0008] To achieve the above-mentioned purpose and other related purposes, the present invention is achieved through the following technical solutions.

[0009] A first aspect of the present invention is to provide a copper foil having a uniformly distributed through-hole structure. The surface density of the copper foil is related to the size and arrangement of the through-holes. The formula for the relationship Γ is as follows:

[0010] And the value range of Γ is 1±0.1;

[0011] Where M is the surface density of the porous area, ranging from 5-180g / m 2 ;

[0012] k represents the density of copper foil, the actual value is 8.96g / cm 3 ;

[0013] η represents the thickness of copper foil (μm);

[0014] a and b represent the long and short radii of the through hole, respectively (mm), ranging from 0.05 to 1.10 mm;

[0015] m and n represent the longest and shortest distances between the centers of adjacent through holes in the horizontal and vertical directions (mm), ranging from 0.12-3.00mm.

[0016] The second aspect of the present invention is to provide a method for preparing copper foil, wherein the copper foil is prepared by electrolysis, wherein:

[0017] The cathode surface of the electrolytic method is spot-coated with an insulating acid-resistant coating to form an insulating acid-resistant layer; the insulating acid-resistant coating is composed of hydroxyethyl methacrylate, isobornyl acrylate, 4-hydroxycyclohexyl phenyl ketone, silicon dioxide, and modified polysiloxane in a mass ratio of 25-35:25-35:25-35:3-8:3-8;

[0018] The anode surface of the electrolytic method is coated with a mixed active material solution and sintered to form an active layer. An inert material is coated on the surface of the active layer at a position opposite to the cathode to form an inert layer. The inert layer is less than 70% of the area of ​​the pore area. The mixed active material solution is composed of iridium oxide, tantalum oxide, and solvent in a mass ratio of 7-10:3-5:85-90.

[0019] The electrolyte used in the electrolysis method includes the following components: 75-125 g / L copper ions, 85-135 g / L sulfuric acid, 15-50 ppm chloride ion concentration, 30-150 ppm brightener, 10-80 ppm moving agent, and 5-50 ppm leveling agent.

[0020] A third aspect of the present invention provides a current collector comprising the copper foil as described above.

[0021] A fourth aspect of the present invention provides a pole piece comprising the current collector as described above.

[0022] A fifth aspect of the present invention provides an energy storage device, comprising the pole piece as described above.

[0023] As described above, the copper foil and its preparation method, current collector, pole piece, and energy storage device of the present invention have the following beneficial effects:

[0024] (1) The present invention provides a method for measuring the surface density of porous copper foil, which defines the relationship between the surface density and the size and arrangement of the through holes. The control range of M is 5-180g / m2 according to the thickness of the copper foil. 2.

[0025] (2) The present invention provides a method for preparing copper foil, which comprises coating the cathode with an insulating acid-resistant coating, and subjecting the anode to a mixed active material treatment and an inert treatment. While ensuring the preparation of a thinner copper foil, the mass per unit area (surface density) thereof is further reduced by forming a through-hole structure. The through-hole structure of the lithium battery copper foil can not only form an "anchoring effect" with the active material, effectively improve the adhesion of the electrode material, improve the infiltration effect of the electrolyte, reduce the glue content in the negative electrode material, and thus load more active materials, thereby increasing the energy density of the battery. Moreover, the porous copper foil can alleviate the volume expansion problem of the battery cell during the charging and discharging process, while regulating the uniform distribution of lithium ions during the deposition process and inhibiting the growth of lithium dendrites.

[0026] (3) The porous copper foil produced by the present invention is both extremely thin and light, with the thinnest thickness reaching 4μm and the lightest weight being 50% of the conventional lithium battery copper foil of the same thickness. The mass and cost of lithium battery copper foil are 13% and 8% of the total mass and total cost of the lithium battery, respectively. Replacing 8μm non-porous lithium battery copper foil with 6μm porous copper foil will increase the battery capacity density by 10% in terms of battery energy density; in terms of copper price, for every RMB10,000 increase in copper unit price, the copper raw material cost will be saved by RMB4.215 million / GWh.

[0027] (4) The current collector provided by the present invention has an extremely thin thickness and light weight, good adhesion to the active material, thicker coating of the active material, excellent wetting effect, low resistance and high conductivity.

[0028] (5) The electrode provided by the present invention can be coated with more active materials. At the same time, during the charging and discharging process, the electrode volume expansion and contraction coefficient is small, and the formation and growth of lithium dendrites can be effectively inhibited, thereby improving the energy density and thermal stability of the battery cell.

[0029] (6) The energy storage device provided by the present invention has high energy density and high rate capability, as well as longer cycle performance and safety.

[0030] (7) The porous structure and thin copper foil of the present invention can be coated with a higher proportion of active materials, thereby improving the capacity density of the battery; the porous structure of the copper foil provides more volume expansion space, reduces the expansion ratio of the battery cell structure, stabilizes the mechanical structure, and reduces the probability of damage to the battery and battery pack; in addition, the porous structure of the copper foil regulates the uniformity of the lithium ion deposition process, inhibits the formation of lithium dendrites during the cyclic charge and discharge process, reduces the risk of short circuit and thermal runaway, and enhances the safety of the battery.

[0031] (8) The porous copper foil prepared by the present invention has a porous structure, and the pore size distribution is more uniform and the size is consistent. At the same time, the part except the holes is a dense copper layer, and the mechanical properties of the material are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a metallographic image of the copper foil prepared in Example 3 of the present invention.

[0033] Figure 2 Shown is the EBSD image of the copper foil prepared in Example 7 of the present invention.

[0034] Figure 3 Shown is a SEM image of the copper foil prepared in Comparative Example 2 of the present invention.

