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, which comprises a base layer and a conductive plating layer, and comprises first regions stacked in the thickness direction of an electrode sheet and a second region located on at least one side of the first region in a first direction, wherein the base layer is located in the first regions and the second region, the conductive plating layer is at least arranged in the second region, the tensile strength of the base layer ranges from 400 MPa to 1000 MPa, and the conductivity of the conductive plating layer is greater than that of the base layer. The relatively high tensile strength of the base layer facilitates the improvement in the cycle stability of the battery. The conductive plating layer facilitates the improvement in the conductivity of the current collector; in addition, the conductive plating layer is at least arranged in the second region, such that a sufficient overcurrent area for currents that are output from the electrode assembly can be provided. Therefore, the current collector can improve the power performance of the battery.

Description

Secondary batteries, current collectors, electrical equipment

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510126656.6, 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; their conductivity affects the battery's power performance, while their strength influences its cycle stability. Therefore, to improve cycle stability, a current collector possessing both high strength and high conductivity is needed. 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, wherein the current collector has the characteristics of high strength and high conductivity, which can improve the cycle stability of the secondary battery.

[0006] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a secondary battery, the secondary battery including an electrode, the electrode including a current collector, the current collector including a base layer and a conductive coating layer stacked along the thickness direction of the electrode, the current collector including a first region and a second region located on at least one side of the first region along a first direction, the base layer being located in the first region and the second region, the conductive coating layer being at least located in the second region, the tensile strength of the base layer being 400MPa~1000MPa, and the conductivity of the conductive coating layer being greater than the conductivity of the base layer.

[0007] The substrate has a high tensile strength of 400MPa~1000MPa, which helps 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. The conductivity of the conductive coating is higher than that of the substrate, optimizing conductivity compared to the substrate itself as a current collector. Simultaneously, the second region, being the edge area of ​​the current collector and typically the connection location of current output components, has a conductive coating at least in this region, providing sufficient overcurrent area for current output from the electrode assembly. Therefore, the cycle stability of the secondary battery is improved.

[0008] In one embodiment, the substrate has a conductivity of 1% IACS to 50% IACS, and the conductive coating has a conductivity of 50% IACS to 100% IACS. The substrate's conductivity of 1% IACS to 50% IACS meets the basic power requirements of the battery, while the conductive coating's conductivity of 50% IACS to 100% IACS further optimizes conductivity compared to the substrate itself as a current collector.

[0009] In one embodiment, the surface density of the base layer is 0.9 mg / cm³. 2 ~3.7mg / cm 2 As the main structure of the current collector, the areal density of the base layer within the above-mentioned range can reduce the weight of the current collector, achieving lightweighting of the current collector, thereby reducing the mass proportion of inactive materials in the electrode and improving the mass energy density of the battery.

[0010] In one embodiment, the thickness of the substrate is 2 μm to 8 μm. When the thickness of the substrate is 2 μm to 8 μm, as the main structure of the current collector, the substrate can provide the current collector with high strength and reliability, while reducing the thickness and weight of the current collector, thereby improving the specific capacity of the electrode.

[0011] In one embodiment, the thickness of the substrate is 4μm to 6μm. With a substrate thickness of 4μm to 6μm, 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.

[0012] In one embodiment, the base material includes at least one of titanium, aluminum, and carbon materials; the carbon materials include at least one of carbon fiber, carbon nanotubes, and graphene. Different base materials and composite materials of various base materials can be adaptively selected to meet the diverse needs of current collector applications, such as lightweighting, high strength, high conductivity, and appropriate ductility.

[0013] In one embodiment, the thickness of the conductive coating is 0.2 μm to 2 μm. When the thickness of the conductive coating is 0.2 μm to 2 μm, the conductive coating has good smoothness and uniformity, and is lightweight, which can effectively improve the conductivity of the current collector, which is beneficial to the lightweighting of the current collector. At the same time, it is beneficial to improve welding reliability and processing performance.

[0014] In one embodiment, the thickness of the conductive coating is 0.3 μm to 1 μm. When the thickness of the conductive coating is 0.3 μm to 1 μm, the conductivity of the current collector can be further improved, which is beneficial for the lightweight design of the current collector and for improving its processing performance.

[0015] In one embodiment, the conductive plating layer is made of any one of copper, silver, and gold. Copper, silver, and gold are metallic materials with high electrical conductivity, making them excellent conductive materials and beneficial for improving the conductivity of the current collector.

[0016] In one embodiment, the current collector further includes an intermediate layer, which is disposed between the base layer and the conductive coating along the thickness direction of the electrode sheet. The material of the intermediate layer includes at least one of nickel, iron, chromium, and manganese. The intermediate layer can improve the plating effect of the conductive coating, increase the density of the conductive coating, improve the interlayer adhesion between the base layer and the conductive coating, and improve the stability and reliability of the current collector. At the same time, the intermediate layer has certain conductivity to meet the conductivity requirements between the base layer and the conductive coating.

[0017] In one embodiment, the thickness of the intermediate layer is 10 nm to 200 nm. When the thickness of the intermediate layer is 10 nm to 200 nm, it can both improve the plating effect of the conductive coating and reduce the weight of the current collector, thereby improving the conductivity of the current collector.

[0018] In one embodiment, the current collector satisfies at least one of the following (1) to (5):

[0019] (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq;

[0020] (2) The tensile strength of the current collector is greater than or equal to 600 MPa;

[0021] (3) The elongation of the current collector is greater than or equal to 1%;

[0022] (4) The thickness of the current collector is 2μm~15μm;

[0023] (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m.

[0024] The current collector has a sheet resistance of less than or equal to 35 mΩ / sq, which gives it good conductivity and helps improve the battery's power performance. Its high tensile strength helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, thus improving the battery's cycle stability. The current collector's elongation is greater than 1%, which improves its flexibility and the bonding tightness between the current collector and the active material layer, thereby improving the battery's cycle stability and safety. The current collector's thickness is in the range of 2 μm to 15 μm, which helps reduce the current collector's weight and its proportion in the electrode, while also improving the reliability of both the current collector and the electrode. The strong bonding strength between the base layer and the conductive coating reduces the separation of the current collector base layer and the conductive coating at the interface caused by the expansion-contraction stress generated during battery charging and discharging, thus improving the current collector's stability and reliability.

[0025] In one embodiment, the sheet resistance of the current collector is less than 20 mΩ / sq. This configuration further improves the conductivity of the current collector, making it more efficient at collecting current and thus contributing to improved battery power performance.

[0026] In one embodiment, the thickness of the current collector is 4 μm to 8 μm. This configuration helps to further reduce the weight of the current collector and its proportion of thickness in the electrode, thereby allowing the electrode to accommodate more active material and improving specific capacity and battery energy density.

[0027] In one embodiment, the interlayer bonding strength between the substrate and the conductive coating is 120 N / m to 1000 N / m. This configuration further increases the bonding strength between the substrate and the conductive coating, thereby improving the stability and reliability of the current collector and enhancing the cycle stability of the battery.

[0028] In one embodiment, a conductive coating is disposed in the first region and the second region, and the conductive coating covers at least one surface of the substrate. In this case, the contact area between the substrate and the conductive coating is large, which is beneficial to increasing the interfacial bonding force between the two and improving the stability of the current collector; at the same time, the larger area of ​​the conductive coating is beneficial to improving the conductivity of the current collector.

