Secondary battery, current collector and electric device

Abstract

Disclosed in the present application are a secondary battery, a current collector and an electric device. The secondary battery comprises a current collector, wherein the current collector comprises a base layer, a reinforcement layer and a conductive layer; the base layer comprises a polymer material; one of the reinforcement layer and the conductive layer is provided between the other and the base layer; the reinforcement layer comprises at least one of a metal material and a non-metal material, the metal material comprises at least one of nickel, chromium, iron, cobalt, tungsten and molybdenum, and the non-metal material comprises at least one of aluminum oxide, nickel oxide, chromium oxide, graphene, acetylene black, carbon black and carbon nanotubes; and on the basis of the total thickness of the reinforcement layer and the conductive layer, the thickness proportion of the reinforcement layer is greater than or equal to 10% and less than 100%. The current collector has a relatively high strength and relatively good ductility and conductivity; therefore, the mechanical properties of the current collector is improved, and the cycling stability and power performance of the secondary battery can be improved.

Description

Secondary batteries, current collectors, electrical equipment

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510126555.9, filed on January 27, 2025, entitled “Secondary Battery, Current Collector, Electrical Equipment”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of new energy technology, and in particular to a secondary battery, current collector, and electrical equipment. Background Technology

[0004] Current collectors play a crucial role in battery performance, and their mechanical properties affect the battery's cycle stability. The mechanical properties of current collectors mainly include their strength and ductility. Currently, it is difficult for current collectors to simultaneously achieve high strength and good ductility, thus limiting their ability to improve battery cycle stability. At the same time, current collectors need to possess good conductivity to meet the battery's power performance requirements. The above statements are for providing background information related to this application only and do not necessarily constitute prior art. Summary of the Invention

[0005] The main technical problem solved by this application is to provide a secondary battery, a current collector, and an electrical device. The current collector has high strength, good ductility, and conductivity, thereby improving the mechanical properties of the current collector and enhancing the cycle stability and power performance of the battery.

[0006] To solve the above-mentioned technical problems, one technical solution adopted in this application is: providing a secondary battery, the secondary battery including a current collector, the current collector including a base layer, a reinforcing layer and a conductive layer, the base layer including a polymer material, one of the reinforcing layer and the conductive layer being disposed between the other and the base layer; the reinforcing layer including at least one of a metallic material and a non-metallic material, the metallic material including at least one of nickel, chromium, iron, cobalt, tungsten and molybdenum, the non-metallic material including at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black and carbon nanotubes; based on the total thickness of the reinforcing layer and the conductive layer, the thickness ratio of the reinforcing layer is greater than or equal to 10% and less than 100%.

[0007] The base layer of the current collector forms its main structure and provides support. This base layer comprises polymer materials, which offer good flexibility, thus improving the current collector's ductility and allowing it to adapt to volume expansion and contraction during battery charging and discharging. This enhances the current collector's stability and the tightness of the bond between it and the active material layer, thereby improving the cycle stability of the secondary battery. The reinforcing layer and conductive layer are the functional layers of the current collector. The reinforcing layer increases the tensile strength of the current collector, helping to alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, reducing the risk of current collector cracking, and further improving the cycle stability of the secondary battery. The conductive layer has good conductivity, improving the conductivity of the current collector and thus enhancing the battery's power performance. Furthermore, based on the total thickness of the reinforcing and conductive layers, optimizing the thickness matching between the reinforcing and conductive layers when the reinforcing layer's thickness accounts for 10% or more but less than 100% is beneficial. This results in better uniformity between the reinforcing and conductive layers, further enhancing strength.

[0008] In one embodiment, the thickness of the reinforcing layer accounts for 30% to 60% of the total thickness of the reinforcing layer and the conductive layer. When the thickness of the reinforcing layer accounts for 30% to 60%, it is beneficial to further optimize the thickness matching degree between the conductive layer and the reinforcing layer. At this time, the uniformity of the reinforcing layer and the conductive layer is better, which is more conducive to the enhancement of strength and the improvement of conductivity. At the same time, it can reduce the negative impact of the reinforcing layer on the current-collecting capacity of the current collector, which is beneficial to improving the power performance of the secondary battery.

[0009] In one embodiment, the metallic material includes a nickel-based alloy, which comprises nickel and alloying elements, including at least one of chromium, iron, cobalt, magnesium, tungsten, copper, molybdenum, and manganese. Nickel-based alloys have high tensile strength, and their application in the reinforcing layer can improve the tensile strength of the current collector, compensating for the insufficient tensile strength of the polymer base layer. This suppresses electrode elongation caused by the volume expansion of the active material system, thereby improving the battery's safety performance.

[0010] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 2 μm. A thickness within this range results in higher tensile strength and better uniformity, while also mitigating the negative impact of the reinforcing layer on the conductivity of the current collector. This improves the tensile strength and conductivity of the current collector, leading to better capacity retention in the battery.

[0011] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 1.8 μm. A thickness within this range results in higher tensile strength and better uniformity, while also mitigating the negative impact of the reinforcing layer on the conductivity of the current collector. This further optimizes the tensile strength and conductivity of the current collector, thereby further improving the battery's capacity retention rate.

[0012] In one embodiment, the nickel-based alloy has a nickel molar content of 50% to 95%. When the nickel molar content is 50% to 95%, the nickel-based alloy has a high tensile strength, resulting in a high strength of the reinforcing layer. At the same time, the plating of the reinforcing layer is less difficult, which is beneficial for production and preparation.

[0013] In one embodiment, when the current collector is used on the negative electrode, the conductive layer material includes at least one of copper, nickel, and gold; or, when the current collector is used on the positive electrode, the conductive layer material includes at least one of aluminum, silver, and gold. The aforementioned conductive layer materials are advantageous for improving the conductivity of the current collector and exhibit stable electrochemical properties.

[0014] In one embodiment, the polymer material includes at least one selected from polypropylene, polyethylene terephthalate, polyimide, polyethylene, and polystyrene. These polymer materials have low density, are lightweight, and possess good flexibility, which helps reduce the weight of the current collector, thereby reducing the weight percentage of inactive material in the negative electrode and increasing the battery's energy density. Simultaneously, they improve the current collector's ductility, allowing it to adapt to volume expansion and contraction during battery charging and discharging, thus enhancing the battery's cycle stability.

[0015] In one embodiment, the thickness of the substrate is 2 μm to 10 μm. In this case, as the main structure of the current collector, the substrate can provide the current collector with a certain strength and reliability, while reducing the thickness and weight of the current collector, thereby improving the specific capacity of the electrode.

[0016] In one embodiment, the current collector further includes a primer layer disposed between the reinforcing layer and the base layer. The primer layer is made of a different material than the reinforcing layer, and the primer layer material includes any one of nickel-chromium alloy and nickel-copper alloy. The primer layer has good affinity with the reinforcing layer, which can improve the plating effect of the reinforcing layer, enhance the adhesion of the reinforcing layer, and improve the stability and reliability of the current collector.

[0017] In one embodiment, the peel strength between the base layer and the reinforcing layer is greater than or equal to 5 N / mm. With this configuration, the reinforcing layer has high bonding strength, is not easily peeled off from the current collector, and can adapt to the volume changes of the electrode during battery charging and discharging, resulting in high stability of the current collector.

[0018] In one embodiment, the tensile strength of the current collector is 300 MPa to 800 MPa. A high tensile strength of the current collector helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, thereby improving the cycle stability of the battery.

[0019] In one embodiment, the current collector has an elongation of 1.5% to 20%. This configuration improves the flexibility of the current collector, allows it to adapt to volume expansion and contraction during battery charging and discharging, enhances its stability, and increases the bonding tightness between the current collector and the active material layer, thereby improving the battery's cycle stability and safety.

[0020] In one embodiment, the sheet resistance of the current collector is less than or equal to 70 mΩ / sq. This configuration ensures good conductivity of the current collector, which helps improve the power performance of the battery.

[0021] In one embodiment, the areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm 2 With the above configuration, the current collector is lighter, which helps to reduce the mass ratio of inactive materials in the electrode and improve the mass energy density of the battery.

[0022] In one embodiment, when the current collector is used for the negative electrode sheet, the negative electrode sheet comprises a silicon-based material, and the mass percentage of silicon in the negative electrode sheet is 9% to 70%. This results in the negative electrode active material of this application having a higher specific capacity compared to traditional graphite negative electrode materials. At the same time, the current collector of this application has higher strength and better ductility, which helps to alleviate the stress caused by the volume expansion and contraction of the silicon-based material during battery charging and discharging, reduces the risk of current collector cracking, and thus helps to improve the cycle stability of the battery.

[0023] To address the aforementioned technical problems, another technical solution adopted in this application is: providing a current collector comprising a base layer, a reinforcing layer, and a conductive layer. The base layer comprises a polymer material, and one of the reinforcing layer and the conductive layer is disposed between the other and the base layer. The reinforcing layer comprises at least one of a metallic material and a non-metallic material. The metallic material comprises at least one of nickel, chromium, iron, cobalt, tungsten, and molybdenum, and the non-metallic material comprises at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black, and carbon nanotubes. Based on the total thickness of the reinforcing layer and the conductive layer, the thickness of the reinforcing layer accounts for more than or equal to 10% and less than 100%. The current collector has high strength, good ductility, and conductivity, thereby improving the mechanical properties of the current collector and enhancing the cycle stability and power performance of the secondary battery.