[0035] Figure 4 It shows a simplified schematic diagram of the coating positions of the cathode roller insulation coating and the anode plate inert layer in the present invention.

[0036] Figure 5 It is a schematic diagram showing the coating position of the inert layer on the anode plate and the through-hole area of ​​the cathode roller according to the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose of the invention, technical solutions and beneficial technical effects of the present invention clearer, the present invention is further described in detail below in conjunction with embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] Where “including,” “having,” and “comprising” are used herein, it is intended to cover a non-exclusive inclusion, and another component may also be added unless a clear limiting term such as “only,” “consisting of,” etc. is used.

[0040] The words "preferably", "more preferably", "preferably", "better", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the statement of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention. That is, in the present invention, "preferably", "more preferably", "preferably", "better", etc. are only used to describe implementation methods or examples with better effects, but do not constitute a limitation on the scope of protection of the present invention.

[0041] In the present invention, “further”, “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content but should not be understood as limiting the scope of protection of the present invention.

[0042] In the present invention, "at least one" means more than one, such as one, two, or more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two, three, etc., unless otherwise specifically defined. In the description of the present invention, "several" means at least one, such as one, two, etc., unless otherwise specifically defined.

[0043] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0044] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc. Unless mentioned to the contrary, terms in the singular may include plural forms and are not to be understood as being one in number.

[0045] In the present invention, "above" or "below" includes the number itself. For example, "1 or below" includes 1.

[0046] In the present invention, room temperature refers to 0-40°C, including but not limited to 10-40°C, or further 20-30°C.

[0047] In the present invention, "the range of the inert layer relative to the hole area" refers to the ratio of the area coated with the inert material to the total area of ​​the hole area. The total area of ​​the hole area here includes the area of ​​the hole and the area of ​​the solid copper foil around the hole. The range of the inert material coating can be within the corresponding range of the total area of ​​the hole area. For example, if the total area of ​​a hole area is 100 square millimeters, then the area coated with the inert material should be less than 70 square millimeters (i.e. 70%). Figure 5As shown in the figure, the blue hole area is the through-hole area, the length of the through-hole area is x, the width is y, and the total area of ​​the hole area is xy (including the area of ​​the hole and the area of ​​the solid copper foil around the hole). When the area coated with inert material is 20%, that is, the red area accounts for 20% of the blue area. The red area is the inert material coating area of ​​the anode plate.

[0048] In order to increase the energy density of lithium batteries, copper foil current collectors are rapidly developing towards being lighter and thinner. For copper foil, surface density is an important indicator. If the surface density is too low (M<5g / m 2 ) may lead to insufficient mechanical strength of the copper foil carrier itself, which may be easily broken during the battery manufacturing process, or structural damage due to volume changes during charging and discharging. In addition, low surface density may mean that the copper foil is thinner and the conductivity may be better, but in fact, it may increase resistance due to being too thin. Because the current collector thickness is insufficient, the electron transmission path becomes longer, which may increase the internal resistance. If the surface density is too high (>180g / m 2 ), overweight current collectors will increase the total weight and volume of the battery and reduce energy density. In addition, overweight copper foil also has too high a thickness, which reduces flexibility and is not conducive to the infiltration of electrolyte, affecting the winding or lamination process of the battery, increasing the transmission distance of lithium ions, resulting in increased polarization and affecting rate performance. On this basis, the inventors provide a method for measuring the surface density of porous copper foil, defining the relationship between surface density and through-hole size and arrangement M. According to the thickness of the copper foil, M is controlled in the range of 5-180g / m 2 .

[0049] A first aspect of the present invention is to provide a copper foil having a uniformly distributed through-hole structure. The surface density of the copper foil is related to the size and arrangement of the through-holes. The formula for the relationship Γ is as follows:

[0050] And the value range of Γ is 1±0.1;

[0051] Where M is the surface density of the porous area, ranging from 5-180g / m 2 ;

[0052] k represents the density of copper foil, the actual value is 8.96g / cm 3 ;

[0053] η represents the thickness of copper foil (μm);

[0054] a and b represent the long and short radii of the through hole, respectively (mm), ranging from 0.05 to 1.10 mm;

[0055] m and n represent the longest and shortest distances between the centers of adjacent through holes in the horizontal and vertical directions (mm), ranging from 0.12-3.00mm.

[0056] The present invention defines the relationship between the surface density, through-hole size, and through-hole arrangement of the copper foil using the degree of connection. When the surface density, through-hole size, and through-hole arrangement of the copper foil meet the requirements of the degree of connection, the overall performance of the copper foil thus obtained is better.

[0057] The through holes of the copper foil of the present invention are arranged in a rectangular array, and the through holes are uniform in size.

[0058] In some embodiments of the present invention, the M may be 5-50 g / m 2 , 50-80g / m 2 , 80-130g / m 2 , 130-180g / m 2 ; Typical but non-limiting, for example, 5g / m 2 , 50g / m 2 , 80g / m 2 , 130g / m 2 , 180g / m 2 .

[0059] In some embodiments of the present invention, the thickness of the copper foil is 4-18 μm. Specifically, the thickness of the copper foil may be 4-8 μm, 8-12 μm, or 12-18 μm. Typical but non-limiting examples include 4 μm, 8 μm, 12 μm, and 18 μm.

[0060] In some embodiments of the present invention, at room temperature, the tensile strength of the copper foil along the long axis of the through hole is 200-600 MPa, and the tensile strength along the short axis of the through hole is 100-400 MPa.

[0061] In some embodiments of the present invention, at room temperature, the elongation at break of the copper foil along the major axis of the through hole is ≥0.8%, and the elongation at break along the minor axis of the through hole is ≥0.4%.

[0062] In some embodiments of the present invention, the copper foil has a uniformly distributed through-hole structure.

