Metal foil, negative electrode material applied to a battery, and battery

Abstract

The present invention discloses a metal foil, a negative electrode material applied to a battery, and a battery. The metal foil includes at least one support layer and a conductive layer located on at least one surface of the support layer. The relationship between the elastic modulus A in the MD direction and the elastic modulus B in the TD direction of the metal foil is: A > B, where A is between 400 and 1500 MPa, and B is between 320 and 1400 MPa. By adopting the technical means of the present invention, through improving the structure of the metal foil, the elastic moduli in the MD direction and the TD direction of the metal foil are optimized, effectively avoiding the occurrence of fracture during the application of the metal foil, and improving the quality of the metal foil and the products using the metal foil.

Description

Technical Field

[0001] The present invention relates to the technical field of metal foils, and in particular, to a metal foil, a negative electrode material for a battery, and a battery. Background Art

[0002] With the rapid development of the electronics industry, metal foils are widely used in fields such as printed circuit boards, negative electrode materials for batteries, and chip packaging. As the current collector of the negative electrode of a new energy battery, the metal foil is the core raw material for manufacturing new energy batteries. The development of its production technology and the quality of its performance directly affect the manufacturing process, performance, and production cost of new energy batteries.

[0003] Generally, during the preparation of a new energy battery, it is necessary to coat the active material of the negative electrode material on the surface of the metal foil. The active material of the negative electrode material and the metal foil need to be wound to more fully complete the battery chemical reaction. However, the inventor found that the prior art at least has the following problems: The existing metal foil is a multi-layer metal laminate, with a large density and a relatively large thickness, resulting in a relatively heavy mass. When used as a negative electrode material in a new energy battery, it will affect the density, thickness, and mass of the battery, and cannot meet the user's requirements for thin, light, and high-energy storage batteries. If the thickness of the existing metal foil is simply reduced, the bending resistance, tensile strength, warpage resistance, and tensile strength of the metal foil will be insufficient, resulting in easy breakage during the winding process of battery preparation, affecting production efficiency and the yield rate; moreover, too thin a metal foil is also prone to problems such as wrinkles and fine stripes during the preparation process, resulting in a decrease in the surface flatness and uniformity of the metal foil, seriously affecting the uniform coating and spreading of the negative electrode active material on its surface, and further causing a large fluctuation in the thickness after the metal foil is coated with the active material, which should be avoided in battery preparation. Moreover, during the subsequent electrochemical reaction of the battery, due to the large thickness and strong rigidity of the existing metal foil, and the performance such as the elastic modulus of the product not being improved, it is difficult for the metal foil material to withstand the expansion or contraction deformation in the battery under accidental or extreme conditions, resulting in easy expansion and rupture or contraction, causing a decrease in battery performance or even scrapping, posing a major safety hazard and quality problem to the use of new energy batteries. At the same time, if the improvement of the elastic modulus in each orientation of the metal foil is insufficient, during the preparation process of the battery, the stretching along the production line direction and the welding after subsequent winding will result in uneven anisotropic properties of the copper foil, which is likely to increase the internal stress of the materials inside the battery, and further greatly increase the possibility of deformation, which is also a practical problem to be avoided. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a metal foil, a negative electrode material for a battery, and a battery. By improving the structure of the metal foil, the situation of breakage of the metal foil during application is effectively avoided, and the quality of the metal foil and the products using the metal foil is improved.

[0005] To achieve the above object, an embodiment of the present invention provides a metal foil, which includes at least one support layer and a conductive layer located on at least one surface of the support layer. The relationship between the elastic modulus A in the MD direction of the metal foil and the elastic modulus B in the TD direction of the metal foil is: A > B, where A is between 400 and 1500 MPa, and B is between 320 and 1400 MPa; in the use state, the support layer of the metal foil does not need to be peeled off from the conductive layer.

[0006] As an improvement to the above solution, the total thickness H of the metal foil satisfies H ≤ 10 μm.

[0007] As an improvement to the above solution, the average elongation in the MD direction and TD direction of the metal foil is greater than or equal to 3%, and / or the average tensile strength in the MD direction and TD direction of the metal foil is not less than 18.5 kgf / mm 2 。

[0008] As an improvement to the above solution, the material of the conductive layer includes at least one metal among copper, aluminum, iron, zinc, titanium, cobalt, gold, silver, nickel, chromium, indium, gallium, tin, thallium, lead, bismuth, germanium, antimony, polonium, beryllium, magnesium, calcium, strontium, barium, radium, lanthanide metals, actinide metals, and transition metals and / or an alloy formed by at least one of them;

[0009] and / or, the thickness of the conductive layer is less than or equal to 1 μm;

[0010] and / or, the surface arithmetic mean roughness Ra of the conductive layer is between 0.05 and 0.95 μm.

[0011] As an improvement to the above solution, when the metal foil is under the baking condition of 140 °C for 15 min to 25 min, the number of oxidation points where the surface of the conductive layer undergoes oxidation is less than or equal to 5.