[0029] In one embodiment, the electrode further includes an active material layer disposed in the first region and covering the conductive coating. The active material layer is loaded on the surface of the current collector and serves to provide active material, responsible for transferring charge to or receiving charge from the electrolyte, and is the main site for electrochemical reactions in the battery.

[0030] In one embodiment, the conductive coating is disposed only in the second region, and the conductive coating covers at least one surface of the substrate in the second region. In this case, the conductive coating is disposed only in the second region, providing sufficient current-carrying area for current output from the electrode assembly, improving battery power performance, while simultaneously reducing the weight of the conductive coating, which is beneficial for lightweighting the current collector and increasing the battery's energy density.

[0031] In one embodiment, the tensile strength of the second region is lower than that of the first region. With this configuration, the second region has lower strength and is more easily deformed, thus facilitating welding and improving the processability of the current collector.

[0032] In one embodiment, the difference between the tensile strength of the second region and the tensile strength of the first region is less than or equal to 100 MPa. This improves the processing performance of the current collector and reduces the strength difference between the second and first regions, thereby increasing the overall strength of the current collector.

[0033] In one embodiment, the elongation of the second region is less than that of the first region.

[0034] In one embodiment, the thickness difference between the second region and the first region is less than or equal to 2 μm. This setting allows the thickness difference between the second and first regions to be controlled within a small range, which is beneficial for improving the flatness of the electrode winding.

[0035] In one embodiment, the thickness difference between the second region and the first region is less than or equal to 1 μm. This setting further reduces the thickness difference between the second and first regions, which is more conducive to improving the flatness of the electrode winding.

[0036] In one embodiment, the electrode further includes an active material layer comprising a first portion covering the base layer and a second portion extending from the first portion onto a portion of the conductive plating layer. The active material layer is loaded on the current collector surface, serving to provide active material; the presence of the second portion also reduces weak areas for current output, improves the battery's overcurrent capability, reduces the distance between thinned areas, thus decreasing the distance between the positive and negative electrodes, shortening the lithium-ion transport path, and reducing the risk of lithium plating in the thinned areas.

[0037] To address the aforementioned technical problems, another technical solution adopted in this application is: providing a current collector comprising a base layer and a conductive coating stacked along the electrode thickness direction. The current collector includes a first region and a second region located on at least one side of the first region along a first direction. The base layer is located in both the first and second regions, and the conductive coating is at least located in the second region. The tensile strength of the base layer is 400 MPa to 1000 MPa, and the conductivity of the conductive coating is greater than that of the base layer. The high tensile strength of the base layer (400 MPa to 1000 MPa) helps 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. The higher conductivity of the conductive coating compared to the base layer itself optimizes conductivity as a current collector. Furthermore, the second region is the edge region of the current collector, typically the connection location of current output components. The conductive coating's presence in the second region provides sufficient overcurrent area for current output from the electrode assembly. Therefore, the cycle stability of the secondary battery is improved.

[0038] In one embodiment, the substrate has a conductivity of 1% IACS to 50% IACS, and the conductive coating has a conductivity of 50% IACS to 100% IACS. The substrate's conductivity of 1% IACS to 50% IACS meets the basic power requirements of the battery, while the conductive coating's conductivity of 50% IACS to 100% IACS further optimizes conductivity compared to the substrate itself as a current collector.

[0039] In one embodiment, the current collector satisfies at least one of the following (1) to (5):

[0040] (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq;

[0041] (2) The tensile strength of the current collector is greater than or equal to 600 MPa;

[0042] (3) The elongation of the current collector is greater than or equal to 1%;

[0043] (4) The thickness of the current collector is 2μm~15μm;

[0044] (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m.

[0045] The current collector has a sheet resistance of less than 35 mΩ / sq, giving it good conductivity; its high tensile strength helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging; its elongation is greater than 1%, which improves its flexibility and the tightness of the bond between the current collector and the active material layer; its thickness is in the range of 2 μm to 15 μm, which helps reduce the weight of the current collector and its proportion of thickness in the electrode, while also improving the reliability of both the current collector and the electrode; and its strong bond strength between the base layer and the conductive coating improves the stability and reliability of the current collector.

[0046] In one embodiment, a conductive coating is disposed in the first region and the second region, and the conductive coating covers at least one surface of the substrate. In this case, the contact area between the substrate and the conductive coating is large, which is beneficial to increasing the interfacial bonding force between the two and improving the stability of the current collector; at the same time, the larger area of ​​the conductive coating is beneficial to improving the conductivity of the current collector.

[0047] In one embodiment, the conductive coating is disposed only in the second region, and the conductive coating covers at least one surface of the substrate in the second region. In this case, the conductive coating is disposed only in the second region, providing sufficient current-carrying area for current output from the electrode assembly, improving battery power performance, while simultaneously reducing the weight of the conductive coating, which is beneficial for lightweighting the current collector and increasing the battery's energy density.

[0048] To address the aforementioned technical problems, another technical solution adopted in this application is to provide an electrical device comprising a battery according to any of the above embodiments, and / or a negative electrode active material according to any of the above embodiments, and / or a negative electrode active material prepared using the method described in any of the above embodiments. The electrical device possesses at least the same advantages as a battery, namely, improved battery life.

[0049] 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, specific embodiments of this application are given below. Attached Figure Description

[0050] 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.

[0051] Figure 1 is a side view of a current collector provided in one embodiment of this application;

[0052] Figure 2 is a side view of a current collector provided in another embodiment of this application;

[0053] Figure 3 is a top view of the current collector corresponding to Figure 1;

[0054] Figure 4 is a top view of the current collector corresponding to Figure 2;

[0055] Figure 5 is a schematic diagram of the structure of a current collector according to an embodiment of this application;

[0056] Figure 6 is a schematic diagram of electrode preparation according to an embodiment of this application;

[0057] Figure 7 is a schematic diagram of electrode preparation according to another embodiment of this application;

[0058] Figure 8 is an exploded structural diagram of a battery according to one or more embodiments of this application;

[0059] Figure 9 is an exploded structural diagram of a battery cell according to one or more embodiments of this application;

[0060] Figure 10 is a structural schematic diagram of a vehicle according to one or more embodiments of this application.

[0061] In the attached image:

[0062] 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, Electrode Sheet; 31, Current Collector; 31a, First Region; 31b, Second Region; 311, Base Layer; 312, Conductive Plating; 313, Intermediate Layer; 32, Active Material Layer; 321, First Part; 322, Second Part. Embodiments of the present invention

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] With the increasing demand for high energy density batteries, especially for aviation batteries with significant future growth potential, it is essential to achieve a balance between high energy density and high power performance. Next-generation high-energy-density battery anode systems, such as silicon and lithium metal anodes, exhibit high volume expansion characteristics. Therefore, current collectors need to possess high strength to suppress electrode elongation caused by the high expansion system, reducing the risk of electrode cracking due to excessive elongation. Simultaneously, current collectors need to possess high conductivity to improve battery power performance. Furthermore, lightweight design of the current collector is necessary to further meet the high energy density requirements of the battery.

[0071] Please refer to Figures 1 to 4. Figure 1 is a side view of a current collector provided in one embodiment of this application, Figure 2 is a side view of a current collector provided in another embodiment of this application, Figure 3 is a top view of the current collector corresponding to Figure 1, and Figure 4 is a top view of the current collector corresponding to Figure 2.