[0063] In some embodiments of the present invention, the surface density of the porous copper foil is reduced by 5-70% compared to the surface density of conventional copper foil of the same thickness. Figure 5As shown, the conventional copper foil is the copper foil portion of the non-porous area when preparing the porous copper foil (i.e., the green portion). It can be further understood that a copper foil (including the green portion and the blue portion) with a thickness of 8 microns, a length of 50m, and a width of 1.38m (1380mm) has a left portion (length 25m, width 0.7m) as the porous area, and the copper foil of this portion is the porous copper foil (i.e., the blue portion), and the remaining non-porous area is the conventional copper foil (i.e., the green portion). The size of the porous area is designed according to demand. The calculation formula for the reduction ratio of the hole area surface density of the present invention is:

[0064]

[0065] Specifically, as in Example 3, the surface density of the non-porous area is 54.32 g / m 2 The surface density of the hole area is 42.22g / m 2 The weight loss ratio is (54.32-42.22) / 54.32≈22.3%.

[0066] The second aspect of the present invention is to provide a method for preparing copper foil, wherein the copper foil is prepared by electrolysis, wherein:

[0067] The cathode surface of the electrolytic method is spot-coated with an insulating acid-resistant coating to form an insulating acid-resistant layer; the insulating acid-resistant coating is composed of hydroxyethyl methacrylate, isobornyl acrylate, 4-hydroxycyclohexyl phenyl ketone, silicon dioxide, and modified polysiloxane in a mass ratio of 25-35:25-35:25-35:3-8:3-8;

[0068] The anode surface of the electrolytic method is coated with a mixed active material solution and sintered to form an active layer. An inert material is applied to the surface of the active layer at a position opposite to the cathode to form an inert layer. The inert layer is less than 70% of the pore area. The mixed active material solution is composed of iridium oxide, tantalum oxide, and solvent in a mass ratio of 7-10:3-5:85-90.

[0069] The electrolyte used in the electrolysis method includes the following components: copper ion 75g / L-125g / L, sulfuric acid 85g / L-135g / L, chloride ion concentration 15-50ppm, brightener 30-150ppm, moving agent 10-80ppm, leveling agent 5-50ppm.

[0070] The copper foil prepared by the present invention has a relatively thin thickness, i.e., 4-18 μm. Conventional processes for preparing porous copper foil, such as punching, electrochemical etching, or dealloying, cannot meet the requirements of through-hole size and uniform arrangement. The present invention coats an insulating acid-resistant coating on the cathode surface and controls the size and distribution of the coating dots. Copper foil cannot be deposited in the area on the cathode surface where the coating is applied, thereby forming through-holes. The size and arrangement of the through-holes are controlled, and the porous areas formed have uniform through-hole size and uniform arrangement. The porous copper foil thus prepared has better mechanical properties. In order to reduce the mass of the copper foil prepared, inert substances are placed at the position of the anode corresponding to the porous area, thereby reducing the amount of copper ion deposition on the cathode, and then reducing the amount of copper ion deposition around the through-holes, thereby reducing the surface density of the porous copper foil compared to the surface density of conventional copper foil of the same thickness, thereby reducing the mass of the copper foil.

[0071] In some embodiments of the present invention, the cathode surface is the surface of the cathode roller. The coating position of the inert substance is the position of the anode plate corresponding to the shielding point (ie, the circular point) of the cathode roller.

[0072] In some embodiments of the present invention, the present invention has no special limitation on the spot coating method of the insulating acid-resistant coating, and the conventional method often used by those skilled in the art is adopted for spot coating. Furthermore, the method of spot coating the insulating acid-resistant coating on the cathode surface of the present application is as follows: a spray pipe is arranged above the axis of the cathode roller, one end of the spray pipe is connected to the motor, a pneumatic valve is arranged in the middle, and the other end is connected to the storage tank. The insulating acid-resistant coating is injected into the storage tank, the motor and the cathode roller are started, and the pneumatic valve is opened. The coating is evenly sprayed on the roller surface of the cathode roller according to a certain size and geometric arrangement. After the cathode roller rotates at a constant speed for one circle, the motor and the air valve are turned off to solidify the coating. The ultraviolet lamp used for the curing is provided in plurality, and the plurality of ultraviolet lamps are arranged at intervals, and the wavelength of the ultraviolet lamp is 365nm. The power is 4000W, and the curing time is 2-4h.

[0073] In some embodiments of the present invention, the anode is an anode plate, and the anode plate is a titanium plate. The processing method of the titanium plate is as follows: a mixed active material solution is coated on the surface of the titanium plate, and sintered into an electrolytic anode plate with a coating of a certain unit area weight, and then a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area position, and the range of the inert layer relative to the hole area is <70%.

[0074] In some embodiments of the present invention, the equipment used in the electrolysis method is an equipment commonly used by technical personnel in this field to prepare copper foil by electrolysis. More specifically, the anode plate is installed in the anode tank, and the cathode roller is adjusted to the bearing seat of the anode tank. High-purity copper sulfate electrolyte is injected through the bottom pipe of the electrolytic tank at a certain flow rate, current is applied and the cathode roller is operated at a uniform speed. The copper ions in the electrolyte are evenly deposited on the surface of the titanium roller through electrochemical reaction, thereby preparing the copper foil.

