Composite current collector, pole piece, secondary battery and electric device

Abstract

The invention provides a composite current collector, a pole piece, a secondary battery and an electric device. The composite current collector comprises a base material layer and a conductive layer; the base material layer is provided with a first surface and a second surface which are opposite to each other; the conductive layer is arranged on the first surface and / or the second surface; and a hole channel is formed in the conductive layer. When the battery is in an abnormal working condition and the stress of the composite current collector is abnormal, the conductive layer is easy to break in time near the pore channels, the current transmission in the current collector is weakened, and the risk of continuous electrochemical reaction in the battery under the abnormal working condition is reduced, so that the risk of thermal runaway such as fire and explosion of the battery is reduced, and the service life of the battery is prolonged. And the safety performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a composite current collector, a pole piece, a secondary battery, and an electrical device. Background Art

[0002] The statements herein only provide background information related to the present application and do not necessarily constitute prior art.

[0003] The composite current collector has many advantages compared with the pure metal current collector. For example, the composite current collector has a conductive layer with a relatively thin thickness and a correspondingly lower weight, etc. With the continuous popularization of secondary batteries, the application scope of the composite current collector has also been expanded. For traditional composite current collectors, a conductive layer is often formed on the surface of the substrate layer. Compared with the pure metal current collector, although the traditional composite current collector has many advantages, in terms of improving the problem of battery thermal runaway, the performance of the traditional composite current collector still needs to be improved. Summary of the Invention

[0004] A first aspect of the present application provides a composite current collector, including a substrate layer and a conductive layer; the substrate layer has opposite first and second surfaces; the conductive layer is disposed on the first surface and / or the second surface; and channels are provided inside the conductive layer.

[0005] In the above composite current collector, channels are mainly provided inside the conductive layer. When the battery is in an abnormal working condition, resulting in abnormal stress on the composite current collector, the conductive layer is prone to break timely near the channels, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal working conditions. This is beneficial to reducing the risk of thermal runaway such as fire and explosion of the battery, and thus can improve the safety performance of the battery.

[0006] In some embodiments, there are multiple channels, and the multiple channels are arranged at intervals. By providing multiple channels, more fracture sites can be provided. When the battery is in an abnormal working condition, the current transmission inside the current collector can be weakened more timely, further reducing the risk of thermal runaway such as fire and explosion of the battery.

[0007] In some embodiments, the distance between adjacent channels is 5 mm to 60 mm. The distance between adjacent channels within this range can maintain a relatively stable intrinsic performance of the conductive layer while providing an appropriate number of channels.

[0008] In some embodiments, the channels include blind-hole channels. Optionally, the openings of the blind-hole channels face the substrate layer. The openings of the blind-hole channels facing the substrate layer may be beneficial for other material layers to be embedded to improve the bonding force between the conductive layer and the substrate layer.

[0009] In some embodiments, the depth of the blind via channels is 30 nm to 500 nm. The blind via channels within this range can provide a good embedding effect, which is beneficial to improving the bonding strength between the conductive layer and the substrate layer.

[0010] In some embodiments, the aperture of the blind via channels is 5 mm to 50 mm. With the aperture of the blind via channels within this range, the blind vias can have an appropriate number and at the same time provide a good embedding effect.

[0011] In some embodiments, the percentage of the cross-sectional area of the blind via channels in the cross-sectional area of the conductive layer is 0.5% to 54.5%. When the percentage of the cross-sectional area of the blind via channels in the cross-sectional area of the conductive layer is within this range, the blind via channels can have an appropriate number and at the same time the conductive layer can maintain relatively stable intrinsic properties.

[0012] In some embodiments, the cross-sectional shape of the blind via channels includes at least one of a circle, an ellipse, and a polygon.

[0013] In some embodiments, the channels include through-hole channels. On the one hand, the setting of the through-hole channels may be beneficial for other material layers to be embedded to improve the bonding strength between the conductive layer and the substrate layer. On the other hand, the through channels can serve as exhaust channels, which is beneficial to discharging the gases that may be generated during the preparation of the composite current collector.

[0014] In some embodiments, the aperture of the through-hole channels is 30 μm to 500 μm. With the aperture of the through-hole channels within this range, the through-hole channels can have an appropriate number and at the same time provide a good embedding effect.

[0015] In some embodiments, the percentage of the cross-sectional area of the through-hole channels in the cross-sectional area of the conductive layer is 0.001% to 0.484%. When the percentage of the cross-sectional area of the through-hole channels in the cross-sectional area of the conductive layer is within this range, the through channels can have an appropriate number and at the same time the conductive layer can maintain relatively stable intrinsic properties.

[0016] In some embodiments, the cross-sectional shape of the through-hole channels includes at least one of a circle, an ellipse, and a polygon.

[0017] In some embodiments, the through-hole channels include a first through-hole channel and a second through-hole channel, and the aperture of the first through-hole channel is larger than that of the second through-hole channel. The larger aperture of the first through-hole channel facilitates the fracture of the conductive layer to spread around from the position of the first through-hole channel when the battery is in an abnormal working condition, which is beneficial to increasing the fracture rate of the conductive layer and weakening the current transmission inside the current collector more timely. The smaller aperture of the second through-hole channel can provide a larger number of through-hole channels per unit area of the conductive layer, further promoting the discharge of the gas that may be generated during the preparation process of the composite current collector.

[0018] In some embodiments, the quantity ratio of the first through-hole channel to the second through-hole channel is (20 - 40):(60 - 80). When the quantity ratio of the first through-hole channel to the second through-hole channel is within this range, the quantities of the first through-hole channel with a larger aperture and the second through-hole channel with a smaller aperture can be better adapted, which is beneficial to further promoting the effects of the fracture of the conductive layer and gas exhaust.

[0019] In some embodiments, the aperture of the first through-hole channel is 300 μm - 500 μm. Optionally, the aperture of the second through-hole channel is 30 μm - 300 μm.

[0020] In some embodiments, the composite current collector further includes an adhesive layer, and the adhesive layer is located between the substrate layer and the conductive layer. By providing the adhesive layer, the bonding force between the substrate layer and the conductive layer can be improved, which is beneficial to keeping the composite current collector in a more stable structure.

[0021] In some embodiments, the adhesive layer includes a main body portion and a protruding portion, the protruding portion protrudes from the main body portion, and the protruding portion is embedded in the through-hole. By embedding the protruding portion into the through-hole of the conductive layer, the contact area between the adhesive layer and the conductive layer can be increased, so that the adhesive layer and the conductive layer form a more stable bonding effect, further improving the bonding force between the conductive layer and the adhesive layer, and then further improving the bonding force between the substrate layer and the conductive layer, promoting the improvement of the structural stability of the composite current collector.

