Copper foil and preparation method thereof, lithium battery copper foil, current collector, pole piece, battery and electric device

Abstract

The invention relates to a copper foil and a preparation method thereof, a lithium battery copper foil, a current collector, a pole piece, a battery and an electric device. The transverse tensile strength of the copper foil is S0, the unit is kgf / mm < 2 > and the transverse elongation is E0 under the room temperature condition, the transverse tensile strength of the copper foil is S1, the unit is kgf / mm < 2 >, the transverse elongation is E1 and the tensile strength attenuation rate is R1 after the copper foil is baked for 1 hour under the 200 DEG C condition, and S0, E0, S1, E1 and R1 meet the following conditions: R1 = (1-S1 / S0) * 100% < 10%, and E1-E0 > 0. The copper foil has excellent thermal stability, can reduce the occurrence of fracture and wrinkling phenomena in the manufacturing process of the copper foil and the manufacturing and using processes of a battery, and can improve the cyclicity and safety of the battery by applying the copper foil to the lithium battery copper foil.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to copper foils and their preparation methods, lithium battery copper foils, current collectors, electrode sheets, batteries, and electrical devices. Background Art

[0002] As a green and environmentally friendly energy storage device, lithium batteries have the advantages of high energy density, excellent cycling performance, and high safety. They have become a key support for industries such as electronic devices, power tools, large-scale energy storage, and new energy vehicles, and are an important basic technology for achieving the "dual carbon" goal.

[0003] Among the many components of lithium batteries, the current collector, as the carrier of the active material, plays an important role in collecting the current generated by the active material and outputting a larger current. It is a key auxiliary material for high-energy density lithium batteries. The advantages of electrolytic copper foils, such as high electrical conductivity, moderate potential, soft texture, stable properties, and low price, determine that it becomes the best choice for the negative electrode current collector of lithium batteries. And lithium battery electrolytic copper foil (or lithium battery copper foil), as one of the important components of lithium batteries, its performance is also a key factor affecting the performance of lithium batteries. Therefore, preparing high-performance lithium battery copper foil is crucial for improving the electrochemical performance of lithium batteries. In addition, the volume expansion and contraction (up to more than 300%) during the lithium insertion and extraction process of silicon negative electrode materials and the thermal effect generated by the fast charging technology of solid-state batteries put forward higher requirements for the thermal stability of the mechanical properties of copper foil materials at high temperatures. However, traditional lithium battery copper foils have the defect of insufficient thermal stability and need to be improved urgently. Summary of the Invention

[0004] Based on this, the present invention provides a copper foil and its preparation method, lithium battery copper foil, current collector, electrode sheet, battery, and electrical device. This copper foil has excellent thermal stability and can be used as a lithium battery copper foil to improve battery performance.

[0005] The technical solution is as follows:

[0006] A copper foil, at room temperature, the transverse tensile strength of the copper foil is S 0 , with the unit of kgf / mm 2 , and the transverse elongation is E 0 . At 200°C, after baking the copper foil for 1 hour, its transverse tensile strength is S 1 , with the unit of kgf / mm 2 , and the transverse elongation is E 1 , and the tensile strength attenuation rate is R 1 . The S 0 , E 0 , S 1 and, E 1 and R 1 satisfy:

[0007] R 1 = (1 - S 1 / S 0 ) * 100% < 10%, and E 1 - E 0 > 0.

[0008] In one embodiment, it is noted that at 200 °C, after baking the copper foil for 2 h, its transverse tensile strength is S 2 , with the unit of kgf / mm 2 , the transverse elongation rate is E 2 , and the tensile strength attenuation rate is R 2 , where the S 0 , E 0 , S 2 , E 2 and R 2 satisfy:

[0009] R 2 = (1 - S 2 / S 0 ) * 100% < 20%, and E 2 - E 0 > 0.

[0010] In one embodiment, it is noted that at 200 °C, after baking the copper foil for 3 h, its transverse tensile strength is S 3 , with the unit of kgf / mm 2 , the transverse elongation rate is E 3 , and the tensile strength attenuation rate is R 3 , where the S 0 , E 0 , S 3 , E 3 and R 3 satisfy:

[0011] R 3 = (1 - S 3 / S 0 ) * 100% < 30%, and E 3 - E 0 > 0.

[0012] In one embodiment, at room temperature, the transverse tensile strength of the copper foil is 40 kgf / mm 2 ~ 90 kgf / mm 2 .

[0013] In one embodiment, at room temperature, the transverse elongation rate of the copper foil is more than 3%.

[0014] In one embodiment, the difference between the longitudinal tensile strength and the transverse tensile strength of the copper foil is 1 kgf / mm 2 or less.

[0015] In one embodiment, at room temperature, calculated as a percentage of the total number of grains in the copper foil, the copper foil comprises more than 90% of grains with a particle size less than 0.6 μm.

[0016] In one embodiment, at 200 °C, after baking the copper foil for 1 h, calculated as a percentage of the total number of grains in the copper foil, the copper foil comprises more than 90% of grains with a particle size less than 0.6 μm.

[0017] In one embodiment, the copper foil has opposite first and second surfaces, the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1 > Gs2, and the average grain difference between the first surface and the second surface satisfies:

[0018] and the average grain difference is less than 0.2 μm;

[0019] wherein, d 1 represents the single grain size of the first surface, in μm, n d1 represents the number of grains with a size of d 1 on the first surface, d 2 represents the single grain size of the second surface, in μm, n d2 represents the number of grains with a size of d 2 on the second surface.

[0020] In one embodiment, the thickness of the copper foil is 3 μm to 12 μm.

[0021] The present invention also provides a preparation method of the copper foil as described above, and the technical solution is as follows:

[0022] A preparation method of the copper foil as described above, the copper foil is prepared by an electrolysis method;

[0023] wherein, the electrolytic solution used in the electrolysis method comprises the following components:

[0024] copper ions 90 g / L ± 2 g / L, sulfuric acid 105 g / L ± 5 g / L, chloride ions 23 ppm ± 2 ppm, brightening agent 40 mg / L ± 20 mg / L, leveling agent 12 mg / L ± 8 mg / L, and leveling agent 12 mg / L ± 8 mg / L;

[0025] Among them, the brightening agent includes a sulfur-containing group compound, the leveling agent includes a nitrogen-containing amine organic compound, the leveling agent includes a variety of polyether compounds, and at least includes polyethylene glycol.

[0026] In one embodiment, the sulfur-containing group compound includes one or more of sodium polydithiopropane sulfonate, sodium mercapto propane sulfonate, sodium 3-mercapto-1-propane sulfonate, and sodium propanesulfonate piperazine dithiocarboxylate.

[0027] In one embodiment, the nitrogen-containing amine organic compound includes one or more of polyethyleneimine alkyl compounds and collagen.