[0075] In some embodiments of the present invention, the thickness of the insulating acid-resistant coating is 150-550 μm. Specifically, the thickness can be 150-250 μm, 250-350 μm, 350-550 μm; typical but non-limiting examples are 150 μm, 250 μm, 350 μm, and 550 μm. The insulating acid-resistant coating is applied to the cathode roller in the form of dots, forming an insulating shielding point at this point. During the electrochemical deposition process of the cathode roller, no copper will be deposited at this point, thereby forming a hole. If the insulating acid-resistant coating is not applied, a porous copper foil cannot be produced. In other words, if the coating is not applied, it is a normal non-porous foil. The coating mainly plays the role of insulation and pore formation, that is, there is an insulating point on the cathode roller, and no copper foil is deposited at this point, so a hole is formed, and foil will be formed around the coating. Different components of insulating acid-resistant coatings affect insulation and acid resistance. The influence trend of these components and proportions is: the more silica, the better the insulation effect, but the poorer the acid resistance; the more hydroxyethyl methacrylate, the better the acid resistance, but the poorer the insulation.

[0076] In some embodiments of the present invention, the thickness of the active layer is 2-5nm. Specifically, the thickness can be 2-4nm, 4-5nm; typical but non-limiting examples include 2nm, 4nm, and 5nm. The active substances in the mixed active substance solution are mainly iridium oxide and tantalum oxide, which form anode electrodes by themselves and form a closed reaction loop with the cathode roller and copper sulfate. If not coated, the closed loop has no anode, that is, no electrode reaction will occur at all, and no copper foil will be deposited, which is equivalent to only a cathode and no anode. When the anode material is a titanium plate, a layer of active substance is coated on the surface of the titanium plate to form an active layer. The active layer has high catalytic activity, which is convenient for reducing the activation energy of the copper dissolution reaction. The coating acts as a "barrier" to isolate the electrolyte from contact with the titanium substrate and prevent titanium from dissolving.

[0077] In some embodiments of the present invention, the sintering temperature is 480-540°C, and the sintering time is 30-45 minutes. Specifically, the temperature may be 480-510°C or 510-540°C, and typically, but not limited to, 480°C, 510°C, or 540°C. The sintering time may be 30-38 minutes or 38-45 minutes, and typically, but not limited to, 30 minutes, 38 minutes, or 45 minutes.

[0078] In some embodiments of the present invention, the inert substance is selected from fluoropolymers. The fluoropolymer is selected from one or more of polytetrafluoroethylene, polyperfluoroethylene propylene, polyvinylidene fluoride, and polyvinyl fluoride. The inert substance mainly plays an insulating role, forming an insulating part of a certain size on the anode plate. If the inert substance is not coated, the surface density of the porous area is relative to the non-porous area, and the weight reduction ratio is only about 6-7%. The size of the inert substance is aligned with the porous area. When 30% is coated, when power is applied, it is equivalent to 30% of the anode being non-energized, that is, only 70% is energized, so only 70% of the copper is deposited in the porous area, and the other non-porous and inert substance-free areas are deposited normally, with a deposition amount of 100%. In this comparison, the surface density of the porous copper foil is reduced by 30% relative to the non-porous foil.

[0079] In some embodiments of the present invention, the thickness of the inert layer is 40-150 μm. Specifically, the thickness may be 40-100 μm, 100-150 μm, and typically but not limited to, 40 μm, 100 μm, or 150 μm.

[0080] In some embodiments of the present invention, the inert material coating method includes the following steps: heating the active layer surface facing the cathode to 40-200°C, then applying the inert material to the heated area, and after the inert material adheres, cooling the temperature to room temperature to complete the coating of the inert material on the active layer surface. The heating is performed using a hot air gun.

[0081] In some embodiments of the present invention, the temperature of the electrolyte is 45-65° C. Specifically, the temperature may be 45-55° C. or 55-65° C.; typically but not limited to, for example, 45° C., 55° C., or 65° C.

[0082] In some embodiments of the present invention, the current applied during the electrolysis process is 8000-45000 A. Specifically, the current may be 8000-15000 A, 15000-30000 A, or 30000-45000 A; typically but not limited to, for example, 8000 A, 15000 A, 30000 A, or 45000 A.

[0083] In some embodiments of the present invention, the inert layer covers an area of ​​10-60% relative to the hole area. Specifically, the inert layer can cover an area of ​​10-20%, 20-40%, or 40-60% relative to the hole area; typical but non-limiting examples include 10%, 20%, 40%, and 60%. If the inert material covers an area that is too large (>70%), the overall resistance of the hole area will increase, forcing the current to bypass the hole area and flow to other areas, which in turn exacerbates the uneven edge current density.

[0084] In some embodiments of the present invention, the choice of leveling agent is not particularly limited; commercially available leveling agents commonly used by those skilled in the art may be used. Specifically, the leveling agent is a nitrogen-containing amine organic compound. Preferably, the leveling agent is selected from one or more of collagen, gelatin, or polyethyleneimine. The addition of the leveling agent facilitates filling microscopic depressions, eliminating surface defects, and improving thickness uniformity. It is typically preferentially adsorbed in areas of high current density to inhibit excessive deposition.

[0085] In some embodiments of the present invention, the present invention is not particularly limited to the selection of the moving agent, and the commercially available products of the moving agent frequently used by those skilled in the art can be used. Specifically, the moving agent is a polyether compound, and preferably, the moving agent is selected from one or more of polyethylene glycol, polypropylene glycol or polyvinylpyrrolidone. The addition of the moving agent facilitates the regulation of the electrolyte mass transfer process, maintains the uniformity of the copper ion concentration gradient, and prevents uneven deposition caused by local concentration polarization. Polyether compounds can effectively inhibit the growth of grains at high temperatures, reduce the size of grain nucleation, generate more interfaces, absorb and release thermal stress, and improve the stability of copper foil under high temperature conditions.

