Composite current collector, electrode sheet, secondary battery, and electric apparatus

Abstract

A composite current collector, an electrode sheet, a secondary battery, and an electric apparatus. The composite current collector comprises a substrate layer, a first filler, a bonding layer and a conductive layer, wherein the bonding layer is located between the substrate layer and the conductive layer, one end of the first filler is embedded into the substrate layer, the other end of the first filler is embedded into the bonding layer, the hardness of the first filler is greater than the hardness of the substrate layer, and the hardness of the first filler is greater than the hardness of the bonding layer. In the composite current collector, a first filler having a hardness greater than that of a substrate layer and that of a bonding layer is introduced, one end of the first filler is embedded into the substrate layer, the other end of the first filler is embedded into the bonding layer, and the first filler can serve as a focal force application point between the substrate layer and the bonding layer, thereby facilitating an improvement to the elastic modulus of the composite current collector, and reducing the risk of wrinkling during the machining of an electrode sheet.

Description

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

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2023115973582, filed on November 24, 2023, entitled “Composite current collector, electrode, secondary battery and electrical device,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a composite current collector, a pole piece, a secondary battery, and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] The current collector is a crucial component in battery structure, supporting the active membrane and collecting current. Its performance significantly impacts the performance of the electrode. Conventional current collectors have a low elastic modulus, making them prone to wrinkling during electrode processing.

[0006] Summary of the Invention

[0007] The first aspect of the present application provides a composite current collector, comprising a substrate layer, a first filler, a bonding layer and a conductive layer; the bonding layer is located between the substrate layer and the conductive layer, one end of the first filler is embedded in the substrate layer, and the other end of the first filler is embedded in the bonding layer, the hardness of the first filler is greater than the hardness of the substrate layer, and the hardness of the first filler is greater than the hardness of the bonding layer.

[0008] In the above-mentioned composite current collector, by introducing a first filler with a hardness greater than that of the substrate layer and the bonding layer, and embedding one end of the first filler into the substrate layer and the other end into the bonding layer, the first filler can serve as a fulcrum between the substrate layer and the bonding layer, which is beneficial to improving the elastic modulus of the composite current collector and reducing the risk of wrinkling during the electrode processing.

[0009] In some embodiments, the first filler is embedded in the substrate layer to a depth of 100 nm to 800 nm. Within this range, the depth of the first filler embedded in the substrate layer can maintain good mechanical properties of the substrate layer, which is beneficial for improving the elastic modulus of the composite current collector. Furthermore, within this range, the depth of the first filler embedded in the substrate layer can maintain good bonding between the substrate layer and the adhesive layer, which is beneficial for maintaining good structural stability of the composite current collector.

[0010] In some embodiments, there are multiple first fillers, each of which is spaced apart. Optionally, the spacing between adjacent first fillers is 5 mm to 50 mm. This ensures a more appropriate distribution density of the first fillers, more effectively utilizing the first fillers and maintaining good mechanical properties such as elastic modulus and strength of the composite current collector.

[0011] In some embodiments, the Dv50 of the first filler is between 150 nm and 1500 nm. A Dv50 of the first filler within this range can maintain a good riveting effect between the substrate layer and the adhesive layer, promote improved bonding between the substrate layer and the adhesive layer, and further promote good structural stability of the composite current collector. Alternatively, the Dv50 of the first filler is between 200 nm and 1000 nm.

[0012] In some embodiments, the first filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide, and a first flame-retardant filler. In this case, the first filler has a relatively suitable hardness, which is conducive to promoting the improvement of the elastic modulus of the composite current collector. In addition, when the first filler includes a first flame-retardant filler, the flame retardant effect of the composite current collector can be improved. After the composite current collector is applied to the battery, the risk of thermal runaway such as fire and explosion in the battery can be reduced. Optionally, the first flame-retardant filler includes at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0013] In some embodiments, the composite current collector further includes a second filler, the second filler is located inside the bonding layer, the hardness of the second filler is greater than the hardness of the substrate layer, the hardness of the second filler is greater than the hardness of the bonding layer, and the Dv50 of the second filler is less than the Dv50 of the first filler. By combining the first filler and the second filler with different particle sizes, more fillers can be introduced into the composite current collector, further promoting the improvement of the elastic modulus of the composite current collector. In addition, when the composite current collector further includes a second filler, the second filler can interact with the first filler, further promoting the riveting effect between the substrate layer and the bonding layer, and further improving the bonding force between the substrate layer and the bonding layer. Optionally, the Dv50 of the second filler is 50nm to 150nm.

[0014] In some embodiments, the mass ratio of the second filler to the first filler is (20-50):(50-80). The first filler and the second filler have a relatively suitable ratio, which can improve the elastic modulus of the composite current collector while maintaining good bonding between the substrate layer and the adhesive layer.