[0028] In one embodiment, the leveling agent is compounded by a first polyether compound and a second polyether compound according to a concentration ratio of (1-2):1. Among them, the first polyether compound is polyethylene glycol, and the second polyether compound includes one or more of octylphenol polyoxyethylene ether and ethylene oxide-propylene oxide block polyether compounds.

[0029] In one embodiment, the temperature of the electrolyte is 52°C ± 3°C.

[0030] In one embodiment, the current applied during the electrolysis process is 25000A ± 5000A.

[0031] The present invention also provides the application of the copper foil as described above, and the technical solution is as follows:

[0032] A lithium-ion copper foil includes the copper foil as described above or a copper foil prepared according to the preparation method of the copper foil as described above.

[0033] A current collector includes the lithium-ion copper foil as described above.

[0034] An electrode includes the current collector as described above.

[0035] A battery includes the electrode as described above.

[0036] An electrical device includes the battery as described above.

[0037] The present invention has at least the following beneficial effects:

[0038] Tensile strength and elongation are important performance indicators of copper foil. Copper foil with high tensile strength and high elongation and excellent thermal stability has strong tolerance to external forces such as rolling and winding of the negative electrode sheet of lithium batteries and better high-temperature resistance during charge and discharge, avoiding the phenomenon of capacity decline caused by copper foil fracture; effectively enhancing the binding energy with the negative electrode material that deforms during the charge and discharge process of lithium-ion batteries and improving the cycle stability of the battery. The copper foil provided by the present invention, after being baked at 200 °C for 1 h, the attenuation rate R of its transverse tensile strength 1 =(1 - S 1 / S 0 ) * 100% < 10%, and the elongation is greater than that in the initial state at room temperature, indicating that it has excellent thermal stability and can still maintain excellent mechanical properties after high-temperature baking, thereby reducing the occurrence of fracture and wrinkling of copper foil during the manufacturing process and during the manufacturing and use of batteries. When it is used in lithium copper foil, it can improve the cycle performance and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 are EBSD photos of the roller surface and the deposition surface of the copper foil prepared in Example 1, where Figure 1 (a) is the EBSD photo of the roller surface, Figure 1 (b) is the EBSD photo of the deposition surface;

[0040] Figure 2 are EBSD photos of the roller surface and the deposition surface of the copper foil prepared in Comparative Example 1, where Figure 2 (a) is the EBSD photo of the roller surface, Figure 2 (b) is the EBSD photo of the deposition surface. DETAILED DESCRIPTION OF THE INVENTION

[0041] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0043] When using "comprising", "having", and "including" as described herein, the intention is to cover non-exclusive inclusion, and unless an explicit limiting term such as "only", "consisting of", etc. is used, another component may also be added.

[0044] The terms "preferably", "more preferably", "more preferably", "even more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention. That is, in the present invention, "preferably", "more preferably", "more preferably", "even more preferably", etc. are only used to describe embodiments or examples with better effects, but do not constitute a limitation on the protection scope of the present invention.

[0045] In the present invention, "further", "even further", "especially", etc. are used for descriptive purposes to indicate differences in content, but should not be construed as a limitation on the protection scope of the present invention.

[0046] In the present invention, the meaning of "at least one" is more than one, such as one, two or more. The meaning of "multiple" or "several" is at least two, such as two, three, etc., and the meaning of "multiple layers" is at least two layers, such as two layers, three layers, etc., unless otherwise specifically defined. In the description of the present invention, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0047] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0048] If there is no special description, all steps of the present invention can be carried out in sequence or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c) in sequence, or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0049] Unless otherwise mentioned, terms in the singular form may include the plural form and should not be construed as having a quantity of one.

[0050] In the present invention, "above" or "below" both include the recited number. For example, "below 1" includes 1.

[0051] In the present invention, room temperature refers to 0°C to 40°C, including but not limited to 10°C to 40°C, or further 20°C to 30°C.

[0052] The fast charging technology is an important development direction for power batteries. During the high-rate fast charging process, a large amount of heat is generated, causing the internal temperature of the battery to rise rapidly. At the same time, the expansion and contraction amount of the negative electrode active material increases significantly, which poses more stringent requirements for the current collector to maintain good mechanical properties at high temperatures. Among them, the tensile strength and elongation are important performance indicators of copper foil. If the tensile strength and elongation of the copper foil are low, the copper foil is prone to breakage and wrinkling during the preparation process and the cell preparation process, greatly affecting production efficiency and battery performance. Further, copper foil with excellent thermal stability, high tensile strength, and high elongation has strong tolerance to external forces such as rolling and winding of the negative electrode sheet of lithium batteries and stronger high-temperature resistance during charge and discharge, avoiding the phenomenon of capacity decline caused by copper foil breakage; effectively enhancing the binding energy with the negative electrode material that deforms during the charge and discharge process of lithium-ion batteries, improving the cycle stability of the battery. However, traditional lithium battery copper foil current collectors have the defect of insufficient thermal stability and urgently need improvement.

[0053] Based on this, the present invention provides a copper foil with excellent thermal stability, which can be used as a lithium battery copper foil to improve battery performance.

[0054] The technical solution is as follows:

[0055] A copper foil, under room temperature conditions (such as 10°C to 40°C, further 25°C), the transverse tensile strength of the copper foil is S 0 , with the unit of kgf / mm 2 , the transverse elongation is E 0 , under 200°C conditions, after baking the copper foil for 1 h, its transverse tensile strength is S 1 , with the unit of kgf / mm 2 , the transverse elongation is E 1 , the tensile strength attenuation rate is R 1 , the S 0 , E 0 , S 1 , E 1 and R 1 satisfy:

[0056] R1 = (1 - S 1 / S 0 ) * 100% < 10%, and E 1 - E 0 > 0.

[0057] The poor thermal stability of the copper foil can be divided into two cases: (1) After high-temperature baking, the tensile strength decays severely, resulting in a reduction in the yield strength ratio and poor thermal stability of the copper foil. Under high-temperature conditions during battery charging, especially fast charging, the copper foil is prone to breakage, affecting the safety and cycle performance of the battery; (2) After high-temperature baking, the elongation decays severely, which also leads to a reduction in the yield strength. In this case, the copper foil of the battery is prone to wrinkle during charging, resulting in battery short circuit. In the present invention, after the copper foil is baked at 200 °C for 1 h, the tensile strength decay is small, and the tensile strength decay rate R 1 = (1 - S 1 / S 0 ) * 100% < 10% (including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%. Further, R 1 < 8%. Further still, R 1 < 6%.), and the elongation increases instead, indicating that it has excellent thermal stability and can still maintain excellent mechanical properties after high-temperature baking, thereby reducing the occurrence of breakage and wrinkling of the copper foil during the manufacturing process and during battery manufacturing and use. When it is used for lithium-ion copper foil, it can improve the cycle performance and safety of the battery.