[0086] In some embodiments of the present invention, the present invention does not specifically limit the selection of brighteners, and commercially available products of brighteners commonly used by those skilled in the art can be used. Specifically, the brightener is a sulfur-containing compound; preferably, the brightener is selected from one or more of sodium methylene dinaphthalene sulfonate, sodium polydisulfide propane sulfonate (SPS), sodium 3-mercapto-1-propanesulfonic acid (MBS), methyl blue or 2-mercaptothiazoline. The addition of brighteners facilitates the inhibition of the two-dimensional growth of copper ions, promotes the formation of crystal nuclei, and refines the grains, thereby reducing the surface roughness of the copper foil and improving the mirror gloss. When an organic sulfide brightener is used in combination with a nitrogen-containing amine organic compound (such as a nitrogen-containing polymer) leveler, the crystal structure of the copper foil becomes smoother and denser, a large number of nanocrystalline regions are generated, and the fine grain strengthening effect is enhanced. The excellent structural interaction of fine crystals and nano-twins improves the tensile strength of the copper foil while increasing the elongation.

[0087] In some embodiments of the present invention, the electrolyte used in the electrolysis method includes the following components: copper ions 75-100 g / L, sulfuric acid 85-110 g / L, chloride ion concentration 15-35 ppm, brightener 30-80 ppm, moving agent 10-50 ppm, leveling agent 5-30 ppm.

[0088] In some embodiments of the present invention, the electrolyte used in the electrolysis method includes the following components: copper ions 100-125 g / L, sulfuric acid 110-135 g / L, chloride ion concentration 35-50 ppm, brightener 80-150 ppm, moving agent 50-80 ppm, leveling agent 30-50 ppm.

[0089] In some embodiments of the present invention, the electrolyte used in the electrolysis method includes the following components: copper ions 75g / L-125g / L, sulfuric acid 85g / L-135g / L, chloride ion concentration 15-50ppm, brightener 60-85ppm, moving agent 30-50ppm, and leveling agent 15-25ppm.

[0090] In some embodiments of the present invention, the electrolyte used in the electrolysis method includes the following components: copper ions 75g / L-125g / L, sulfuric acid 85g / L-135g / L, chloride ion concentration 15-50ppm, brightener 125-150ppm, moving agent 55-80ppm, leveling agent 35-50ppm.

[0091] In some embodiments of the present invention, the electrolyte is prepared by dissolving copper sulfate, sulfuric acid, sodium chloride, a leveling agent, a brightener, and a moving agent in water, and stirring and mixing them thoroughly so that the concentration of each component in the electrolyte meets the above requirements.

[0092] The main function of brightener is to promote the nucleation of copper ions; leveler can mainly promote the face-center growth of copper foil grains, making the grains flatter; when brightener and leveler are used together, the crystal structure of copper foil becomes flatter and denser; positioning agent can mainly form a more stable and uniform barrier layer, thereby effectively limiting certain growth directions of copper crystals, and interacting evenly with other additives on various parts of the copper foil, making the grains smaller and more uniform.

[0093] A third aspect of the present invention is to provide a current collector comprising the copper foil as described above.

[0094] A fourth aspect of the present invention is to provide a pole piece comprising the current collector as described above.

[0095] A fifth aspect of the present invention is to provide an energy storage device, comprising the pole piece as described above.

[0096] The present invention is further described below by way of examples, but the scope of the invention is not limited thereto.

[0097] If specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. All reagents or instruments without manufacturer's indication are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the examples, any methods, equipment, and materials of the prior art that are similar or equivalent to the methods, equipment, and materials described in the examples of the present invention can also be used to implement the present invention based on the prior art knowledge of those skilled in the art and the description of the present invention.

[0098] Example

[0099] Example 1

[0100] This embodiment provides a method for preparing copper foil, wherein the copper foil is prepared by electrolysis, and the specific steps are as follows:

[0101] S1. Preparation of insulating holes: The insulating acid-resistant coating is evenly sprayed on the cathode roller surface in the form of circular dots with a diameter of 450 μm, a horizontal spacing of 1 mm between the center points, and a vertical spacing of 0.73 mm. After the cathode roller rotates at a constant speed for one circle, the coating is cured to form an insulating acid-resistant layer. The curing is performed using an ultraviolet lamp with a power of 4000 W and a wavelength of 365 nm and a curing time of 2-4 hours. The thickness of the insulating acid-resistant layer is 250 μm. The insulating acid-resistant coating is composed of hydroxyethyl methacrylate, isobornyl acrylate, 4-hydroxycyclohexyl phenyl ketone, silica, and modified polysiloxane in a ratio of 30:30:30:5:5.

[0102] S2. Special treatment of the anode plate: A certain proportion of mixed active material solution is applied to the surface of the titanium plate and sintered to form an active layer. Subsequently, an inert material is applied to the surface of the active layer opposite the cathode dot coating to form an inert layer. The inert layer covers an area of ​​5% relative to the pore area. The thickness of the active layer is 5 nm. The thickness of the inert layer is 80 μm. The sintering temperature is 480-540°C and the time is 30-45 minutes. The mixed active material solution consists of iridium oxide, tantalum oxide, and water in a mass ratio of 7:3:90. The inert material is polytetrafluoroethylene. The inert material is applied at the position of the anode plate corresponding to the cathode roller shielding point (i.e., the circular point).

[0103] S3. Production of porous copper foil: Install the anode plate into the anode tank, and adjust the cathode roller to the anode tank bearing seat, and pass the bottom pipe of the electrolytic cell at 42m 3 / h flow rate into high-purity copper sulfate electrolyte, the copper sulfate electrolyte includes the following mass concentrations of components: Cu 2+95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 22ppm, MPS 63ppm, PEG 14ppm, PVP 31ppm, collagen 18ppm, PEG weight-average molecular weight 8000. Applying a current of 25,000A and running the cathode roller at a constant speed, the copper ions in the electrolyte are evenly deposited on the surface of the titanium roller through an electrochemical reaction. The deposited surface rotates out of the reaction interface as the cathode roller rotates, and the deposited porous copper foil is continuously peeled off from the roller surface. After anti-oxidation, baking and winding, it becomes the original foil, which is then placed in an oven for annealing. After the warpage is qualified, it is cut into pieces to prepare the porous copper foil used for lithium batteries. The temperature of the electrolyte is 50°C.