[0012] As an improvement to the above solution, the total number of pinholes on the surface of the conductive layer is less than or equal to 98 per m 2 。

[0013] As an improvement to the above solution, the metal foil further includes an antioxidant layer, which is located on at least one surface of the conductive layer, and the thickness of the antioxidant layer is 5% to 30% of the thickness of the conductive layer.

[0014] As an improvement to the above solution, the metal foil further includes a bonding layer, which is located on the surface of the conductive layer away from the support layer, and the adhesion amount of the bonding layer on the surface of the conductive layer is less than or equal to 150 mg / m 2 。

[0015] An embodiment of the present invention provides a negative electrode material for a battery. The negative electrode material includes a negative electrode active material and a metal foil as described in any one of the above, and the metal foil is tightly adhered to the negative electrode active material.

[0016] As an improvement to the above solution, the support layer in the metal foil is an insulating material.

[0017] An embodiment of the present invention provides a battery. The negative electrode material of the battery is the negative electrode material for a battery as described above.

[0018] Compared with the prior art, the present invention discloses a metal foil, a negative electrode material applied to a battery, and a battery. The metal foil includes at least one support layer and a conductive layer located on at least one surface of the support layer. The relationship between the elastic modulus A in the MD direction and the elastic modulus B in the TD direction of the metal foil is: A > B, where A is between 400 and 1500 MPa, and B is between 320 and 1400 MPa. By adopting the technical means of the embodiments of the present invention, the elastic moduli of the metal foil in the MD direction and the TD direction are within a reasonable range, thereby enabling the metal foil to have excellent bending resistance, tensile strength, warping resistance, tensile strength, and reasonable deformation ability. When the metal foil is applied to a new energy battery, the lattice parameters of the negative electrode material increase and decrease during the lithiation and delithiation chemical reactions during charge and discharge, and the excessive expansion and contraction of the thickness of the negative electrode sheet are avoided. That is, when the metal foil of the embodiments of the present invention is used as the negative electrode material of a new energy battery and participates in the battery chemical reaction, the thickness of the negative electrode material can be effectively controlled during the chemical reaction process, ensuring that the expansion rate of the metal foil is within a reasonable deformation range, and preventing the occurrence of unsafe accidents such as the rupture of the negative electrode material and short circuit due to the inability to expand when the internal heat of the battery is too high in extreme cases, or the expansion and rupture of the battery outer packaging caused by the material deformation brought about by the above-mentioned electrochemical reaction, resulting in battery failure. At the same time, it can also improve or reduce the possibility of unsafe accidents such as internal short circuit of the battery and battery ignition caused by excessive shrinkage of the material and the resulting indentation of the support layer in the middle of the metal foil under adverse conditions such as low temperature, external force impact, and collision. In addition, by setting the elastic modulus A in the MD direction of the metal foil to be greater than the elastic modulus B in the TD direction, it can better adapt to the winding scenario required in the process of preparing the battery negative electrode material, and avoid the occurrence of easy fracture during the winding process in the MD direction. At the same time, the improvement of the present invention can also reduce or improve problems such as easy wrinkling and fine stripes of the thinner metal foil during the preparation process, ensure the surface flatness and uniformity of the metal foil, improve the uniformity of the coating and spreading of the negative electrode active material on its surface and the surface flatness, avoid large fluctuations in the thickness after the metal foil is coated with the active material, improve the gap uniformity during battery winding, and improve the quality and performance of the battery. Moreover, through the improvement of the present invention, the stretching along the production line direction (MD direction) during the battery preparation process and the anisotropy of the copper foil performance during welding after subsequent winding are reduced, the internal stress increase of the battery internal materials themselves is reduced, and thus the possibility of material deformation itself is also reduced, improving the stability and reliability of the material and the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic structural diagram of the first metal foil provided by an embodiment of the present invention;

[0020] Figure 2 It is a schematic structural diagram of the second metal foil provided by an embodiment of the present invention;

[0021] Figure 3 It is a schematic structural diagram of the third metal foil provided by an embodiment of the present invention;

[0022] Figure 4 It is a schematic structural diagram of the fourth metal foil provided by an embodiment of the present invention;

[0023] Figure 5 It is a schematic structural diagram of the fifth metal foil provided by an embodiment of the present invention;

[0024] Wherein, 1 is the support layer; 2 is the conductive layer; 21 is the first conductive layer; 22 is the second conductive layer; 3 is the antioxidant layer; 4 is the bonding layer. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0026] In the description of the specification and claims, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of the present invention.

[0027] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features.

[0028] See Figure 1, which is a schematic structural diagram of the first metal foil provided by the embodiments of the present invention. The embodiments of the present invention provide a metal foil, which includes at least one support layer 1 and a conductive layer 2 located on at least one surface of the support layer 1, and the support layer 1 and the conductive layer 2 are stacked. The relationship between the elastic modulus A in the MD direction of the metal foil and the elastic modulus B in the TD direction of the metal foil is: A > B, and A is between 400 and 1500 MPa, and B is between 320 and 1400 MPa.

[0029] It should be noted that the MD direction of the metal foil refers to the length direction of the metal foil, that is, parallel to the conveying direction of the production line, and the TD direction of the metal foil refers to the thickness direction of the metal foil, that is, perpendicular to the conveying direction of the production line.