[0058] It can be understood that the present invention does not impose special restrictions on the test methods for the tensile strength and elongation of the copper foil, and conventional test methods in the art can be used. Optionally, in the embodiments of the present invention, according to the test method of GB / T29847-2013, a HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd. is used to test the tensile strength and elongation of the sample at room temperature and a strain rate of 50 mm / min.

[0059] In one of the embodiments, at 200 °C, after the copper foil is baked for 2 h, its transverse tensile strength is S 2 , with the unit of kgf / mm 2 , the transverse elongation is E 2 , the tensile strength decay rate is R 2 , and the S 0 , E 0 , S 2 , E 2 and R 2 satisfy:

[0060] R 2 = (1 - S 2 / S 0 ) * 100% < 20%, and E 2 -E 0 > 0.

[0061] After the copper foil is baked at 200°C for 2 hours, the tensile strength attenuation rate R 2 = (1 - S 2 / S 0 ) * 100% < 20% (including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%. Further, R 2 < 15%. Further still, R 2 < 10%. Even further, R 2 < 8%.), The elongation is greater than the initial value, indicating that the copper foil still has excellent thermal stability and can maintain excellent mechanical properties after high-temperature baking, thus reducing the occurrence of fracture and wrinkling of the copper foil during the manufacturing process and during the manufacturing and use of the battery. When it is used for lithium-ion copper foil, it can improve the cycle performance and safety of the battery.

[0062] In one embodiment, it is noted that under the condition of 200°C, after the copper foil is baked for 3 hours, its transverse tensile strength is S 3 , with the unit of kgf / mm 2 , the transverse elongation is E 3 , the tensile strength attenuation rate is R 3 , and the S 0 , E 0 , S 3 , E 3 and R 3 satisfy:

[0063] R 3 = (1 - S 3 / S 0 ) * 100% < 30%, and E 3 -E 0 > 0.

[0064] After the copper foil is baked at 200°C for 3 hours, the tensile strength attenuation rate R 3 = (1 - S 3 / S 0 ) * 100% < 30% (including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or 29%. Further, R 3< 20%. Further, R 3 < 15%. Still further, R 3 < 10%.), The elongation rate is greater than the initial value, indicating that the copper foil also has very excellent thermal stability and can still maintain excellent mechanical properties after high-temperature baking, thereby reducing the occurrence of breakage and wrinkling of the copper foil during the manufacturing process and during the manufacturing and use of the battery. Using it for lithium-ion copper foil can improve the cycle performance and safety of the battery.

[0065] It has been found through research that if the tensile strength and elongation rate of the copper foil are low, the copper foil is prone to tape breakage and wrinkling during the preparation process and the cell preparation process, which greatly affects the production efficiency and battery performance.

[0066] In one embodiment, at room temperature (such as 10°C to 40°C, further 25°C), the transverse tensile strength of the copper foil is 40 kgf / mm 2 ~90 kgf / mm 2 , The copper foil that meets this requirement can reduce the occurrence of tape breakage and wrinkling of the copper foil during the preparation process and the cell preparation process, can improve the copper foil manufacturing and battery production efficiency, and improve the capacity and safety performance of the battery. When the tensile strength of the copper foil is less than 40 kgf / mm 2 , During the processes of copper foil curling, rolling, and winding formation, tape breakage is likely to occur, seriously affecting the safety performance and cycle performance of the battery. On the other hand, when the tensile strength of the copper foil is higher than 90 kgf / mm 2 , It may not be possible to balance the elongation rate, which will result in a low elongation rate. Although the occurrence of tape breakage is reduced, the wrinkling phenomenon increases and the usability of the copper foil decreases. For example, during the production of copper foil or during the process of using copper foil to produce electrodes for secondary batteries, tearing may occur, which may make it difficult to stably obtain products.

[0067] It can be understood that the transverse tensile strength of the copper foil described in the present invention at room temperature (such as 10°C to 40°C, further 25°C) includes but is not limited to 40 kgf / mm 2 , 42 kgf / mm 2 , 44 kgf / mm 2 , 46 kgf / mm 2 , 48 kgf / mm 2 , 50 kgf / mm 2 , 52 kgf / mm 2 , 54 kgf / mm 2 , 56 kgf / mm 2 , 58 kgf / mm 2 , 60 kgf / mm 2 , 65 kgf / mm 2 , 70 kgf / mm2 , 75 kgf / mm 2 , 80 kgf / mm 2 , 85 kgf / mm 2 or 90 kgf / mm 2 .

[0068] In one of the embodiments, at room temperature (such as 10°C to 40°C, further 25°C), the transverse elongation rate of the copper foil is more than 3%, and the copper foil meeting this requirement can reduce the phenomena of tape breakage and wrinkling during the preparation process of the copper foil and the preparation process of the battery cell, improve the production efficiency of copper foil manufacturing and battery production, and improve the capacity and safety performance of the battery. It can be understood that the transverse elongation rate of the copper foil of the present invention at room temperature (such as 10°C to 40°C, further 25°C) includes but is not limited to 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0069] In one of the embodiments, the difference between the longitudinal (MD) tensile strength and the transverse (TD) tensile strength of the copper foil is 1 kgf / mm 2 Hereinafter, the difference between the MD and TD tensile strengths of the copper foil is controlled within 1 kgf / mm 2 . In addition to improving the production efficiency and qualified rate during the copper foil manufacturing process, it can also improve the production stability of the coating and rolling processes. The tensile fluctuations in the MD and TD directions are mainly related to the copper foil thickness and the stability of additives. The greater the copper foil thickness fluctuation and the imbalance of additive ratio will both lead to greater transverse and longitudinal tensile fluctuations. When the difference in tensile strength in the MD direction exceeds 1 kgf / mm 2 , when the tension of each roll system in the coating and rolling processes remains unchanged, it is easy to cause sudden wrinkling or tape breakage of the electrode sheet, and a large amount of time is required for recovery. When the difference in tensile strength in the TD direction exceeds 1 kgf / mm 2 , in the case of high-tension parameters for coating and rolling, transverse wrinkling may occur, resulting in battery short circuit.

[0070] It has been found through research that when the thickness of the copper foil remains unchanged, the tensile strength of the copper foil increases with the decrease of the grain size. The tensile strength is closely related to the transfer of slip from the plastically deformed grain to the adjacent grain, and whether this transfer can occur mainly depends on whether the stress concentration generated by the dislocation pile-up group near the grain boundary of the slipped grain can activate the dislocation source in the slip system of the adjacent grain and make it start to carry out coordinated multi-slip. In addition, refining the grains can produce more grain boundaries. The more grain boundaries there are, the greater the hindrance to dislocation slip, and a greater external force is required to cause the fracture of the copper foil; and more grain boundaries can absorb and release thermal stress, improving the stability of the copper foil under high-temperature conditions.