[0104] This embodiment provides a pole piece, and a method for preparing the pole piece includes the following steps: placing commercially available conductive agent carbon nanotubes (CNTs), adhesive carboxymethyl cellulose (CMC), and active material graphite in a ratio of 3:3:94 into a high-temperature mixing system within a high-temperature mixing and coating machine. The high-temperature mixing system parameters are set to a revolution speed of 35 rpm, a dispersion speed of 400 rpm, and a stirring time of 40 minutes to uniformly mix the powders. Subsequently, a heating device is activated to melt the mixed powders, i.e., the stirring screw is heated to 400°C, stirring is continued, and the temperature is maintained for 55 minutes to produce a molten negative electrode slurry. The molten negative electrode slurry is transferred via an insulated pipe to the coating system of the high-temperature mixing and coating machine, where it is applied to the surface of the porous copper foil prepared above by extrusion or spraying. The coated pole piece is then pulled from the tail of the coating machine to a 25°C constant temperature oven located between the head and tail of the coating machine for constant temperature cooling and drying. Finally, the negative electrode piece is rolled and punched into a sheet. Among them, the coating surface density is 10mg / cm 2 The compaction density of the negative electrode is 1.55g / cm 3 ;

[0105] Similarly, the difference between the preparation method of the positive electrode sheet and the preparation method of the negative electrode sheet is that the positive electrode material is composed of lithium manganese iron phosphate, conductive graphite, and adhesive PVDF in a mass ratio of 93:5:2, and the coating surface density is 22mg / cm 3 The compaction density of the positive electrode is 2.4g / cm 3 The N / P ratio between the positive and negative electrodes is 1.10.

[0106] This embodiment provides an energy storage device. The preparation method of the energy storage device includes the following steps: sequentially recycling the negative electrode sheet, separator, and positive electrode sheet prepared above into a core, hot pressing the core, assembling the core into pairs, placing the core in an aluminum-plastic composite film, and performing top and side sealing processes. After vacuum baking to test for moisture content, injecting battery cell electrolyte, and performing high-temperature activation, formation, secondary fluid replenishment, sealing, room-temperature aging, and capacity separation, 30 pieces of soft-pack battery cells with a capacity of 15Ah are obtained.

[0107] Example 2

[0108] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0109] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 10% of the hole area;

[0110] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 46ppm, MPS 82ppm, PEG 18ppm, PVP 40ppm, collagen 42ppm.

[0111] The rest is exactly the same as in Example 1.

[0112] Example 3

[0113] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0114] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 20% of the hole area;

[0115] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS46ppm, MPS 82ppm, PEG16ppm, PVP55ppm, collagen 42ppm.

[0116] The rest is exactly the same as in Example 1.

[0117] The metallographic picture of the copper foil prepared in this embodiment is as follows: Figure 1 As shown, through Figure 1 It can be seen that the circular hole area of ​​the porous copper foil prepared in the present application is round and uniform. The presence of the hole area not only makes the negative electrode active material and the current collector more closely combined, but also reduces the surface density of the hole area by 22.3% relative to the non-porous copper foil, thereby reducing the internal resistance and improving the energy density of the battery cell.

[0118] Example 4

[0119] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0120] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 30% relative to the hole area;

[0121] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 34ppm, MPS 77ppm, PEG16ppm, PVP40ppm, collagen 30ppm.

[0122] The rest is exactly the same as in Example 1.

[0123] Example 5

[0124] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0125] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 40% of the hole area;

[0126] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 34ppm, MPS 77ppm, PEG 16ppm, PVP 40ppm, collagen 21ppm.

[0127] The rest is exactly the same as in Example 1.

[0128] Example 6

[0129] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0130] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 50% of the hole area;

[0131] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 34ppm, MPS 82ppm, PEG 18ppm, PVP 31ppm, collagen 21ppm.

[0132] The rest is exactly the same as in Example 1.

[0133] Example 7

[0134] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0135] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 60% of the hole area;

[0136] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS34ppm, MPS77ppm, PEG 16ppm, PVP 55ppm, collagen 31ppm.

[0137] The rest is exactly the same as in Example 1.

[0138] The EBSD image of the copper foil prepared in this embodiment is as follows: Figure 2 As shown, by analyzing the EBSD image of the copper foil, the grain size and size as well as the crystal growth mode of the copper foil prepared in this embodiment are similar to those of the conventional copper foil. Compared with the conventional copper foil, the presence of the porous area can, on the one hand, alleviate the volume expansion problem of the battery cell during the charge and discharge process, and on the other hand, can also adjust the uniform distribution of lithium ions during the deposition process and inhibit the growth of lithium dendrites.

[0139] Example 8

[0140] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0141] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 65% of the hole area;

[0142] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 34ppm, MPS 63ppm, PEG 18ppm, PVP 40ppm, gelatin 18ppm.

[0143] The rest is exactly the same as in Example 1.

[0144] Example 9

[0145] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0146] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 30% relative to the hole area;

[0147] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 46ppm, MPS 63ppm, PEG 16ppm, PVP 31ppm, gelatin 21ppm.

[0148] The rest is exactly the same as in Example 1.

[0149] Example 10

[0150] This embodiment provides a method for preparing copper foil, which differs from Example 1 in that:

[0151] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 60% of the hole area;

[0152] The copper sulfate electrolyte includes the following components in mass concentrations: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS 34ppm, MPS 63ppm, PEG 14ppm, PVP 31ppm, gelatin 18ppm.