[0024] In one embodiment, the thickness of the reinforcing layer accounts for 30% to 60% of the total thickness of the reinforcing layer and the conductive layer. When the thickness of the reinforcing layer accounts for 30% to 60%, it is beneficial to further optimize the thickness matching degree between the conductive layer and the reinforcing layer. At this time, the uniformity of the reinforcing layer and the conductive layer is better, which is more conducive to the enhancement of strength and the improvement of conductivity. At the same time, it can reduce the negative impact of the reinforcing layer on the current-collecting capacity of the current collector, which is beneficial to improving the power performance of the secondary battery.

[0025] In one embodiment, the metallic material includes a nickel-based alloy, which comprises nickel and alloying elements, including at least one of chromium, iron, cobalt, magnesium, tungsten, copper, molybdenum, and manganese. Nickel-based alloys have high tensile strength, and their application in the reinforcing layer can improve the tensile strength of the current collector, compensating for the insufficient tensile strength of the polymer base layer. This suppresses electrode elongation caused by the volume expansion of the active material system, thereby improving the battery's safety performance.

[0026] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 2 μm. A thickness within this range results in higher tensile strength and better uniformity, while also mitigating the negative impact of the reinforcing layer on the conductivity of the current collector, thus improving both the tensile strength and conductivity of the current collector.

[0027] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 1.8 μm. Within this range, the reinforcing layer exhibits high tensile strength and good uniformity, while also mitigating the negative impact of the reinforcing layer on the conductivity of the current collector, thus further optimizing the tensile strength and conductivity of the current collector.

[0028] In one embodiment, the nickel-based alloy has a nickel molar content of 50% to 95%. When the nickel molar content is 50% to 95%, the nickel-based alloy has a high tensile strength, resulting in a high strength of the reinforcing layer. At the same time, the plating of the reinforcing layer is less difficult, which is beneficial for production and preparation.

[0029] In one embodiment, when the current collector is used on the negative electrode, the conductive layer material includes at least one of copper, nickel, and gold; or, when the current collector is used on the positive electrode, the conductive layer material includes at least one of aluminum, silver, and gold. The aforementioned conductive layer materials are advantageous for improving the conductivity of the current collector and exhibit stable electrochemical properties.

[0030] In one embodiment, the polymer material includes at least one selected from polypropylene, polyethylene terephthalate, polyimide, polyethylene, and polystyrene. These polymer materials have low density, are lightweight, and possess good flexibility, which helps reduce the weight of the current collector, thereby reducing the weight percentage of inactive material in the negative electrode and increasing the battery's energy density. Simultaneously, they improve the current collector's ductility, allowing it to adapt to volume expansion and contraction during battery charging and discharging, thus enhancing the battery's cycle stability.

[0031] In one embodiment, the thickness of the substrate is 2 μm to 10 μm. In this case, as the main structure of the current collector, the substrate can provide the current collector with a certain strength and reliability, while reducing the thickness and weight of the current collector, thereby improving the specific capacity of the electrode.

[0032] In one embodiment, the current collector further includes a primer layer disposed between the reinforcing layer and the base layer. The primer layer is made of a different material than the reinforcing layer, and the primer layer material includes any one of nickel-chromium alloy and nickel-copper alloy. The primer layer has good affinity with the reinforcing layer, which can improve the plating effect of the reinforcing layer, enhance the adhesion of the reinforcing layer, and improve the stability and reliability of the current collector.

[0033] In one embodiment, the peel strength between the base layer and the reinforcing layer is greater than or equal to 5 N / mm. With this configuration, the reinforcing layer has high bonding strength, is not easily peeled off from the current collector, and can adapt to the volume changes of the electrode during battery charging and discharging, resulting in high stability of the current collector.

[0034] In one embodiment, the tensile strength of the current collector is 300 MPa to 800 MPa; and / or the elongation of the current collector is 1.5% to 20%; and / or the sheet resistance of the current collector is less than or equal to 70 mΩ / sq; and / or the areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm 2 The high tensile strength of the current collector helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, thereby improving the cycle stability of the battery. A current collector elongation greater than or equal to 3% improves its flexibility, allowing it to adapt to volume expansion and contraction during charging and discharging, thus enhancing its stability and the bonding tightness between the current collector and the active material layer, ultimately improving the battery's cycle stability and safety. A low sheet resistance gives the current collector good conductivity, contributing to improved battery power performance. A low areal density makes the current collector lighter, reducing the mass proportion of inactive materials in the electrode and increasing the battery's mass energy density.

[0035] To address the aforementioned technical problems, another technical solution adopted in this application is to provide an electrical device that includes a secondary battery according to any of the above embodiments, and / or a current collector according to any of the above embodiments. The electrical device has at least the same advantages as a secondary battery, namely, improved battery life.

[0036] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 is a schematic diagram of the structure of a current collector provided in an embodiment of this application;

[0039] Figure 2 is a schematic diagram of the structure of the current collector provided in one embodiment of this application;

[0040] Figure 3 is an exploded structural diagram of a battery according to one or more embodiments of this application;

[0041] Figure 4 is an exploded structural diagram of a battery cell according to one or more embodiments of this application;

[0042] Figure 5 is a structural schematic diagram of a vehicle according to one or more embodiments of this application.

[0043] In the attached image:

[0044] 1000, Vehicle; 300, Motor; 200, Controller; 100, Battery; 10, Housing; 11, First Part; 12, Second Part; 20, Battery Cell; 21, End Cap; 21a, Electrode Terminal; 22, Housing; 23, Electrode Assembly; 30, Current Collector; 31, Base Layer; 31a, First Surface; 31b, Second Surface; 32, Reinforcing Layer; 33, Conductive Layer; 34, Undercoat. Embodiments of the present invention

[0045] To make the objectives, technical solutions, and effects of this application clearer and more explicit, the embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0047] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0050] Quantities, ratios, and other numerical values ​​are presented in range format in this document. It should be understood that this range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0051] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) may be performed simultaneously in parallel. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0052] Currently, the anode system of high-energy-density batteries is mainly a silicon-containing anode system, and the silicon content is gradually increasing to improve the specific capacity of the anode active material. However, the coefficient of thermal expansion of silicon is more than ten times greater than that of graphite. During battery charging and discharging, excessive volume expansion can easily lead to cracking of the anode sheet, resulting in a series of problems such as lithium plating, posing safety risks and seriously affecting the cycle stability of the battery. Therefore, it is necessary to provide a current collector with high strength and excellent ductility to improve the mechanical properties of the current collector, suppress and adapt to the electrode stretching caused by the high expansion system, reduce the risk of electrode cracking due to excessive stretching, and at the same time, the current collector needs to have good conductivity to improve the power performance of the battery.

[0053] During battery charging and discharging, both the positive and negative electrode active materials may experience volume expansion, which can easily lead to instability in the material structure. This is especially true in the negative electrode systems of current high-energy-density batteries, where silicon-containing negative electrode active materials are commonly used, and the silicon content tends to increase gradually to improve the specific capacity of the negative electrode active material. However, the coefficient of thermal expansion of silicon is more than ten times greater than that of graphite. During battery charging and discharging, excessive volume expansion can easily lead to cracking of the negative electrode sheet, resulting in a series of problems such as lithium plating, posing safety risks, and seriously affecting the cycle stability of the battery.

[0054] Therefore, a current collector with high strength and excellent ductility is needed to improve its mechanical properties, suppress and accommodate electrode stretching caused by high expansion systems, and reduce the risk of electrode cracking due to excessive stretching. Applying this current collector to the negative electrode can directly suppress negative electrode stretching caused by the volume expansion of the negative electrode active material; applying it to the positive electrode can also, to some extent, suppress negative electrode stretching caused by the volume expansion of the negative electrode active material by binding the positive electrode to the negative electrode, while also reducing positive electrode stretching caused by the volume expansion of the positive electrode active material.

[0055] Based on this, this application provides a secondary battery, which includes a current collector. Please refer to Figure 1, which is a schematic diagram of the current collector structure provided in one embodiment of this application. The current collector 30 includes a base layer 31, a reinforcing layer 32, and a conductive layer 33. The base layer 31 includes a polymer material. One of the reinforcing layer 32 and the conductive layer 33 is disposed between the other and the base layer 31. The reinforcing layer 32 includes at least one of a metallic material and a non-metallic material. The metallic material includes at least one of nickel, chromium, iron, cobalt, tungsten, and molybdenum. The non-metallic material includes at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black, and carbon nanotubes. Based on the total thickness of the reinforcing layer 32 and the conductive layer 33, the thickness ratio of the reinforcing layer 32 is greater than or equal to 10% and less than 100%.