[0071] In one embodiment, at room temperature (such as 10°C to 40°C, further 25°C), calculated as a percentage of the total number of grains in the copper foil, the copper foil includes more than 90% of grains with a particle size less than 0.6 μm.

[0072] In one embodiment, at 200°C, after baking the copper foil for 1 h, calculated as a percentage of the total number of grains in the copper foil, the copper foil includes more than 90% of grains with a particle size less than 0.6 μm.

[0073] In one embodiment, at 200°C, after baking the copper foil for 2 h, calculated as a percentage of the total number of grains in the copper foil, the copper foil includes more than 90% of grains with a particle size less than 0.6 μm.

[0074] In one embodiment, at 200°C, after baking the copper foil for 3 h, calculated as a percentage of the total number of grains in the copper foil, the copper foil includes more than 90% of grains with a particle size less than 0.6 μm.

[0075] In one embodiment, the copper foil has opposite first and second surfaces, the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1 > Gs2, and the average grain difference between the first surface and the second surface satisfies:

[0076] And the average grain difference is less than 0.2 μm;

[0077] Wherein, d 1 represents the single grain size of the first surface, in μm, n d1 represents the number of grains with a size of d 1 on the first surface, d 2 represents the single grain size of the second surface, in μm, n d2 represents the number of grains with a size of d 2 on the second surface.

[0078] In the present invention, the difference in average grain size between the two surfaces of the copper foil (for lithium battery copper foil obtained by electrolysis, the two surfaces refer to the deposition surface and the roller surface, respectively) is calculated by the above average grain difference formula to be less than 0.2μm. Small grains can produce more grain boundaries. The more grain boundaries there are, the greater the external force required to cause the copper foil to break; and more grain boundaries can absorb and release thermal stress, thereby improving the stability of the copper foil under high temperature conditions. In addition, the difference in average grain size between the two surfaces of the copper foil will affect the warpage. The greater the difference in grain size between the two surfaces, the higher the warpage. Taking electrolytic copper foil as an example, in the crystal structure, the generation of warpage is usually related to the grain size of the deposition surface and the roller surface. The smaller the grains on the roller surface, the greater the compressive stress. The larger the grains on the deposition surface, the smaller the compressive stress. Therefore, the warpage of the copper foil is from the roller surface to the deposition surface. When the difference in grain size between the deposition surface and the roller surface exceeds 0.2μm, the difference in compressive stress between the two surfaces is too large, and the warpage of the copper foil is greater. Excessive warping will have the following effects on the copper foil and the battery: (1) It will cause the copper foil to tear and the baking time to be long, affecting production efficiency and qualification rate; (2) In the process of power battery preparation, due to the warping defects of the copper foil, the negative electrode laser cutting ear situation is serious, and it is necessary to arrange special personnel to pick the ear, which is time-consuming and labor-intensive, seriously affecting production efficiency and quality. If the inserted ear is not picked out to form a battery, the internal resistance of the battery will be reduced or there will be a risk of short circuit.

[0079] In one embodiment, the thickness of the copper foil is 3μm to 12μm. Too thick or too thin copper foil is not conducive to the stability of the process or causes a decrease in battery performance. When the thickness of the copper foil is less than 3μm, after the battery tab is formed, it is easy to cause the tab to fold or insert during the high-speed operation of laser die-cutting and winding, which greatly reduces the production efficiency of the process and reduces the internal resistance of the battery. When the thickness of the copper foil is greater than 12μm, the content of active materials in the battery is reduced due to the high thickness, affecting the capacity density of the battery. The thickness of the copper foil can be regulated by the current and line speed during the preparation process.

[0080] The present invention also provides a method for preparing the copper foil as described above, and the technical scheme is as follows:

[0081] A method for preparing the copper foil as described above, wherein the copper foil is prepared by electrolysis;

[0082] The electrolyte used in the electrolysis method includes the following components:

[0083] Copper ion 90g / L±2g / L, sulfuric acid 105g / L±5g / L, chloride ion 23ppm±2ppm, brightener 40mg / L±20mg / L, leveler 12mg / L±8mg / L and moving agent 12mg / L±8mg / L;

[0084] Among them, the brightener includes a sulfur-containing group compound, the leveling agent includes a nitrogen-containing amine organic compound, the leveling agent includes a variety of polyether compounds, and at least includes polyethylene glycol.

[0085] In the present invention, adding a certain proportion of brightener, leveling agent and leveling agent in the electrolyte (or plating solution) can change the deposition rate of the copper foil and improve the mechanical properties of the copper foil. The brightener is mainly composed of a sulfur-containing group compound, and its main function is to promote the nucleation of copper ions; the leveling agent is mainly composed of a nitrogen-containing amine organic compound, which can promote the face-centered growth of the copper foil grains and make the grains more flat; when the brightener of organic sulfide and the leveling agent of nitrogen-containing amine organic compound (such as nitrogen-containing polymer) are used in combination, the crystal structure of the copper foil is more flat and dense, a large number of nanocrystalline regions are generated, the effect of fine grain strengthening is strengthened, and the excellent structures of fine grains and nano-twins interact with each other to improve the elongation while improving the tensile strength of the copper foil. The leveling agent is compounded by a variety of polyether compounds, and at least includes polyethylene glycol, which can form a more stable and uniform hindrance layer, thereby effectively restricting certain growth directions of copper crystals, and interacting with other additives evenly in each part of the copper foil to make the grains finer and more uniform. In addition, the polyether compound can effectively inhibit the growth of grains at high temperature, reduce the grain nucleation size, generate more interfaces, absorb and release thermal stress, and improve the stability of the copper foil under high temperature conditions.

[0086] In one embodiment, the sulfur-containing group compound includes one or more of sodium polydithiopropane sulfonate, sodium mercaptoalkyl propane sulfonate, sodium 3-mercapto-1-propane sulfonate, and sodium propanesulfonate piperazine dithiocarboxylate.

[0087] In one embodiment, the nitrogen-containing amine organic compound includes one or more of polyethyleneimine alkyl compounds and collagen.

[0088] In one embodiment, the leveling agent is compounded by a first polyether compound and a second polyether compound according to a concentration ratio of (1-2):1, wherein the first polyether compound is polyethylene glycol, and the second polyether compound includes one or more of octylphenol polyoxyethylene ether and ethylene oxide-propylene oxide block polyether compounds.

[0089] In one embodiment, the temperature of the electrolyte is 52°C ± 3°C.

[0090] In one embodiment, the current applied during the electrolysis process is 25000A ± 5000A.