[0153] The rest is exactly the same as in Example 1.

[0154] Comparative Example

[0155] Comparative Example 1

[0156] This comparative example provides a method for preparing copper foil, which differs from Example 1 in that:

[0157] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 30% relative to the hole area; the copper sulfate electrolyte includes the following components by mass concentration: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, SPS22ppm, MPS 77ppm, PEG16ppm, PVP55ppm, collagen 53ppm.

[0158] The rest is exactly the same as in Example 1.

[0159] Comparative Example 2

[0160] This comparative example provides a method for preparing copper foil, which differs from Example 1 in that:

[0161] S2. Special treatment of anode plate: a certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 60% relative to the hole area; the copper sulfate electrolyte includes the following components by mass concentration: Cu 2+ 95g / L, sulfuric acid 113g / L, chloride ion 25ppm, methyl blue 128ppm, PEG28ppm, PVP55ppm, collagen 40ppm.

[0162] The rest is exactly the same as in Example 1.

[0163] The morphology of the copper foil was tested, and the test results were as follows: Figure 3 As shown, according to Figure 3 It can be seen that the shape of the copper foil hole area obtained in Comparative Example 2 not only has defects, such as uneven distribution of hole size, but also the tensile strength and elongation of the porous copper foil are low. During the battery cell manufacturing process, the presence of holes may cause stress concentration. Especially in the cycling process, the insertion and extraction of lithium ions will cause volume changes, which may easily cause belt breakage and low production efficiency. At the same time, after the battery cell obtained by the process is cyclically charged and discharged, the electrode piece is prone to micro-fractures, which leads to the destruction of the continuity of the electrode material, the obstruction of the electron transmission path, the increase of internal resistance, low capacity and easy to cause thermal runaway.

[0164] Comparative Example 3

[0165] This comparative example provides a method for preparing copper foil, which differs from Example 6 in that:

[0166] S2. Special treatment of anode plate: A certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 70% relative to the hole area.

[0167] The rest is exactly the same as in Example 1.

[0168] Comparative Example 4

[0169] This comparative example provides a method for preparing copper foil, which differs from Example 6 in that:

[0170] S2. Special treatment of anode plate: A certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 75% relative to the hole area.

[0171] The rest is exactly the same as in Example 1.

[0172] Comparative Example 5

[0173] This comparative example provides a method for preparing copper foil, which differs from Example 6 in that:

[0174] S2. Special treatment of anode plate: A certain size of inert material is coated on the surface of the anode plate at the corresponding hole area, and the range of the inert layer is 80% relative to the hole area.

[0175] The rest is exactly the same as in Example 1.

[0176] Comparative Example 6

[0177] This comparative example provides a method for preparing a copper foil, which differs from Example 1 in that the surface of the active layer of the anode plate in S2 is not coated with an inert substance.

[0178] The rest is exactly the same as in Example 1.

[0179] Performance Testing

[0180] The copper foils prepared in Examples 1-10 and Comparative Examples 1-6 were tested for tensile strength, elongation, and connectivity. The test results are shown in Tables 1 and 2. The tensile strength and elongation were measured according to the test methods specified in GB / T 29847-2013, "Test Methods for Copper Foil for Printed Circuit Boards," using a HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd., at room temperature and a strain rate of 50 mm / min. Generally, the samples were cut into strips with a length of 100 mm and a width of 12.7 mm. Each sample was tested five times, and the average value was used as the final tensile strength or elongation.

[0181] The initial coulombic efficiencies of the energy storage devices prepared in Examples 1-10 and Comparative Examples 1-6 were tested, and the test results are shown in Table 1.

[0182] Table 1 Performance test results of copper foil and energy storage devices of Examples 1-10 and Comparative Examples 1-6

[0183]

[0184]

[0185] Table 2 Copper foil connection test related values ​​of Examples 1-10 and Comparative Examples 1-6

[0186] Serial number Γ m(mm) n(mm) a(mm) b(mm) Weight reduction ratio of hole area density (%) Example 1 0.91 2.00 1.57 0.25 0.2 5.17 Example 2 1.04 2.00 0.79 0.25 0.2 10.91 Example 3 1.08 1.00 0.79 0.25 0.2 22.28 Example 4 0.98 0.80 0.65 0.25 0.2 30.11 Example 5 0.96 0.65 0.60 0.25 0.2 39.11 Example 6 1.03 1.41 1.00 0.5 0.45 51.73 Example 7 0.98 1.18 1.00 0.5 0.45 58.82 Example 8 1.01 1.09 1.00 0.5 0.45 65.70 Example 9 0.98 2.00 1.18 0.5 0.45 30.17 Example 10 0.97 1.18 1.00 0.5 0.45 58.40 Comparative Example 1 1.01 0.80 0.65 0.25 0.2 31.11 Comparative Example 2 0.97 1.18 1.00 0.5 0.45 58.63 Comparative Example 3 1.01 1.00 1.00 0.5 0.45 71.51 Comparative Example 4 1.14 1.00 0.94 0.5 0.45 85.70 Comparative Example 5 1.14 0.95 0.93 0.5 0.45 91.04 Comparative Example 6 0.12 1.41 1.00 0.5 0.45 7.06

[0187] In combination with Examples 1-10, and in combination with the data in Tables 1 and 2, it can be seen that the copper foil prepared by the preparation method of the present application meets the requirements of the degree of connection, and its tensile strength and elongation are mainly negatively correlated with the area of ​​the anode plate coated with the inert substance. The larger the coating area, the lower the surface density of the porous copper foil, the thinner the relative thickness, and the lower the tensile strength and elongation; the first coulomb efficiency of the battery cell and the area of ​​the anode plate coated with the inert substance show a trend of first increasing and then decreasing. The highest first coulomb efficiency (96.4%) corresponds to an anode plate coated with an inert substance area of ​​20%. As the area of ​​the anode plate coated with the inert substance increases, the surface density of the porous copper foil continues to decrease. The lower the surface density, the thinner the copper foil thickness, the better the conductivity. However, as the current collector is too thin, the path for electrons in the active material to be transmitted to the current collector becomes longer, and the internal resistance increases, resulting in a downward trend in the first coulomb efficiency.