[0015] In some embodiments, the second filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide, and a second flame-retardant filler. The second filler has a relatively suitable hardness, which helps to improve the elastic modulus of the composite current collector. In addition, when the second filler includes a second flame-retardant filler, the flame retardant effect of the composite current collector can be improved. After the composite current collector is applied to the battery, the risk of thermal runaway such as fire and explosion in the battery can be reduced.

[0016] In some embodiments, the second flame-retardant filler accounts for 30% to 50% of the second filler by mass. A second flame-retardant filler within this range can further improve the flame retardancy of the composite current collector while maintaining a good elastic modulus. Optionally, the second flame-retardant filler includes at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0017] In some embodiments, the adhesive layer comprises an adhesive. Optionally, the adhesive comprises 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.

[0018] In some embodiments, the substrate layer is provided with pores, and the adhesive layer is embedded in the pores. By designing the adhesive layer embedded in the pores, the bonding strength between the adhesive layer and the substrate layer can be further improved, promoting the composite current collector to maintain good structural stability.

[0019] In some embodiments, the pores have a pore diameter of 30 μm to 500 μm. Within this pore diameter range, the bonding layer embedded in the pores improves the bonding force between the bonding layer and the substrate layer, while maintaining good integrity of the substrate layer, maintaining relatively stable intrinsic properties of the substrate layer, and thus maintaining good mechanical properties of the substrate layer.

[0020] In some embodiments, there are multiple channels, and the multiple channels are spaced apart. The design of multiple channels is more conducive to improving the bonding force between the substrate layer and the adhesive layer, and can maintain good structural stability of the composite current collector.

[0021] In some embodiments, the spacing between adjacent channels is 5 mm to 50 mm. Within this range, the spacing between adjacent channels can provide a suitable number of channels while maintaining relatively stable intrinsic properties of the substrate layer.

[0022] In some embodiments, the channels include at least one of through-hole channels and blind-hole channels. Optionally, the blind-hole channels have a depth of 50 nm to 1200 nm. This depth range provides a good embedding effect, which helps improve the bonding strength between the adhesive layer and the substrate layer.

[0023] In some embodiments, the composite current collector further includes a passivation layer disposed on the surface of the conductive layer. The passivation layer can protect the conductive layer, reducing electrolyte corrosion on the conductive layer, thereby improving the structural stability of the composite current collector. Optionally, the passivation layer comprises at least one of chromate, phosphate, aluminum oxide, silicon dioxide, and silicon nitride.

[0024] In some embodiments, the thickness of the substrate layer is 2 μm to 15 μm. Within this range, the thickness of the substrate layer can provide good support while maintaining a relatively suitable thickness for the composite current collector as a whole.

[0025] In some embodiments, the thickness of the bonding layer is 0.5 μm to 3 μm. When the thickness of the bonding layer is within this range, a good bonding effect can be achieved while maintaining a relatively suitable thickness of the composite current collector as a whole.

[0026] In some embodiments, the thickness of the conductive layer is 0.5 μm to 5 μm. The thickness of the conductive layer within this range can provide relatively suitable conductivity while maintaining a relatively suitable weight and thickness of the composite current collector.

[0027] In some embodiments, the composite current collector has an elastic modulus of 7.2 GPa to 9.0 GPa. The elastic modulus of the composite current collector within this range can reduce the risk of wrinkling during processing.

[0028] A second aspect of the present application provides a pole piece comprising the composite current collector.

[0029] A third aspect of the present application provides a secondary battery, comprising the pole piece.

[0030] A fourth aspect of the present application provides an electrical device comprising at least one of the composite current collector, the pole piece, and the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0032] FIG1 is a schematic diagram of a composite current collector according to one embodiment of the present application.

[0033] FIG2 is a schematic diagram of a composite current collector according to another embodiment of the present application.

[0034] FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0035] FIG. 4 is an exploded view of the secondary battery shown in FIG. 3 according to one embodiment of the present application.

[0036] FIG5 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0037] Explanation of the accompanying drawings: 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device; 3. Composite current collector; 31. Substrate layer; 311. Pores; 32. First filler; 33. Adhesive layer; 34. Conductive layer; 35. Second filler; 351. Second flame-retardant filler. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] The "ranges" disclosed in this application can be defined in the form of lower limits and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this way can be inclusive or exclusive of the end values, any end value can be included or excluded independently, and can be arbitrarily combined, 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 particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also expected. 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, the following ranges are all expected: 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" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0041] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0044] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, and in some embodiments are performed sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0046] In this application, unless otherwise specified, 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.

[0047] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0048] One embodiment of the present application provides a composite current collector. The composite current collector includes a substrate layer, a first filler, a bonding layer, and a conductive layer. The bonding layer is positioned between the substrate layer and the conductive layer. One end of the first filler is embedded in the substrate layer, and the other end of the first filler is embedded in the bonding layer. The hardness of the first filler is greater than the hardness of the substrate layer, and the hardness of the first filler is greater than the hardness of the bonding layer.