[0091] In one embodiment, the method for preparing the copper foil as described above includes the following steps:

[0092] High-purity copper plates and / or copper wires (such as purity greater than or equal to 99.99%) are used as raw materials, dissolved in sulfuric acid solution to prepare copper sulfate electrolyte, and filtered through three stages to obtain pure copper sulfate electrolyte, and then filtered and subjected to a constant temperature system to generate an electrolyte solution, wherein the concentration of copper ions in the electrolyte is 90±2g / L, the concentration of sulfuric acid is 105±5g / L, the concentration of chloride ions is controlled at 23±2ppm, and the temperature of the electrolyte is controlled at 52°C±3°C, and then a uniformly mixed additive solution of a brightener, a positioning agent and a leveling agent is added to the electrolyte, an iridium-plated titanium sheet is used as an anode, and a pure titanium sheet is used as a cathode. Under the action of a DC power supply, the current is controlled to be 25000A±5000A, and a primary electrolytic copper foil is generated on a cathode roller.

[0093] It can be understood that for copper foil prepared by electrolysis, during the preparation process, for the copper foil, the roller surface that is in direct contact with the cathode roller surface and has low glossiness is the glossy surface, and the deposition surface is the matte surface with higher glossiness.

[0094] The present invention also provides the application of the copper foil as described above, and the technical solution is as follows:

[0095] A lithium battery copper foil, comprising the copper foil as described above or the copper foil prepared according to the method for preparing the copper foil as described above. It can be understood that the lithium battery copper foil has the advantages of the copper foil described in the present invention, has excellent thermal stability, high tensile strength and high elongation, and can still maintain excellent mechanical properties after high-temperature baking, thereby reducing the occurrence of fracture and wrinkling of the lithium battery copper foil during the manufacturing process and during the manufacturing and use of the battery. Using it for the lithium battery copper foil can improve the cycle and safety of the battery.

[0096] A current collector comprises the lithium battery copper foil as described above.

[0097] A pole piece, comprising the current collector as described above. Further, the pole piece comprises a first active material layer, a current collector and a second active material layer stacked in layers. Furthermore, the pole piece is a cathode pole piece, the first active material layer at least comprises one or more active material combinations of graphite materials, metal oxides, and silicon-based materials, and the second active material layer at least comprises one or more active material combinations of graphite materials, metal oxides, and silicon-based materials.

[0098] A battery comprises the pole piece as described above.

[0099] An electrical device includes the battery as described above. It can be understood that the electrical device is a conventional electrical device in the art, including but not limited to digital products, lighting products, cars, etc.

[0100] Specific embodiments are listed below to illustrate the present invention.

[0101] In an embodiment of the present invention, according to the test method of GB / T 29847-2013, using a HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd., the tensile strength and elongation of the sample were tested at room temperature and a strain rate of 50 mm / min. Generally, a strip-shaped sample with a length and width of 100 and 12.7 mm respectively was cut from the sample, and the data of each group of samples were tested five times, and the calculated average value was used as the final tensile strength or elongation.

[0102] Example 1

[0103] (1) Electrolytic copper foil and its preparation method:

[0104] The copper raw material was dissolved in sulfuric acid solution to obtain the original electrolyte solution, and then a certain concentration of chloride ions and additive solution were added thereto to obtain the electrolyte solution. The Cu 2+ concentration in the electrolyte solution was 90±2 g / L, and the concentration of H 2 SO 4 was 105±5 g / L, 3-mercapto-1-propanesulfonic acid sodium salt was 33 mg / L, polyethyleneimine alkyl salt was 9 mg / L, polyethylene glycol was 7 mg / L, octylphenol polyoxyethylene ether was 5 mg / L, and Cl - was provided by hydrochloric acid, and the flow rate of hydrochloric acid was 5.5 L / H. The Cl - concentration was controlled at 23±2 ppm, the electrolyte flow rate was 42±2 m 3 / h, and the temperature of the electrolyte was controlled at 52°C±3°C. Under the action of a DC power supply (current: 25000 A), a redox reaction occurred to the copper ions, and a copper foil precursor was formed on the surface of the cathode roller. Then, after passivation and aging, a copper foil sample with stable physical properties at room temperature was obtained, and its tensile strength and elongation were tested. The detailed results are shown in Table 1.

[0105] The room temperature sample was placed in an electrothermal constant temperature forced air drying oven with heating and air blowing functions, and baked at the set temperature T = 200°C for 1, 2, and 3 h respectively. The tensile strength and elongation of the baked samples were tested. The detailed results are shown in Table 1.

[0106] (2) Preparation method of secondary battery electrode

[0107] 95 parts of commercially available graphite anode materials, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) were dissolved in high-purity water and stirred evenly to form a stable slurry with a certain viscosity. Then, the obtained slurry was evenly coated on both surfaces of the electrolytic copper foil prepared above by using a scraper. Through the processes of rolling and die-cutting, the coated copper foil was rolled and cut into negative electrode sheets with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembling, the positive electrode sheet, separator, and negative electrode sheet were wound into a tightly fitting core. After the core was paired and put into the shell, a sealed lithium-ion battery single cell was formed. Finally, 20 PCS of the above single cells were selected. After charge-discharge cycling, the battery was disassembled, and the breakage (the electrode sheet was disconnected) and wrinkling (the electrode sheet was wrinkled) of the negative electrode sheet were observed visually. The results are shown in Table 2.

[0108] Example 2

[0109] (1) Preparation method of electrolytic copper foil:

[0110] The copper raw material was dissolved in sulfuric acid solution to obtain the original electrolyte solution. Then, a certain concentration of chloride ions and additive solution were added thereto to obtain the electrolyte solution. The concentration of Cu 2+ in the electrolyte solution was 90 ± 2 g / L, and the concentration of H 2 SO 4 was 105 ± 5 g / L, 3-mercapto-1-propanesulfonic acid sodium salt was 37 mg / L, polyethyleneimine alkyl salt was 12 mg / L, polyethylene glycol was 7 mg / L, octylphenol polyoxyethylene ether was 5 mg / L. Cl - was provided by hydrochloric acid, and the flow rate of hydrochloric acid was 5.5 L / H. The concentration of Cl - was controlled at 23 ± 2 ppm, the flow rate of the electrolyte solution was 42 ± 2 m 3 / h, and the temperature of the electrolyte solution was controlled at 52°C ± 3°C. Under the action of a DC power supply (current: 25000 A), copper ions underwent redox reaction, and copper foil preliminaries were formed on the surface of the cathode roller. Then, through passivation and aging, a copper foil normal-temperature sample with stable physical properties was obtained, and its tensile strength and elongation were tested. The detailed results are shown in Table 1.