[0056] The current collector 30 in the electrode sheet serves to carry the active material and simultaneously collect and output the current generated by the electrode active material. The base layer 31 in the current collector 30 is the main structure of the current collector 30, providing support. Its mechanical properties affect the mechanical properties of the current collector 30. The base layer 31 is made of polymer material. The polymer material has good flexibility, which can improve the ductility of the current collector 30. This is beneficial for the current collector 30 to adapt to the volume expansion and contraction during battery charging and discharging, improve the stability of the current collector 30 and the tightness of the bond between the current collector 30 and the active material layer, thereby improving the cycle stability of the secondary battery.

[0057] The reinforcing layer 32 and the conductive layer 33 are functional layers of the current collector 30. The reinforcing layer 32 in the current collector 30 includes metallic and non-metallic materials, both of which have high tensile strength. Therefore, the reinforcing layer 32 can improve the tensile strength of the current collector 30, which helps to alleviate the stress caused by the volume expansion and contraction of the active material during battery charging and discharging, and reduces the risk of cracking of the current collector 30. The conductive layer 33 in the current collector 30 has good conductivity and its function is to improve the conductivity of the current collector 30, thereby improving the power performance of the battery.

[0058] Meanwhile, based on the total thickness of the reinforcing layer 32 and the conductive layer 33, when the thickness ratio of the reinforcing layer 32 is greater than or equal to 10% and less than 100%, it is beneficial to optimize the thickness matching degree between the conductive layer 33 and the reinforcing layer 32. At this time, the uniformity of the reinforcing layer 32 is better, which is more conducive to the enhancement of strength.

[0059] In summary, the current collector 30 has high strength and good ductility, which improves the mechanical properties of the current collector 30 and enhances the cycle stability of the secondary battery.

[0060] Furthermore, the polymer material has a lower density and lighter weight, which is beneficial for the lightweighting of the current collector 30, thereby contributing to the improvement of battery energy density.

[0061] The thickness percentage of the reinforcing layer 32 can be 10%, 15%, 20%, 30%, 40%, 50%, 60%, 80%, 90%, 99%, etc., based on the total thickness of the reinforcing layer 32 and the conductive layer 33, or a range of any two of the above values, such as 10%~20%, 30%~40%, 50%~80%, 90%~99%, etc.

[0062] In one embodiment, as shown in FIG1, the base layer 31 includes a first surface 31a and a second surface 31b disposed opposite to each other, a conductive layer 33 is disposed on the first surface 31a and / or the second surface 31b of the base layer 31, and a reinforcing layer 32 is disposed between the base layer 31 and the conductive layer 33.

[0063] In one embodiment, the base layer 31 includes a first surface 31a and a second surface 31b disposed opposite to each other, the reinforcing layer 32 is disposed on the first surface 31a and / or the second surface 31b of the base layer 31, and the conductive layer 33 is disposed between the base layer 31 and the reinforcing layer 32.

[0064] In one embodiment, the thickness of the reinforcing layer 32 accounts for 30% to 60% of the total thickness of the reinforcing layer 32 and the conductive layer 33.

[0065] Based on the total thickness of the reinforcing layer 32 and the conductive layer 33, when the thickness ratio of the reinforcing layer 32 is 30% to 60%, it is beneficial to further optimize the thickness matching degree between the conductive layer 33 and the reinforcing layer 32. At this time, the uniformity of the reinforcing layer 32 and the conductive layer 33 is better, which is more conducive to the enhancement of strength and the improvement of conductivity. At the same time, it can reduce the negative impact of the reinforcing layer 32 on the current carrying capacity of the current collector 30, which is beneficial to improving the power performance of the secondary battery.

[0066] Specifically, when the thickness of the reinforcing layer 32 is greater than or equal to 30%, the uniformity of the reinforcing layer 32 is better, which is conducive to the strength enhancement effect, and the overall strength of the reinforcing layer 32 and the conductive layer 33 is higher. When the thickness of the reinforcing layer 32 is less than or equal to 60%, the uniformity of the conductive layer 33 is better, which is conducive to the improvement of conductivity, and the overall conductivity of the conductive layer 33 and the reinforcing layer 32 is better. Based on the total thickness of the reinforcing layer 32 and the conductive layer 33, the thickness percentage of the reinforcing layer 32 can be 30%, 35%, 38%, 40%, 44%, 47%, 50%, 55%, 60%, etc., or a range of any two of the above values, such as 30%~35%, 38%~44%, 47%~50%, 55%~60%, etc.

[0067] In one embodiment, the conductive layer 33 (or the reinforcing layer 32) is disposed on the first surface 31a and the second surface 31b of the base layer 31. That is, the conductive layer 33 is disposed on opposite sides of the base layer 31.

[0068] In one embodiment, the conductive layer 33 (or the reinforcing layer 32) is disposed on the first surface 31a or the second surface 31b of the base layer 31. That is, the conductive layer 33 is disposed only on one side of the base layer 31.

[0069] In one embodiment, the reinforcing layer 32 is a single-layer structure. That is, the chemical composition inside the reinforcing layer 32 is uniform, which is convenient for preparation and also helps to improve the uniformity of the mechanical properties of the reinforcing layer 32.

[0070] In one embodiment, the reinforcing layer 32 has a multi-layer structure. That is, the chemical components within the reinforcing layer 32 have clear boundaries, with at least two uniform chemical components present in each layer. For example, in one embodiment, the reinforcing layer 32 includes a nickel-iron alloy layer and a nickel oxide layer. The multi-layer structure of the reinforcing layer 32 can combine the performance advantages of each layer to adapt to different application requirements.

[0071] In one embodiment, the metallic material includes a nickel-based alloy, which includes nickel (Ni) and alloying elements, including one or two of chromium (Cr), iron (Fe), cobalt (Co), magnesium (Mg), tungsten (W), copper (Cu), molybdenum (Mo), and manganese (Mn).

[0072] Nickel-based alloys are metallic materials with nickel as the base and other alloying elements added. Nickel possesses excellent mechanical, physical, and chemical properties, while the added alloying elements act as strengthening agents, improving the oxidation resistance, corrosion resistance, high-temperature strength, and certain physical properties of nickel-based alloys, such as reducing the coefficient of thermal expansion. Nickel-based alloys have high tensile strength; when used as a reinforcing layer, they can enhance the tensile strength of the current collector, compensating for the insufficient tensile strength of the polymer base layer. This suppresses electrode elongation caused by the volume expansion of the active material system, thereby improving the cycle stability of the battery. The metallic materials in this application also include other alloys with high tensile strength, such as aluminum-magnesium alloys (Al-Mg alloys). In Al-Mg alloys, magnesium atoms can be dissolved into the aluminum lattice, thus increasing the alloy's strength.

[0073] In one embodiment, the molar content of nickel in the nickel-based alloy is 50% to 95%. When the molar content of nickel is 50% to 95%, the nickel-based alloy has a higher tensile strength, resulting in a stronger reinforcing layer. Simultaneously, the plating of the reinforcing layer is easier, which is beneficial for production. The molar content of nickel can be 50%, 55%, 65%, 70%, 80%, 90%, 95%, etc., or a range of any two of the above values, such as 50% to 65%, 70% to 80%, 90% to 95%, etc.

[0074] In one embodiment, the metallic material includes elemental nickel (Ni), tungsten (W), molybdenum (Mo), and cobalt (Co). These elemental metals have high tensile strength and can be used as a reinforcing layer to improve the tensile strength of the current collector.

[0075] In one embodiment, the reinforcing layer comprises elemental nickel (Ni). This reinforced layer exhibits high tensile strength, high electrical conductivity, good uniformity, and a simple fabrication process.

[0076] In one embodiment, the reinforcing layer comprises a nickel-iron alloy. This can reduce the cost of the reinforcing layer.

[0077] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 2 μm.

[0078] Within the aforementioned thickness range, the reinforcing layer exhibits higher tensile strength and better uniformity, while also mitigating its negative impact on the conductivity of the current collector, thus improving both the tensile strength and conductivity of the current collector. The thickness of the reinforcing layer can be 0.3μm, 0.8μm, 1μm, 1.2μm, 1.35μm, 1.5μm, 1.7μm, 2μm, or any range of two of the aforementioned values, such as 0.3μm~0.8μm, 1μm~1.35μm, 1.5μm~2μm, etc.

[0079] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 1.8 μm.

[0080] Within the aforementioned thickness range, the reinforcing layer exhibits high tensile strength and good uniformity, while also mitigating its negative impact on the conductivity of the current collector, thus further optimizing the tensile strength and conductivity of the current collector. The thickness of the reinforcing layer can be 0.3μm, 0.5μm, 0.7μm, 0.75μm, 0.8μm, 0.9μm, 1μm, 1.8μm, or any range of two of the aforementioned values, such as 0.3μm~0.5μm, 0.7μm~0.75μm, 0.8μm~0.9μm, 1μm~1.8μm, etc.

[0081] In one embodiment, the current collector is used for the negative electrode sheet, and the material of the conductive layer includes at least one of copper (Cu), silver (Ag), and gold (Au).

[0082] Copper, silver, and gold are metallic materials with high electrical conductivity, making them excellent conductive materials. This is beneficial for improving the conductivity of the negative electrode current collector, and these metallic materials also exhibit stable electrochemical properties in the negative electrode current collector.