[0030] The metal foil of the embodiments of the present invention is formed by providing at least one support layer 1 and providing a conductive layer 2 on the surface of the support layer 1. Compared with the metal foil formed by stacking multiple metal layers in the prior art, the thickness and weight of the metal foil of the embodiments of the present invention can be significantly reduced, avoiding excessive density, thickness and weight of the metal foil, resulting in excessive thickness and weight of the products using the metal foil subsequently, such as new energy battery products, etc., and being unable to meet the user's requirements for thin, light and high-energy storage battery products.

[0031] Moreover, to avoid the problem that the bending resistance, tensile strength and tensile modulus of the thinner metal foil are insufficient, resulting in easy breakage during the winding process of battery preparation, which affects the production efficiency and the yield rate, the embodiments of the present invention further optimize the elastic modulus A in the MD direction and the elastic modulus B in the TD direction of the metal foil, such that the elastic modulus A is greater than the elastic modulus B, and the elastic modulus A is controlled to be between 400 and 1500 MPa. For example, it can be 400 MPa, 450 MPa, 580 MPa, 690 MPa, 720 MPa, 750 MPa, 780 MPa, 800 MPa, 810 MPa, 830 MPa, 860 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 970 MPa, 1000 MPa, 1020 MPa, 1050 MPa, 1080 MPa, 1100 MPa, 1130 MPa, 1160 MPa, 1190 MPa, 1200 MPa, 1220 MPa, 1250 MPa, 1300 MPa, 1400 MPa or 1500 MPa. Of course, the elastic modulus A can also be any other value between 400 and 1500 MPa, which will not be elaborated here. And the elastic modulus B is controlled to be between 320 and 1400 MPa. For example, it can be 300 MPa, 400 MPa, 460 MPa, 580 MPa, 600 MPa, 640 MPa, 670 MPa, 690 MPa, 720 MPa, 750 MPa, 780 MPa, 800 MPa, 810 MPa, 830 MPa, 860 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 970 MPa, 1000 MPa, 1020 MPa, 1050 MPa, 1080 MPa, 1100 MPa, 1130 MPa, 1160 MPa, 1180 MPa, 1250 MPa, 1380 MPa or 1400 MPa. Of course, the elastic modulus B can also be any other value between 320 and 1400 MPa, which will not be elaborated here.

[0032] More preferably, A is between 690 and 1250 MPa, and B is between 580 and 1180 MPa.

[0033] By adopting the technical means of the embodiments of the present invention, the elastic moduli of the metal foil in the MD direction and the TD direction are within a reasonable range, so that the metal foil has excellent bending resistance, tensile strength, warpage resistance, tensile strength and reasonable deformation ability. When the metal foil is applied to a new energy battery, the lattice parameters of the negative electrode material of the lithium-ion battery increase and decrease during the lithium intercalation and deintercalation chemical reactions during charging and discharging, and the excessive expansion and contraction of the thickness of the negative electrode material are avoided. That is, when the metal foil of the embodiment of the present invention is used as the negative electrode material of the new energy battery to participate in the battery chemical reaction, the thickness of the negative electrode material can be effectively controlled during the chemical reaction process, ensuring that the expansion rate of the metal foil is within a reasonable deformation range, and avoiding or improving in extreme cases, such as the battery internal heat is too high to cause explosion and short circuit due to inability to expand, and the metal foil rupture caused by the deformation of the material due to the above-mentioned electrochemical reaction or external collision and other external forces (if the elastic modulus of the material is insufficiently designed, the material rigidity is too strong, the brittleness increases, and the deformation of the material becomes more difficult. When heated or affected by external forces and expands, it will show poor deformation and is easy to rupture), resulting in unsafe accidents such as battery failure. At the same time, it can also prevent the puncture of the support layer in the middle of the metal foil caused by the excessive shrinkage of the material under conditions such as low temperature, resulting in internal short circuit of the battery and unsafe accidents such as battery fire. In addition, by setting the elastic modulus A in the MD direction of the metal foil to be greater than the elastic modulus B in the TD direction, it can better adapt to the winding scenario required in the process of preparing the battery negative electrode material and avoid the easy breakage during the winding process in the MD direction. At the same time, the above improvements can also reduce or improve problems such as easy wrinkling and fine stripes of the thinner metal foil during the preparation process, ensure the surface flatness and uniformity of the metal foil, improve the coating and spreading uniformity and surface flatness of the negative electrode active material on its surface, avoid large fluctuations in the thickness after the metal foil is coated with the active material, improve the gap uniformity during battery winding, and improve the quality and performance of the battery. In addition, through the above improvements, the stretching along the production line direction (MD direction) during the battery preparation process and the anisotropic performance imbalance of the copper foil during welding after subsequent winding are reduced, the internal stress increase of the battery internal material itself is reduced, and thus the possibility of the material itself deforming is also reduced, and the stability and reliability of the material and the battery are improved.