[0022] In some embodiments, the thickness of the main body portion is 0.5 μm - 5 μm. The thickness of the main body portion within this range can enable the adhesive layer to play a good bonding role, and at the same time keep the composite current collector within a more appropriate overall thickness range.

[0023] In some embodiments, the adhesive layer comprises an adhesive. Optionally, the adhesive includes one or more of isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide.

[0024] In some embodiments, the adhesive layer comprises filler particles. By introducing filler particles into the adhesive layer, it is beneficial to improve the elastic modulus of the composite current collector. Furthermore, it may improve the wrinkling problem during the processing of the electrode sheet.

[0025] In some embodiments, the mass percentage of the filler particles in the adhesive layer is 10% - 20%. When the mass percentage of the filler particles in the adhesive layer is within this range, the adhesive layer can have appropriate adhesive properties and an appropriate elastic modulus.

[0026] In some embodiments, the Dv50 of the filler particles is 30 nm - 500 nm. Filler particles with a particle size distribution within this range can be more evenly dispersed in the adhesive layer, promoting further improvement of the elastic modulus of the composite current collector.

[0027] In some embodiments, the filler particles include insulating filler particles. The use of insulating filler particles can reduce the risk of adverse effects on the electrical conductivity of the composite current collector caused by the introduction of filler particles, which is beneficial to maintaining a relatively appropriate and stable electrical conductivity of the composite current collector.

[0028] In some embodiments, the filler particles include at least one of alumina, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide.

[0029] In some embodiments, the filler particles include first filler particles, one end of the first filler particles extends into the main body portion, and the other end extends into the protruding portion. A part of the first filler particles is located in the main body portion of the adhesive layer, and the other part is located in the protruding portion of the adhesive layer. This can provide a support site between the conductive layer and the adhesive layer, which is beneficial to improving the support force of the adhesive layer on the conductive layer and further improving the elastic modulus of the composite current collector.

[0030] In some embodiments, the Dv50 of the first filler particles is 200 nm - 500 nm.

[0031] In some embodiments, the filler particles further include second filler particles, and the Dv50 of the second filler particles is less than that of the first filler particles. The second filler particles have a smaller particle size distribution and can be more uniformly dispersed in the adhesive layer, further promoting the improvement of the elastic modulus of the composite current collector. In addition, the second filler particles with a smaller particle distribution can be better dispersed in the convex portions of the adhesive layer, that is, the second filler particles can be better dispersed in the pores of the conductive layer, which is beneficial to improving the mutual support between the adhesive layer and the conductive layer and enhancing the elastic modulus of the composite current collector.

[0032] In some embodiments, the Dv50 of the second filler particles is 30 nm to 200 nm.

[0033] In some embodiments, the mass ratio of the second filler particles to the first filler particles is (30 - 50):(50 - 70). The mass ratio of the second filler particles to the first filler particles within this range can make the second filler particles and the first filler particles better adapted, further enhancing the elastic modulus of the composite current collector.

[0034] In some embodiments, the adhesive layer contains a flame retardant. By introducing the flame retardant, the flame retardant effect of the composite current collector can be improved, and the risk of thermal runaway such as fire and explosion of the battery under abnormal conditions can be further reduced.

[0035] In some embodiments, the mass percentage of the flame retardant in the adhesive layer is 20% - 40%. The mass percentage of the flame retardant within this range can enable the composite current collector to have a good flame retardant effect while enabling the adhesive layer to have good adhesive properties.

[0036] In some embodiments, the flame retardant includes at least one of decabromodiphenyl ether, hexabromocyclododecane, polyvinyl chloride, tris(2,3 - dibromopropyl) isocyanurate, sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0037] In some embodiments, the flame retardant includes an organic flame retardant and an inorganic flame retardant. The mass percentage of the organic flame retardant in the adhesive layer is 10% - 20%, and the mass percentage of the inorganic flame retardant in the adhesive layer is 10% - 20%. The organic flame retardant can be better mixed with the adhesive layer through the principle of similar compatibility. The inorganic flame retardant can play a corresponding supporting role for the adhesive layer while playing a flame retardant role.

[0038] In some embodiments, the surface of the conductive layer further includes a passivation layer. The passivation layer can protect the conductive layer, reduce the corrosion of the conductive layer by the electrolyte, and is beneficial to improving the structural stability of the composite current collector. Optionally, the passivation layer includes at least one of chromate, phosphate, alumina, silica, and silicon nitride.

[0039] The second aspect of the present application provides an electrode sheet. The electrode sheet includes the composite current collector.

[0040] The third aspect of the present application provides a secondary battery. The secondary battery includes the electrode sheet.

[0041] The fourth aspect of the present application provides an electrical device. The electrical device includes at least one of the composite current collector, the electrode sheet, and the secondary battery. Description of the Drawings

[0042] To better describe and illustrate the embodiments or examples provided in the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed application, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0043] Figure 1 Schematic diagram of a composite current collector according to an embodiment of the present application.

[0044] Figure 2 Schematic diagram of a composite current collector according to another embodiment of the present application.

[0045] Figure 3 Schematic diagram of a secondary battery according to an embodiment of the present application.

[0046] Figure 4 For Figure 3 Exploded view of the secondary battery shown in an embodiment of the present application.

[0047] Figure 5 Schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0048] Description of the Reference Numerals in the Drawings:

[0049] 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device; 3. Composite current collector; 31. Substrate layer; 32. Conductive layer; 321. Blind hole channel; 322. Through hole channel; 33. Adhesive layer; 331. Main body part; 332. Protrusion part; 34. First filler particle; 35. Second filler particle; 36. Flame retardant. Detailed Embodiments

[0050] For ease of understanding the present application, the present application will be described more comprehensively below with reference to the relevant accompanying drawings. Preferred embodiments of the present application are shown in the accompanying drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0052] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include or not include the end values, and any one of the end values can be independently included or not included, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are also listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer greater than or equal to 2, it is equivalent to listing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a certain parameter is an integer selected from "2 to 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0053] In this application, the terms "a plurality of", "a variety of", etc., unless otherwise specified, refer to a quantity greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0054] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0055] Reference to "embodiment" in this document means that the specific features, structures, or characteristics described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments. The same understanding applies to "implementation" mentioned in this document.

[0056] Those skilled in the art can understand that in the methods of various embodiments or implementations, the written order of each step does not mean a strict execution order that constitutes any limitation to the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Without special instructions, all steps of this application can be carried out sequentially or randomly, and in some embodiments, they are carried out sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0057] In this application, in an open-ended technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed-ended feature or solution composed of the listed members and an open-ended feature or solution that further includes additional members outside the listed members. For example, A includes a1, a2, and a3. Without other instructions, it may also include other members or may not include additional members, and it can be regarded as providing both a feature or solution of "A is composed of a1, a2, and a3" and a feature or solution of "A not only includes a1, a2, and a3, but also includes other members".