[0083] In one embodiment, the current collector is used for the negative electrode sheet, and the conductive layer is made of copper. This configuration improves the conductivity, ductility, and welding reliability of the negative electrode current collector.

[0084] In one embodiment, the current collector is used for the positive electrode, and the material of the conductive layer includes at least one of aluminum (Al), silver (Ag), and gold (Au).

[0085] Aluminum, silver, and gold are metallic materials with high electrical conductivity, making them excellent conductive materials. This is beneficial for improving the conductivity of the positive electrode current collector, and these metallic materials also exhibit stable electrochemical properties in the positive electrode current collector.

[0086] In one embodiment, the polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE), and polystyrene (PS).

[0087] The aforementioned polymer materials have low density, light weight, and good flexibility, which helps to reduce the weight of the current collector, thereby reducing the weight ratio of inactive materials in the negative electrode sheet, increasing the energy density of the battery, and improving the ductility of the current collector, which helps the negative electrode current collector adapt to the volume expansion and contraction during the battery charging and discharging process, thus improving the cycle stability of the battery. Meanwhile, each polymer material has its own specific advantages. Specifically, polypropylene has strong acid resistance, which can improve the durability of the current collector in acidic electrolyte environments. It is also relatively inexpensive, which helps reduce the cost of the current collector. Polyethylene terephthalate has good tensile strength, bending performance, high and low temperature resistance, and insulation properties, which helps improve the ductility of the current collector and makes it more suitable for the battery environment. Polyimide has outstanding comprehensive advantages in mechanical properties, electrochemical properties, and high temperature resistance, which helps improve the strength and stability of the current collector. Polyethylene has good chemical stability and is not prone to chemical reactions with electrolytes and active materials in the battery. It can maintain its own chemical structure and performance stability during battery use, thereby ensuring the long-term reliability of the current collector and helping to extend the battery's lifespan. Polystyrene has high hardness and rigidity, which can provide good mechanical support for the current collector, allowing it to maintain a stable shape and size during battery assembly and use. At the same time, it is easy to process and mold, and can be made into current collectors of various shapes and sizes to meet the needs of different battery designs. It can realize complex current collector structure designs and improve the utilization rate of the battery's internal space.

[0088] In one embodiment, the base layer comprises at least two layers of polymer material. This allows for the integration of the advantages of different polymer materials to meet the needs of various battery designs.

[0089] In one embodiment, the polymer material includes polyimide. Polyimide has high tensile strength, which is beneficial for further improving the strength of the current collector, helping to alleviate the stress caused by the volume expansion and contraction of the active material during battery charging and discharging, reducing the risk of current collector cracking, and improving the cycle stability of the battery.

[0090] In one embodiment, the thickness of the base layer is 2μm to 10μm.

[0091] When the thickness of the substrate is 2μm to 10μm, as the main structure of the current collector, the substrate can provide the current collector with certain strength and reliability, while reducing the thickness and weight of the current collector, thereby improving the specific capacity of the electrode. The thickness of the substrate can be 2μm, 3μm, 3.5μm, 4.5μm, 5μm, 5.6μm, 6μm, 6.8μm, 7μm, 8μm, 10μm, etc., or any range of two of the above values, such as 2μm~3.5μm, 4.5μm~5.6μm, 6μm~6.8μm, 7μm~8μm, 8μm~10μm, etc.

[0092] In one embodiment, the thickness of the substrate is 4μm to 5μm. With a substrate thickness of 4μm to 5μm, the strength and weight of the substrate can be further balanced, making the current collector more suitable for the application requirements of the electrode in terms of strength and weight. This is beneficial for improving the strength and stability of the electrode and enhancing the cycle stability of the battery. The thickness of the substrate can be 4μm, 4.15μm, 4.3μm, 4.5μm, 4.7μm, 4.9μm, 5μm, etc., or a range of any two of the above values, such as 4μm to 4.15μm, 4.3μm to 4.5μm, 4.7μm to 5μm, etc.

[0093] In one embodiment, please refer to FIG2. FIG2 is a schematic diagram of the structure of the current collector provided in an embodiment of the present application. As shown in FIG2, the current collector 30 further includes a base layer 34, which is disposed between the reinforcing layer 32 and the base layer 31. The material of the base layer 34 is different from the material of the reinforcing layer 32. The material of the base layer 34 includes any one of nickel-chromium alloy and nickel-copper alloy.

[0094] The good affinity between the base layer 34 and the reinforcement layer 32 can improve the plating effect of the reinforcement layer 32, enhance the adhesion of the reinforcement layer 32, and reduce the peeling of the reinforcement layer 32 of the current collector 30 caused by the expansion-contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector 30.

[0095] In one embodiment, the thickness of the underlayer is 10nm to 100nm. When the thickness of the underlayer is 10nm to 100nm, it improves the plating effect of the reinforcement layer, reduces the weight of the current collector, and improves the conductivity of the current collector. The thickness of the underlayer can be 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 70nm, 90nm, 100nm, etc., or a range of any two of the above values, such as 10nm to 20nm, 30nm to 40nm, 50nm to 70nm, 50nm to 100nm, etc.

[0096] In one embodiment, the peel strength of the base layer and the reinforcing layer is greater than or equal to 5 N / mm.

[0097] Peel strength refers to the average force required to stably peel bonded materials from their contact surface per unit width. Peel strength reflects the adhesive strength of the materials. A peel strength of 5 N / mm or greater than or equal to the base layer and reinforcement layer indicates that the reinforcement layer in this application has high adhesive strength, is not easily peeled from the current collector, and can adapt to the volume changes of the electrode during battery charging and discharging, resulting in high stability of the current collector. The peel strength of the base layer and reinforcement layer can be 5 N / mm, 6 N / mm, 10 N / mm, 15 N / mm, 20 N / mm, etc., or a range of any two of the above values, such as 5 N / mm~6 N / mm, 6 N / mm~15 N / mm, 15 N / mm~20 N / mm, etc.

[0098] The peel strength test method is as follows: an adhesive tape (with an adhesive strength > 20 N / mm) is tightly attached to one side of the substrate. One end of the tape is separated by Mylar (a release film with PET as the main component) to prevent the substrate from sticking to the tape. After repeated rolling and pressing, the tape / substrate connection part is prepared into a sample with a width of 20 mm and a length of 100 mm. Then, the upper and lower clamps of the tensile testing machine are used to clamp the tape and the substrate at the Mylar-separated end, respectively. The tensile testing machine is started to separate the tape and the substrate to obtain the peel strength.

[0099] In one embodiment, the tensile strength of the current collector is 300 MPa to 800 MPa.

[0100] The tensile strength of a current collector refers to its ability to withstand the maximum stress without breaking under tensile force, reflecting its overall strength. A current collector with a tensile strength between 300 MPa and 800 MPa is considered high, which helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, thereby improving the battery's cycle stability. The tensile strength of a current collector can be 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 750 MPa, 800 MPa, or any range of two of these values, such as 300 MPa~500 MPa, 600 MPa~700 MPa, 750 MPa~800 MPa, etc.

[0101] In one embodiment, the elongation of the current collector is 1.5% to 20%.

[0102] Elongation at break, also known as elongation at break, refers to the rate of change of length of a specimen under external force from its initial state to the point of fracture. Elongation at break = (L...) f -L0) / L f ×100%, where L0 refers to the initial sample length, L f This refers to the sample length at the time of fracture. An elongation greater than 3% in the current collector improves its flexibility, helps it adapt to volume expansion and contraction during battery charging and discharging, enhances its stability, and strengthens the bond between the current collector and the active material layer, thereby improving the battery's cycle stability and safety. The elongation of the current collector can be 1.5%, 3%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, etc., or a range of any two of the above values, such as 1.5%~6%, 5%~8%, 8%~10%, 12%~15%, 18%~20%, etc.

[0103] The test methods for tensile strength and elongation are as follows: Take a sample with a specification of 15mm×150mm, with the upper and lower jaws of the tensile testing machine spaced 50mm apart. After clamping the sample, ensure that the sample is wrinkle-free. Set the tensile testing machine speed to 2mm / min. Ensure that the fracture point is between the upper and lower jaws of the tensile testing machine. If not, the test must be repeated. Record the instantaneous tensile force and displacement at the time of fracture. Tensile strength = tensile force / 0.015 (substrate width) / substrate thickness. Elongation at break (elongation) = displacement / 50mm.

[0104] In one embodiment, the sheet resistance of the current collector is less than or equal to 70 mΩ / sq. This setting ensures good conductivity of the current collector, which helps improve the power performance of the battery. The sheet resistance of the current collector can be 30 mΩ / sq, 35 mΩ / sq, 40 mΩ / sq, 45 mΩ / sq, 50 mΩ / sq, 60 mΩ / sq, 70 mΩ / sq, etc., or a range consisting of any two of the above values, such as 30 mΩ / sq~35 mΩ / sq, 40 mΩ / sq~45 mΩ / sq, 50 mΩ / sq~70 mΩ / sq, etc.

[0105] The sheet resistance test method is as follows: cut a 10cm×10cm sample and use an FT-3110 four-probe resistor meter to test the sheet resistance at the middle position.