[0072] Based on this, this application provides a secondary battery, which includes an electrode sheet, the electrode sheet including a current collector 31, the current collector 31 including a base layer 311 and a conductive plating layer 312 stacked along the thickness direction of the electrode sheet, the current collector 31 including a first region 31a and a second region 31b located on at least one side of the first region 31a along a first direction x, the base layer 311 being located in the first region 31a and the second region 31b, the conductive plating layer 312 being disposed at least in the second region 31b, the tensile strength of the base layer 311 being 400MPa~1000MPa, and the conductivity of the conductive plating layer being greater than the conductivity of the base layer.

[0073] The current collector 31 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 311 of the current collector 31 forms the main structure of the current collector 31, providing its primary mechanical properties. The tensile strength of the base layer 311 is 400MPa~1000MPa, which is relatively high and helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, reducing the risk of cracking of the current collector 31 and thus improving the cycle stability of the battery. The conductive plating layer 312 in the current collector 31 improves the conductivity of the current collector 31. The conductivity of the conductive plating layer 312 is greater than that of the base layer 311, thus optimizing conductivity compared to the base layer 311 itself as a current collector. Simultaneously, the current collector 31 includes a first region 31a and a second region 31b located along a first direction x on at least one side of the first region 31a. In the side view of the current collector 31 (Figures 1 and 2), it can be seen that the first direction x is perpendicular to the thickness direction of the current collector. Combining this with the top view of the current collector 31 (Figures 3 and 4), it can be seen that the first region 31a is located in the middle along the first direction x, and the second region 31b is located on both sides of the first region 31a. That is, the second region 31b is the edge region of the current collector, typically the connection location of the current output component. The conductive plating layer 312 is at least disposed in the second region 31b, providing sufficient current-carrying area for current output from the electrode assembly. Therefore, the cycle stability of the secondary battery is improved.

[0074] The tensile strength of the base layer 311 refers to its ability to withstand the maximum stress without breaking under tensile force. It reflects the strength of the base layer 311. A stronger base layer 311 provides greater strength to the current collector 31, thereby suppressing electrode stretching caused by the volume expansion of the active material system and improving battery safety. The tensile strength of the base layer can be 400MPa, 500MPa, 550MPa, 600MPa, 700MPa, 900MPa, 1000MPa, or any range of two of these values, such as 400MPa~500MPa, 550MPa~700MPa, 900MPa~1000MPa, etc.

[0075] Electrical conductivity reflects a material's ability to conduct electricity; the higher the conductivity, the better the material's conductivity. This application uses the relative value of IACS conductivity to represent conductivity. IACS conductivity (International Annealed Copper Standard) defines the conductivity of a material based on the conductivity of annealed pure copper, defined at 20°C with a purity of 99.99% and a resistivity of 1.7241 x 10⁻⁶. -8The conductivity value of copper wire with Ω·m and a conductivity of 58.0 MS / m is 100% IACS. The ratio of the conductivity of other materials to the conductivity of annealed pure copper, expressed as a percentage, is the IACS conductivity of that material, which can be calculated using the following formula: Conductivity (%IACS) = (Conductivity (MS / m) / 58.0 × 100%). The conductive coating 312 has better conductivity than the base layer 311, which can improve the conductivity of the current collector 31.

[0076] In one embodiment, the conductivity of the substrate is 1% IACS to 50% IACS, and the conductivity of the conductive coating is 50% IACS to 100% IACS.

[0077] The conductivity of the base layer 311 can be 1% IACS, 5% IACS, 10% IACS, 15% IACS, 20% IACS, 30% IACS, 40% IACS, 50% IACS, etc., or a range consisting of any two of the above values, such as 1% IACS~5% IACS, 10% IACS~15% IACS, 20% IACS~40% IACS, 40% IACS~50% IACS, etc. The conductivity of the conductive coating 312 can be 50% IACS, 55% IACS, 60% IACS, 70% IACS, 85% IACS, 100% IACS, etc., or a range consisting of any two of the above values, such as 50% IACS~55% IACS, 60% IACS~70% IACS, 85% IACS~100% IACS, etc.

[0078] The conductivity of the base layer 311 is 1% IACS to 50% IACS, which can meet the basic power requirements of the battery. The conductivity of the conductive coating 312 is 50% IACS to 100% IACS, which further optimizes the conductivity compared to the base layer 311 itself as a current collector.

[0079] In the embodiments shown in Figures 1 and 2, the second region 31b is disposed on both sides of the first region 31a along the first direction x. In other embodiments, the second region 31b may also be disposed on only one side of the first region 31a along the first direction x.

[0080] In the embodiments shown in Figures 1 and 2, the conductive plating layer 312 is disposed on both opposite sides of the current collector 31. In other embodiments, the conductive plating layer 312 may be disposed only on one side of the current collector 31.

[0081] As the main structure of the current collector, the surface density, thickness, and material of the base layer affect the performance of the base layer, which in turn affects the performance of the current collector, including mechanical and electrical properties.

[0082] In one embodiment, the surface density of the base layer is 0.9 mg / cm³. 2 ~3.7mg / cm 2 .

[0083] The areal density of the substrate refers to the mass of the substrate over a given area; the lower the areal density, the lighter the substrate. As the main structure of the current collector, a substrate areal density within the aforementioned range can reduce the weight of the current collector, achieving weight reduction, thereby reducing the mass proportion of inactive materials in the electrode and improving the battery's mass energy density. The areal density of the substrate can be 0.9 mg / cm³. 2 1.0 mg / cm 2 1.4 mg / cm 2 1.6 mg / cm 2 2.0 mg / cm 2 2.5 mg / cm 2 3.0 mg / cm 2 3.7 mg / cm 2 Etc., or a range consisting of any two of the above values, for example, 0.9 mg / cm³. 2 ~1.0mg / cm 2 1.4 mg / cm 2 ~1.6mg / cm 2 2.5 mg / cm 2 ~3.7mg / cm 2 wait.

[0084] In one embodiment, the thickness of the base layer is 2μm to 8μm.

[0085] When the thickness of the substrate is 2μm to 8μm, as the main structure of the current collector, the substrate can provide the current collector with high 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, etc., or any range of two of the above values, such as 2μm~3.5μm, 4.5μm~5.6μm, 6μm~6.8μm, 7μm~8μm, etc.

[0086] In one embodiment, the thickness of the substrate is 4μm to 6μm. With a substrate thickness of 4μm to 6μm, 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.

[0087] In one embodiment, the base material includes at least one of titanium, aluminum, and carbon materials; the carbon materials include at least one of carbon fiber, carbon nanotubes, and graphene.

[0088] Titanium (Ti) and aluminum (Al) are metallic materials with good electrical conductivity. Titanium is characterized by its light weight, high strength, and excellent corrosion resistance. Therefore, using titanium in base materials can improve the tensile strength of the base layer, reduce its weight, improve its electrical conductivity, and enhance its corrosion resistance. Aluminum is also lightweight and possesses good ductility, electrical conductivity, and thermal conductivity. Therefore, using aluminum in base materials can reduce the weight of the base layer, improve its electrical conductivity and ductility, and also facilitate heat dissipation for current collectors.

[0089] Among carbon materials, carbon fiber has a small mass and high strength, and its three-dimensional porous structure can effectively alleviate the volume expansion of the negative electrode during battery cycling. Carbon nanotubes have advantages such as high flexibility, low density, high chemical stability and mechanical durability. When applied to the base layer of current collectors, they can significantly reduce the total weight of the current collector. At the same time, the porous structure of carbon nanotube films is also conducive to the wetting and penetration of electrode slurry, which helps to improve structural stability and reduce interfacial resistance. Graphene has good mechanical flexibility and is very thin, which is beneficial to the lightweight and ductility improvement of current collectors.