[0058] In this application, without other instructions, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0059] In this application, "optionally", "optional", "option" mean that it is optional, that is, it refers to any one of two parallel options of "having" or "not having". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual constraints, each "optional" is independent.

[0060] An embodiment of the present application provides a composite current collector, including a substrate layer and a conductive layer. The substrate layer has opposite first and second surfaces; the conductive layer is disposed on the first surface and / or the second surface; and the conductive layer has channels inside. In this embodiment, channels are mainly provided inside the conductive layer. When the battery is in an abnormal working condition, resulting in abnormal stress on the composite current collector, the conductive layer is prone to break in a timely manner near the channels, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal working conditions. This is beneficial to reducing the risk of thermal runaway such as fire and explosion in the battery, thereby improving the safety performance of the battery.

[0061] It can be understood that during the use of the battery, due to the existence of electrochemical reactions, there will be a certain temperature inside the battery. When the battery is working normally, the temperature inside the battery is maintained at a relatively appropriate level. However, when the battery is in an abnormal working condition, the temperature inside the battery may rise significantly. As the temperature inside the battery continues to rise, the pressure inside the battery will also increase accordingly, and the battery is prone to risks such as thermal runaway like fire and explosion. When the composite current collector in this embodiment is applied to the battery, when the battery is in an abnormal working condition and the temperature and pressure rise significantly, the stress on the composite current collector will also increase abnormally. When the stress on the composite current collector increases abnormally, the conductive layer is prone to break in a timely manner near the channels, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal working conditions. This is beneficial to reducing the risk of thermal runaway such as fire and explosion in the battery.

[0062] Furthermore, in this embodiment, by providing channels inside the conductive layer, the weight of the composite current collector can be reduced, which may provide a better basis for improving the mass density of the battery.

[0063] In some embodiments, there are multiple channels, and the multiple channels are arranged at intervals. By providing multiple channels, more fracture sites can be provided. When the battery is in an abnormal working condition, the current transmission inside the current collector can be weakened more timely, further reducing the risk of thermal runaway such as fire and explosion in the battery.

[0064] In some embodiments, the distance between adjacent channels is 5 mm to 60 mm. The distance between adjacent channels within this range can maintain a relatively stable intrinsic property of the conductive layer on the basis of providing an appropriate number of channels. It can be understood that the distance between adjacent channels represents the distance between the centers of adjacent channels. Optionally, the distance between adjacent channels can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 45 mm, 60 mm, etc.

[0065] In some embodiments, the pore channels include blind pore channels. It can be understood that a blind pore channel refers to a pore channel that does not penetrate through the conductive layer in the thickness direction of the conductive layer. Optionally, the opening of the blind pore channel faces the substrate layer. The opening of the blind pore channel facing the substrate layer may be beneficial for other material layers to be embedded to improve the bonding strength between the conductive layer and the substrate layer. It can also be understood that blind pore channels can be processed on the conductive layer by means such as laser drilling, etching drilling, and hot melt drilling.

[0066] As some examples of the depth of the blind pore channel, the depth of the blind pore channel is 30 nm to 500 nm. The depth of the blind pore channel within this range can provide a good embedding effect and is beneficial for improving the bonding strength between the conductive layer and the substrate layer. Optionally, the depth of the blind pore channel can be 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0067] As some examples of the pore diameter of the blind pore channel, the pore diameter of the blind pore channel is 5 mm to 50 mm. When the pore diameter of the blind pore channel is within this range, the blind pores can have an appropriate number and at the same time provide a good embedding effect. For example, the pore diameter of the blind pore channel can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, etc.

[0068] Optionally, the shape of the cross-section of the blind pore channel includes at least one of a circle, an ellipse, and a polygon. It can be understood that the cross-section of the blind pore channel refers to the section perpendicular to the thickness direction of the conductive layer. It can also be understood that when the shape of the cross-section of the blind pore channel is a circle, the pore diameter of the blind pore channel refers to the diameter of the circle. When the shape of the cross-section of the blind pore channel is an ellipse, the pore diameter of the blind pore channel refers to the length of the major axis of the ellipse. When the shape of the cross-section of the blind pore channel is a polygon, the pore diameter of the blind pore channel refers to the length of the longest side of the polygon.

[0069] In some embodiments, the percentage of the pore area of the blind pore channel in the cross-sectional area of the conductive layer is 0.5% to 54.5%. It can be understood that the pore area of the blind pore channel refers to the area of the cross-section of the blind pore channel. Optionally, the percentage of the pore area of the blind pore channel in the cross-sectional area of the conductive layer can be 0.5%, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 54.5%, etc. The percentage of the pore area of the blind pore channel in the cross-sectional area of the conductive layer within this range can make the blind pore channels have an appropriate number and at the same time keep the conductive layer having relatively stable intrinsic properties.

[0070] In some embodiments, the pore channels include through-hole channels. It can be understood that the through-hole channels refer to the channels that penetrate the conductive layer in the thickness direction of the conductive layer. On the one hand, the arrangement of the through-hole channels may be beneficial for other material layers to be embedded to improve the bonding force between the conductive layer and the substrate layer. On the other hand, the through channels can serve as exhaust channels, which is beneficial for discharging the gases that may be generated during the preparation of the composite current collector.

[0071] As some examples of the aperture of the through-hole channels, the aperture of the through-hole channels is 30 μm to 500 μm. When the aperture of the through-hole channels is within this range, the through-holes can have an appropriate number and at the same time provide a good embedding effect. For example, the aperture of the through-hole channels can be 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, etc.

[0072] Optionally, the cross-sectional shape of the through-hole channels includes at least one of a circle, an ellipse, and a polygon. It can be understood that the cross-section of the through-hole channels refers to the section perpendicular to the thickness direction of the conductive layer. It can also be understood that when the cross-sectional shape of the through-hole channels is a circle, the aperture of the through-hole channels refers to the diameter of the circle. When the cross-sectional shape of the through-hole channels is an ellipse, the aperture of the through-hole channels refers to the length of the major axis of the ellipse. When the cross-sectional shape of the through-hole channels is a polygon, the aperture of the through-hole channels refers to the length of the longest side of the polygon.

[0073] In some embodiments, the percentage of the pore area of the through-hole channels in the cross-sectional area of the conductive layer is 0.001% to 0.484%. It can be understood that the pore area of the through-hole channels refers to the cross-sectional area of the through-hole channels. When the percentage of the pore area of the through-hole channels in the cross-sectional area of the conductive layer is within this range, the through-hole channels can have an appropriate number and at the same time keep the conductive layer having relatively stable intrinsic properties. Optionally, the percentage of the pore area of the through-hole channels in the cross-sectional area of the conductive layer can be 0.001%, 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.484%, etc.