[0106] In one embodiment, the areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm 2 With the above configuration, the current collector is lighter, which helps reduce the mass percentage of inactive materials in the electrode and improves the battery's energy density. The areal density of the current collector can be 3.3 mg / cm³. 2 3.4 mg / cm 2 4mg / cm 2 4.75 mg / cm 2 5mg / cm 2 6mg / cm 2 6.8 mg / cm 2 etc., or a range consisting of any two of the above values, for example, 3.3 mg / cm³. 2 ~3.4mg / cm 2 4mg / cm 2 ~4.75mg / cm 2 5mg / cm 2 ~6.8mg / cm 2 wait.

[0107] In one embodiment, when the current collector is used for the negative electrode, the negative electrode comprises a silicon-based material, and the mass percentage of silicon in the negative electrode is 9% to 70%.

[0108] In this application, silicon-based materials are used as negative electrode active materials, and the mass ratio of silicon elements in the negative electrode sheet is 9% to 70%. This makes the negative electrode active material of this application have a higher specific capacity than traditional graphite negative electrode materials. At the same time, the current collector of this application has high strength and good ductility, which helps to alleviate the stress caused by the volume expansion and contraction of silicon-based materials during battery charging and discharging, reduces the risk of current collector cracking, and thus helps to improve the cycle stability of the battery.

[0109] Besides silicon-based materials, negative electrode active materials also include other types, including but not limited to graphite, hard carbon, and graphene. The mass percentage of silicon in the negative electrode sheet can be 9%, 15%, 20%, 30%, 33%, 40%, 45%, 48%, 50%, 55%, 60%, 70%, or any range of two of the above values, such as 9%~20%, 30%~40%, 45%~50%, 55%~70%, etc.

[0110] This application also provides a current collector 30, as shown in FIG1. ​​The current collector 30 includes a base layer 31, a reinforcing layer 32, and a conductive layer 33. The base layer 31 includes a polymer material. One of the reinforcing layer 32 and the conductive layer 33 is disposed between the other and the base layer 31. The reinforcing layer 32 includes at least one of a metallic material and a non-metallic material. The metallic material includes at least one of nickel, chromium, iron, cobalt, tungsten, and molybdenum. The non-metallic material includes at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black, and carbon nanotubes. Based on the total thickness of the reinforcing layer 32 and the conductive layer 33, the thickness ratio of the reinforcing layer 32 is greater than or equal to 10% and less than 100%.

[0111] The base layer 31 includes a polymer material. The polymer material has good flexibility, which can improve the ductility of the current collector 30. This helps the current collector 30 adapt to the volume expansion and contraction during the charging and discharging process of the battery, improves the stability of the current collector 30 and the tightness of the bond between the current collector 30 and the active material layer, thereby improving the cycle stability of the secondary battery.

[0112] The reinforcing layer 32 and the conductive layer 33 are functional layers of the current collector 30. The reinforcing layer 32 in the current collector 30 includes metallic and non-metallic materials, both of which have high tensile strength. Therefore, the reinforcing layer 32 can improve the tensile strength of the current collector 30, which helps to alleviate the stress caused by the volume expansion and contraction of the active material during battery charging and discharging, and reduces the risk of cracking of the current collector 30. The conductive layer 33 in the current collector 30 has good conductivity and its function is to improve the conductivity of the current collector 30, thereby improving the power performance of the battery.

[0113] Meanwhile, based on the total thickness of the reinforcing layer 32 and the conductive layer 33, when the thickness ratio of the reinforcing layer 32 is greater than or equal to 10% and less than 100%, it is beneficial to optimize the thickness matching degree between the conductive layer 33 and the reinforcing layer 32. Specifically, at this time, the uniformity of the reinforcing layer 32 is better, which is more conducive to the enhancement of strength.

[0114] In summary, the current collector 30 has high strength and good ductility, which improves the mechanical properties of the current collector 30 and enhances the cycle stability of the secondary battery.

[0115] The thickness percentage of the reinforcing layer 32 can be 10%, 15%, 20%, 30%, 40%, 50%, 60%, 80%, 90%, 100%, etc., based on the total thickness of the reinforcing layer 32 and the conductive layer 33, or a range of any two of the above values, such as 10%~20%, 30%~40%, 50%~80%, 90%~100%, etc.

[0116] In one embodiment, the thickness of the reinforcing layer 32 accounts for 30% to 60% of the total thickness of the reinforcing layer 32 and the conductive layer 33.

[0117] Based on the total thickness of the reinforcing layer 32 and the conductive layer 33, when the thickness ratio of the reinforcing layer 32 is 30% to 60%, it is beneficial to further optimize the thickness matching degree between the conductive layer 33 and the reinforcing layer 32. At this time, the uniformity of the reinforcing layer 32 and the conductive layer 33 is better, which is more conducive to the enhancement of strength and the improvement of conductivity. At the same time, it can reduce the negative impact of the reinforcing layer 32 on the current carrying capacity of the current collector 30, which is beneficial to improving the power performance of the secondary battery.

[0118] In one embodiment, the metallic material includes a nickel-based alloy, which comprises nickel and alloying elements, including at least one selected from chromium (Cr), iron (Fe), cobalt (Co), magnesium (Mg), tungsten (W), copper (Cu), molybdenum (Mo), and manganese (Mn). Nickel-based alloys have high tensile strength; when applied to the reinforcing layer, they can improve the tensile strength of the current collector, compensating for the insufficient tensile strength of the polymer base layer. This suppresses electrode elongation caused by the volume expansion of the active material system, thereby improving the cycle stability of the battery.

[0119] In one embodiment, the molar content of nickel in the nickel-based alloy is 50% to 95%. When the molar content of nickel is 50% to 95%, the nickel-based alloy has a higher tensile strength, resulting in a stronger reinforcing layer. Simultaneously, the plating of the reinforcing layer is easier, which is beneficial for production. The molar content of nickel can be 50%, 55%, 65%, 70%, 80%, 90%, 95%, etc., or a range of any two of the above values, such as 50% to 65%, 70% to 80%, 90% to 95%, etc.

[0120] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 2 μm. A thickness within this range results in higher tensile strength and better uniformity, while also mitigating the negative impact of the reinforcing layer on the conductivity of the current collector, thus improving both the tensile strength and conductivity of the current collector. The thickness of the reinforcing layer can be 0.3 μm, 0.8 μm, 1 μm, 1.2 μm, 1.35 μm, 1.5 μm, 1.7 μm, 2 μm, or any range of two of the above values, such as 0.3 μm to 0.8 μm, 1 μm to 1.35 μm, 1.5 μm to 2 μm, etc.

[0121] In one embodiment, the thickness of the reinforcing layer is 0.3 μm to 1.8 μm. A thickness within this range can further optimize the tensile strength and conductivity of the current collector. The thickness of the reinforcing layer can be 0.7 μm, 0.75 μm, 0.8 μm, 0.9 μm, 1 μm, 1.8 μm, or any combination of two of the above values, such as 0.7 μm to 0.75 μm, 0.8 μm to 0.9 μm, 1 μm to 1.8 μm, etc.

[0122] In one embodiment, the current collector is used on the negative electrode, and the conductive layer material includes at least one of copper (Cu), silver (Ag), and gold (Au); or, the current collector is used on the positive electrode, and the conductive layer material includes at least one of aluminum (Al), silver (Ag), and gold (Au). The aforementioned conductive layer materials are beneficial for improving the conductivity of the current collector and exhibit stable electrochemical properties.

[0123] In one embodiment, the polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE), and polystyrene (PS). These polymer materials have low density, are lightweight, and possess good flexibility, which helps reduce the weight of the current collector, thereby reducing the weight percentage of inactive material in the negative electrode and increasing the battery's energy density. Simultaneously, they improve the current collector's ductility, allowing it to adapt to volume expansion and contraction during battery charging and discharging, thus enhancing the battery's cycle stability.

[0124] In one embodiment, the thickness of the base layer is 2μm to 10μm.

[0125] When the thickness of the substrate is 2μm to 10μm, as the main structure of the current collector, the substrate can provide the current collector with certain strength and reliability, while reducing the thickness and weight of the current collector, thereby improving the specific capacity of the electrode. The thickness of the substrate can be 2μm, 3μm, 3.5μm, 4.5μm, 5μm, 5.6μm, 6μm, 6.8μm, 7μm, 8μm, 10μm, etc., or any range of two of the above values, such as 2μm~3.5μm, 4.5μm~5.6μm, 6μm~6.8μm, 7μm~8μm, 8μm~10μm, etc.

[0126] In one embodiment, the thickness of the substrate is 4 μm to 5 μm. With a substrate thickness of 4 μm to 5 μm, the strength and weight of the substrate can be further balanced, which is more conducive to improving the cycle stability of the battery. The thickness of the substrate can be 4 μm, 4.15 μm, 4.3 μm, 4.5 μm, 4.7 μm, 4.9 μm, 5 μm, etc., or a range of any two of the above values, such as 4 μm to 4.15 μm, 4.3 μm to 4.5 μm, 4.7 μm to 5 μm, etc.

