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

Abstract

A composite current collector, an electrode sheet, a secondary battery and an electric device. The composite current collector comprises a substrate layer and an electrically conductive layer, wherein the substrate layer has a first surface and a second surface, which are opposite each other; the electrically conductive layer is arranged on the first surface and / or the second surface; and a hole channel is provided inside the electrically conductive layer. When a battery is in an abnormal working condition and causes the composite current collector to be stressed abnormally, the electrically conductive layer tends to fracture near the hole channel in a timely manner, such that the current transmission inside the current collector is weakened, and the risk of ongoing electrochemical reactions inside the battery under the abnormal working condition is reduced, which is conducive to reducing the risk of thermal runaway of the battery such as fire and explosion, thereby improving the safety performance of the battery.

Description

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

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2023116176116, filed on November 28, 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] Composite current collectors have many advantages over pure metal current collectors. For example, composite current collectors have thinner conductive layers and correspondingly lower weight. With the increasing popularity of secondary batteries, the application range of composite current collectors has also expanded. For traditional composite current collectors, a conductive layer is often formed on the surface of the substrate layer. Compared with pure metal current collectors, although this traditional composite current collector has many advantages, its performance in improving battery thermal runaway problems still needs to be improved.

[0006] Summary of the Invention

[0007] The first aspect of the present application provides a composite current collector, comprising a substrate layer and a conductive layer; the substrate layer has a first surface and a second surface relative to each other; the conductive layer is arranged on the first surface and / or the second surface; and a channel is provided inside the conductive layer.

[0008] The composite current collector described above primarily features pores within the conductive layer. When the battery experiences abnormal operating conditions, resulting in abnormal stress on the composite current collector, the conductive layer readily breaks near the pores, weakening current flow within the current collector and reducing the risk of continued electrochemical reactions within the battery under abnormal operating conditions. This reduces the risk of thermal runaway, such as fire or explosion, and thus improves battery safety.

[0009] In some embodiments, the plurality of channels are spaced apart. This provides more fracture sites. When the battery is in abnormal operating conditions, current flow within the current collector is more promptly reduced, further reducing the risk of thermal runaway, such as fire or explosion.

[0010] In some embodiments, the spacing between adjacent channels is 5 mm to 60 mm. Within this range, the spacing between adjacent channels can maintain relatively stable intrinsic properties of the conductive layer on the basis of providing an appropriate number of channels.

[0011] In some embodiments, the vias include blind vias. Optionally, the blind vias open toward the substrate layer. Openings of the blind vias toward the substrate layer may facilitate embedding of other material layers to improve the bonding strength between the conductive layer and the substrate layer.

[0012] In some embodiments, the blind via has a depth of 30 nm to 500 nm, which can provide a good embedding effect and improve the bonding strength between the conductive layer and the substrate layer.

[0013] In some embodiments, the blind hole channel has a diameter of 5 mm to 50 mm. When the diameter of the blind hole channel is within this range, a suitable number of blind holes can be provided while providing a good embedding effect.

[0014] In some embodiments, the percentage of the blind via area to the cross-sectional area of ​​the conductive layer is 0.5% to 54.5%. Within this range, the percentage of the blind via area to the cross-sectional area of ​​the conductive layer can ensure an appropriate number of blind vias while maintaining relatively stable intrinsic properties of the conductive layer.

[0015] In some embodiments, the cross-section of the blind via includes at least one of a circular shape, an elliptical shape, and a polygonal shape.

[0016] In some embodiments, the channels include through-hole channels. The provision of through-hole channels can facilitate the embedding of other material layers to improve the bonding strength between the conductive layer and the substrate layer. Furthermore, the through-hole channels can serve as exhaust channels, facilitating the removal of gases that may be generated during the preparation of the composite current collector.

[0017] In some embodiments, the through-hole channel has a pore diameter of 30 μm to 500 μm. When the pore diameter of the through-hole channel is within this range, the through-hole channel can have a suitable number and provide a good embedding effect.

[0018] In some embodiments, the percentage of the hole area of ​​the through-hole channel to the cross-sectional area of ​​the conductive layer is 0.001% to 0.484%. The percentage of the hole area of ​​the through-hole channel to the cross-sectional area of ​​the conductive layer within this range can ensure that the number of through-hole channels is appropriate while maintaining relatively stable intrinsic properties of the conductive layer.