[0090] To meet the diverse application requirements of current collectors, different base materials and composite materials of various base materials can be selected to satisfy the needs of current collectors in terms of lightweight, high strength, high conductivity, and appropriate ductility.

[0091] In one embodiment, the base material includes titanium. This can improve the tensile strength of the base, reduce its weight, give it better electrical conductivity, and improve its corrosion resistance.

[0092] In one embodiment, the base material includes at least two of titanium, aluminum, and titanium-aluminum alloy.

[0093] In one embodiment, the base material includes a composite material of carbon and metal materials. The carbon material includes at least one of carbon fiber, carbon nanotubes, and graphene, and the metal material includes at least one of titanium and aluminum. The composite material can be formed by coating the surface of the metal material with carbon material, or by chemical bonding of the carbon material and the metal material at the grain level.

[0094] As a functional structure for current collectors, the performance of conductive coatings is mainly affected by their thickness and material. The performance of conductive coatings primarily influences the conductivity and processing performance of current collectors.

[0095] In one embodiment, the thickness of the conductive coating is 0.2 μm to 2 μm. This thickness range refers to the thickness range of a single-layer conductive coating. When the thickness of the conductive coating is 0.2 μm to 2 μm, the conductive coating exhibits good flatness and uniformity, and is lightweight. This effectively improves the conductivity of the current collector, facilitating its weight reduction, and also enhances welding reliability and processing performance. The thickness of the conductive coating can be 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, etc., or a range consisting of any two of the above values, such as 0.2 μm to 0.5 μm, 0.8 μm to 1 μm, 1.4 μm to 1.6 μm, 1.8 μm to 2 μm, etc.

[0096] In one embodiment, the thickness of the conductive coating is 0.3 μm to 1 μm. This thickness range refers to the thickness range of a single-layer conductive coating. When the thickness of the conductive coating is 0.3 μm to 1 μm, the conductivity of the current collector can be further improved, which is beneficial for the weight reduction of the current collector and for improving its processing performance. The thickness of the conductive coating can be 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, etc., or a range consisting of any two of the above values, such as 0.3 μm to 0.5 μm, 0.5 μm to 8 μm, 0.8 μm to 1 μm, etc.

[0097] In one embodiment, the conductive coating material includes any one of copper, silver, and gold. Copper (Cu), silver (Ag), and gold (Au) are metallic materials with high electrical conductivity, making them excellent conductive materials and beneficial for improving the conductivity of the current collector. In other embodiments, the conductive coating material can also be other materials with high electrical conductivity.

[0098] Please refer to Figure 5, which is a schematic diagram of the current collector structure according to one embodiment of this application. In one embodiment, the current collector 31 further includes an intermediate layer 313, which is located between the base layer 311 and the conductive plating layer 312 along the thickness direction of the electrode sheet. The material of the intermediate layer 313 includes at least one of nickel, iron, chromium, and manganese.

[0099] The intermediate layer 313 is located between the base layer 311 and the conductive plating layer 312. The material of the intermediate layer 313 includes at least one of nickel (Ni), iron (Fe), chromium (Cr), and manganese (Mn). It can improve the plating effect of the conductive plating layer 312, increase the density of the conductive plating layer 312, improve the interlayer bonding force between the base layer 311 and the conductive plating layer 312, and reduce the separation of the base layer 311 and the conductive plating layer 312 at the interface caused by the expansion-contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector 31.

[0100] In one embodiment, the intermediate layer 313 has a conductivity of 1% IACS to 30% IACS, which has certain conductivity and can meet the conductivity requirements between the base layer 311 and the conductive plating layer 312.

[0101] In one embodiment, the thickness of the intermediate layer is 10nm to 200nm. When the thickness of the intermediate layer is 10nm to 200nm, it can both improve the plating effect on the conductive coating and reduce the weight of the current collector, thereby improving the conductivity of the current collector. The thickness of the intermediate layer can be 10nm, 20nm, 50nm, 70nm, 90nm, 100nm, 120nm, 150nm, 175nm, 200nm, etc., or a range consisting of any two of the above values, such as 10nm~50nm, 70nm~100nm, 120nm~150nm, 175nm~200nm, etc.

[0102] By designing the structure of the current collector, and setting the tensile strength, conductivity, areal density, material and thickness of the base layer, the conductivity, material and thickness of the conductive coating, and the material, conductivity and thickness of the intermediate layer, the current collector can exhibit good performance in different aspects.

[0103] In one embodiment, the current collector satisfies at least one of the following (1) to (5):

[0104] (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq;

[0105] (2) The tensile strength of the current collector is greater than or equal to 600 MPa;

[0106] (3) The elongation of the current collector is greater than or equal to 1%;

[0107] (4) The thickness of the current collector is 2μm~15μm;

[0108] (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m.

[0109] Sheet resistance refers to the voltage drop caused by the current density per unit area (i.e., the amount of current per unit area) along the thickness direction of the material. A sheet resistance of less than 35 mΩ / sq ensures good conductivity of the current collector, which facilitates current collection and thus helps improve the battery's power performance. The sheet resistance of the current collector can be 5 mΩ / sq, 8 mΩ / sq, 10 mΩ / sq, 12 mΩ / sq, 16 mΩ / sq, 20 mΩ / sq, 24 mΩ / sq, 30 mΩ / sq, 35 mΩ / sq, or any range of two of these values, such as 5 mΩ / sq~10 mΩ / sq, 12 mΩ / sq~16 mΩ / sq, 20 mΩ / sq~24 mΩ / sq, 30 mΩ / sq~35 mΩ / sq, etc.

[0110] Tensile strength refers to the maximum stress a sample can withstand under tensile force without breaking, reflecting the strength of the current collector. A current collector with a tensile strength greater than 600 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 the current collector can be 600 MPa, 800 MPa, 950 MPa, 1000 MPa, 1200 MPa, etc., or any range of two of these values, such as 600 MPa~800 MPa, 950 MPa~1000 MPa, 1000 MPa~1200 MPa, etc.

[0111] 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 1% in the current collector improves its flexibility, allows it to 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%, 2%, 2.5%, 3%, 5%, 8%, 10%, 12%, 13.5%, 15%, 16%, etc., or a range of any two of these values, such as 1%~3%, 5%~8%, 10%~12%, 13.5%~16%, etc.

[0112] A current collector thickness within the range of 2μm to 15μm is beneficial for reducing the current collector's weight and its proportion within the electrode thickness. This allows the electrode to accommodate more active material, improving specific capacity and battery energy density. Simultaneously, the current collector's high strength enhances the reliability of both the current collector and the electrode, as well as the battery's safety and cycle performance. The current collector thickness can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 15μm, or any combination of two of these values, such as 2μm~4μm, 4μm~6μm, 8μm~10μm, 12μm~15μm, etc.

[0113] The interlayer bonding force between the substrate and the conductive coating reflects the strength of their bond. When the interlayer bonding force is between 50 N / m and 1000 N / m, the bond strength between the substrate and the conductive coating is relatively high, making them less prone to separation. This reduces the risk of separation at the interface between the current collector substrate and the conductive coating due to expansion and contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector and enhancing the cycle stability of the battery. The interlayer bonding force between the substrate and the conductive coating can be 50 N / m, 100 N / m, 150 N / m, 200 N / m, 280 N / m, 340 N / m, 500 N / m, 600 N / m, 800 N / m, 1000 N / m, etc., or any range of two of these values, such as 50 N / m to 150 N / m, 200 N / m to 280 N / m, 340 N / m to 600 N / m, 800 N / m to 1000 N / m, etc.