[0188] Combining Example 1 with Comparative Examples 1-6, and the data in Tables 1 and 2, it can be seen that adjusting the composition and ratio of the electrolyte significantly affects the mechanical properties of the resulting copper foil. The proportion and amount of any additive can significantly affect the tensile strength and elongation of the porous copper foil. At the same time, excessive coating of the anode plate with an inert material can significantly reduce the physical properties of the porous copper foil and the efficiency of the energy storage device. Excessive coating area and low surface density can lead to insufficient mechanical strength of the copper foil itself, which can easily cause breakage during the battery cell manufacturing process or structural damage due to the expansion and contraction of the battery cell during charge and discharge, increasing internal resistance and the risk of thermal runaway.

[0189] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A copper foil, characterized in that The copper foil has a uniformly distributed through-hole structure. The surface density of the copper foil has a correlation Γ with the size and arrangement of the through-holes. The formula of the correlation Γ is as follows: And the value range of Γ is 1±0.1; Where M is the surface density of the porous area, ranging from 5-180g / m 2 ; k represents the density of copper foil, the actual value is 8.96g / cm 3 ; η represents the thickness of copper foil (μm); a and b represent the long and short radii of the through hole, respectively (mm), ranging from 0.05 to 1.10 mm; m and n represent the longest and shortest distances between the centers of adjacent through holes in the horizontal and vertical directions (mm), ranging from 0.12-3.00mm.

2. The copper foil according to claim 1, wherein: Also includes one or more of the following characteristics: A1) the thickness of the copper foil is 4-18 μm; A2) at room temperature, the tensile strength of the copper foil along the major axis of the through hole is 200-600 MPa, and the tensile strength along the minor axis of the through hole is 100-400 MPa; A3) At room temperature, the elongation at break of the copper foil along the major axis of the through hole is ≥0.8%, and the elongation at break along the minor axis of the through hole is ≥0.4%.

3. A method for preparing the copper foil according to any one of claims 1 to 2, characterized in that: The copper foil is prepared by electrolysis, wherein The cathode surface of the electrolytic method is spot-coated with an insulating acid-resistant coating to form an insulating acid-resistant layer; the insulating acid-resistant coating is composed of hydroxyethyl methacrylate, isobornyl acrylate, 4-hydroxycyclohexyl phenyl ketone, silicon dioxide, and modified polysiloxane in a mass ratio of 25-35:25-35:25-35:3-8:3-8; The anode surface of the electrolytic method is coated with a mixed active material solution and sintered to form an active layer. An inert material is coated on the surface of the active layer at a position opposite to the cathode to form an inert layer. The inert layer is less than 70% of the area of ​​the pore area. The mixed active material solution is composed of iridium oxide, tantalum oxide, and solvent in a mass ratio of 7-10:3-5:85-90. The electrolyte used in the electrolysis method includes the following components: 75-125 g / L copper ions, 85-135 g / L sulfuric acid, 15-50 ppm chloride ion concentration, 30-150 ppm brightener, 10-80 ppm moving agent, and 5-50 ppm leveling agent.

4. The preparation method according to claim 3, wherein: Also includes one or more of the following characteristics: 11) The thickness of the insulating acid-resistant coating is 150-550 μm; 12) The thickness of the active layer is 2-5 nm; 13) The inert substance is selected from fluoropolymers; preferably, the fluoropolymer is selected from one or more of polytetrafluoroethylene, polyperfluoroethylene propylene, polyvinylidene fluoride, and polyvinyl fluoride; 14) The thickness of the inert layer is 40-150 μm; 15) The temperature of the electrolyte is 45-65°C; 16) The current applied during the electrolysis process is 8000-45000A; 17) The inert layer covers an area of ​​10-60% relative to the hole area; 18) The inert material coating method includes the following steps: heating the surface of the active layer facing the cathode to 40-200°C, then attaching the inert material to the heated area, and after the inert material is adhered, cooling to room temperature to complete the coating of the inert material on the surface of the active layer.

5. The preparation method according to claim 3, wherein: Also includes one or more of the following characteristics: 21) The leveling agent is a nitrogen-containing amine organic compound; 22) The moving agent is a polyether compound; 23) The brightener is a sulfur-containing compound.

6. The preparation method according to claim 5, characterized in that: Also includes one or more of the following characteristics: 211) The leveling agent is selected from one or more of collagen, gelatin or polyethyleneimine; 221) The displacement agent is selected from one or more of polyethylene glycol, polypropylene glycol or polyvinylpyrrolidone; 231) The brightener is selected from one or more of sodium methylene dinaphthalene sulfonate, sodium polydisulfide propane sulfonate, sodium 3-mercapto-1-propanesulfonic acid, methyl blue or 2-mercaptothiazoline.

7. A current collector, characterized in that: The invention comprises the copper foil according to any one of claims 1 to 2.

8. A pole piece, characterized in that: Comprising the current collector as claimed in claim 7.

9. An energy storage device, characterized in that: Comprising the pole piece as claimed in claim 8.

10. The energy storage device according to claim 9, characterized in that: The first coulombic efficiency of the energy storage device is greater than 90%.

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