[0127] In one embodiment, please refer to FIG2. FIG2 is a schematic diagram of the structure of the current collector provided in an embodiment of the present application. As shown in FIG2, the current collector 30 further includes a base layer 34, which is disposed between the reinforcing layer 32 and the base layer 31. The material of the base layer 34 is different from the material of the reinforcing layer 32. The material of the base layer 34 includes any one of nickel-chromium alloy and nickel-copper alloy.

[0128] The good affinity between the base layer 34 and the reinforcement layer 32 can improve the plating effect of the reinforcement layer 32, enhance the adhesion of the reinforcement layer 32, and reduce the peeling of the reinforcement layer 32 of the current collector 30 caused by the expansion-contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector 30.

[0129] In one embodiment, the thickness of the underlayer is 10nm to 100nm. When the thickness of the underlayer is 10nm to 100nm, it improves the plating effect of the reinforcement layer, reduces the weight of the current collector, and improves the conductivity of the current collector. The thickness of the underlayer can be 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 70nm, 90nm, 100nm, etc., or a range of any two of the above values, such as 10nm to 20nm, 30nm to 40nm, 50nm to 70nm, 50nm to 100nm, etc.

[0130] In one embodiment, the peel strength of the base layer and the reinforcing layer is greater than or equal to 5 N / mm.

[0131] A peel strength between the base layer and the reinforcing layer greater than or equal to 5 N / mm indicates that the reinforcing layer in this application has high bonding strength, is not easily peeled off from the current collector, and can adapt to the volume changes of the electrode during battery charging and discharging, resulting in high stability of the current collector. The peel strength between the base layer and the reinforcing layer can be 5 N / mm, 6 N / mm, 10 N / mm, 15 N / mm, 20 N / mm, etc., or a range of any two of the above values, such as 5 N / mm~6 N / mm, 6 N / mm~15 N / mm, 15 N / mm~20 N / mm, etc.

[0132] In one embodiment, the tensile strength of the current collector is 300 MPa to 800 MPa. A higher tensile strength of the current collector helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, thereby improving the cycle stability of the battery. The tensile strength of the current collector can be 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 750 MPa, 800 MPa, etc., or a range of any two of the above values, such as 300 MPa to 500 MPa, 600 MPa to 700 MPa, 750 MPa to 800 MPa, etc.

[0133] In one embodiment, the elongation of the current collector is 1.5% to 20%. This configuration improves the flexibility of the current collector, allowing it to adapt to volume expansion and contraction during battery charging and discharging, thus enhancing its stability and the bonding tightness between the current collector and the active material layer, thereby improving the battery's cycle stability and safety. The elongation of the current collector can be 1.5%, 3%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, or a range of any two of the above values, such as 1.5% to 6%, 5% to 8%, 8% to 10%, 12% to 15%, 18% to 20%, etc.

[0134] In one embodiment, the sheet resistance of the current collector is less than or equal to 70 mΩ / sq. This setting ensures good conductivity of the current collector, which helps improve the power performance of the battery. The sheet resistance of the current collector can be 30 mΩ / sq, 35 mΩ / sq, 40 mΩ / sq, 45 mΩ / sq, 50 mΩ / sq, 60 mΩ / sq, 70 mΩ / sq, etc., or a range consisting of any two of the above values, such as 30 mΩ / sq~35 mΩ / sq, 40 mΩ / sq~45 mΩ / sq, 50 mΩ / sq~70 mΩ / sq, etc.

[0135] In one embodiment, the areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm2 With the above configuration, the current collector is lighter, which helps reduce the mass percentage of inactive materials in the electrode and improves the battery's energy density. The areal density of the current collector can be 3.3 mg / cm³. 2 3.4 mg / cm 2 4mg / cm 2 4.75 mg / cm 2 5mg / cm 2 6mg / cm 2 6.8 mg / cm 2 etc., or a range consisting of any two of the above values, for example, 3.3 mg / cm³. 2 ~3.4mg / cm 2 4mg / cm 2 ~4.75mg / cm 2 5mg / cm 2 ~6.8mg / cm 2 wait.

[0136] For example, in one embodiment, the current collector provided in this application can be prepared by the following method:

[0137] Provide for the grassroots;

[0138] Magnetron sputtering is used to prepare the base layer on the substrate;

[0139] An enhancement layer is prepared on the base layer using electroplating;

[0140] A conductive layer is prepared on the reinforcing layer by electroplating.

[0141] In other embodiments, the method for preparing the current collector provided in this application is not limited to the steps described above.

[0142] In one embodiment, the secondary battery provided in this application can be used as a battery cell. Please refer to Figure 3, which is an exploded structural diagram of a battery according to one or more embodiments of this application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a accommodating space for the battery cell 20, and the housing 10 can adopt various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, and together define a accommodating space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, with the first portion 11 covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the accommodating space; alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0143] In battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, battery 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0144] Each battery cell 20 includes at least the secondary battery provided in this application, and may also include other secondary or primary batteries; including but not limited to lithium-sulfur batteries, sodium-ion batteries, or magnesium-ion batteries. The battery cell 20 may be cylindrical, flat, cuboid, or other shapes.

[0145] Please refer to Figure 4, which is an exploded structural diagram of a battery cell according to one or more embodiments of this application. A battery cell 20 refers to the smallest unit that makes up a battery. As shown in Figure 4, the battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0146] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. In one embodiment, end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that end cap 21 is less prone to deformation under pressure and impact, allowing battery cell 20 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 to output or input electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0147] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, and plastic.

[0148] Electrode assembly 23 is the component in the battery cell 100 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the electrode assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0149] In some embodiments, the positive electrode includes a current collector and a layer of positive electrode material disposed on the current collector.

[0150] The positive electrode material layer includes a positive electrode active material, which may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0151] In one embodiment, the active layer of the positive electrode material further includes a conductive agent and a binder; the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, Ketjen black, and acetylene black; the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, acrylate, and polyurethane.

[0152] A conductive agent imparts conductivity to the electrode. The positive electrode conductive material can include any conductive material as long as it does not cause a chemical change. Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. In one embodiment, the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, Ketjen black, and acetylene black.

[0153] The adhesive improves the adhesion stability of the active layer and reduces the probability of powder shedding. The adhesive can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). In one embodiment, the adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, acrylate, and polyurethane.

[0154] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0155] In one embodiment, the electrolyte includes one or more of carbonate solvents and ether solvents.

[0156] Carbonates are typically small-molecule cyclic or chain carbonates; including but not limited to one or more of ethylene carbonate, propylene carbonate, butene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluorocarbonates; and may also be at least one ester solvent selected from γ-butyrolactone, dimethyl sulfite, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl acetate, and fluorocarboxylic acid esters.

[0157] Ether solvents include, but are not limited to, one or more of dimethyl ether, diethyl ether, tetrahydrofuran, methyltetrahydrofuran, ethylene oxide, 1,3-dioxolane, fluoroethers, DME (ethylene glycol dimethyl ether), DEE (ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), TRGDME (triethylene glycol dimethyl ether), TEGDME (tetraethylene glycol dimethyl ether), dipropyl ether, and dibutyl ether.

[0158] In other embodiments, the electrolyte may further comprise any one or a mixture of several of amine solvents, sulfone solvents, and nitrile solvents. Amine solvents include at least one of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide. Sulfone solvents include at least one of dimethyl sulfoxide, sulfolane, diphenyl sulfoxide, thionyl chloride, and dipropyl sulfone. Nitrile solvents include at least one of acetonitrile, succinic anionizer, adiponitrile, and glutaronitrile. A high-voltage resistant electrolyte is preferred, as its acidity decreases under high voltage, facilitating the transport of active ions, significantly reducing side reactions on the electrode surface, and improving battery stability.

[0159] In some embodiments, the electrolyte further includes an electrolyte salt, which may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0160] In some embodiments, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0161] In some embodiments, the negative electrode includes a current collector and a negative electrode material layer disposed on the current collector.

[0162] The anode material layer includes the anode active material, which includes carbon-based anode materials, silicon-based anode materials, tin-based anode materials, lithium titanate anode materials, and lithium metal anode materials, etc.; specifically including but not limited to graphite materials, silicon-carbon materials, graphite-silicon suboxide materials, nano-silicon materials, silicon suboxide materials, and tin-based materials; more specifically including natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys.

[0163] In one embodiment, the negative electrode sheet comprises a silicon-based material, wherein the mass percentage of silicon in the negative electrode sheet is 9% to 70%. In this case, the negative electrode active material has a higher specific capacity than traditional graphite negative electrode materials. At the same time, the current collector of this application has higher strength and better ductility, which helps to alleviate the stress caused by the volume expansion and contraction of the silicon-based material during battery charging and discharging, reduces the risk of current collector cracking, and thus helps to improve the cycle stability of the battery.

[0164] In some embodiments, the negative electrode active layer may further include a binder, a conductive agent, and other optional additives. As examples, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers. As examples, the binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). As examples, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0165] In some embodiments, this application also provides an electrical device, such as an electrochemical device. The application of this electrochemical device is not particularly limited and can be used in any electronic device known in the prior art. The battery disclosed in the embodiments of this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. That is, an electrical device is provided. In some embodiments, the electrical device of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0166] Electrical equipment can be equipped with individual battery cells, battery modules, or battery packs depending on its usage requirements.