[0114] In one embodiment, the sheet resistance of the current collector is less than 20 mΩ / sq. This setting further improves the conductivity of the current collector, making it more conducive to current collection and thus helping to improve the battery's power performance. The sheet resistance of the current collector can be 5 mΩ / sq, 8 mΩ / sq, 10 mΩ / sq, 12 mΩ / sq, 16 mΩ / sq, 20 mΩ / sq, etc., or a range consisting of any two of the above values, such as 5 mΩ / sq~10 mΩ / sq, 12 mΩ / sq~16 mΩ / sq, 16 mΩ / sq~20 mΩ / sq, etc.

[0115] In one embodiment, the thickness of the current collector is 4 μm to 8 μm. This configuration helps to further reduce the weight of the current collector and its proportion of thickness in the electrode, thereby allowing the electrode to accommodate more active material, improving specific capacity and battery energy density. The thickness of the current collector can be 4 μm, 5 μm, 6 μm, 7 μm, 7.5 μm, 8 μm, or any range of two of these values, such as 4 μm to 5 μm, 6 μm to 7 μm, 7.5 μm to 8 μm, etc.

[0116] In one embodiment, the interlayer bonding force between the substrate and the conductive coating is 120 N / m to 1000 N / m. This configuration further increases the bonding strength between the substrate and the conductive coating, making them less prone to separation. This reduces the risk of separation at the interface between the current collector substrate and the conductive coating due to expansion-contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector and enhancing the cycle stability of the battery. The interlayer bonding force between the substrate and the conductive coating can be 120 N / m, 150 N / m, 200 N / m, 280 N / m, 340 N / m, 500 N / m, 600 N / m, 800 N / m, 1000 N / m, etc., or a range consisting of any two of the above values, such as 120 N / m to 150 N / m, 200 N / m to 280 N / m, 340 N / m to 600 N / m, 800 N / m to 1000 N / m, etc.

[0117] The structural design of the current collector also includes the selection of the area where the conductive plating layer is set, which will be described in detail in the following embodiments.

[0118] In one embodiment, referring to Figures 2 and 4, a conductive plating layer 312 is disposed in a first region 31a and a second region 31b, and the conductive plating layer 312 covers at least one surface of the base layer 311.

[0119] At this point, the contact area between the base layer 311 and the conductive plating layer 312 is relatively large, which is beneficial to increase the interfacial bonding force between the two and improve the stability of the current collector 31; at the same time, the larger area of ​​the conductive plating layer 312 is beneficial to improve the conductivity of the current collector 31.

[0120] Please also refer to Figure 6, which is a schematic diagram of electrode preparation according to one embodiment of this application. In one embodiment, the electrode 30 further includes an active material layer 32, which is disposed in the first region 31a and covers the conductive plating layer 312.

[0121] The active material layer 32 is loaded on the surface of the current collector 31, serving to provide active material and responsible for transferring charge to or receiving charge from the electrolyte. It is the main site for electrochemical reactions in the battery. In one embodiment, the active material layer 32 can be disposed on opposite sides of the current collector 31, in which case the conductive plating layer 312 covers the two opposite surfaces of the base layer 311. In other embodiments, the current collector 31 can also be disposed on one side of the current collector 31, in which case the conductive plating layer 312 covers one surface of the base layer 311.

[0122] In one embodiment, referring to Figures 1 and 3, the conductive plating layer 312 is disposed only in the second region 31b, and the conductive plating layer 312 covers at least one surface of the base layer 311 in the second region 31b.

[0123] At this time, the conductive plating layer 312 is only disposed in the second region 31b. While providing sufficient current output from the electrode assembly and improving the battery power performance, it can also reduce the weight of the conductive plating layer 312, which is beneficial to the lightweighting of the current collector 31 and the improvement of the battery energy density.

[0124] In one embodiment, the tensile strength of the second region 31b is less than the tensile strength of the first region 31a.

[0125] With the above configuration, the second region 31b has lower strength and is more easily deformed, which is beneficial for welding and can improve the processing performance of the current collector 31.

[0126] In one embodiment, the difference between the tensile strength of the second region 31b and the tensile strength of the first region 31a is less than 100 MPa. In this case, the processing performance of the current collector 31 can be improved, the strength difference between the second region 31b and the first region 31a can be reduced, and the overall strength of the current collector 31 can be improved.

[0127] In one embodiment, the thickness difference between the second region 31b and the first region 31a is less than 2 μm. This setting allows the thickness difference between the second region 31b and the first region 31a to be controlled within a small range, which is beneficial for improving the flatness of the electrode winding.

[0128] In one embodiment, the thickness difference between the second region 31b and the first region 31a is less than 1 μm. This setting further reduces the thickness difference between the second region 31b and the first region 31a, which is more conducive to improving the flatness of the electrode winding.

[0129] In one embodiment, please also refer to FIG7, which is a schematic diagram of electrode preparation according to another embodiment of this application. The electrode 30 further includes an active material layer 32, which includes a first portion 321 covering the base layer 311 and a second portion 322 extending from the first portion 321 to a portion of the conductive plating layer 312.

[0130] The active material layer 32 is loaded on the surface of the current collector 31 and serves to provide active material. It is responsible for transferring charge to the electrolyte or receiving charge from the electrolyte and is the main site of electrochemical reactions in the battery. The presence of the second part 322 can also reduce the weak area of ​​current output, improve the battery's overcurrent capability, reduce the distance between the thinned areas, make the distance between the positive and negative electrodes smaller, shorten the lithium ion transport path, and reduce the risk of lithium plating in the thinned areas.

[0131] In one embodiment, the active material layer 32 may be disposed on opposite sides of the current collector 31, in which case the conductive plating layer 312 covers the two opposite surfaces of the base layer 311 in the second region 31b. In other embodiments, the current collector 31 may also be disposed on one side of the current collector 31, in which case the conductive plating layer 312 covers one surface of the base layer 311 in the second region 31b.

[0132] Please refer to Figures 1 to 4. This application also provides a current collector 31, which includes a base layer 311 and a conductive plating layer 312 stacked along the thickness direction of the electrode sheet. The current collector 31 includes a first region 31a and a second region 31b located on at least one side of the first region 31a along a first direction. The base layer 311 is located in the first region 31a and the second region 31b. The conductive plating layer 312 is at least located in the second region 31b. The tensile strength of the base layer 311 is 400MPa to 1000MPa. The conductivity of the conductive plating layer is greater than that of the base layer.

[0133] The current collector 31 serves to carry the active material and simultaneously collects and outputs the current generated by the electrode active material. The base layer 311 within the current collector 31 forms its main structure, providing the primary mechanical properties. The base layer 311 has a tensile strength of 400MPa~1000MPa, which is relatively high and helps alleviate stress caused by the volume expansion and contraction of the active material during battery charging and discharging, reducing the risk of cracking and thus improving the battery's cycle stability. The conductive plating layer 312 in the current collector 31 improves its conductivity. The conductivity of the conductive plating layer 312 is greater than that of the base layer 311, thus optimizing conductivity compared to the base layer 311 itself as a current collector. Meanwhile, the current collector 31 includes a first region 31a and a second region 31b located at least on one side of the first region 31a along the first direction x. That is, the second region 31b is the edge region of the current collector, which is usually the connection location of the current output component. The conductive plating layer 312 is at least disposed in the second region 31b, which can provide sufficient current output from the electrode assembly for the overcurrent area. Therefore, the cycle stability of the secondary battery is improved.