[0034] Preferably, when randomly selecting n metal foil samples and testing the elastic moduli of at least 3 test points for each metal foil sample, the average elastic modulus in the MD direction of the n metal foil samples can be obtained as 882.56 Mpa, and the average elastic modulus in the TD direction is 790.669 Mpa, where n > 10; optionally, n = 13.

[0035] By adopting the embodiment of the present invention, by controlling the average elastic modulus of multiple metal foils within a reasonable range, the elastic deformation of each metal foil product can be ensured to be within a reasonable range, ensuring the stability and qualification rate of the metal foil product, and further reducing the occurrence of problems such as battery breakage and short circuit.

[0036] It should be noted that in practical applications, the metal foil is preferably used in the field of new energy batteries. Of course, the metal foil can also be applied to many other fields, such as the field of circuit boards and the field of semiconductor materials. In an optional embodiment, when the metal foil is applied in the field of new energy batteries, the metal foil serves as the negative electrode material of the battery and is thermally pressed and bonded to the negative electrode active material in the negative electrode material through the conductive layer.

[0037] As a preferred embodiment, refer to Figure 2 , which is a schematic structural diagram of the second metal foil provided by the embodiment of the present invention. The metal foil is provided with three layers of structures, including one support layer 1 and two conductive layers 2, namely the first conductive layer 21 and the second conductive layer 22. The first conductive layer 21, the support layer 1, and the second conductive layer 22 are sequentially stacked.

[0038] By adopting the technical means of the embodiment of the present invention, when the metal foil serves as the negative electrode material of the new energy battery, through the design of the three-layer structure, active substances for battery reactions are arranged on the surfaces of the conductive layers on both sides of the support layer, enabling the metal foil to fully undergo electrochemical reactions with the negative electrode material, improving the utilization rate of the negative electrode material of the battery. At the same time, in coordination with the preferred reasonable thickness and weight control of each layer of material in this application, it is possible to achieve the distribution of more negative electrode materials within the limited internal space of the battery, thereby effectively improving the energy density of the battery and reducing the weight of the battery compared with traditional metal foils. At the same time, the setting of the three-layer symmetric structure is more beneficial and stable for the material performance and overall electrochemical reaction of the battery.

[0039] Of course, an auxiliary layer can also be added between the support layer 1 and the conductive layer 2, so as to assist the conductive layer 2 to adhere more firmly to the surface of the support layer 1, reduce the occurrence of peeling or flaking, and at the same time, enhance the peeling force between the conductive layer 2 and the support layer 1. However, the introduction of the auxiliary layer is based on the premise of not significantly increasing the internal resistance and thickness of the battery.

[0040] As a preferred embodiment, on the basis of the above embodiment, further implemented, the total thickness H of the metal foil is ≤ 10 μm.

[0041] By adopting the technical means of the embodiments of the present invention, the overall thickness of the metal foil is optimized, making the structure of the metal foil thinner and lighter. When the metal foil is applied to new energy batteries, it is beneficial to reduce the battery weight. And in a battery pack with a certain volume, the thinner and lighter the metal foil structure, the more metal foil materials can be wound, and the more electrolyte and negative electrode material active substances are coated on the surface. Thus, the energy density and weight of the battery are effectively improved, and further the battery's endurance mileage is effectively increased.

[0042] Preferably, the total thickness H of the metal foil satisfies H≤6μm.

[0043] More preferably, the total thickness H of the metal foil satisfies 3≤H≤5.5μm. For example, it can be 3μm, 3.2μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 5μm, 4.2μm or 4.5μm. Of course, the thickness of the metal foil can also be any other value between 3 and 5.5μm, which will not be elaborated here.

[0044] By adopting the technical means of the embodiments of the present invention, the overall thickness of the metal foil is further optimized, making the total thickness of the metal foil neither too thin nor too thick, but within an optimal and reasonable range. The thickness of the metal foil is not too thin, thus avoiding the situation that the metal foil is easily damaged or the negative electrode material breaks during the winding process in the battery preparation. Nor is it too thick, thus avoiding the excessive weight and volume of the metal foil, which is not conducive to reducing the battery weight and increasing the energy density.

[0045] As a preferred embodiment, the average elongation rates in the MD direction and TD direction of the metal foil are greater than or equal to 3%; the average tensile strengths in the MD direction and TD direction of the metal foil are not less than 18.5 kgf / mm 2 .

[0046] Preferably, the average elongation rates in the MD direction and TD direction of the metal foil are greater than or equal to 4.5%.

[0047] By adopting the technical means of the embodiments of the present invention, through specifically optimizing and improving the elongation rate and tensile strength of the metal foil, the elongation rate and tensile strength of the metal foil are within a reasonable range, which can reduce the situation of breakage during the winding process of the metal foil as the battery negative electrode material, and avoid excessive increase of the internal stress of the materials inside the battery after winding, resulting in easy deformation of the materials themselves, such as cracking and warping, and further avoid the deformation, warping and swelling of the battery negative electrode material in the electrochemical reaction.