[0019] In some embodiments, the cross-section of the through-hole channel includes at least one of a circular shape, an elliptical shape, and a polygonal shape.

[0020] In some embodiments, the through-hole channels include a first through-hole channel and a second through-hole channel, wherein 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 propagation of fractures in the conductive layer from the first through-hole channel to the surrounding area when the battery is in abnormal operating conditions, thereby increasing the fracture rate of the conductive layer and more promptly reducing current transmission within the current collector. The smaller aperture of the second through-hole channel provides a greater number of through-hole channels per unit area of ​​the conductive layer, further facilitating the discharge of gases that may be generated during the preparation of the composite current collector.

[0021] In some embodiments, the ratio of the number of the first through-hole channels to the second through-hole channels is (20-40):(60-80). Within this range, the number of the first through-hole channels to the second through-hole channels can better match the number of the first through-hole channels with larger pore diameters to the number of the second through-hole channels with smaller pore diameters, which is beneficial for further promoting the fracture of the conductive layer and the degassing effect.

[0022] In some embodiments, the pore size of the first through-hole channel is 300 μm to 500 μm. Alternatively, the pore size of the second through-hole channel is 30 μm to 300 μm.

[0023] In some embodiments, the composite current collector further includes a bonding layer located between the substrate layer and the conductive layer. The bonding layer can improve the bonding strength between the substrate layer and the conductive layer, thereby helping to maintain a more stable structure of the composite current collector.

[0024] In some embodiments, the bonding layer includes a main body and a protruding portion, wherein the protruding portion protrudes from the main body and is embedded in the pores. By embedding the protruding portion in the pores of the conductive layer, the contact area between the bonding layer and the conductive layer can be increased, thereby forming a more stable bonding effect between the bonding layer and the conductive layer, further improving the bonding force between the conductive layer and the bonding layer, and further improving the bonding force between the substrate layer and the conductive layer, thereby promoting the improvement of the structural stability of the composite current collector.

[0025] In some embodiments, the thickness of the main body is 0.5 μm to 5 μm. The thickness of the main body within this range can enable the adhesive layer to perform better bonding while maintaining a relatively suitable overall thickness range for the composite current collector.

[0026] 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.

[0027] In some embodiments, the bonding layer contains filler particles. Introducing filler particles into the bonding layer can improve the elastic modulus of the composite current collector, potentially alleviating wrinkling issues during electrode processing.

[0028] In some embodiments, the mass percentage of the filler particles in the bonding layer is 10% to 20%. When the mass percentage of the filler particles in the bonding layer is within this range, the bonding layer can have suitable bonding properties and a suitable elastic modulus.

[0029] In some embodiments, the filler particles have a Dv50 of 30 nm to 500 nm. Filler particles with a particle size distribution within this range can be more evenly dispersed in the bonding layer, promoting further improvement of the elastic modulus of the composite current collector.

[0030] In some embodiments, the filler particles include insulating filler particles. The use of insulating filler particles can reduce the risk of the introduction of filler particles adversely affecting the conductive properties of the composite current collector, thereby helping the composite current collector maintain relatively suitable and stable conductive properties.

[0031] In some embodiments, the filler particles include 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, and boron carbide.

[0032] In some embodiments, the filler particles include first filler particles, one end of which extends into the main body and the other end extends into the raised portion. A portion of the first filler particles is located in the main body of the bonding layer, while another portion is located in the raised portion of the bonding layer. This provides a support site between the conductive layer and the bonding layer, thereby improving the bonding layer's support for the conductive layer and further increasing the elastic modulus of the composite current collector.

[0033] In some embodiments, the Dv50 of the first filler particles is 200 nm to 500 nm.

[0034] In some embodiments, the filler particles further include second filler particles, wherein the Dv50 of the second filler particles is smaller than the Dv50 of the first filler particles. The second filler particles have a smaller particle size distribution and can be more evenly dispersed in the bonding layer, further promoting an improvement in the elastic modulus of the composite current collector. In addition, the second filler particles with a smaller particle size distribution can be better dispersed in the raised portions of the bonding 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 bonding layer and the conductive layer and improving the elastic modulus of the composite current collector.

[0035] In some embodiments, the Dv50 of the second filler particles is 30 nm to 200 nm.

[0036] In some embodiments, the mass ratio of the second filler particles to the first filler particles is (30-50):(50-70). A mass ratio of the second filler particles to the first filler particles within this range can better match the second filler particles to the first filler particles, further improving the elastic modulus of the composite current collector.