[0134] In one embodiment, the conductivity of the substrate is 1% IACS to 50% IACS, and the conductivity of the conductive coating is 50% IACS to 100% IACS. The conductivity of the substrate 311 can be 1% IACS, 5% IACS, 10% IACS, 15% IACS, 20% IACS, 30% IACS, 40% IACS, 50% IACS, etc., or a range consisting of any two of the above values, such as 1% IACS to 5% IACS, 10% IACS to 15% IACS, 20% IACS to 40% IACS, 40% IACS to 50% IACS, etc. The conductivity of the conductive coating 312 can be 50% IACS, 55% IACS, 60% IACS, 70% IACS, 85% IACS, 100% IACS, or any range of two of the above values, such as 50% IACS~55% IACS, 60% IACS~70% IACS, 85% IACS~100% IACS, etc.

[0135] The conductivity of the substrate is 1% IACS to 50% IACS, which can meet the basic power requirements of the battery. The conductivity of the conductive coating is 50% IACS to 100% IACS, which further optimizes the conductivity compared to the substrate itself as a current collector.

[0136] In one embodiment, the current collector satisfies at least one of the following (1) to (5):

[0137] (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq;

[0138] (2) The tensile strength of the current collector is greater than or equal to 600 MPa;

[0139] (3) The elongation of the current collector is greater than or equal to 1%;

[0140] (4) The thickness of the current collector is 2μm~15μm;

[0141] (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m.

[0142] Specifically, the current collector has a sheet resistance of less than 35 mΩ / sq, giving it good conductivity, which is beneficial for current collection and thus helps improve the battery's power performance. The current collector has a tensile strength greater than 600 MPa, 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 current collector has an elongation greater than 1%, which improves its flexibility, allowing it to adapt to volume expansion and contraction during charging and discharging, thus improving 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 current collector thickness is between 2 μm and... Within a 15μm range, it is beneficial to reduce the weight of the current collector and its thickness ratio in the electrode, thereby allowing the electrode to accommodate more active material, improving specific capacity and battery energy density. At the same time, the current collector has high strength, which is beneficial to improving the reliability of the current collector and the electrode, as well as the safety and cycle performance of the battery. When the interlayer bonding force between the base layer and the conductive coating is 50N / m~1000N / m, the bonding strength between the base layer and the conductive coating is relatively large, and the two are not easy to separate. This can reduce the separation of the current collector base layer and the conductive coating at the interface caused by the expansion-contraction stress generated during battery charging and discharging, thereby improving the stability and reliability of the current collector and improving the cycle stability of the battery.

[0143] In one embodiment, referring to Figures 2 and 4, a conductive plating layer 312 is disposed in a first region 31a and a second region 31b, and the conductive plating layer 312 covers at least one surface of the base layer 311.

[0144] At this point, the contact area between the base layer 311 and the conductive plating layer 312 is relatively large, which is beneficial to increase the interfacial bonding force between the two and improve the stability of the current collector 31; at the same time, the larger area of ​​the conductive plating layer 312 is beneficial to improve the conductivity of the current collector 31.

[0145] In one embodiment, referring to Figures 1 and 3, the conductive plating layer 312 is disposed only in the second region 31b, and the conductive plating layer 312 covers at least one surface of the base layer 311 in the second region 31b.

[0146] At this time, the conductive plating layer 312 is only disposed in the second region 31b. While providing sufficient current output from the electrode assembly and improving the battery power performance, it can also reduce the weight of the conductive plating layer 312, which is beneficial to the lightweighting of the current collector 31 and the improvement of the battery energy density.

[0147] For example, in one embodiment, the current collector provided in this application can be prepared by the following method:

[0148] S100: The base layer is produced using a multi-stage rolling method;

[0149] S200: Activate the substrate in an acid solution for 5 min to 30 min. The acid solution includes at least one of dilute sulfuric acid and dilute nitric acid, and the concentration of the acid solution is 5% to 20% (mass fraction).

[0150] S300: An intermediate layer is electroplated on the base surface;

[0151] Taking a nickel intermediate layer as an example, the electroplating solution formula is as follows: nickel sulfate 100g / L~250g / L, sodium chloride 1g / L~10g / L, boric acid 20g / L~40g / L, sodium dodecyl sulfonate 0~1g / L, pH value 4~4.5, temperature 40℃~60℃, and current density 1A / dm³. 2 ~1.5A / dm 2 .

[0152] S400: Electroplating a conductive coating onto the surface of the intermediate layer;

[0153] Taking copper as the conductive plating layer as an example, the electroplating solution formula is as follows: copper sulfate 150g / L~250g / L, sulfuric acid 30g / L~60g / L, polyethylene glycol (PEG) 0.5g / L~1.5g / L, sodium polydisulfide dipropane sulfonate 0~10mg / L, pH value 3~5, temperature 20℃~30℃, and current density 5A / dm³. 2 ~30A / dm 2 .

[0154] In other embodiments, the method for preparing the current collector provided in this application is not limited to the steps described above.

[0155] In one embodiment, the secondary battery provided in this application can be used as a battery cell. Please refer to Figure 8, 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.

[0156] 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.

[0157] 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.

[0158] Please refer to Figure 9, 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 9, the battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0159] 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. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 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.

[0160] 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.

[0161] 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.

[0162] In some embodiments, the positive electrode includes a current collector and a layer of positive electrode material disposed on the current collector.

[0163] 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 Mn0.3 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.

[0164] 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.

[0165] The 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, artificial 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. Optionally, the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, Ketjen black, and acetylene black.

[0166] 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). Optionally, the adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, acrylate, and polyurethane.

[0167] 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.

[0168] In one embodiment, the electrolyte includes one or more of carbonate solvents and ether solvents.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] In some embodiments, the electrolyte may optionally include 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.

[0174] In some embodiments, the negative electrode includes a current collector and a negative electrode material layer disposed on the current collector.

[0175] 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.

[0176] In one embodiment, the negative electrode active material includes a silicon-based negative electrode material. In this case, the negative electrode active material has a higher specific capacity compared to traditional graphite negative electrode materials. Simultaneously, the current collector of this application has high strength, which helps alleviate the stress caused by the volume expansion and contraction of the silicon-based material during battery charging and discharging, reducing the risk of current collector cracking, thereby improving the cycle stability of the battery.

[0177] 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.

[0178] 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.

[0179] Electrical equipment can be equipped with individual battery cells, battery modules, or battery packs depending on its usage requirements.

[0180] Please refer to Figure 10, which is a schematic diagram of the structure 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.

[0181] 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.

[0182] 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.

[0183] (I) Battery manufacturing

[0184] Example 1:

[0185] 1. Preparation of negative electrode current collector

[0186] The base layer, designated TA1, was prepared using a multi-stage rolling process. The base layer material was Ti, and its thickness was 5 μm. A mixed acid solution was prepared by mixing 98% concentrated sulfuric acid (mass fraction), 65% concentrated nitric acid (mass fraction), and water in a molar ratio of 1:1:18 (the concentration of sulfuric acid was based on the molar amount of sulfuric acid, and the concentration of nitric acid on the molar amount of nitric acid). The base layer was activated in the mixed acid solution for 10 min. A conductive plating layer was electroplated on two surfaces of the base layer perpendicular to its thickness direction. Both the base layer and the conductive plating layer were located in the first and second regions, with the second region situated on either side of the first region along the first direction. The conductive plating layer was a copper layer. The electroplating solution consisted of 200 g / L copper sulfate, 50 g / L sulfuric acid, 0.8 g / L polyethylene glycol (PEG), 5 mg / L sodium didithiopropane sulfonate, a pH of 4.5, a temperature of 25°C, a time of 2 min, and a current density of 10 A / dm³.2 The thickness of the copper layer on one side is 1μm.