[0167] Please refer to Figure 5, which is a structural schematic diagram of a vehicle according to one or more embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0168] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0169] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0170] (I) Battery manufacturing

[0171] Example 1:

[0172] 1. Preparation of current collectors

[0173] A base layer is provided, the material of which is PI and the thickness is 6.5μm;

[0174] A base layer of nickel-chromium alloy with a thickness of 50 nm was prepared on two opposing surfaces of the substrate using magnetron sputtering. A reinforcing layer of nickel-iron alloy was then electroplated onto the base layer surface. The electroplating solution consisted of 120 g / L nickel sulfate, 40 g / L nickel chloride, 40 g / L ferrous sulfate, 30 g / L boric acid, and 0.1 g / L sodium dodecyl sulfate, with a pH of 2.5, a temperature of 45 °C, a plating time of 2 min, and a current density of 1 A / dm³. 2The nickel-iron alloy layer has a thickness of 0.5 μm. A conductive layer, made of copper, is electroplated onto the surface of the reinforcing layer. The electroplating solution consists of 200 g / L copper sulfate, 50 g / L sulfuric acid, 0.8 g / L polyethylene glycol (PEG), and 5 mg / L sodium dipropane sulfonate, with a pH of 4.5, a temperature of 25℃, a plating time of 1 min, and a current density of 2 A / dm³. 2 The copper layer thickness is 0.5 μm. The thicknesses of the underlayer, reinforcement layer, and conductive layer are all single-sided thicknesses.

[0175] 2. Preparation of positive electrode sheet

[0176] A positive electrode slurry was prepared by uniformly mixing the positive electrode active material NCM955 (a nickel-cobalt-manganese ternary material with a molar ratio of Ni, Co, and Mn of 9:0.5:0.5), the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone (NMP) solution at a mass ratio of 96:2:2, with a solid content of 71%. The slurry was then coated onto both sides of an aluminum foil with a thickness of 13 μm using an extrusion coating machine and dried to obtain a positive electrode film. The coated electrode was then cold-pressed using a cold press to obtain the final positive electrode sheet, in which the thickness of the single-sided positive electrode active layer was 88 μm.

[0177] 3. Preparation of negative electrode sheet

[0178] Silicon-carbon-graphite composite material, conductive carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 93.5:1.8:3.5:1.2 to form a uniform negative electrode slurry with a solid content of 45%. The silicon-carbon-graphite composite material was prepared by uniformly mixing silicon-carbon material and graphite material at a mass ratio of 7:3. The negative electrode slurry was coated on both sides of the prepared current collector, and after drying and other processes, a negative electrode sheet was obtained, wherein the thickness of the single-layer negative electrode active layer was 37.8 μm.

[0179] 4. Separating membrane

[0180] A polyethylene diaphragm with a thickness of 7 μm is used as the separator.

[0181] 5. Electrolyte

[0182] Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. The fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0183] 6. Battery assembly

[0184] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked to obtain an electrode assembly; the electrode assembly is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a lithium-ion secondary battery is obtained.

[0185] Example 2

[0186] The difference from Example 1 lies in the preparation of the current collector, as detailed below:

[0187] A base layer is provided, the material of which is PI and the thickness is 6.5μm;

[0188] A base layer of nickel-chromium alloy with a thickness of 50 nm was prepared on two opposing surfaces of the substrate using magnetron sputtering. A conductive layer of copper was then electroplated onto the base layer surface. The electroplating solution consisted of 200 g / L copper sulfate, 50 g / L sulfuric acid, 0.8 g / L polyethylene glycol (PEG), and 5 mg / L sodium dipropane sulfonate, with a pH of 4.5, a temperature of 20℃~30℃, a plating time of 1 min, and a current density of 2 A / dm³. 2 The copper layer thickness is 0.5 μm. A reinforcing layer is electroplated on the conductive layer surface. The reinforcing layer is a nickel-iron alloy. The electroplating solution formula is: nickel sulfate 120 g / L, nickel chloride 40 g / L, ferrous sulfate 40 g / L, boric acid 30 g / L, sodium dodecyl sulfonate 0.1 g / L, pH value 2.5, temperature 45℃, time 2 min, and current density 1 A / dm³. 2 ~1.5A / dm 2 The nickel-iron alloy layer has a thickness of 0.5 μm. The thicknesses of the underlayer, reinforcing layer, and conductive layer are all single-sided thicknesses.

[0189] Example 3:

[0190] Some parameters in the preparation of the current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1, wherein the reinforcing layer was a nickel layer, and the electroplating solution was formulated as follows: nickel sulfate 120 g / L, nickel chloride 40 g / L, boric acid 30 g / L, and sodium dodecyl sulfonate 0.1 g / L.

[0191] Example 4:

[0192] Some parameters in the preparation of the current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1. The step of preparing the graphene reinforcement layer on the PI substrate was as follows: graphene was deposited onto the PI surface using chemical vapor deposition (CVD), and the gas source was acetylene gas.

[0193] Example 5:

[0194] Some parameters in the preparation of the current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1, except that the electroplating time of the nickel-iron alloy reinforcing layer was adjusted to 1.2 min and the electroplating time of the copper conductive layer was adjusted to 1.4 min.

[0195] Example 6:

[0196] Some parameters in the preparation of the current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1, except that the electroplating time of the nickel-iron alloy reinforcing layer was adjusted to 7.2 min and the electroplating time of the copper conductive layer was adjusted to 2.4 min.

[0197] Example 7:

[0198] The difference from Example 1 is that the positive electrode current collector and the negative electrode current collector are changed. The preparation method of the positive electrode current collector is as follows:

[0199] A substrate is provided, made of PET with a thickness of 7.5 μm. An underlayer, made of nickel-chromium alloy with a thickness of 50 nm, is prepared on two opposing surfaces of the substrate using magnetron sputtering. A reinforcing layer, made of nickel-iron alloy, is then electroplated onto the underlayer surface. The electroplating solution consists of 120 g / L nickel sulfate, 40 g / L nickel chloride, 40 g / L ferrous sulfate, 30 g / L boric acid, and 0.1 g / L sodium dodecyl sulfate, with a pH of 2.5, a temperature of 45 °C, a plating time of 2 min, and a current density of 1 A / dm³. 2 The nickel-iron alloy layer has a thickness of 0.5 μm. A conductive layer is prepared on the surface of the reinforcing layer using a vapor deposition method: an Al ingot is placed in a heated boat and heated to 1200°C, where Al volatilizes and deposits on the surface of the reinforcing layer at a speed of 10 m / min, forming a 5 μm conductive layer. The thicknesses of the base layer, reinforcing layer, and conductive layer are all single-sided thicknesses.

[0200] The negative electrode current collector is a 6-micrometer copper foil.

[0201] Example 8:

[0202] The difference from Example 1 is that, based on the total thickness of the reinforcing layer and the conductive layer, the thickness ratio of the nickel-iron alloy reinforcing layer is 10%, and the electroplating time of the reinforcing layer is adjusted to 0.4 min, while the electroplating time of the conductive layer is adjusted to 1.8 min.

[0203] Comparative Example 1:

[0204] The difference from Example 1 is that there is no preparation step of reinforcing layer and underlayer, and the electroplating time of copper conductive layer is adjusted to 2 minutes.

[0205] Comparative Example 2:

[0206] The difference from Example 3 is that there is no preparation step of reinforcing layer and underlayer, and the electroplating time of copper conductive layer is adjusted to 2 minutes.

[0207] (ii) Performance Testing

[0208] 1. Test methods for tensile strength and elongation at break

[0209] Take a 15mm×150mm sample, with the upper and lower jaws of the tensile testing machine spaced 50mm apart. After clamping the sample, ensure there are no wrinkles. Set the tensile testing machine speed to 2mm / min. Ensure the fracture point is between the upper and lower jaws of the tensile testing machine. If not, retest. Record the instantaneous tensile force and displacement at the moment of fracture. Tensile strength = tensile force / 0.015 (substrate width) / substrate thickness. Elongation at break = displacement / 50mm.

[0210] 2. Test methods for the composition, thickness, and morphology of the reinforcing layer, conductive layer, and underlayment.

[0211] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to test the negative electrode sheet by disassembling the battery cell and removing it. A cross-section, substantially perpendicular to the thickness, was obtained using plasma quenching. This cross-section corresponds to the cross-section of the negative electrode sheet. The elemental composition, thickness, and morphology of the negative electrode sheet cross-section were observed using a scanning electron microscope (SEM, specifically a ZEISS Sigma 300 from Germany) combined with energy dispersive spectroscopy (EDS).

[0212] 3. Test methods for elemental composition and content of the reinforcing layer

[0213] The test was performed using a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS).

[0214] 4. Test method for current collector thickness

[0215] Use a micrometer to measure the flatness of the manifold, take 10 points for testing, and take the average value as the thickness of the manifold.