[0048] As a preferred embodiment, the conductive layer 2 includes a single-metal conductive layer and / or an alloy conductive layer; wherein, the single-metal conductive layer is made of any one of copper, aluminum, iron, zinc, titanium, cobalt, gold, silver, nickel, chromium, indium, gallium, tin, thallium, lead, bismuth, germanium, antimony, polonium, beryllium, magnesium, calcium, strontium, barium, radium, lanthanide metals, actinide metals, and transition metals, and the alloy conductive layer is made of any two or more of copper, aluminum, iron, zinc, titanium, cobalt, gold, silver, nickel, chromium, indium, gallium, tin, thallium, lead, bismuth, germanium, antimony, polonium, beryllium, magnesium, calcium, strontium, barium, radium, lanthanide metals, actinide metals, and transition metals, or can be made of any two or more of the above metals and other materials mixed together.

[0049] Furthermore, the thickness of the conductive layer is less than or equal to 1 μm, and the arithmetic mean roughness Ra of the surface of the conductive layer is between 0.05 and 0.95 μm.

[0050] It should be noted that the arithmetic mean roughness Ra is specifically the arithmetic mean of the absolute values of the profile ordinate values Z(x) within a sampling length, and the ordinate value Z(x) refers to the distance from each point on the profile to the profile center line. The arithmetic mean roughness Ra is used to evaluate the arithmetic mean deviation of the surface profile, and it can fully reflect the characteristics of the surface microgeometry in terms of height.

[0051] By adopting the technical means of the embodiments of the present invention, the material of the conductive layer 2 of the metal foil is further optimized, so that the conductive layer 2 has the characteristics of good conductivity, low resistance, and good tensile strength, and the thickness of the metal foil and the arithmetic mean roughness Ra of the surface are further optimized. The thickness of the conductive layer is less than or equal to 1 μm, for example, it can be 0.8 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, or 0.1 μm, etc. The thinner thickness of the conductive layer also further reduces the overall thickness of the metal foil, avoiding excessive volume and weight of the metal foil. Moreover, by optimizing the arithmetic mean roughness of the surface of the conductive layer to be between 0.05 and 0.95 μm, for example, it can be 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.9 μm, or 0.95 μm, etc., the rough performance of the surface of the conductive layer is ensured. Furthermore, when applied to the field of new energy batteries, the adhesion force between the conductive layer and the negative active material is effectively improved, the adhesion effect is greatly enhanced, the shedding of the active material during the winding process is avoided, and the battery quality and life are improved.

[0052] As a preferred embodiment, when the metal foil is under the baking conditions of 140 °C for 15 min to 25 min, the number of oxidation points on the surface of the conductive layer is less than or equal to 5.

[0053] By adopting the technical means of the embodiments of the present invention and controlling aspects such as the structure and manufacturing process of the metal foil, the number of oxidation points on the surface of the conductive layer is controlled within a reasonable and acceptable range under extreme conditions such as high temperature and high pressure, ensuring the stability of various performances when the metal foil is applied to the negative electrode material of the battery, and avoiding the ineffective increase of the battery internal resistance caused by too many oxidation points, thereby reducing the battery energy conversion efficiency. At the same time, controlling the reasonable range of oxidation points avoids the poor adhesion between the negative electrode active material and the surface of the metal foil due to too many oxidation points, such as problems of loose adhesion and bubbles, assisting in promoting the uniformity and surface flatness of the coating and spreading of the negative electrode active material on the surface of the metal foil, reducing the shedding and cracking of the negative electrode material during the winding process, and improving the quality of the battery product and the stability and reliability of the electrochemical reaction.

[0054] As a preferred embodiment, the embodiments of the present invention are further implemented on the basis of any of the above embodiments. Inevitably, there are a number of pinholes on the surface of the conductive layer 2. And the total number of pinholes on the surface of the conductive layer 2 is less than or equal to 98 per m 2 . Preferably, the total number of pinholes is less than or equal to 50 per m 2 .

[0055] By adopting the technical means of the embodiments of the present invention, the surface of the conductive layer 2 of the metal foil inevitably has a certain number of pinholes. By controlling the number of pinholes in the conductive layer within an acceptable range, the stability of the structure and various performances of the metal foil is further ensured, and the penetration of the negative electrode active substance, electrolyte, etc. through the pinholes and the large reaction with the support layer of the metal foil are avoided in the application in the field of new energy batteries, thereby preventing damage to the support layer, effectively maintaining the reasonable stiffness and normal structure of the metal foil, and ensuring that the electrochemical reaction and function of the battery are not affected.

[0056] As a preferred embodiment, referring to Figure 3 , which is a schematic structural diagram of the third metal foil provided by the embodiments of the present invention. The embodiments of the present invention are further implemented on the basis of any of the above embodiments. The metal foil further includes an antioxidant layer 3, the antioxidant layer 3 is located on at least one surface of the conductive layer 2, and the thickness of the antioxidant layer 3 is 5% to 30% of the thickness of the conductive layer 2.

[0057] In an embodiment of the present invention, an antioxidant layer 3 is coated on one or two surfaces of each conductive layer 2 or on the surface of a material in contact with the surface of the conductive layer. As an example, when the metal foil has a three-layer structure in which a first conductive layer 21, a support layer 1, and a second conductive layer 22 are sequentially stacked, an antioxidant layer 3 is added on one or two surfaces of the first conductive layer 21, and / or an antioxidant layer 3 is added on one or two surfaces of the second conductive layer 22.