[0074] Please refer to Figure 1, which shows the structural schematic of the composite current collector 3 in an embodiment of the present application. Among them, the composite current collector 3 includes a substrate layer 31 and a conductive layer 32. The substrate layer 31 has opposite first and second surfaces. The conductive layer 32 is provided on both the first surface and the second surface. The interior of the conductive layer 32 is provided with pores. Further, the pores include blind hole pores 321 and through hole pores 322. The opening of the blind hole pores 321 faces the substrate layer 31. After applying the composite current collector 3 in this embodiment to the battery, when the battery is in an abnormal working condition and causes abnormal stress on the composite current collector, the conductive layer is prone to break in time near the pores, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal working conditions. This is beneficial to reducing the risk of thermal runaway such as fire and explosion of the battery, and thus can improve the safety performance of the battery.

[0075] In some embodiments, the through hole pores include a first through hole pore and a second through hole pore, and the aperture of the first through hole pore is larger than that of the second through hole pore. The aperture of the first through hole pore is larger. When the battery is in an abnormal working condition, the breakage of the conductive layer is facilitated to spread around from the position of the first through hole pore, which is beneficial to increasing the breakage rate of the conductive layer and more timely weakening the current transmission inside the current collector. While the aperture of the second through hole pore is smaller, which can provide a larger number of through hole pores per unit area of the conductive layer, further promoting the discharge of gases that may be generated during the preparation process of the composite current collector.

[0076] In some embodiments, the quantity ratio of the first through hole pores to the second through hole pores is (20 - 40):(60 - 80). When the quantity ratio of the first through hole pores to the second through hole pores is within this range, the quantities of the first through hole pores with a larger aperture and the second through hole pores with a smaller aperture can be better adapted, which is beneficial to further promoting the effects of conductive layer breakage and gas exhaust. Optionally, the quantity ratio of the first through hole pores to the second through hole pores can be 20:80, 25:75, 30:70, 35:65, 40:60, etc.

[0077] In some embodiments, the aperture of the first through hole pore is 300μm - 500μm. Optionally, the aperture of the first through hole pore can be 300μm, 320μm, 350μm, 380μm, 400μm, 420μm, 450μm, 480μm, 500μm, etc.

[0078] In some embodiments, the aperture of the second through hole pore is 30μm - 300μm. Optionally, the aperture of the second through hole pore can be 30μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, 280μm, 300μm, etc.

[0079] In some embodiments, the composite current collector further includes an adhesive layer located between the substrate layer and the conductive layer. By providing the adhesive layer, the bonding strength between the substrate layer and the conductive layer can be improved, which is conducive to maintaining a more stable structure of the composite current collector. It can be understood that the adhesive layer can be prepared by coating an adhesive slurry and then curing it.

[0080] In some embodiments, the adhesive layer includes a main body portion and a protruding portion. The protruding portion protrudes from the main body portion and is embedded in the pore channels. By embedding the protruding portion into the pore channels of the conductive layer, the contact area between the adhesive layer and the conductive layer can be increased, forming a more stable bonding effect between the adhesive layer and the conductive layer, further improving the bonding strength between the conductive layer and the adhesive layer, and thus further improving the bonding strength between the substrate layer and the conductive layer, promoting the improvement of the structural stability of the composite current collector.

[0081] It can be understood that the main body portion and the protruding portion can be made of the same material. It can also be understood that the main body portion and the protruding portion can be an integrally formed structure.

[0082] In some embodiments, the thickness of the main body portion is 0.5 μm to 5 μm. When the thickness of the main body portion is within this range, the adhesive layer can exert a good bonding effect, while keeping the overall thickness of the composite current collector within a more appropriate range. Optionally, the thickness of the main body portion can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0083] In some embodiments, the protruding portions correspond one-to-one with the pore channels of the conductive layer, and the protruding portions completely fill the pore channels of the conductive layer.

[0084] It can be understood that the adhesive layer contains an adhesive. Optionally, the adhesive includes one or more of isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide. Optionally, the isocyanate includes polyfunctional isocyanate. Optionally, the adhesive layer contains one or more of a composition containing polyfunctional isocyanate and polyester polyol and polyurethane. Optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0085] In some embodiments, the adhesive layer contains filler particles. By introducing filler particles into the adhesive layer, it is beneficial to increase the elastic modulus of the composite current collector. This may further improve the wrinkling problem during the processing of the electrode sheet. It can be understood that the filler particles are dispersed in the main body portion and the protruding portion of the adhesive layer.

[0086] Optionally, the mass percentage of the filler particles in the adhesive layer is 10% to 20%. When the mass percentage of the filler particles in the adhesive layer is within this range, the adhesive layer can have appropriate adhesive properties and an appropriate elastic modulus. Further optionally, the mass percentage of the filler particles in the adhesive layer can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0087] Optionally, the Dv50 of the filler particles is 30 nm to 500 nm. The filler particles with a particle size distribution within this range can be more uniformly dispersed in the adhesive layer, promoting further improvement of the elastic modulus of the composite current collector. Further optionally, the Dv50 of the filler particles can be 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0088] It can be understood that in this application, Dv50 refers to: in the volume cumulative distribution curve, the particle size corresponding to when the cumulative particle size distribution number of the particles reaches 50%. Its physical meaning is that 50% of the particles have a particle size smaller than (or larger than) it. As an example, Dv50 can be obtained by referring to the test method of GB / T 19077-2016 and using the particle size distribution curve obtained by a laser diffraction particle size analyzer Mastersizer3000.

[0089] In some embodiments, the filler particles include insulating filler particles. The use of insulating filler particles can reduce the risk of adverse effects on the electrical conductivity of the composite current collector due to the introduction of the filler particles, which is beneficial to maintaining a relatively appropriate and stable electrical conductivity of the composite current collector.

[0090] In some embodiments, the filler particles include inorganic filler particles. Optionally, the filler particles include at least one of alumina, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide.

[0091] In some embodiments, the filler particles include first filler particles. One end of the first filler particles extends into the main body portion, and the other end extends into the convex portion. At this time, a part of the first filler particles is located in the main body portion of the adhesive layer, and the other part is located in the convex portion of the adhesive layer. This can provide a support site between the conductive layer and the adhesive layer, which is beneficial to improving the support force of the adhesive layer on the conductive layer and further increasing the elastic modulus of the composite current collector. Optionally, the Dv50 of the first filler particles is 200 nm to 500 nm. For example, the Dv50 of the first filler particles can be 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, etc.