[0049] In the composite current collector of this embodiment, by introducing a first filler with a hardness greater than that of the substrate layer and the bonding layer, and embedding one end of the first filler into the substrate layer and the other end into the bonding layer, the first filler can serve as a fulcrum between the substrate layer and the bonding layer, which is beneficial to improving the elastic modulus of the composite current collector and reducing the risk of wrinkling during the electrode processing.

[0050] In addition, one end of the first filler is embedded in the substrate layer and the other end is embedded in the bonding layer, so that a riveted structure can be formed between the substrate layer, the first filler and the bonding layer, which is beneficial to improving the bonding force between the bonding layer and the substrate layer and improving the structural stability of the composite current collector.

[0051] It will be understood that the hardness in this application refers to Vickers hardness.

[0052] As an illustration of a composite current collector structure, please refer to Figure 1, which shows a composite current collector 3. Composite current collector 3 includes a substrate layer 31, a first filler 32, an adhesive layer 33, and a conductive layer 34. Adhesive layer 33 is located between substrate layer 31 and conductive layer 34. One end of first filler 32 is embedded in substrate layer 31, and the other end of first filler 32 is embedded in adhesive layer 33. The hardness of first filler 32 is greater than that of substrate layer 31, and the hardness of first filler 32 is greater than that of adhesive layer 33.

[0053] It is understood that when preparing a composite current collector, the surface of the substrate layer can be heat-treated to soften or melt the surface of the substrate layer, and then the first filler can be transferred to the surface of the heat-treated substrate layer. Then, pressure can be applied to allow one end of the first filler to be embedded in the substrate layer, while the other end of the first filler is exposed. After one end of the first filler is embedded in the substrate layer, a bonding layer slurry can be transferred to the surface of the substrate layer, and the conductive layer can be transferred to the surface of the slurry. After the slurry is cured, a bonding layer is formed. At this time, the other end of the first filler can be embedded in the bonding layer, and the conductive layer and the bonding layer are composited to form a composite current collector.

[0054] In some embodiments, the first filler is embedded in the substrate layer to a depth of 100 nanometers (nm) to 800 nm. Within this range, the depth of the first filler embedded in the substrate layer can maintain good mechanical properties of the substrate layer, which is beneficial for improving the elastic modulus of the composite current collector. Furthermore, within this range, the depth of the first filler embedded in the substrate layer can maintain good bonding between the substrate layer and the adhesive layer, which is beneficial for maintaining good structural stability of the composite current collector.

[0055] In some embodiments, the Dv50 of the first filler is 150nm to 1500nm. The Dv50 of the first filler within this range can maintain a good riveting effect between the substrate layer and the adhesive layer, promote the improvement of the bonding force between the substrate layer and the adhesive layer, and further promote the composite current collector to maintain good structural stability. Optionally, the Dv50 of the first filler can be 150nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, etc. Further optionally, the Dv50 of the first filler is 200nm to 1000nm. Further optionally, the first filler is granular.

[0056] It is understood that in this application, Dv50 refers to the particle size corresponding to the 50% cumulative particle size distribution in the volume cumulative distribution curve. Its physical meaning is that particles with a smaller (or larger) size account for 50%. As an example, Dv50 can be obtained by referring to the GB / T 19077-2016 test method and using a laser diffraction particle size distribution analyzer Mastersizer3000 to obtain a particle size distribution curve.

[0057] In some embodiments, there are multiple first fillers, and the multiple first fillers are spaced apart. Optionally, the spacing between adjacent first fillers is 5 millimeters (mm) to 50 mm. In this case, the first filler can have a more appropriate distribution density, more fully play the role of the first filler, and enable the composite current collector to maintain good mechanical properties such as elastic modulus and strength. Optionally, the spacing between adjacent first fillers can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, etc.

[0058] As an optional example of the first filler, the first filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide, and a first flame retardant filler. In this case, the first filler has a relatively suitable hardness, which is conducive to promoting the improvement of the elastic modulus of the composite current collector. In addition, when the first filler includes the first flame retardant filler, the flame retardant effect of the composite current collector can be improved. After the composite current collector is applied to the battery, the risk of thermal runaway such as fire and explosion in the battery can be reduced. As an optional example of the first flame retardant filler, the first flame retardant filler includes at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0059] In some embodiments, the composite current collector further includes a second filler. The second filler is located inside the bonding layer. The hardness of the second filler is greater than the hardness of the substrate layer, the hardness of the second filler is greater than the hardness of the bonding layer, and the Dv50 of the second filler is less than the Dv50 of the first filler. By combining the first filler and the second filler with different particle sizes, more fillers can be introduced into the composite current collector, further promoting the improvement of the elastic modulus of the composite current collector. In addition, when the composite current collector further includes a second filler, the second filler can interact with the first filler, further promoting the riveting effect between the substrate layer and the bonding layer, and further improving the bonding force between the substrate layer and the bonding layer.

[0060] In some embodiments, the Dv50 of the second filler is 50 nm to 150 nm. Alternatively, the Dv50 of the second filler can be 145 nm, 140 nm, 130 nm, 120 nm, 110 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, etc.