[0058] By adopting the technical means of the embodiment of the present invention, by coating an antioxidant layer on the surface of the conductive layer or on the surface of a material in contact with the surface of the conductive layer, the antioxidant performance of the surface of the conductive layer is effectively improved. When applied to the field of new energy batteries, it can well avoid the occurrence of the adhesion oxidation reaction between the surface of the conductive layer and the active material, and the occurrence of oxidation when the surface of the conductive layer is in contact with the electrolyte, improving the service life of the metal foil and the stability of the battery. And, through the optimized design of the thickness of the antioxidant layer, without excessively increasing the weight of the metal foil and the internal resistance of the battery reaction, the antioxidant property of the conductive layer and the utilization rate of the battery material are effectively improved.

[0059] As a preferred embodiment, the metal foil further includes a bonding layer 4.

[0060] In an alternative embodiment, referring to Figure 4 , it is a schematic structural diagram of a fourth metal foil provided by an embodiment of the present invention. The metal foil includes a support layer 1, a conductive layer 2, and a bonding layer 4, and the bonding layer 4 is located on the surface of the conductive layer 2 away from the support layer 1. As an example, when the metal foil has a three-layer structure in which a first conductive layer 21, a support layer 1, and a second conductive layer 22 are sequentially stacked, a bonding layer 4 is added on the outer surface of the first conductive layer 21, and a bonding layer 4 is added on the outer surface of the second conductive layer 22. And the adhesion amount of the bonding layer on the surfaces of the first conductive layer 21 and the second conductive layer 22 is less than or equal to 150 mg / m 2 .

[0061] In another alternative embodiment, referring to Figure 5 , it is a schematic structural diagram of a fifth metal foil provided by an embodiment of the present invention. The metal foil includes a support layer 1, a conductive layer 2, an antioxidant layer 3, and a bonding layer 4, and the bonding layer 4 is located on the surface of the antioxidant layer 3 away from the conductive layer 2. As an example, when the metal foil has a multi-layer structure in which an antioxidant layer 3, a first conductive layer 21, a support layer 1, a second conductive layer 22, and an antioxidant layer 3 are sequentially stacked, a bonding layer 4 is added on the surfaces of the two antioxidant layers 3, that is, the antioxidant layer 3 is located between the conductive layer 2 and the bonding layer 4, and the adhesion amount of the bonding layer on the surface of the antioxidant layer is less than or equal to 150 mg / m 2 .

[0062] By adopting the technical means of the embodiments of the present invention, through designing the bonding layer and optimizing its adhesion amount, when applied in the field of new energy batteries, it can not only ensure the maximum adhesion and combination between the conductive layer surface of the metal foil and the negative electrode active material of the battery, avoiding the occurrence of situations such as peeling and falling off of the negative electrode active material on the conductive layer surface. At the same time, ensuring that the adhesion amount of the bonding layer is within a reasonable range can avoid the increase in the weight and volume of the metal foil itself caused by too much amount of the bonding aid of the bonding layer, affecting the control of the battery weight and the improvement of the energy density.

[0063] It should be noted that the bonding aid for forming the bonding layer is specifically an organic bonding aid, or an inorganic aid, or a mixture obtained by mixing the two in a certain proportion. It can not only improve the adhesion between the active material and the metal foil, but also contain groups in its own chemical bonds that can crosslink or bond with the negative electrode active material through chemical bonds, such as carboxyl groups, hydroxyl groups, etc. The specific types of bonding aids are not limited.

[0064] As a preferred embodiment, the adhesion amount of the bonding layer on the surface of the conductive layer or the antioxidant layer is less than or equal to 120 mg / m 2 and greater than or equal to 26 mg / m 2 .

[0065] By adopting the technical means of the embodiments of the present invention, the adhesion amount of the bonding layer is further optimized to be within a reasonable range, neither too large nor too small, which not only ensures the adhesion and combination between the conductive layer and the negative electrode active material, but also avoids the increase in the weight and volume of the metal foil itself, ensuring that the battery has a light weight and a large energy density.

[0066] Taking the ordinary metal foil as a control sample, the winding process fracture rate, elongation rate and tensile strength of the metal foil with the structure of the embodiments of the present invention and the control sample were respectively tested. Among them, S represents the metal foil with the structure of the embodiments of the present invention, including sample S1, S2, S3, S4 and S5; R represents the ordinary metal foil, including control samples R1 and R2.

[0067] The specific test data and comparison results are shown in Table 1:

[0068] Table 1

[0069]

[0070] It should be noted that the elastic modulus in the MD direction, the elastic modulus in the TD direction, the elongation rate, and the tensile strength of the metal foil can be tested by an electronic universal testing machine and obtained by inputting parameters such as the thickness, length, and width of the metal foil into the testing software. To improve the accuracy of the test results, each set of data is tested more than 30 times, and all the results are averaged as the final test result. Among them, the length of the metal foil test sample is taken to be greater than 150 mm, and the width is taken to be 10 mm.