[0111] The normal-temperature sample was placed in an electrothermal constant-temperature forced-air drying oven with heating and air-blowing functions. Under the condition of setting the temperature T = 200°C, it was baked for 1, 2, and 3 h respectively, and the tensile strength and elongation of the baked samples were tested. The detailed results are shown in Table 1.

[0112] (2) Preparation method of secondary battery electrodes

[0113] Dissolve 95 parts of commercially available graphite anode material, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) in high-purity water and stir evenly to form a stable slurry with a certain viscosity. Then, evenly coat the obtained slurry on both surfaces of the electrolytic copper foil prepared above. Through the processes of rolling and die-cutting, roll and cut the coated copper foil into a negative electrode plate with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembly, wind the positive electrode plate, separator, and negative electrode plate into a tightly fitting core. After the core is paired and put into the shell, a sealed lithium-ion battery single cell is formed. Finally, select 20 PCS of the above single cells. After charge and discharge cycles, disassemble the battery and observe the breakage (the electrode plate breaks) and wrinkling (the electrode plate wrinkles) of the negative electrode plate by appearance. The results are shown in Table 2.

[0114] Example 3

[0115] (1) Preparation method of electrolytic copper foil:

[0116] Dissolve the copper raw material in sulfuric acid solution to obtain the original electrolyte solution, and then add a certain concentration of chloride ions and additive solution to it to obtain the electrolyte solution. The concentration of Cu 2+ in the electrolyte solution is 90 ± 2 g / L, and the concentration of H 2 SO 4 is 105 ± 5 g / L, 3-mercapto-1-propanesulfonic acid sodium salt 37 mg / L, sodium polydithiopropanesulfonate 13 mg / L, polyethyleneimine alkyl salt 15 mg / L, polyethylene glycol 9 mg / L, octylphenol polyoxyethylene ether 7 mg / L. Cl - is provided by hydrochloric acid, and the flow rate of hydrochloric acid is 5.5 L / H. The concentration of Cl - is controlled at 23 ± 2 ppm, the flow rate of the electrolyte solution is 42 ± 2 m 3 / h, and the temperature of the electrolyte solution is controlled at 52 °C ± 3 °C. Under the action of a DC power supply (current is 25000 A), copper ions undergo redox reactions to form a copper foil primary product on the surface of the cathode roller. Then, through passivation and aging, a physically stable copper foil room temperature sample is obtained, and its tensile strength and elongation are tested. The detailed results are shown in Table 1.

[0117] Place the room temperature sample in an electrothermal constant temperature forced air drying oven with heating and air blowing functions, and bake it at the set temperature T = 200 °C for 1, 2, and 3 h respectively. Test the tensile strength and elongation of the baked samples. The detailed results are shown in Table 1.

[0118] (2) Preparation method of secondary battery electrodes

[0119] Dissolve 95 parts of commercially available graphite anode materials, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) in high-purity water and stir evenly to form a stable slurry with a certain viscosity. Then, uniformly coat the obtained slurry on both surfaces of the electrolytic copper foil prepared above. Through the processes of rolling and die-cutting, the coated copper foil is rolled and cut into negative electrode sheets with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembling, the positive electrode sheet, separator, and negative electrode sheet are wound into a tightly fitting core. After the core is paired and put into the shell, a sealed lithium-ion battery single cell core is formed. Finally, select 20 PCS of the above single cells. After charge and discharge cycles, disassemble the battery and observe the breakage (the electrode sheet breaks) and wrinkling (the electrode sheet wrinkles) of the negative electrode sheet on the appearance. The results are shown in Table 2.

[0120] Example 4

[0121] (1) Preparation method of electrolytic copper foil:

[0122] Dissolve the copper raw material in sulfuric acid solution to obtain the original electrolyte solution, and then add a certain concentration of chloride ions and additive solution to it to obtain the electrolyte solution. The Cu 2+ concentration in the electrolyte is 90 ± 2 g / L, and the concentration of H 2 SO 4 is 105 ± 5 g / L, 3-mercapto-1-propanesulfonic acid sodium 37 mg / L, sodium polydithiopropanesulfonate 18 mg / L, polyethyleneimine alkyl salt 15 mg / L, polyethylene glycol 9 mg / L, octylphenol polyoxyethylene ether 7 mg / L. Cl - is provided by hydrochloric acid, and the flow rate of hydrochloric acid is 5.5 L / H. The Cl - concentration is controlled at 23 ± 2 ppm, the electrolyte flow rate is 42 ± 2 m 3 / h, and the temperature of the electrolyte is controlled at 52 °C ± 3 °C. Under the action of a DC power supply (current is 25000 A), copper ions undergo redox reactions, and a copper foil precursor is formed on the surface of the cathode roller. Then, through passivation and aging, a copper foil room temperature sample with stable physical properties is obtained. Test its tensile strength and elongation. The detailed results are shown in Table 1.

[0123] Place the room temperature sample in an electrothermal constant temperature blast drying oven with heating and air-blowing functions, and bake it at the set temperature T = 200 °C for 1, 2, and 3 h respectively. Test the tensile strength and elongation of the baked sample. The detailed results are shown in Table 1.

[0124] (2) Preparation method of secondary battery electrodes

[0125] 95 parts of commercially available graphite anode materials, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) were dissolved in high-purity water and stirred evenly to form a stable slurry with a certain viscosity. Then, the obtained slurry was evenly coated on both surfaces of the electrolytic copper foil prepared above. Through the processes of rolling and die-cutting, the coated copper foil was rolled and cut into negative electrode sheets with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembling, the positive electrode sheet, separator, and negative electrode sheet were wound into a tightly fitting core. After the core was paired and put into the shell, a sealed lithium-ion battery single cell was formed. Finally, 20 PCS of the above single cells were selected. After charge and discharge cycles, the battery was disassembled, and the breakage (the electrode sheet was broken) and wrinkling (the electrode sheet was wrinkled) of the negative electrode sheet were observed visually. The results are shown in Table 2.

[0126] Comparative Example 1

[0127] (1) Preparation method of electrolytic copper foil:

[0128] The copper raw material was dissolved in sulfuric acid solution to obtain the original electrolyte solution. Then, a certain concentration of chloride ions and additive solution were added to it to obtain the electrolyte solution. The concentration of Cu 2+ in the electrolyte solution was 90 ± 2 g / L, and the concentration of H 2 SO 4 was 105 ± 5 g / L, sodium polydithiopropanesulfonate was 37 mg / L, collagen was 12 mg / L, polyethylene glycol was 6 mg / L, and Cl - was provided by hydrochloric acid, and the flow rate of hydrochloric acid was 5.5 L / H. The concentration of Cl - was controlled at 23 ± 2 ppm, the flow rate of the electrolyte solution was 42 ± 2 m 3 / h, and the temperature of the electrolyte solution was controlled at 52 °C ± 3 °C. Under the action of a DC power supply (current: 25000 A), copper ions underwent redox reactions, and copper foil preliminaries were formed on the surface of the cathode roller. Then, through passivation and aging, copper foil room-temperature samples with stable physical properties were obtained, and their tensile strength and elongation were tested. The detailed results are shown in Table 1.