[0061] In some embodiments, the mass ratio of the second filler to the first filler is (20-50): (50-80). At this time, the first filler and the second filler have a relatively suitable ratio, which can maintain good bonding between the substrate layer and the adhesive layer on the basis of improving the elastic modulus of the composite current collector. Optionally, the mass ratio of the second filler to the first filler can be 20:80, 30:70, 40:60, 50:50, etc. Further optionally, in terms of the mass percentage of the total mass of the first filler and the second filler, the mass percentage of the second filler is 20% to 50%. Further optionally, in terms of the mass percentage of the total mass of the first filler and the second filler, the mass percentage of the second filler can be 20%, 30%, 40%, 50%, etc.

[0062] In some embodiments, the second filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide, and a second flame-retardant filler. In this case, the second filler has a relatively suitable hardness, which helps to improve the elastic modulus of the composite current collector. Furthermore, when the second filler includes a second flame-retardant filler, the flame retardancy of the composite current collector can be improved. When the composite current collector is used in a battery, the risk of thermal runaway, such as fire or explosion, can be reduced.

[0063] Optionally, the second flame-retardant filler accounts for 30% to 50% of the second filler by mass. Within this range, the second flame-retardant filler can further improve the flame-retardant effect of the composite current collector while ensuring a good elastic modulus. Furthermore, the second flame-retardant filler can account for 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, or the like by mass of the second filler. Furthermore, the second flame-retardant filler comprises at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate, and antimony oxide.

[0064] It is understandable that the bonding layer comprises a bonding agent. Alternatively, the bonding agent comprises 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 the polyamide. Alternatively, the isocyanate comprises polyfunctional isocyanate. Alternatively, the bonding layer comprises one or more of the composition and polyurethane containing polyfunctional isocyanate and polyester polyol. Alternatively, the polyurethane comprises one or more of thermoplastic polyurethane and reactive polyurethane.

[0065] In some embodiments, the thickness of the bonding layer is 0.5 micrometers (μm) to 3 μm. The thickness of the bonding layer within this range can maintain a relatively suitable thickness of the composite current collector as a whole on the basis of obtaining a good bonding effect. Alternatively, the thickness of the bonding layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, etc. It will be understood that the thickness of the bonding layer represents the thickness of the bonding layer located between the conductive layer and the substrate layer.

[0066] In some embodiments, the substrate layer is provided with a pore, and the adhesive layer is embedded in the pore. By designing the adhesive layer embedded in the pore, the bonding force between the adhesive layer and the substrate layer can be further improved, and the composite current collector can be promoted to maintain good structural stability. It is understood that the adhesive layer embedded in the pore means that a portion of the adhesive layer is embedded in the pore, that is, a portion of the adhesive layer extends into the pore. Optionally, the adhesive layer extending into the pore completely fills the pore. It is also understood that when the adhesive layer contains a second filler, the portion of the adhesive layer embedded in the pore also contains the second filler.

[0067] In some embodiments, the pore size of the channel is 30 μm to 500 μm. Within this range, the pore size of the channel can maintain good integrity of the substrate layer, maintain relatively stable intrinsic properties of the substrate layer, and thus maintain good mechanical properties, while utilizing the bonding layer embedded in the channel to improve the bonding strength between the bonding layer and the substrate layer. Optionally, the pore size of the channel can be 30 μm, 40 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.

[0068] Optionally, the cross-sectional shape of the duct includes at least one of a circle, an ellipse, and a polygon. It is understood that the cross-sectional shape of the duct represents a cross-section perpendicular to the thickness direction of the substrate layer. It is also understood that when the cross-sectional shape of the duct is a circle, the pore size of the duct represents the diameter of the circle. When the cross-sectional shape of the duct is an ellipse, the pore size of the duct represents the length of the major axis of the ellipse. When the cross-sectional shape of the duct is a polygon, the pore size of the duct represents the length of the longest side of the polygon.

[0069] In some embodiments, there are multiple channels, and the multiple channels are spaced apart. The design of multiple channels is more conducive to promoting the improvement of the bonding force between the substrate layer and the adhesive layer, and the composite current collector can maintain good structural stability. Optionally, the spacing between adjacent channels is 5mm to 50mm. The spacing between adjacent channels within this range can enable the substrate layer to maintain relatively stable intrinsic properties on the basis of providing a suitable number of channels. It is understandable that the spacing between adjacent channels represents the distance between the centers of adjacent channels. Optionally, the spacing between adjacent channels can be 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, etc.