[0187] 2. Preparation of positive electrode sheet

[0188] A positive electrode slurry was prepared by uniformly mixing NCM811 (a nickel-cobalt-manganese ternary material with a Ni, Co, and Mn molar ratio of 8:1:1), carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solution at a mass ratio of 96:2:2, with a solid content of 71%. This slurry was then coated onto both sides of a 13 μm thick aluminum foil using an extrusion coating machine and dried to obtain the positive electrode film. The coated electrode was then cold-pressed using a cold press to obtain the final positive electrode sheet. The thickness of the single-layer positive electrode active layer was 38.2 μm, and the areal density of the single-layer positive electrode active layer was 200 mg / 1540.25 mm². 2 The compaction density of the single-layer positive electrode active layer is 3.4 g / cm³. 3 .

[0189] 3. Preparation of negative electrode sheet

[0190] Silicon-carbon-graphite composite material, conductive carbon black, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener 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 current collector prepared in step 1, and after drying and other processes, a negative electrode sheet was obtained. The thickness of the single-layer negative electrode active layer was 36.8 μm, and the areal density of the single-layer negative electrode active layer was 73.7 mg / 1540.25 mm². 2 The compaction density of the single-layer negative electrode active layer is 1.3 g / cm³. 3 .

[0191] 4. Separating membrane

[0192] A polyethylene diaphragm with a thickness of 7 μm is used as the separator.

[0193] 5. Electrolyte

[0194] 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.

[0195] 6. Battery assembly

[0196] The positive electrode, separator, and negative electrode are wound in sequence 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, a lithium-ion secondary battery is obtained.

[0197] Example 2:

[0198] Some parameters in the preparation of the negative electrode 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 copper conductive coating was adjusted to 1.2 min.

[0199] Example 3:

[0200] Some parameters in the preparation of the negative electrode current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1, wherein the base layer was located in the first region and the second region, and the conductive coating was located in the second region.

[0201] Examples 4-7:

[0202] Some parameters in the preparation of the negative electrode current collector were adjusted, as detailed in Table 1. The preparation steps were the same as in Example 1. The greater the thickness of the conductive coating, the longer the electroplating time. The electroplating time was 0.4 min in Example 4, 0.6 min in Example 5, and 4 min in Example 6. In Example 7, the electroplating solution for the gold conductive coating consisted of 200 g / L gold sulfite, 80 g / L ammonium sulfite, 30 g / L ammonium sulfate, and 0.8 g / L polyethylene glycol (PEG), with a pH of 6.8 and a current density of 1 A / dm³. 2 Electroplating time: 20 minutes.

[0203] Example 8:

[0204] The difference from Example 1 is that, in the preparation step of the negative electrode current collector, an intermediate layer preparation step is added before electroplating the conductive coating: an intermediate layer is electroplated on two surfaces of the substrate perpendicular to the thickness direction of the substrate. The intermediate layer is a nickel layer. The electroplating solution formula is: nickel sulfate 200 g / L, sodium chloride 5 g / L, boric acid 30 g / L, sodium dodecyl sulfonate 0.1 g / L, pH value 4.5, temperature 45°C, time 4 min, and current density 5 A / dm³. 2 The nickel layer is 50 nm thick; the intermediate layer is located in the first and second regions of the current collector.

[0205] The other steps are the same as in Example 1, and will not be repeated here.

[0206] Example 9:

[0207] The difference from Example 1 lies in the change of the positive and negative current collectors. The preparation method of the negative current collector is as follows: A base layer is prepared using a multi-stage rolling method. The base layer grade is TA1, the material of the base layer is Ti, and the thickness is 5 μm. A mixed acid solution is prepared by mixing 98% concentrated sulfuric acid (mass fraction), 65% concentrated nitric acid (mass fraction), and water in a molar ratio of 1:1:18 (the concentrated sulfuric acid is based on the molar number of sulfuric acid, and the concentrated nitric acid is based on the molar number of nitric acid). The base layer is activated in the mixed acid solution for 10 min. A conductive plating layer is electroplated on two surfaces of the base layer perpendicular to the thickness direction of the base layer. The base layer and the conductive plating layer are both located in the first and second regions, with the second region located on both sides of the first region along the first direction. The conductive plating layer is a gold layer. The electroplating solution formula is: 200 g / L gold sulfite, 80 g / L ammonium sulfite, 30 g / L ammonium sulfate, 0.8 g / L polyethylene glycol (PEG), pH value 6.8, and current density 1 A / dm³. 2 Electroplating time: 20 minutes.

[0208] The preparation method of the positive electrode current collector is as follows: a Ti foil is provided as the base layer with a thickness of 6 μm; an Al ingot is placed in a heating boat and heated to 1200℃, and Al is deposited on both sides of the Ti foil. The Al volatilizes and deposits on the surface of the Ti foil. The Ti foil travel speed is 10 m / min, and the thickness of the Al layer on one side is 1 μm.

[0209] Comparative Example 1:

[0210] The difference from Example 1 is that conventional copper foil is used as the negative electrode current collector, and the specific parameters are detailed in Table 1.

[0211] (ii) Performance Testing

[0212] 1. Tensile strength and elongation

[0213] Lay the negative electrode current collector flat on a horizontal table and cut it into sections, each about 10cm long and 1.5cm wide. Turn on the tensile testing machine, pass the negative electrode current collector through the upper and lower clamps, step on the air valve to clamp the upper clamp first, maintaining a weak connection, and then clamp the lower clamp. Perform the test by pulling both clamps outward at a speed of 50mm / min until the negative electrode current collector breaks in the middle. The test is complete. The stress at which the negative electrode current collector breaks is the tensile strength, and the elongation at break is the elongation rate.

[0214] 2. Conductivity

[0215] A strong adhesive tape (ethylene-propylene copolymer) was used to adhere to the surface of the current collector, and a 10×10cm sample was cut. The strong adhesive was then torn off, and the surface layer was glued together. The conductivity of the tape / surface layer composite was then tested using the four-probe method on the area where the test surface was exposed metal.

[0216] 3. 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] 4. Restriction

[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] 5. Thickness

[0222] Use a micrometer to measure the flatness of the manifold, take 10 points to measure the thickness, and then take the average value.

[0223] 6. Interlayer bonding strength

[0224] Apply adhesive tape with an adhesion strength of 100N / m, 120N / m, 150N / m, or 200N / m to the sample surface. Roll the tape back and forth three times with a 2kg roller and then tear it off. If the surface coating separates from the substrate along with the tape, the adhesion strength is less than that specification.

[0225] 7. Battery internal resistance

[0226] At 25℃, the battery is charged at a constant current of 1 / 3C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C. After resting for 5 minutes, it is discharged at a constant current of 1 / 3C for 90 minutes and then rested for 120 minutes. The voltage V1 is recorded. Then it is discharged at 4C for 30 seconds, and the voltage V2 is recorded. The internal resistance DCR of the battery is obtained by dividing (V2-V1) / 4C.