[0129] The room-temperature samples were placed in an electrothermal constant-temperature forced-air drying oven with heating and air-blowing functions. Under the condition of setting the temperature T = 200 °C, they were baked for 1, 2, and 3 h respectively, and their tensile strength and elongation after baking were tested. The detailed results are shown in Table 1.

[0130] (2) Preparation method of secondary battery electrodes

[0131] Dissolve 95 parts of commercially available graphite anode material, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) in high-purity water and stir evenly to form a stable slurry with a certain viscosity. Then, use a scraper to evenly coat the obtained slurry on both surfaces of the electrolytic copper foil prepared above. Through the processes of rolling and die-cutting, the coated copper foil is rolled and cut into negative electrode sheets with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembly, the positive electrode sheet, separator, and negative electrode sheet are wound into a tightly fitting core. After the core is paired and put into the shell, a sealed lithium-ion battery single cell core is formed. Finally, select 20 PCS of the above single cells. After charge-discharge cycling, disassemble the battery and observe the breakage (the electrode sheet breaks) and wrinkling (the electrode sheet wrinkles) of the negative electrode sheet visually. The results are shown in Table 2.

[0132] Comparative Example 2

[0133] Dissolve the copper raw material in sulfuric acid solution to obtain the original electrolyte, and then add a certain concentration of chloride ions and additive solution to it to obtain the electrolyte solution. The concentration of Cu 2+ in the electrolyte is 90 ± 2 g / L, and the concentration of H 2 SO 4 is 105 ± 5 g / L, 3-mercapto-1-propanesulfonic acid sodium salt is 37 mg / L, polyethyleneimine alkyl salt is 12 mg / L, polyethylene glycol is 7 mg / L, and Cl - is provided by hydrochloric acid, and the flow rate of hydrochloric acid is 5.5 L / H. The concentration of Cl - is controlled at 23 ± 2 ppm, the flow rate of the electrolyte is 42 ± 2 m 3 / h, and the temperature of the electrolyte is controlled at 52°C ± 3°C. Under the action of a DC power supply (current is 25000 A), copper ions undergo redox reactions, and copper foil precursors are formed on the surface of the cathode roller. Then, through passivation and aging, copper foil room-temperature samples with stable physical properties are obtained, and their tensile strength and elongation are tested. The detailed results are shown in Table 1.

[0134] Place the room-temperature samples in an electrothermal constant-temperature forced-air drying oven with heating and air-blowing functions. Bake them at the set temperature T = 200°C for 1, 2, and 3 h respectively, and test the tensile strength and elongation of the baked samples. The detailed results are shown in Table 1.

[0135] (2) Preparation method of secondary battery electrodes

[0136] Dissolve 95 parts of commercially available graphite anode material, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) in high-purity water and stir evenly to form a stable slurry with a certain viscosity. Then, evenly coat the obtained slurry on both surfaces of the electrolytic copper foil prepared above. Through the processes of rolling and die-cutting, roll and cut the coated copper foil into a negative electrode sheet with a thickness of 105 μm and a width of 82.5 mm. Then, through processes such as winding and assembling, wind the positive electrode sheet, separator, and negative electrode sheet into a tightly fitting core. After the core is paired and put into the shell, a sealed lithium-ion battery single cell is formed. Finally, select 20 PCS of the above single cells. After charge and discharge cycles, disassemble the battery and observe the breakage (the electrode sheet breaks) and wrinkling (the electrode sheet wrinkles) of the negative electrode sheet visually. The results are shown in Table 2.

[0137] Comparative Example 3

[0138] Dissolve copper raw materials in sulfuric acid solution to obtain the original electrolyte, and then add a certain concentration of chloride ions and additive solution to it to obtain the electrolyte solution. The concentration of Cu 2+ in the electrolyte is 90 ± 2 g / L, and the concentration of H 2 SO 4 is 105 ± 5 g / L, 3-mercapto-1-propanesulfonic acid sodium salt is 37 mg / L, polyethylenimine alkyl salt is 12 mg / L, octylphenol polyoxyethylene ether is 5 mg / L, and Cl - is provided by hydrochloric acid, and the flow rate of hydrochloric acid is 5.5 L / H. The concentration of Cl - is controlled at 23 ± 2 ppm, the flow rate of the electrolyte is 42 ± 2 m 3 / h, and the temperature of the electrolyte is controlled at 52°C ± 3°C. Under the action of a DC power supply (current is 25000 A), copper ions undergo redox reactions, and copper foil initial products are formed on the surface of the cathode roller. Then, through passivation and aging, copper foil room-temperature samples with stable physical properties are obtained, and their tensile strength and elongation are tested. The detailed results are shown in Table 1.

[0139] Place the room-temperature samples in an electrothermal constant-temperature forced-air drying oven with heating and air-blowing functions, and bake them at the set temperature T = 200°C for 1, 2, and 3 h respectively. Test the tensile strength and elongation of the baked samples. The detailed results are shown in Table 1.

[0140] (2) Preparation method of secondary battery electrodes

[0141] 95 parts of commercially available graphite negative electrode materials, 1 part of CMC (carboxymethyl cellulose), 2 parts of conductive carbon black, and 1 part of (styrene-butadiene rubber) were dissolved in high-purity water and stirred evenly to form a stable slurry with a certain viscosity. Then, the obtained slurry was evenly coated on the two surfaces of the electrolytic copper foil prepared above using a scraper. Through rolling and die-cutting processes, the coated copper foil was rolled and cut into negative electrode sheets with a thickness of 105 μm and a width of 82.5 mm. Then, through winding, assembly and other processes, the positive electrode sheet, diaphragm and negative electrode sheet were wound into a tightly fitting core, and the core was paired into the shell to form a sealed lithium-ion battery cell. Finally, 20 PCS of the above-mentioned single cells were selected. After the charge and discharge cycle, the battery was disassembled, and the appearance of the negative electrode sheet was observed for broken bands (pole sheet disconnection) and wrinkles (pole sheet wrinkles). The results are shown in Table 2.