[0070] In some embodiments, the pores include at least one of through-hole pores and blind-hole pores. It is understood that the through-hole pores refer to pores that penetrate the substrate layer in the thickness direction of the substrate layer. On the one hand, the provision of through-hole pores may be beneficial for embedding the bonding layer to improve the bonding strength between the bonding layer and the substrate layer. On the other hand, the pores can be used as exhaust channels, which are beneficial for discharging gases that may be generated during the preparation of the composite current collector. It is understood that the blind-hole pores refer to pores that do not penetrate the substrate layer in the thickness direction of the substrate layer. Optionally, the opening of the blind-hole pores faces the bonding layer. The opening of the blind-hole pores facing the bonding layer may be beneficial for embedding the bonding layer to improve the bonding strength between the bonding layer and the substrate layer. It is also understood that the pores can be prepared on the substrate layer by laser pore making, etching pore making, hot melt pore making, and the like.

[0071] Optionally, the blind via hole depth is 50 nm to 1200 nm. This blind via hole depth range provides a good embedding effect, which helps improve the bonding strength between the adhesive layer and the substrate layer. Optionally, the blind via hole depth can be 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, etc.

[0072] Please refer to Figure 2, which shows a schematic diagram of a composite current collector in one embodiment of the present application. The composite current collector 3 includes a substrate layer 31, a first filler 32, a second filler 35, an adhesive layer 33, and a conductive layer 34. The adhesive layer 33 is located between the substrate layer 31 and the conductive layer 34. One end of the first filler 32 is embedded in the substrate layer 31, and the other end of the first filler 32 is embedded in the adhesive layer 33. The hardness of the first filler 32 is greater than that of the substrate layer 31, and the hardness of the first filler 32 is greater than that of the adhesive layer 33. The second filler 35 is located within the adhesive layer 33. The Dv50 of the second filler 35 is less than that of the first filler 32. The second filler 35 includes a second flame-retardant filler 351. Pores 311 are provided in the substrate layer 31, and the adhesive layer 33 is embedded in the pores 311 of the substrate layer 31. The second filler 35 is distributed in the adhesive layer 33 embedded in the pores 311 of the substrate layer 31. In the embodiment shown in Figure 2, the pores 311 are through-holes.

[0073] In some embodiments, the composite current collector further includes a passivation layer, which is disposed on the surface of the conductive layer. Optionally, the passivation layer comprises at least one of chromate, phosphate, aluminum oxide, silicon dioxide, and silicon nitride. The passivation layer can protect the conductive layer, reduce electrolyte corrosion on the conductive layer, and help improve the structural stability of the composite current collector. Optionally, the passivation layer is located between the conductive layer and the bonding layer. The provision of the passivation layer can maintain a good bonding effect between the conductive layer and the bonding layer after the composite current collector is infiltrated by the electrolyte.

[0074] In some embodiments, the thickness of the substrate layer is 2 μm to 15 μm. Within this range, the thickness of the substrate layer can provide good support while maintaining a relatively suitable thickness for the composite current collector as a whole. Alternatively, the thickness of the substrate layer can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. Optionally, the substrate layer comprises one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their cross-linked products and their copolymers.

[0075] In some embodiments, the thickness of the conductive layer is 0.5 μm to 5 μm. The thickness of the conductive layer can provide a relatively suitable conductivity within this range, so that the composite current collector maintains a relatively suitable weight and thickness. Optionally, the thickness of the conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, etc. Optionally, the conductive layer comprises a metal material. Optionally, the metal material includes at least one of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

[0076] In some embodiments, the elastic modulus of the composite current collector is 7.2 GPa to 9.0 GPa. The elastic modulus of the composite current collector within this range can reduce the risk of wrinkling during processing. Alternatively, the elastic modulus of the composite current collector can be 7.2 GPa, 7.5 GPa, 7.8 GPa, 8 GPa, 8.2 GPa, 8.5 GPa, 8.8 GPa, 9 GPa, etc.

[0077] Another embodiment of the present application provides a pole piece. The pole piece includes the composite current collector described above. It is understood that the pole piece can be a positive pole piece or a negative pole piece.

[0078] Another embodiment of the present application provides a secondary battery. The secondary battery includes the above-mentioned electrode.

[0079] Another embodiment of the present application provides an electrical device, which includes at least one of the composite current collector, the electrode, and the secondary battery.

[0080] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0081] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0082] Positive electrode

[0083] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0084] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0085] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may be the above-mentioned composite current collector. The composite current collector may also 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 may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0086] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), 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. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0087] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0088] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments, the positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side of the positive electrode current collector, and performing drying, cold pressing, and other processes to obtain the positive electrode sheet. The type of solvent can be selected from, but is not limited to, any of the aforementioned 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 both 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 both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40% by weight (wt%) to 80% by weight. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 millipascals·seconds (mPa·s) to 25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm2 (mg / cm 2 )~35mg / cm 2 The compacted density of the positive electrode can be 3.0 g / cm3 (g / cm 3 )~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0090] Negative electrode

[0091] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0092] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0093] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may be the above-mentioned composite current collector. The composite current collector may also 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 a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0094] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0095] In some embodiments, the negative electrode active material layer may further include a binder. The binder may 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).