[0092] In some embodiments, the filler particles further include second filler particles, and the Dv50 of the second filler particles is smaller than that of the first filler particles. The second filler particles have a smaller particle size distribution and can be more uniformly dispersed in the adhesive layer, further promoting the improvement of the elastic modulus of the composite current collector. In addition, the second filler particles with a smaller particle distribution can be better dispersed in the convex portion of the adhesive layer, that is, the second filler particles can be better dispersed in the pores of the conductive layer, which is beneficial to improving the mutual support between the adhesive layer and the conductive layer and enhancing the elastic modulus of the composite current collector. Optionally, the Dv50 of the second filler particles is 30 nm to 200 nm. Further optionally, the Dv50 of the second filler particles can be 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, etc.

[0093] In some embodiments, the mass ratio of the second filler particles to the first filler particles is (30 - 50):(50 - 70). When the mass ratio of the second filler particles to the first filler particles is within this range, the second filler particles and the first filler particles can be better adapted, further enhancing the elastic modulus of the composite current collector.

[0094] In some embodiments, the adhesive layer contains a flame retardant. By introducing the flame retardant, the flame retardant effect of the composite current collector can be improved, and the risk of thermal runaway such as fire and explosion of the battery under abnormal conditions can be further reduced. It can be understood that the flame retardant is dispersed in the main body portion and the convex portion of the adhesive layer.

[0095] Optionally, the mass percentage of the flame retardant in the adhesive layer is 20% - 40%. When the mass percentage of the flame retardant is within this range, the composite current collector can have a good flame retardant effect, and at the same time, the adhesive layer can have good adhesive performance. Further optionally, the mass percentage of the flame retardant in the adhesive layer can be 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0096] In some embodiments, the flame retardant includes particulate flame retardants. The particulate flame retardants can play a flame retardant role while providing corresponding support to the adhesive layer, which is beneficial to improving the elastic modulus of the composite current collector.

[0097] Optionally, the flame retardant includes at least one of decabromodiphenyl ether, hexabromocyclododecane, polyvinyl chloride, tris(2,3-dibromopropyl)isocyanurate, sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0098] In some embodiments, the flame retardant includes organic flame retardants and inorganic flame retardants. The organic flame retardants can be better mixed with the adhesive layer based on the principle of similar compatibility. The inorganic flame retardants can provide corresponding support to the adhesive layer while playing a flame retardant role. Optionally, the mass percentage of the organic flame retardant in the adhesive layer is 10% - 20%, and the mass percentage of the inorganic flame retardant in the adhesive layer is 10% - 20%. Further optionally, the mass percentage of the organic flame retardant in the adhesive layer can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc. Further optionally, the mass percentage of the inorganic flame retardant in the adhesive layer can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0099] Please refer to Figure 2 , which shows a schematic structure of the composite current collector 3 according to an embodiment of the present application. Among them, the composite current collector 3 includes a substrate layer 31 and a conductive layer 32. The substrate layer 31 has opposite first and second surfaces. The conductive layer 32 is provided on both the first surface and the second surface. The interior of the conductive layer 32 is provided with channels. There are multiple channels, and the multiple channels are spaced apart. The channels include blind hole channels. The channels include through hole channels. The composite current collector 3 further includes an adhesive layer 33, and the adhesive layer 33 is located between the substrate layer 31 and the conductive layer 32. The adhesive layer 33 includes a main body portion 331 and a protruding portion 332. The protruding portion 332 protrudes from the main body portion 331, and the protruding portion 332 is embedded in the channel. The adhesive layer 33 contains filler particles. The filler particles are dispersed in the main body portion 331 and the protruding portion 332 of the adhesive layer 33. The filler particles include first filler particles 34. One end of the first filler particles 34 extends into the main body portion 331, and the other end extends into the protruding portion 332. The filler particles further include second filler particles 35, and the Dv50 of the second filler particles 35 is less than the Dv50 of the first filler particles 34. The adhesive layer contains a flame retardant 36. The flame retardant 36 is dispersed in the main body portion 331 and the protruding portion 332 of the adhesive layer 33.

[0100] In some embodiments, the surface of the conductive layer further includes a passivation layer. Optionally, the passivation layer includes at least one of chromate, phosphate, alumina, silica, and silicon nitride. The passivation layer can protect the conductive layer and reduce the corrosion of the conductive layer by the electrolyte, which is beneficial to improving the structural stability of the composite current collector. Optionally, the passivation layer is located between the conductive layer and the adhesive layer. The setting of the passivation layer can maintain a good bonding effect between the conductive layer and the adhesive layer after the electrolyte infiltrates the composite current collector.

[0101] In some embodiments, the conductive layer includes a metallic material. Optionally, the metallic material includes at least one of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium, and tin.

[0102] In some embodiments, the substrate layer includes one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymers, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products, and their copolymers.

[0103] Another embodiment of the present application provides a pole piece. The pole piece includes the above-mentioned composite current collector.

[0104] Another embodiment of the present application provides a secondary battery. The secondary battery includes the above-mentioned pole piece.

[0105] Another embodiment of the present application provides an electrical device. The electrical device includes at least one of the above-mentioned composite current collector, the above-mentioned pole piece, and the above-mentioned secondary battery.

[0106] The secondary battery and the electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0107] Generally, a secondary battery includes a positive electrode pole piece, a negative electrode pole piece, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode pole piece and the negative electrode pole piece. The electrolyte plays a role in conducting ions between the positive electrode pole piece and the negative electrode pole piece. The separator is disposed between the positive electrode pole piece and the negative electrode pole piece, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0108] Positive electrode pole piece

[0109] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0110] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0111] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material can include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive electrode current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0112] In some of these embodiments, the positive electrode active material can be a positive electrode active material for batteries well-known in the art. As a non-limiting example, the positive electrode active material can include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include but are not limited to lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc. Non-limiting examples of lithium-containing phosphates with an olivine structure can include but are not limited to lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, composites of lithium manganese iron phosphate and carbon, etc. Non-limiting examples of lithium cobalt oxide can include LiCoO 2 ; non-limiting examples of lithium nickel oxide can include LiNiO 2 ; non-limiting examples of lithium manganese oxide can include LiMnO 2 , LiMn 2 O 4 etc.; non-limiting examples of lithium nickel cobalt manganese oxide can include LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide can include LiNi 0.8 Co 0.15 Al 0.05 O 2 .

[0113] In some of these embodiments, the positive electrode active material layer may also optionally include a binder. As non-limiting examples, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0114] In some of these embodiments, the positive electrode active material layer may also optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some of these embodiments, the positive electrode plate can be prepared in the following manner: dispersing the above-mentioned components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained. The type of the solvent can be selected from but not limited to any one of the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s to 25000mPa·s. When coating the positive electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 15 - 35mg / cm 2 ³. The tap density of the positive electrode plate can be 3.0g / cm 3 ³ to 3.6g / cm 3 ³, and can be optionally 3.3g / cm 3 ³ to 3.5g / cm 3 ³.