[0227] 8. Energy density

[0228] At 25℃, the corresponding battery is first weighed and its mass m is recorded. It is then charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. After resting for 5 minutes, it is discharged at 1 / 3C to 2.5V. This cycle is repeated 3 times. The discharge capacity of the third cycle is taken, and the energy of the battery is calculated and recorded as W. Energy density = W / m, unit: Wh / kg.

[0229] 9. Cyclic performance

[0230] The prepared battery was left to stand for 30 minutes at 25℃, then discharged to 2.8V with a constant current of 1 / 3C. Afterwards, charge-discharge cycles were performed as follows: left to stand for 5 minutes, charged to 4.15V with a constant current of 1 / 2C, then charged at a constant voltage until the current dropped to 0.05C, recording the charging capacity as C0; left to stand for 5 minutes; then discharged to 2.8V with a constant current of 1 / 2C, recording the discharging capacity as C0'. This cycle was repeated 500 times, and the discharge capacity C500 of the 500th cycle was recorded. The capacity retention rate of the battery after 500 cycles was calculated using the following formula:

[0231] Capacity retention rate (%) after 500 cycles: C500 / C0'×100%.

[0232] Table 1. Parameter table for each embodiment and comparative example.

[0233]

[0234] Note: In Example 3, the sheet resistance, tensile strength, and elongation data of the current collector in the table are the data of the second region of the current collector. The sheet resistance of the first region of the current collector is 112 mΩ / sq, the tensile strength is 815 MPa, and the elongation is 2.90%. Therefore, the difference in tensile strength between the second region and the first region is 20 MPa; at the same time, the difference in thickness between the second region and the first region is 2 μm.

[0235] (III) Analysis of Lithium-ion Battery Performance Test Results

[0236] 1. In Examples 1 to 9 provided in this application, the current collector has a large tensile strength, and the substrate of the current collector is a lightweight material. The battery using the above-mentioned current collector exhibits high energy density and good cycle stability.

[0237] 2. Compared with Example 1, Example 3 only provides a conductive coating in the second region, which is beneficial to the weight reduction of the current collector. Therefore, Example 3 exhibits higher energy density and lower battery internal resistance.

[0238] 3. Compared with Example 1, Example 8 adds an intermediate layer between the conductive coating and the base layer along the electrode thickness direction, which significantly improves the interfacial bonding force between the conductive coating and the base layer, and is beneficial to improving the cycle stability of the battery.

[0239] 4. Compared with Example 1, Comparative Example 1 uses copper foil as the base layer. Since copper foil has a higher density, the current collector of Comparative Example 1 is heavier, resulting in lower energy density and lower cycle stability of the battery.

[0240] 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

A secondary battery wherein, The device includes an electrode sheet, which includes a current collector. The current collector includes a base layer and a conductive coating stacked along the thickness direction of the electrode sheet. The current collector includes a first region and a second region located on at least one side of the first region along a first direction. The base layer is located in the first region and the second region. The conductive coating is located in at least the second region. The tensile strength of the base layer is 400MPa to 1000MPa, and the conductivity of the conductive coating is greater than the conductivity of the base layer. The secondary battery as described in claim 1, wherein, The conductivity of the base layer is 1% IACS to 50% IACS, and the conductivity of the conductive coating is 50% IACS to 100% IACS. The secondary battery as described in claim 1 or 2, wherein, The areal density of the base layer is 0.9 mg / cm 2 3.7 mg / cm 2 . The secondary battery as described in claims 1-3, wherein, The thickness of the base layer is 2μm~8μm. The secondary battery as described in claim 4, wherein, The thickness of the base layer is 4μm~6μm. The secondary battery according to any one of claims 1 to 5, wherein, The base material includes at least one of titanium, aluminum, and carbon materials; The carbon material includes at least one of carbon fiber, carbon nanotubes, and graphene. The secondary battery according to any one of claims 1 to 5, wherein, The thickness of the conductive coating is 0.2μm to 2μm. The secondary battery as described in claim 7, wherein, The thickness of the conductive coating is 0.3μm~1μm. The secondary battery according to any one of claims 1 to 8, wherein, The material of the conductive coating includes any one of copper, silver, and gold. The secondary battery according to any one of claims 1 to 9, wherein, The current collector further includes an intermediate layer, which is disposed between the base layer and the conductive plating layer along the thickness direction of the electrode sheet. The material of the intermediate layer includes at least one of nickel, iron, chromium, and manganese. The secondary battery as described in claim 10, wherein, The thickness of the intermediate layer is 10nm~200nm. The secondary battery according to any one of claims 1 to 11, wherein The current collector satisfies at least one of the following (1) to (5): (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq; (2) The tensile strength of the current collector is greater than or equal to 600 MPa; (3) The elongation of the current collector is greater than or equal to 1%; (4) The thickness of the current collector is 2μm~15μm; (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m. The secondary battery according to claim 12, wherein The sheet resistance of the current collector is less than or equal to 20 mΩ / sq; and / or The thickness of the current collector is 4μm~8μm; and / or The interlayer bonding force between the base layer and the conductive coating is 120 N / m to 1000 N / m. The secondary battery according to any one of claims 1 to 13, wherein The conductive coating is disposed in the first region and the second region, and the conductive coating covers at least one surface of the base layer. The secondary battery according to claim 14, wherein The electrode also includes an active material layer, which is disposed in the first region and covers the conductive plating layer. The secondary battery according to any one of claims 1 to 13, wherein The conductive coating is disposed only in the second region, and the conductive coating covers at least one surface of the base layer located in the second region. The secondary battery according to claim 16, wherein The tensile strength of the second region is less than that of the first region. The secondary battery according to claim 17, wherein The difference between the tensile strength of the second region and the tensile strength of the first region is less than or equal to 100 MPa. The secondary battery according to any one of claims 16 to 18, wherein The difference between the thickness of the second region and the thickness of the first region is less than or equal to 2 μm. The secondary battery as described in claim 19, wherein, The difference between the thickness of the second region and the thickness of the first region is less than or equal to 1 μm. The secondary battery according to any one of claims 16 to 20, wherein, The electrode also includes an active material layer, which comprises a first portion covering the base layer and a second portion extending from the first portion onto a portion of the conductive plating layer. A current collector, wherein, The current collector includes a base layer and a conductive coating stacked along the thickness direction of the electrode sheet. The current collector includes a first region and a second region located on at least one side of the first region along a first direction. The base layer is located in the first region and the second region. The conductive coating is at least located in the second region. The tensile strength of the base layer is 400MPa~1000MPa. The conductivity of the conductive coating is greater than that of the base layer. The current collector as described in claim 22, wherein, The conductivity of the base layer is 1% IACS to 50% IACS, and the conductivity of the conductive coating is 50% IACS to 100% IACS. The current collector as described in claim 22 or 23, wherein, The current collector satisfies at least one of the following (1) to (5): (1) The sheet resistance of the current collector is less than or equal to 35 mΩ / sq; (2) The tensile strength of the current collector is greater than or equal to 600 MPa; (3) The elongation of the current collector is greater than or equal to 1%; (4) The thickness of the current collector is 2μm~15μm; (5) The interlayer bonding force between the base layer and the conductive coating is 50 N / m to 1000 N / m. The current collector according to any one of claims 22 to 24, wherein, The conductive coating is disposed in the first region and the second region, and the conductive coating covers at least one surface of the base layer; or The conductive coating is disposed only in the second region, and the conductive coating covers at least one surface of the base layer located in the second region. An electrical appliance, wherein, It includes a secondary battery as described in any one of claims 1 to 21, and / or includes a current collector as described in any one of claims 22 to 25.

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