[0096] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0098] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet 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% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s to 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75 grams per square meter (g / m 2 )~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0099] electrolytes

[0100] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0101] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0102] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0103] In some embodiments, the solvent may 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), butylene carbonate One or more of 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.

[0104] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0105] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0106] Isolation film

[0107] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0108] In some 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.

[0109] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0110] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0111] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0112] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0113] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0114] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0115] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG3 shows a secondary battery 1 with a square structure as an example.

[0116] In some embodiments, referring to Figure 4, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination 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 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to actual needs.

[0117] The secondary battery may be a battery module or a battery pack.

[0118] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0119] In a battery module, multiple battery cells can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Further, the multiple battery cells can be fixed by fasteners.

[0120] Optionally, the battery module may further include a housing having an accommodation space, wherein the plurality of battery cells are accommodated in the accommodation space.

[0121] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0122] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0123] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0124] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0125] Figure 5 shows an example of an electric device 2. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0126] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0127] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0128] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0129] Example 1

[0130] In this embodiment, the composite current collector includes a substrate layer, a first filler, an adhesive layer, and a conductive layer. The adhesive layer is located between the substrate layer and the conductive layer. One end of the first filler is embedded in the substrate layer, and the other end of the first filler is embedded in the adhesive layer. The substrate layer is 6 μm thick PET. The first filler is aluminum oxide with a Dv50 of 300 nm. The adhesive layer is made of modified polypropylene and has a thickness of 1 μm. The conductive layer is made of aluminum and has a thickness of 1 μm.

[0131] The preparation method of the composite current collector in this embodiment includes:

[0132] S101: performing passivation treatment on the metal conductive layer to obtain a chromate passivation layer on the surface of the conductive layer.

[0133] S102: heat-treating the surface of the substrate layer, transferring the first filler to the surface of the substrate layer, and applying pressure so that one end of the first filler is embedded in the substrate layer.

[0134] S103: Apply adhesive layer slurry on the surface of the substrate layer, transfer the metal conductive layer to the surface of the slurry, and age at 80° C. for 72 hours.

[0135] S104: etching and thinning the metal conductive layer to obtain a conductive layer of target thickness.

[0136] Example 2

[0137] Compared with Example 1, this embodiment differs in that the composite current collector further includes a second filler, which is located within the bonding layer. The second filler comprises a sodium chloride flame retardant filler. When preparing the composite current collector, the second filler is dispersed in the slurry so that the second filler in the composite current collector is located within the bonding layer.

[0138] Example 3 to Example 16

[0139] Compared with Example 2, Examples 3 to 16 differ in that through-hole channels are provided on the substrate layer. Specific parameters are shown in Table 1. When preparing the composite current collector, holes are first formed in the substrate layer to obtain through-hole channels, and then operations S102 to S104 are performed.

[0140] Comparative Example 1

[0141] Compared with Example 1, the difference in this comparative example is that the composite current collector does not contain the first filler.

[0142] Table 1

[0143] In Table 1, the unit of Dv50 of the first filler is nm. The unit of Dv50 of the second filler is nm. The spacing between first fillers represents the spacing between adjacent first fillers, and the unit is mm. The embedding depth of the first filler represents the depth to which the first filler is embedded in the substrate layer, and the unit is nm. The mass percentage of the second filler represents the mass percentage of the second filler as a percentage of the total mass of the first filler and the second filler. The mass percentage of the second flame-retardant filler represents the mass percentage of the second flame-retardant filler in the second filler. Whether there is a through-hole channel indicates whether the substrate layer has a through-hole channel. "Yes" indicates that the substrate layer has a through-hole channel. "No" indicates that the substrate layer has no through-hole channel, and there are no blind holes or through-hole channels. The pore size of the pore channel represents the pore size of the through-hole channel, and the unit is μm. The pore spacing represents the spacing between adjacent through-hole channels, and the unit is mm.

[0144] Battery preparation

[0145] (1) Preparation of positive electrode sheets.

[0146] LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiN i0.5 Co 0.2 Mn 0.3 O2 was mixed in a ratio of 17:3 as the positive electrode active material. The positive electrode active material, superconductive carbon black SP as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were dispersed in a solvent of N-methylpyrrolidone (NMP) at a mass ratio of 95:3:2 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on a composite current collector aluminum foil, dried at 85 degrees Celsius (°C), and then cold-pressed. The positive electrode sheets were then die-cut and slit. The composite current collector was the same as that described in the Examples and Comparative Examples.

[0147] (2) Preparation of negative electrode sheets.

[0148] The negative electrode active material graphite, conductive agent acetylene black, thickener sodium hydroxymethyl cellulose, and binder styrene-butadiene rubber were added to the solvent water at a mass ratio of 96:2:1:1 and mixed evenly to form a negative electrode slurry. The negative electrode slurry was evenly coated on the negative electrode current collector, dried at 85°C, and then cold-pressed with a 40-ton pressure using cylindrical cold-pressing rollers at a speed of 20 meters per minute (m / min) and a temperature of 25°C to form the negative electrode sheet.