[0116] Negative electrode plate

[0117] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0118] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0119] In some of these embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0120] In some of these embodiments, the negative electrode active material can be the negative electrode active material for batteries known in the art. As non-limiting examples, the negative electrode active material can include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0121] In some of these embodiments, the negative electrode active material layer may also optionally include a binder. The binder can include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0122] In some of these embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0124] In some of these embodiments, the negative electrode plate can be prepared in the following manner: dispersing the above components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% - 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s - 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density calculated by dry weight (deducting the solvent) can be 75g / m 2 ~220g / m 2 。The tap density of the negative electrode plate can be 1.0g / cm 3 ~1.8g / cm 3 。

[0125] Electrolyte

[0126] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. There is no particular limitation on the type of the electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0127] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0128] In some of these embodiments, the electrolyte salt can include lithium hexafluorophosphate (LiPF 6 )、lithium tetrafluoroborate (LiBF 4 )、lithium perchlorate (LiClO 4 )、lithium hexafluoroarsenate (LiAsF 6 )、lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2 )、lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or one or more of them.

[0129] In some of these embodiments, the solvent can include ethylene carbonate (EC, )、propylene carbonate (PC, )、ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone, or one or more of them.

[0130] In some of these embodiments, the electrolytic solution may optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performance, such as additives for improving battery overcharge performance, additives for improving battery high-temperature or low-temperature performance, etc.

[0131] In some embodiments, the additives in the electrolytic solution can include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate (TFPC), etc.

[0132] Separator

[0133] In some of these embodiments, a separator is further included in the secondary battery. There is no particular limitation on the type of the separator in this application, and any well-known porous separator with good chemical stability and mechanical stability can be selected.

[0134] In some of these embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0135] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and may be selected to be 12 μm to 20 μm.

[0136] In some of these embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0137] In some of these embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0138] In some of these embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. Further, non-limiting examples of the plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0139] The secondary battery includes at least one battery cell. The secondary battery may include 1 or more battery cells.

[0140] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0141] There is no particular limitation on the shape of the battery cell in this application, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 is a secondary battery 1 with a square structure as an example.

[0142] In some of these embodiments, referring to Figure 4, the outer packaging may include a housing 11 and a cover plate 13. Among them, the housing 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 included in the secondary battery 1 can be one or more, and those skilled in the art can select according to actual needs.

[0143] The secondary battery can be a battery module or a battery pack.

[0144] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0145] In the battery module, multiple battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other way. Further, the multiple battery cells can be fixed by fasteners.

[0146] Optionally, the battery module can further include a housing having a receiving space, and multiple battery cells are received in the receiving space.

[0147] In some embodiments, the above battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0148] The battery pack can include a battery box and multiple battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body. The upper box body can be disposed on the lower box body to form a closed space for receiving the battery modules. The multiple battery modules can be arranged in the battery box in any way.

[0149] In addition, the present application also provides an electrical device, and the electrical device includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto. Among them, the mobile device can be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle can be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0150] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0151] Figure 5 The electrical device 2 is taken as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for the high power and high energy density of the secondary battery, a battery pack or a battery module can be adopted.

[0152] The device taken as another example can be a mobile phone, a tablet computer, a laptop computer, etc. The device usually requires being thin and light, and a secondary battery can be adopted as the power source.

[0153] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation on the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0154] For those not specified in the embodiments, the techniques or conditions are described according to the techniques or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0155] Embodiment 1

[0156] The preparation method of the composite current collector in this embodiment includes:

[0157] S101: Etch and create holes on the surface of the aluminum foil to form blind hole channels and through hole channels, and passivate the aluminum foil.

[0158] S102: Cast PET onto the etched surface of the aluminum foil.

[0159] S103: Etch and create holes on the surface of another piece of aluminum foil to form blind hole channels and through hole channels, and passivate the aluminum foil, and cover the aluminum foil on the PET surface so that the etched surface of the aluminum foil contacts the PET.

[0160] S104: Hot press the product obtained in S103 to form a structure in which the aluminum foil and the PET substrate layer are composite, and then cure for 72 h.

[0161] S105: Etch and thin the aluminum foil.

[0162] Embodiment 2

[0163] The preparation method of the composite current collector in this embodiment includes:

[0164] S101: Etch and create holes on the surface of the aluminum foil to form blind hole channels and through hole channels, and passivate the aluminum foil.

[0165] S102: Coat the bonding paste on the surface of the aluminum foil, dry it, and then laminate the PET substrate layer onto the surface of the bonding paste. The bonding paste contains a binder, filler particles, and a flame retardant.

[0166] S103: Hot press the product obtained in S102 to form a structure composed of the aluminum foil, bonding layer, and PET substrate layer, and then cure it for 72 hours.

[0167] S104: Etch and create holes on the surface of another piece of aluminum foil to form blind hole channels and through hole channels, and passivate the aluminum foil.

[0168] S105: Coat the bonding paste on the surface of the aluminum foil, dry it, and then laminate the product obtained in S103 onto the surface of the bonding paste, making the PET substrate layer contact the bonding paste. The bonding paste contains modified polypropylene as the binder, alumina as the filler particles, and decabromodiphenyl ether as the flame retardant.

[0169] S106: Hot press the product obtained in S105 to form a structure composed of the aluminum foil, bonding layer, and PET substrate layer, and then cure it for 72 hours.

[0170] S107: Etch and thin the aluminum foil.

[0171] Examples 3 - 24

[0172] Compared with Example 2, the differences in Examples 3 - 24 lie in that the blind hole channels, through hole channels, filler particles, and flame retardants are different, as specifically shown in Table 1.

[0173] Comparative Example 1

[0174] Compared with Example 1, the difference in this comparative example is that the aluminum foil is not subjected to etching and hole - creating treatment.

[0175] Comparative Example 2

[0176] Compared with Example 2, the difference in this comparative example is that the aluminum foil is not hole - created, and the bonding paste does not contain filler particles and flame - retardant particles.

[0177] Table 1

[0178]

[0179]

[0180] In Table 1, the unit of the aperture of the blind hole channel is mm. The unit of the depth of the blind hole channel is nm. The unit of the spacing of the blind hole channels is mm. The unit of the aperture of the second through-hole channel is μm. The unit of the aperture of the first through-hole channel is μm. The unit of the spacing of the through-hole channels is mm. The unit of Dv50 of the second filler particles is nm. The unit of Dv50 of the first filler particles is nm.

[0181] Preparation of the battery

[0182] (1) Preparation of the positive electrode sheet.