[0216] 5. Methods for testing areal density

[0217] The electrode sheet is punched to obtain a circular sample, and the cross-sectional area A of the circular sample is measured; the mass m1 of the obtained sample is weighed; the number of faces of the electrode sheet is confirmed, whether it is 1 or 2; the sample is cleaned to remove the active material, resulting in an anode substrate and / or a cathode substrate. Specifically, the anode sample is cleaned with water, and the cathode sample is cleaned with NMP (N-methylpyrrolidone) solution.

[0218] The mass m2 of the obtained substrate is given, and the areal density of the active layer on one side of the electrode is given by (m1-m2) / (number of surfaces × A).

[0219] 6. Sheet resistance test method

[0220] Cut a 10cm×10cm sample and use an FT-3110 four-probe resistor meter to test the sheet resistance at the middle position.

[0221] 7. Test method for peel strength

[0222] Use adhesive tape (with an adhesion strength > 20 N / mm) to tightly adhere to one side of the substrate. Separate one end of the tape with Mylar (a release film with PET as the main component) to prevent the substrate from sticking to the tape. After repeated rolling and pressing, prepare a sample with a width of 20 mm and a length of 100 mm for the tape / substrate connection. Then, use the upper and lower clamps of a tensile testing machine to clamp the tape and substrate at the Mylar-separated end, and start the tensile testing machine to separate the tape and substrate to obtain the peel strength.

[0223] 8. Test method for storage capacity retention at 60℃

[0224] Maintain a temperature of 25℃, charge and discharge once at a rate of 0.33C / 0.33C, with a voltage range of 2.5V~4.25V, and record the discharge capacity C0. Then charge the battery at a constant current of 0.33C to 4.25V, and then charge it at a constant voltage of 4.25V to 0.04C. After that, place it in a constant temperature oven at 60℃ for 30 days. After that, take it out and discharge it at a rate of 0.33C and record the discharge capacity C1. The capacity retention rate is C1 / C0.

[0225] 9. Test method for capacity retention rate after 1000 cycles

[0226] The ratio of the capacity to the initial capacity after 1000 charge-discharge cycles at 0.5C / 0.5C at room temperature is the capacity retention rate after 1000 cls cycles.

[0227] Table 1. Parameter table for each embodiment and comparative example.

[0228]

[0229] Note: "Thickness percentage" refers to the thickness percentage of the reinforcing layer based on the total thickness of the reinforcing layer and the conductive layer; the thicknesses of the current collector reinforcing layer, conductive layer and base layer in Table 1 are the thickness values ​​of the above layers on one surface of the base layer, and the reinforcing layer, conductive layer and base layer are all located on the first and second surfaces of the current collector base layer.

[0230] (III) Analysis of Lithium-ion Battery Performance Test Results

[0231] 1. Compared with Comparative Example 1 and Comparative Example 2, the negative electrode current collector of the embodiment has higher tensile strength and appropriate ductility, thus having good mechanical properties. The secondary battery based on the above negative electrode current collector has good cycle stability.

[0232] 2. The current collector surface density of the embodiment is relatively small, thus achieving the weight reduction of the current collector, which is beneficial to reducing the weight ratio of inactive materials in the electrode; the sheet resistance is small, which is beneficial to current transmission.

[0233] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A secondary battery, wherein, include: A current collector includes a base layer, a reinforcing layer, and a conductive layer, wherein the base layer comprises a polymer material, and one of the reinforcing layer and the conductive layer is disposed between the other and the base layer; The reinforcing layer includes at least one of a metallic material and a non-metallic material. The metallic material includes at least one of nickel, chromium, iron, cobalt, tungsten, and molybdenum. The non-metallic material includes at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black, and carbon nanotubes. Based on the total thickness of the reinforcing layer and the conductive layer, the thickness of the reinforcing layer accounts for more than or equal to 10% and less than 100%.

2. The secondary battery as described in claim 1, wherein, Based on the total thickness of the reinforcing layer and the conductive layer, the thickness of the reinforcing layer accounts for 30% to 60%.

3. The secondary battery as described in claim 1 or 2, wherein, The metallic material includes a nickel-based alloy, which includes nickel and alloying elements, wherein the alloying elements include at least one of chromium, iron, cobalt, magnesium, tungsten, copper, molybdenum, and manganese.

4. The secondary battery according to any one of claims 1 to 3, wherein, The thickness of the reinforcing layer is 0.3μm to 2μm.

5. The secondary battery as described in claim 4, wherein, The thickness of the reinforcing layer is 0.3μm to 1.8μm.

6. The secondary battery according to any one of claims 3 to 5, wherein, In the nickel-based alloy, the molar content of nickel is 50% to 95%.

7. The secondary battery according to any one of claims 1 to 6, wherein, When the current collector is used for the negative electrode, the material of the conductive layer includes at least one of copper, silver, and gold; or, When the current collector is used for the positive electrode, the material of the conductive layer includes at least one of aluminum, silver, and gold.

8. The secondary battery according to any one of claims 1 to 7, wherein, The polymer material includes at least one of polypropylene, polyethylene terephthalate, polyimide, polyethylene, and polystyrene.

9. The secondary battery according to any one of claims 1 to 8, wherein, The thickness of the base layer is 2μm to 10μm.

10. The secondary battery according to any one of claims 1 to 9, wherein, The current collector also includes a base layer, which is disposed between the reinforcing layer and the base layer. The material of the base layer is different from that of the reinforcing layer, and the material of the base layer includes any one of nickel-chromium alloy and nickel-copper alloy.

11. The secondary battery according to any one of claims 1 to 10, wherein, The peel strength of the base layer and the reinforcing layer is greater than or equal to 5 N / mm.

12. The secondary battery according to any one of claims 1 to 11, wherein, The tensile strength of the current collector is 300MPa~800MPa.

13. The secondary battery according to any one of claims 1 to 12, wherein, The elongation of the current collector is 1.5% to 20%.

14. The secondary battery according to any one of claims 1 to 13, wherein, The sheet resistance of the current collector is less than or equal to 70 mΩ / sq.

15. The secondary battery according to any one of claims 1 to 14, wherein, The areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm 2 .

16. The secondary battery according to any one of claims 1 to 15, wherein, When the current collector is used in the negative electrode sheet, the negative electrode sheet comprises silicon-based material, and the mass percentage of silicon element in the negative electrode sheet is 9% to 70%.

17. A current collector, wherein, The current collector includes a base layer, a reinforcing layer, and a conductive layer. The base layer includes a polymer material, and one of the reinforcing layer and the conductive layer is disposed between the other and the base layer. The reinforcing layer includes at least one of a metallic material and a non-metallic material. The metallic material includes at least one of nickel, chromium, iron, cobalt, tungsten, and molybdenum. The non-metallic material includes at least one of alumina, nickel oxide, chromium oxide, graphene, acetylene black, carbon black, and carbon nanotubes. Based on the total thickness of the reinforcing layer and the conductive layer, the thickness ratio of the reinforcing layer is greater than or equal to 10% and less than 100%.

18. The secondary battery as claimed in claim 17, wherein, Based on the total thickness of the reinforcing layer and the conductive layer, the thickness of the reinforcing layer accounts for 30% to 60%.

19. The current collector as claimed in claim 17 or 18, wherein, The metallic material includes a nickel-based alloy, which includes nickel and alloying elements, wherein the alloying elements include at least one of chromium, iron, cobalt, magnesium, tungsten, copper, molybdenum, and manganese.

20. The current collector according to any one of claims 17 to 19, wherein, The thickness of the reinforcing layer is 0.3μm to 2μm.

21. The current collector as claimed in claim 20, wherein, The thickness of the reinforcing layer is 0.3μm to 1.8μm.

22. The current collector as described in claims 19-21, wherein, In the nickel-based alloy, the molar content of nickel is 50% to 95%.

23. The current collector according to any one of claims 17 to 22, wherein, When the current collector is used for the negative electrode, the material of the conductive layer includes at least one of copper, silver, and gold; or, When the current collector is used for the positive electrode, the material of the conductive layer includes at least one of aluminum, silver, and gold.

24. The current collector according to any one of claims 17 to 23, wherein, The polymer material includes at least one of polypropylene, polyethylene terephthalate, polyimide, polyethylene, and polystyrene.

25. The current collector according to any one of claims 17 to 24, wherein, The thickness of the base layer is 2μm to 10μm.

26. The current collector according to any one of claims 17 to 25, wherein, The current collector also includes a base layer, which is disposed between the reinforcing layer and the base layer. The material of the base layer is different from that of the reinforcing layer, and the material of the base layer includes any one of nickel-chromium alloy and nickel-copper alloy.

27. The current collector according to any one of claims 17 to 26, wherein, The peel strength between the base layer and the reinforcing layer is greater than or equal to 5 N / mm.

28. The current collector according to any one of claims 17 to 27, wherein, The tensile strength of the current collector is 300 MPa to 800 MPa; and / or The elongation of the current collector is 1.5%~20%; and / or The sheet resistance of the current collector is less than or equal to 70 mΩ / sq; and / or The areal density of the current collector is 3.3 mg / cm³. 2 ~6.8mg / cm 2 .

29. An electrical appliance, wherein, The electrical equipment includes a secondary battery as described in any one of claims 1 to 16; and / or includes a current collector as described in any one of claims 17 to 28.

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