[0149] (3) The isolation film is made of polypropylene isolation film.

[0150] (4) Preparation of electrolyte.

[0151] LiPF6 was dissolved 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 was 1:2:1), and fluoroethylene carbonate (FEC) was added as an additive to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L, and the mass percentage of FEC was 5 wt%.

[0152] Test Case

[0153] (1) The elastic modulus of the composite current collector was tested by cutting the current collector into 15 mm × 150 mm strips and performing a tensile test using a universal tensile testing machine with a 50 mm gauge length and a tensile speed of 50 mm / min until the test piece broke. The chord slope method was used to calculate the chord slope corresponding to a strain of 0.05% to 0.5%. The results are shown in Table 2.

[0154] (2) Test whether the coating is wrinkled. The test method is: use a one-out-four coating design, observe the coating process, whether the tab is wrinkled, and whether the tab position bulges when winding. If the bulge exceeds 1mm, it is judged to be wrinkled. The results are shown in Table 2.

[0155] (3) Adhesion test: The test method is as follows: After laminating the sample to the non-corona surface of the ethylene-acrylic acid copolymer (EAA) film, 12 μm thick PET is covered on the EAA film, and the film is placed on a heat sealer and laminated at a temperature of 120°C and a pressure of 0.2 MPa. The laminated sample is cut into 100 mm long and 20 mm wide samples, and the non-laminated surface of the conductive layer is attached to a steel plate with 3M double-sided tape; the sample is clamped in the fixture of a tensile testing machine with a spacing of 50 mm and a speed of 300 mm / min. A 180°C peel test is performed, and the peel force is read and converted into Newtons per meter (N / m). Five parallel samples are tested, and the average peel force is finally calculated; the average peel force = the sum of the peel forces of the five test samples / 5. The results are shown in Table 2.

[0156] (4) The battery was subjected to a DCR test. The test method was as follows: a battery cell was adjusted to a 50% SOC state and discharged at a rate of 4 coulombs (C) (corresponding to a discharge current of I) for 30 seconds (s). The voltage difference ΔV before and after the 30-second discharge was recorded. The DCR corresponding to 50% SOC was calculated using the following formula: DCR = ΔV / I. The DCR data for each battery cell was obtained. The results are shown in Table 2.

[0157] (5) The battery was subjected to a cycling test. The test method was to cycle the battery cells at a high temperature of 60°C at a 1C charge and discharge rate until the capacity decayed to 80% of the initial capacity. The number of cycles corresponding to this decay was recorded, which is the corresponding cycling performance of the battery. The results are shown in Table 2.

[0158] (6) The battery was subjected to a needle penetration test. The test method was as follows: After fully charging the battery cell, it was fixed on a fixture and a 3mm diameter high-temperature resistant steel needle was inserted into the battery cell at a speed of 80 mm / s. If smoke, fire, or the explosion-proof valve was opened after the nail penetration, it was judged as a failure. If there was no smoke, fire, or explosion-proof valve opening after the nail penetration, it was judged as a passing rate. A total of 5 parallel sample cells were tested. If the number of cells that passed the needle penetration was x, the passing rate was x / 5*100%. The results are shown in Table 2.

[0159] Table 2

[0160] In Table 2, the unit of elastic modulus is GPa. The unit of adhesive strength is N / m. The unit of cycle number is cycle. The unit of DCR is milliohm (mΩ).

[0161] It can be seen from Table 1 and Table 2 that the elastic modulus of the composite current collectors in Examples 1 to 16 is higher than that in Comparative Example 1, indicating that the addition of the first filler is beneficial to improving the elastic modulus of the composite current collector.

[0162] As can be seen from Examples 1 and 2, the addition of the second filler improves the elastic modulus of the composite current collector and the safety performance of the battery cell. The second filler can increase the elastic modulus of the adhesive layer, thereby improving the elastic modulus of the current collector; at the same time, the flame retardant component in the second filler can improve the safety performance of the battery cell.

[0163] As can be seen from Examples 2 and 3, the presence of pores in the substrate layer is beneficial for improving the elastic modulus and adhesion of the composite current collector. The presence of pores allows bubbles at the interface between the adhesive layer and the substrate layer to be expelled through the pores during the current collector preparation process, thereby making the adhesive layer and the substrate layer more tightly bonded and improving adhesion. Furthermore, the adhesive layer can better leverage the pores, which, combined with the improved adhesion, also leads to a certain improvement in the elastic modulus.

[0164] It can be seen from Examples 5 and 9 to 10 that when the spacing between adjacent first fillers is within an appropriate range, it is beneficial to further improve the elastic modulus of the composite current collector.

[0165] As can be seen from Examples 5, 11, and 12, when the depth of the first filler embedded in the substrate layer is within an appropriate range, it is beneficial to further improve the elastic modulus of the composite current collector. Furthermore, when the depth of the first filler embedded in the substrate layer is greater, the corresponding Dv50 of the first filler is greater, which may reduce the elastic modulus of the composite current collector.