[0071] The test method for the breakage rate during the winding process is as follows: Take a certain number of metal foil products for a battery negative electrode winding processing simulation experiment, calculate the ratio of the number of breaks to the total number of experiments to obtain the breakage rate during the winding process. The specific steps of the winding processing simulation experiment include: Coating the same amount of negative electrode active material on both surfaces of each metal foil, using a press double-sided roller for pressing to promote the tight bonding of the active material with the metal foil surface, performing winding, calculating the breakage situation of the metal foil during the winding process, and observing the bonding situation of the active material with the metal foil surface, such as phenomena like peeling off, separation, and cracking. Each single sample is cumulatively experimented 10 - 30 times in total.

[0072] From the above comparison table, it can be seen that compared with the control sample, the metal foil sample provided in the embodiment of the present invention has better elastic moduli in the MD direction and TD direction of the metal foil than those of the MD direction and TD direction of the control sample when the total thickness is thinner or equivalent, resulting in a lower breakage rate, higher elongation rate and tensile strength during the winding process when the metal foil is applied to make new energy batteries, and also showing a certain degree of anti-warpage property, and all performance indicators are better than those of the control sample.

[0073] The embodiment of the present invention also provides a negative electrode material for a battery. The negative electrode material includes a negative electrode active material and the metal foil as described in any one of the above embodiments. At this time, the structure of the metal foil is specifically: At least one layer of conductive layer is formed on each of the two side surfaces of the support layer, the negative electrode active material is formed on the outer side surfaces of the outermost conductive layers on both sides of the support layer, and the metal foil is tightly bonded to the negative electrode active material.

[0074] The embodiment of the present invention also provides a battery, and the negative electrode material of the battery is the negative electrode material for a battery as described above.

[0075] It should be noted that the structure of the metal foil can refer to the structure of the metal foil described in any of the above embodiments, and will not be elaborated here.

[0076] By adopting the technical means of the embodiments of the present invention, the application of using the metal foil as the negative electrode carrier or current collector of the above battery has the following advantages: Through the optimization of the value ranges and magnitude relationships of the elastic modulus in the MD direction and the elastic modulus in the TD direction of the metal foil, and further in cooperation with the improvements in aspects such as the thickness and structural composition of the metal foil, the metal foil has excellent bending resistance, tensile strength, warping resistance, tensile strength and reasonable deformation ability. Furthermore, when the metal foil is used as the negative electrode material of a new energy battery and participates in the battery chemical reaction, it ensures that the expansion rate of the metal foil is within a reasonable deformation range, and it will not cause, in extreme cases, for example, when the internal heat of the battery is too high to expand and then explosion and short circuit occur, or when the battery outer packaging expands and ruptures due to the material deformation caused by the above electrochemical reaction, resulting in unsafe accidents such as battery failure. At the same time, it can also prevent, under conditions such as low temperature, external force or collision, excessive shrinkage of the material leading to the indentation of the negative electrode material itself and piercing of the support layer in the middle of the metal foil, resulting in internal short circuit of the battery and unsafe accidents such as battery fire. In addition, it can better adapt to the scenario of winding required in the process of preparing the battery negative electrode material and avoid the situation of easy fracture during the winding process. At the same time, the above improvements can also reduce or improve problems such as easy wrinkling and fine stripes of the thinner metal foil during the preparation process, ensure the surface flatness and uniformity of the metal foil, improve the coating spreading uniformity and surface flatness of the negative electrode active material on its surface, avoid large fluctuations in thickness after the metal foil is coated with the active material, improve the gap uniformity during battery winding, and improve the quality and performance of the battery. In addition, through the above improvements, the stretching along the production line direction (MD direction) during the battery preparation process and the anisotropic performance imbalance of the copper foil during welding after subsequent winding are reduced, the internal stress increase of the battery internal materials themselves is reduced, and thus the possibility of the materials themselves deforming is also reduced, enhancing the stability and reliability of the materials and the battery.

[0077] As a preferred embodiment, the support layer in the metal foil is an insulating material.

[0078] Specifically, the insulating material can be any one of polyethylene naphthalate (PEN), polyamide, polyethylene terephthalate (PET), polyimide (PI), polyterephthalate, polytetrafluoroethylene, polyethylene (PE), polyvinyl chloride, polystyrene, polypropylene (PP), acrylonitrile-butadiene-styrene copolymer, silicone rubber, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, polycarbonate, phenolic resin, polyvinylidene fluoride.

[0079] By adopting the technical means of the embodiments of the present invention, using an insulating material as the support layer of the metal foil can effectively reduce the occurrence of short circuits in extreme cases inside the battery, such as when the internal heat of the battery is too high, etc., and improve the safety of the battery.

[0080] The material of the support layer is preferably polyethylene terephthalate, that is, PET film, so that the thickness of the support layer is very thin, between 2 and 4 μm, which is beneficial to reducing the weight of the battery, and can enable more metal foil materials to be wound in a battery pack of a certain volume. Furthermore, more electrolyte and negative electrode active material can be coated, thus effectively improving the energy density of the battery, and then effectively improving the battery's endurance mileage. And the PET film has good elasticity, high tensile resistance and tensile strength, effectively improving the anti-fracture performance of the battery.