[0183] Mix LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 in a ratio of 17:3 as the positive electrode active material. Disperse the positive electrode active material, super-conductive carbon black SP as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder in N-methylpyrrolidone (NMP) as the solvent in a mass ratio of 95:3:2 and mix evenly to obtain the positive electrode slurry; coat the positive electrode slurry evenly on the composite current collector aluminum foil, dry it at 85 °C and then cold press it, and then perform die cutting and slitting to make the positive electrode sheet. The composite current collector is the composite current collector in the examples and comparative examples.

[0184] (2) Preparation of the negative electrode sheet.

[0185] Mix the negative electrode active material graphite, conductive agent acetylene black, thickening agent sodium carboxymethyl cellulose, and binder styrene-butadiene rubber in a mass ratio of 96:2:1:1 and add them to water as the solvent and mix evenly to make the negative electrode slurry. Coat the negative electrode slurry evenly on the negative current collector, dry it at 85 °C and then perform cold pressing under a pressure of 40 tons. The cold pressing is carried out using a cylindrical cold pressing roller, the cold pressing speed is 20 m / min, and the temperature is 25 °C to make the negative electrode sheet.

[0186] (3) The separator is a polypropylene separator.

[0187] (4) Preparation of the electrolyte.

[0188] Dissolve LiPF 6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is 1:2:1), and add the fluorinated ethylene carbonate (FEC) additive to obtain the electrolyte. The concentration of LiPF 6 in the electrolyte is 1 mol / L, and the mass percentage content of FEC is 5 wt%.

[0189] Test Example

[0190] (1) Test the elastic modulus of the composite current collector. The test method is as follows: Cut the current collector into strips with a size of 15 mm × 150 mm, and conduct tensile tests using a universal tensile testing machine with a gauge length of 50 mm and a tensile speed of 50 mm / min until the test breaks. The chord slope method is adopted, and the chord slope corresponding to the strain from 0.1% to 1% is calculated; E = (σ2 - σ1) / (ε2 - ε1), where E is the elastic modulus, σ1 is the stress measured when the strain value ε1 = 0.001 (0.1%), and the unit is GPa; σ2 is the stress measured when the strain value ε2 = 0.01 (1%), and the unit is GPa. The results are shown in Table 2.

[0191] (2) Test the peel strength of the conductive layer in the composite current collector. The test method is as follows: After laminating the sample with the non-corona surface of the ethylene-acrylic copolymer (EAA) film, cover a 12-μm-thick PET on the EAA film, and place it on a heat sealer for lamination at a temperature of 120°C and a pressure of 0.2 MPa. Cut the laminated sample into samples with a length of 100 mm and a width of 20 mm, and stick the non-laminated surface of the conductive layer on a steel plate with 3M double-sided tape; clamp the sample on the fixture of the tensile testing machine, with a spacing of 50 mm, and conduct a 180° peel test at a speed of 300 mm / min. Read the peel force value, convert it to the unit of N / m, and there are 5 parallel samples. Finally, take the average value of the peel force; average peel force = sum of peel forces of 5 test samples / 5. The results are shown in Table 2.

[0192] (3) Test whether the coating is wrinkled. The test method is as follows: Adopt a one-out-of-four coating design, observe the coating process, whether the tab is wrinkled, and whether the tab bulges during winding. If the bulge exceeds 1 mm, it is determined that there is wrinkling. The results are shown in Table 2.

[0193] (4) Test the puncture pass rate of the battery. The test method is as follows: Fix the fully charged battery cell on the fixture, and a 3-mm-diameter high-temperature-resistant steel needle passes through the battery cell at a speed of 80 mm / s; if there is smoking, fire or the explosion-proof valve bursts after the nail penetration, it is determined that the nail penetration test fails; if there is no smoking, no fire and the explosion-proof valve does not burst after the nail penetration, it is determined that the nail penetration test passes. A total of 5 parallel battery cell samples are tested. If the number of battery cells passing the puncture is x, then the pass rate is x / 5 * 100%. The results are shown in Table 2.

[0194] (5) Conduct a cycle test on the battery. The test method is as follows: Perform cycles of 1C charge and 1C discharge on the battery monomer under the condition of 60°C high temperature until the capacity decays to 80% of the initial capacity, and record the corresponding number of cycles at this time, which is the cycle performance of the corresponding battery. The results are shown in Table 2.

[0195] (6) Perform a DCR test on the battery. The test method is as follows: Adjust the battery cell to a state of 50% SOC, discharge it at a rate of 4C (corresponding discharge current is I) for 30 s, and record the voltage difference ΔV before and after the 30-s discharge. Calculate the DCR corresponding to 50% SOC according to the following formula: DCR = ΔV / I to obtain the DCR data of each battery cell. The results are shown in Table 2.

[0196] Table 2

[0197]

[0198]

[0199] In Table 2, the unit of the elastic modulus of the current collector is GPa. The unit of the peel strength of the conductive layer is N / m. The unit of the number of cycles is cycle. The unit of DCR is mΩ.

[0200] As can be seen from Table 1 and Table 2, in terms of the needle penetration pass rate, the needle penetration pass rates of the batteries in Examples 1 to 24 are higher than those of the batteries in Comparative Examples 1 to 2. It shows that in the composite current collector, the safety performance of the battery can be improved by setting channels in the conductive layer.

[0201] As can be seen from Examples 2 to 16, when the aperture of the blind hole channel, the depth of the blind hole channel, the spacing of the blind hole channels, the aperture of the second through-hole channel, the aperture of the first through-hole channel, the spacing of the through-hole channels, the quantity ratio of the second through-hole channel to the first through-hole channel, the Dv50 of the second filler particle, the Dv50 of the first filler particle, the mass ratio of the second filler particle to the first filler particle, the mass percentage of the filler particle in the adhesive layer, the mass percentage of the organic flame retardant in the adhesive layer, and the mass percentage of the inorganic flame retardant in the adhesive layer are within the corresponding appropriate ranges, better results can be obtained in the corresponding tests. For example, the composite current collector has a higher elastic modulus, a greater peel strength of the conductive layer, no wrinkling during coating, a higher needle penetration pass rate of the battery, a larger number of cycles, and a smaller DCR, etc.

[0202] As can be seen by comparing Example 17 with Example 3: When there are no through-hole channels in the conductive layer, the elastic modulus of the current collector decreases. This may be because the supporting effect between the conductive layer and the adhesive layer decreases, resulting in a decrease in the elastic modulus. The peel strength of the conductive layer decreases. This may be because the gas generated during the preparation of the composite current collector is difficult to discharge in time through the through-hole channels, resulting in a decrease in the peel strength of the conductive layer. The needle penetration pass rate decreases. This may be because the trigger points for the fracture of the conductive layer decrease, making it difficult for the conductive layer to break in time, resulting in a decrease in the needle penetration pass rate.