[0166] As can be seen from Examples 5, 13, and 14, when the mass percentage of the second filler is within an appropriate range, it is beneficial to further improve the elastic modulus of the composite current collector. Furthermore, when the mass percentage of the second filler is relatively low, the amount of the second flame-retardant filler used is reduced, which may reduce the needle penetration rate of the battery.

[0167] It can be seen from Examples 5 and 15 that a larger pore size may reduce the elastic modulus of the composite current collector.

[0168] It can be seen from Example 5 and Example 16 that a larger spacing between the pores may reduce the elastic modulus of the composite current collector.

[0169] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A composite current collector, comprising a substrate layer, a first filler, a bonding layer and a conductive layer; the bonding layer is located between the substrate layer and the conductive layer, one end of the first filler is embedded in the substrate layer, the other end of the first filler is embedded in the bonding layer, the hardness of the first filler is greater than the hardness of the substrate layer, and the hardness of the first filler is greater than the hardness of the bonding layer.

2. The composite current collector according to claim 1, wherein: The first filler is embedded in the substrate layer to a depth of 100 nm to 800 nm.

3. The composite current collector according to claim 1 or 2, wherein: There are a plurality of the first fillers, and the plurality of the first fillers are arranged at intervals.

4. The composite current collector according to claim 3, wherein: The distance between adjacent first fillers is 5 mm to 50 mm.

5. The composite current collector according to any one of claims 1 to 4, wherein The Dv50 of the first filler is 150nm to 1500nm.

6. The composite current collector according to any one of claims 1 to 5, wherein: The Dv50 of the first filler is 200nm-1000nm.

7. The composite current collector according to any one of claims 1 to 6, wherein: The first filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide and a first flame retardant filler.

8. The composite current collector according to claim 7, wherein: The first flame retardant filler includes at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate and antimony oxide.

9. The composite current collector according to any one of claims 1 to 8, wherein The composite current collector also includes a second filler, which is located inside the bonding layer, has a hardness greater than that of the substrate layer, has a hardness greater than that of the bonding layer, and has a Dv50 less than that of the first filler.

10. The composite current collector according to claim 9, wherein: The Dv50 of the second filler is 50nm to 150nm.

11. The composite current collector according to claim 9 or 10, wherein: The mass ratio of the second filler to the first filler is (20-50):(50-80).

12. The composite current collector according to any one of claims 9 to 11, wherein: The second filler includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxide, calcium oxide, boehmite, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium sulfate, boron carbide and a second flame retardant filler.

13. The composite current collector according to claim 12, wherein: The mass percentage of the second flame retardant filler to the second filler is 30% to 50%.

14. The composite current collector according to claim 12 or 13, wherein: The second flame retardant filler includes at least one of sodium chloride, sodium acetate, zinc borate, ammonium molybdate, zirconium phosphate and antimony oxide.

15. The composite current collector according to any one of claims 1 to 14, wherein: The adhesive layer includes an adhesive.

16. The composite current collector according to claim 15, wherein: 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.

17. The composite current collector according to any one of claims 1 to 16, wherein: The substrate layer is provided with channels, and the bonding layer is embedded in the channels.

18. The composite current collector according to claim 17, wherein: The pore size of the pores is 30 μm to 500 μm.

19. The composite current collector according to claim 17 or 18, wherein: There are multiple channels, and the multiple channels are arranged at intervals.

20. The composite current collector according to claim 19, wherein: The spacing between adjacent holes is 5 mm to 50 mm.

21. The composite current collector according to any one of claims 17 to 20, wherein: The hole channel includes at least one of a through hole channel and a blind hole channel.

22. The composite current collector according to claim 21, wherein: The depth of the blind hole is 50nm to 1200nm.

23. The composite current collector according to any one of claims 1 to 22, wherein: The composite current collector further includes a passivation layer, and the passivation layer is located on the surface of the conductive layer.

24. The composite current collector according to claim 23, wherein: The passivation layer includes at least one of chromate, phosphate, aluminum oxide, silicon dioxide and silicon nitride.

25. The composite current collector according to any one of claims 1 to 24, wherein: The thickness of the substrate layer is 2 μm to 15 μm.

26. The composite current collector according to any one of claims 1 to 25, wherein: The thickness of the bonding layer is 0.5 μm to 3 μm.

27. The composite current collector according to any one of claims 1 to 26, wherein: The thickness of the conductive layer is 0.5 μm to 5 μm.

28. The composite current collector according to any one of claims 1 to 27, wherein: The elastic modulus of the composite current collector is 7.2 Gpa to 9.0 Gpa.

29. A pole piece, wherein: A composite current collector comprising any one of claims 1 to 28.

30. A secondary battery, wherein: Including the pole piece as described in claim 29.

31. An electrical device, wherein: The invention comprises at least one of the composite current collector according to any one of claims 1 to 28, the pole piece according to claim 29, and the secondary battery according to claim 30.

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