[0142] Table 1 Physical properties of lithium battery copper foil before and after high temperature baking in various examples and comparative examples

[0143]

[0144] Table 2 Test results of microstructure and basic physical properties of electrolytic copper foil prepared in each embodiment and each comparative example

[0145]

[0146] It can be seen from Table 1 and Table 2 that, compared with Comparative Examples 1 to 3, the copper foils provided by Examples 1 to 4 of the present invention have lower tensile strength attenuation rates after being baked at 200°C for 1h, 2h or 3h, and their elongation is greater than that in the initial state at room temperature, indicating that they have better thermal stability and can still maintain excellent mechanical properties after high-temperature baking. When used for lithium battery copper foil, it can reduce the occurrence of breakage and wrinkling during use, and improve the cycle and safety of the battery.

[0147] Figure 1 EBSD photos of the copper foil thickness roller surface and the deposition surface prepared in Example 1, wherein Figure 1 (a) is the EBSD image of the roller surface. Figure 1 (b) is the EBSD image of the deposition surface. Figure 1 It can be seen that the grain size of the roller surface is smaller than that of the deposition surface. According to calculation, the grain size of the roller surface <0.6 μm accounts for 92%.

[0148] Figure 2 EBSD photos of the copper foil thickness roller surface and deposition surface prepared in Comparative Example 1, where Figure 2 (a) is the EBSD image of the roller surface. Figure 2 (b) is the EBSD image of the deposition surface. Figure 2It can be seen that the grain size of the roller surface is smaller than that of the deposition surface, and the proportion of the grain size of the roller surface less than 0.6 μm is 79%.

[0149] In summary, according to the copper foil provided by the present invention, the grains are fine and uniform, the crystal structure is flat and dense, so that the tensile strength and elongation rate of the copper foil are both improved, and the thermal stability is good. After baking at 200 °C for 1 h, 2 h or 3 h, its tensile strength attenuation rate is low, and the elongation rate is larger than that in the initial state at room temperature, indicating that it can still maintain excellent mechanical properties after high-temperature baking. Therefore, it can reduce the occurrence of fracture and wrinkling of the copper foil during the manufacturing process and during the manufacturing and use of the battery. When it is used for lithium-ion copper foil, it can improve the cycle performance and safety of the battery.

[0150] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0151] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A copper foil, characterized in that: At room temperature, the transverse tensile strength of the copper foil is S0, in kgf / mm 2 , the transverse elongation is E0, and the transverse tensile strength of the copper foil after baking for 1 hour at 200°C is S1, the unit is kgf / mm 2 , the transverse elongation is E1, the tensile strength attenuation rate is R1, and the S0, E0, S1, E1 and R1 satisfy: R1=(1-S1 / S0)*100%<10%, and E1-E0>0.

2. The copper foil according to claim 1, characterized in that The copper foil satisfies one or more of the following (1) to (2): (1) The transverse tensile strength of the copper foil after baking for 2 hours at 200°C is S2, in kgf / mm 2 , the transverse elongation is E2, the tensile strength attenuation rate is R2, and the S0, E0, S2, E2 and R2 satisfy: R2=(1-S2 / S0)*100%<20%, ​​and E2-E0>0; (2) The transverse tensile strength of the copper foil after baking for 3 hours at 200°C is S3, in kgf / mm 2 , the transverse elongation is E3, the tensile strength attenuation rate is R3, and the S0, E0, S3, E3 and R3 satisfy: R3=(1-S3 / S0)*100%<30%, and E3-E0>0.

3. The copper foil according to claim 1, characterized in that The copper foil satisfies one or more of the following (1) to (2): (1) At room temperature, the transverse tensile strength of the copper foil is 40 kgf / mm 2 ~90kgf / mm 2 ; (2) Under room temperature conditions, the lateral elongation of the copper foil is greater than 3%.

4. The copper foil according to any one of claims 1 to 3, characterized in that The difference between the longitudinal tensile strength and the transverse tensile strength of the copper foil is 1 kgf / mm 2 the following.

5. The copper foil according to any one of claims 1 to 3, characterized in that The copper foil satisfies one or more of the following (1) to (2): (1) At room temperature, the copper foil includes more than 90% of the grains having a grain size less than 0.6 μm, as a percentage of the total number of grains in the copper foil; (2) After the copper foil is baked at 200° C. for 1 hour, the copper foil includes more than 90% of the grains having a particle size less than 0.6 μm, as a percentage of the total number of grains in the copper foil.

6. The copper foil according to any one of claims 1 to 3, characterized in that The copper foil has a first surface and a second surface opposite to each other, the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1>Gs2, and the average grain difference between the first surface and the second surface satisfies: And the average grain difference is less than 0.2 μm; Wherein, d1 represents the single grain size of the first surface, in μm, n d1 represents the number of grains with a size of d1 on the first surface, and d2 represents the size of a single grain on the second surface, in μm, n d2 Represents the number of grains with a size of d2 in the second surface.

7. The copper foil according to any one of claims 1 to 3, characterized in that The copper foil has a thickness of 3 μm to 12 μm.

8. A method for preparing the copper foil according to any one of claims 1 to 7, characterized in that: Prepare the copper foil by electrolysis; The electrolyte used in the electrolysis method includes the following components: Copper ion 90g / L±2g / L, sulfuric acid 105g / L±5g / L, chloride ion 23ppm±2ppm, brightener 40mg / L±20mg / L, leveler 12mg / L±8mg / L and moving agent 12mg / L±8mg / L; The brightener includes a sulfur-containing group compound, the leveler includes a nitrogen-containing amine organic compound, and the displacement agent includes a plurality of polyether compounds and at least includes polyethylene glycol.

9. The preparation method according to claim 8, characterized in that: Satisfy one or more of the following (1) to (3): (1) The sulfur-containing group compound includes one or more of sodium polydisulfide propane sulfonate, sodium alcoholthiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate and sodium piperazine dithiocarboxylate propane sulfonate; (2) The nitrogen-containing amine organic matter includes one or more of polyethyleneimine alkyl compounds and collagen; (3) The moving agent is prepared by compounding a first polyether compound and a second polyether compound in a concentration ratio of (1-2):1, wherein the first polyether compound is polyethylene glycol, and the second polyether compound includes one or more of octylphenol polyoxyethylene ether and ethylene oxide propylene oxide block polyether compounds.

10. The preparation method according to claim 8 or 9, characterized in that: Satisfy one or more of the following (1) to (2): (1) The temperature of the electrolyte is 52°C ± 3°C; (2) The current applied during the electrolysis process is 25000A±5000A.

11. A lithium battery copper foil, characterized in that: The invention comprises the copper foil according to any one of claims 1 to 7, or the copper foil prepared by the method for preparing the copper foil according to any one of claims 8 to 10.

12. A current collector, characterized in that: Including the lithium battery copper foil as described in claim 11.

13. A pole piece, characterized in that: Comprising the current collector as claimed in claim 12.

14. A battery, characterized in that: Including the pole piece as claimed in claim 13.

15. An electrical device, characterized in that: Comprising the battery of claim 14.

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