[0203] As can be seen by comparing Example 18 with Example 3: when there are no blind hole channels in the conductive layer, the elastic modulus of the current collector decreases. This may be because the supporting effect between the conductive layer and the adhesive layer decreases, resulting in a decrease in the elastic modulus. The peel strength of the conductive layer decreases. This may be because the contact area between the adhesive layer and the conductive layer decreases, resulting in a decrease in the peel strength of the conductive layer. The needle penetration rate decreases. This may be because the number of fracture sites of the conductive layer decreases, making it difficult for the conductive layer to break in time, resulting in a decrease in the needle penetration rate.

[0204] As can be seen from Example 19 and Example 3, when the depth of the blind hole channel is relatively large, it may cause the conductivity of the conductive layer to decrease, thereby leading to a reduction in the number of cycles and an increase in DCR.

[0205] As can be seen from Example 20 and Example 3, when the aperture of the first through-hole channel is relatively large, it may cause the mechanical properties of the conductive layer to decrease, thereby leading to coating wrinkling. At the same time, when the aperture of the first through-hole channel is relatively large, it may cause the conductivity of the conductive layer to decrease, thereby leading to a reduction in the number of cycles and an increase in DCR.

[0206] As can be seen from Example 21 and Example 3, when the spacing of the through-hole channels is relatively large, the arrangement of the through-hole channels is relatively sparse, reducing the triggering points for the conductive layer to break, thereby reducing the needle penetration rate.

[0207] As can be seen from Example 22 and Example 3, when the spacing of the through-hole channels is relatively small, the arrangement of the through-hole channels is relatively dense, which may affect the conductivity of the conductive layer, thereby leading to a reduction in the number of cycles and an increase in DCR.

[0208] As can be seen from Example 23, Example 24 and Example 3, when the first filler particles or the second filler particles are not contained, the elastic modulus decreases, coating wrinkling occurs, and the needle penetration rate decreases. This may be because the filling effect of the filler particles is not sufficient, resulting in a decrease in the elastic modulus and coating wrinkling. At the same time, when the filling effect of the filler particles is not sufficient, the flame retardant effect may be reduced, thereby leading to a decrease in the needle penetration rate.

[0209] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0210] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A composite current collector, characterized in that, it includes a substrate layer and a conductive layer; the substrate layer has opposite first and second surfaces; the conductive layer is disposed on the first surface and / or the second surface; and pores are provided inside the conductive layer.

2. The composite current collector according to claim 1, characterized in that, there are multiple pores, and the multiple pores are spaced apart; optionally, the distance between adjacent pores is 5 mm to 60 mm.

3. The composite current collector according to any one of claims 1 to 2, characterized in that, the pores include blind hole pores; optionally, the openings of the blind hole pores face the substrate layer.

4. The composite current collector according to claim 3, characterized in that, the depth of the blind hole pores is 30 nm to 500 nm; and / or, the diameter of the blind hole pores is 5 mm to 50 mm; and / or, the percentage of the pore area of the blind hole pores in the cross-sectional area of the conductive layer is 0.5% to 54.5%; and / or, the cross-sectional shape of the blind hole pores includes at least one of a circle, an ellipse, and a polygon.

5. The composite current collector according to any one of claims 1 to 4, characterized in that, the pores include through hole pores.

6. The composite current collector according to claim 5, characterized in that, the diameter of the through hole pores is 30 μm to 500 μm; and / or, the percentage of the pore area of the through hole pores in the cross-sectional area of the conductive layer is 0.001% to 0.484%; and / or, the cross-sectional shape of the through hole pores includes at least one of a circle, an ellipse, and a polygon.

7. The composite current collector according to any one of claims 5 to 6, characterized in that, the through hole pores include a first through hole pore and a second through hole pore, and the diameter of the first through hole pore is larger than that of the second through hole pore; optionally, the number ratio of the first through hole pores to the second through hole pores is (20 to 40):(60 to 80); optionally, the diameter of the first through hole pore is 300 μm to 500 μm; optionally, the diameter of the second through hole pore is 30 μm to 300 μm.

8. The composite current collector according to any one of claims 1 to 7, characterized in that, the composite current collector further includes an adhesive layer, and the adhesive layer is located between the substrate layer and the conductive layer.

9. The composite current collector according to claim 8, characterized in that, the adhesive layer includes a main body portion and a protruding portion, the protruding portion protrudes from the main body portion, and the protruding portion is embedded in the pores; optionally, the thickness of the main body portion is 0.5 μm to 5 μm.

10. The composite current collector according to any one of claims 8 to 9, characterized in that, the adhesive layer contains an adhesive; Optionally, the binder includes one or more of isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide.

11. The composite current collector according to any one of claims 8 to 10, wherein, the adhesive layer contains filler particles; Optionally, the mass percentage of the filler particles in the adhesive layer is 10% to 20%; Optionally, the Dv50 of the filler particles is 30 nm to 500 nm; Optionally, the filler particles include insulating filler particles; Optionally, the filler particles include at least one of alumina, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, and boron carbide.

12. The composite current collector according to claim 11, wherein, the filler particles include first filler particles, one end of the first filler particles extends into the main body portion, and the other end extends into the convex portion; Optionally, the Dv50 of the first filler particles is 200 nm to 500 nm.

13. The composite current collector according to claim 12, wherein, the filler particles further include second filler particles, and the Dv50 of the second filler particles is less than that of the first filler particles; Optionally, the Dv50 of the second filler particles is 30 nm to 200 nm; Optionally, the mass ratio of the second filler particles to the first filler particles is (30 - 50):(50 - 70).

14. The composite current collector according to any one of claims 8 to 13, wherein, the adhesive layer contains a flame retardant; Optionally, the mass percentage of the flame retardant in the adhesive layer is 20% to 40%; Optionally, the flame retardant includes at least one of decabromodiphenyl ether, hexabromocyclododecane, polyvinyl chloride, tris(2,3-dibromopropyl) isocyanurate, sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

15. The composite current collector according to claim 14, wherein, the flame retardant includes an organic flame retardant and an inorganic flame retardant, the mass percentage of the organic flame retardant in the adhesive layer is 10% to 20%, and the mass percentage of the inorganic flame retardant in the adhesive layer is 10% to 20%.

16. The composite current collector according to any one of claims 1 to 15, wherein, the surface of the conductive layer further includes a passivation layer; Optionally, the passivation layer includes at least one of chromate, phosphate, alumina, silica, and silicon nitride.

17. An electrode sheet, wherein, it includes the composite current collector according to any one of claims 1 to 16.

18. A secondary battery, wherein, it includes the electrode sheet according to claim 17.

19. An electrical device, wherein, At least one of the composite current collector according to any one of claims 1 to 16, the electrode tab according to claim 17, and the secondary battery according to claim 18.

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