[0081] It should be noted that the battery provided by the embodiments of the present invention can be applied to various device types, including but not limited to portable electronic devices, electric transportation vehicles, electric toys and electric tools. By way of example, portable electronic devices include mobile phones and laptops, electric transportation vehicles include battery cars, electric vehicles, electric ships and spacecraft, electric toys include game consoles and electric vehicle toys, and electric tools include electric drills, electric wrenches and electric screwdrivers, etc. Of course, it can also be applied to other devices according to actual situations, which will not be elaborated here.

[0082] The embodiments of the present invention also provide a conductive material applying the metal foil provided in any of the above embodiments. The structure of the metal foil can refer to the structure of the metal foil described in any of the above embodiments, which will not be elaborated here.

[0083] When applied as other conductive materials, the support layer of the metal foil is a conductive material, and the specific form is not limited. In an optional manner, several conductive particles can be dispersed in the support layer for conduction. The conductive particles can be one or several metal ions among the material selection types of the conductive layer listed previously in this application. The particle size of the metal particles is less than or equal to 30 nm; preferably less than or equal to 15 nm.

[0084] In another alternative manner, a conduction channel is formed in the support layer, and a conduction material is disposed in the channel for conduction. The shape of the conduction channel can be square, circular, irregular, etc. The opening area of the conduction channel accounts for 30% to 70% of the largest lateral surface area of the support layer. After the conduction channel is provided, the weight ratio of the conduction material is more than 50% of that before the conduction channel is formed, preferably 60% to 85%. The conduction material can also be divided into metal or non-metal materials. When it is a metal material, specifically, it can be one or several of the material selection types of the conductive layer in the above embodiments. When the conduction material is a non-metal, it can be graphite conductive carbon black, graphene, CNT (carbon nanotube), etc. The conduction material is disposed inside the conduction channel, specifically, it can be disposed on the inner wall or filled in the conduction channel, which does not affect the beneficial effects of the present invention.

[0085] In yet another alternative manner, the support layer is made of a modified metal or non-metal conductive material with strong ductility and elastic modulus. Examples of the non-metal conductive material include conductive carbon black, graphite, graphene, CNT (carbon nanotube), etc.

[0086] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A metal foil, characterized in that, It includes a support layer with at least one layer, and a conductive layer located on at least one surface of the support layer. The relationship between the elastic modulus A in the MD direction of the metal foil and the elastic modulus B in the TD direction of the metal foil is: A > B, and A is between 720 and 1100 MPa, and B is between 640 and 1080 MPa; in the use state, the support layer of the metal foil does not need to be peeled off from the conductive layer; the total thickness H of the metal foil is H ≤ 10 μm; wherein, the MD direction of the metal foil refers to the length direction of the metal foil, and the TD direction of the metal foil refers to the thickness direction of the metal foil.

2. The metal foil according to claim 1, characterized in that, The average elongation rate of the metal foil in the MD direction and the TD direction is greater than or equal to 3%, and / or the average tensile strength of the metal foil in the MD direction and the TD direction is not less than 18.5 kgf / mm 2 .

3. The metal foil according to claim 1 or 2, characterized in that, The material of the conductive layer includes at least one metal among copper, aluminum, iron, zinc, titanium, cobalt, gold, silver, nickel, chromium, indium, gallium, tin, thallium, lead, bismuth, germanium, antimony, polonium, beryllium, magnesium, calcium, strontium, barium, radium, lanthanide metals, actinide metals and transition metals and / or an alloy formed by at least one of them; and / or, the thickness of the conductive layer is less than or equal to 1 μm; and / or, the surface arithmetic mean roughness Ra of the conductive layer is between 0.05 and 0.95 μm.

4. The metal foil according to claim 1 or 2, characterized in that, When the metal foil is under the baking condition of 140 °C for 15 min to 25 min, the number of oxidation points where the surface of the conductive layer is oxidized is less than or equal to 5.

5. The metal foil according to claim 1 or 2, characterized in that, The total number of pinholes on the surface of the conductive layer is less than or equal to 98 per m 2 .

6. The metal foil according to claim 1 or 2, characterized in that, The metal foil further includes an antioxidant layer, the antioxidant layer is located on at least one surface of the conductive layer, and the thickness of the antioxidant layer is 5% to 30% of the thickness of the conductive layer.

7. The metal foil according to claim 1 or 2, wherein The metal foil further includes a bonding layer, which is located on the surface of the conductive layer away from the support layer, and the adhesion amount of the bonding layer on the surface of the conductive layer is less than or equal to 150 mg / m 2 .

8. A negative electrode material applied to a battery, characterized in that, The negative electrode material includes a negative electrode active material and the metal foil as described in any one of claims 1 to 7, and the metal foil is tightly adhered to the negative electrode active material.

9. The negative electrode material for a battery according to claim 8, wherein, The support layer in the metal foil is an insulating material.

10. A battery, characterized in that, The negative electrode material of the battery is the negative electrode material for a battery as described in claim 8 or 9.

Images