[0037] In some embodiments, the adhesive layer includes a flame retardant. The introduction of the flame retardant can improve the flame retardancy of the composite current collector and further reduce the risk of thermal runaway such as fire and explosion in abnormal battery operating conditions.

[0038] In some embodiments, the mass percentage of the flame retardant in the bonding layer is 20% to 40%. The mass percentage of the flame retardant in this range can make the composite current collector have a good flame retardant effect and the bonding layer have good bonding properties.

[0039] 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.

[0040] In some embodiments, the flame retardant includes an organic flame retardant and an inorganic flame retardant, with the organic flame retardant comprising 10% to 20% by weight of the adhesive layer, and the inorganic flame retardant comprising 10% to 20% by weight of the adhesive layer. The organic flame retardant can be better mixed with the adhesive layer based on the principle of like dissolves like. The inorganic flame retardant can provide support for the adhesive layer while also providing flame retardancy.

[0041] In some embodiments, the conductive layer further comprises a passivation layer. The passivation layer protects the conductive layer, reduces electrolyte corrosion on the conductive layer, and improves 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.

[0042] A second aspect of the present application provides a pole piece, wherein the pole piece includes the composite current collector.

[0043] A third aspect of the present application provides a secondary battery, wherein the secondary battery includes the electrode sheet.

[0044] A fourth aspect of the present application provides an electrical device, which includes at least one of the composite current collector, the pole piece, and the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] 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:

[0046] FIG1 is a schematic diagram of a composite current collector according to one embodiment of the present application.

[0047] FIG2 is a schematic diagram of a composite current collector according to another embodiment of the present application.

[0048] FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0049] FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .

[0050] 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.

[0051] Description of reference numerals:

[0052] 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 via; 322. Through via; 33. Adhesive layer; 331. Main body; 332. Raised portion; 34. First filler particles; 35. Second filler particles; 36. Flame retardant. DETAILED DESCRIPTION

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0058] 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.

[0059] 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.

[0060] 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."

[0061] 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.

[0062] 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.

[0063] One embodiment of the present application provides a composite current collector, including a substrate layer and a conductive layer. The substrate layer has a first surface and a second surface relative to each other; the conductive layer is arranged on the first surface and / or the second surface; and a pore is provided inside the conductive layer. In this embodiment, the pores are mainly provided inside the conductive layer. When the battery is in an abnormal operating condition and the composite current collector is subjected to abnormal stress, the conductive layer is likely to break in time near the pore, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal operating conditions. This is conducive to reducing the risk of thermal runaway such as fire and explosion in the battery, thereby improving the safety performance of the battery.

[0064] It is understandable that during the use of the battery, due to the existence of electrochemical reactions, the internal temperature of the battery will reach a certain level. When the battery is operating normally, the temperature inside the battery is maintained at a relatively suitable temperature. However, when the battery is in an abnormal operating 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, and the battery is prone to the risk of thermal runaway such as fire and explosion. When the composite current collector in this embodiment is applied to a battery, when the battery is in an abnormal operating condition and the temperature and pressure rise significantly, the force on the composite current collector will also increase abnormally. When the force on the composite current collector increases abnormally, the conductive layer is likely to break in time near the pores, weakening the current transmission inside the current collector and reducing the risk of continued electrochemical reactions inside the battery under abnormal operating conditions. This helps to reduce the risk of thermal runaway such as fire and explosion in the battery.

[0065] Furthermore, in this embodiment, by providing pores inside the conductive layer, the weight of the composite current collector can be reduced, which may provide a good basis for improving the mass density of the battery.

[0066] In some embodiments, multiple channels are provided, spaced apart. This provides more fracture sites. When the battery is in abnormal operating conditions, current flow within the current collector is more promptly reduced, further reducing the risk of thermal runaway, such as fire or explosion.

[0067] In some embodiments, the spacing between adjacent channels is 5 millimeters (mm) to 60 mm. The spacing between adjacent channels within this range can maintain a relatively stable intrinsic performance of the conductive layer on the basis of providing an appropriate number of channels. It will be understood that the spacing between adjacent channels represents the distance between the centers of adjacent channels. Optionally, the spacing 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.

[0068] In some embodiments, the vias include blind vias. It is understood that blind vias refer to vias that do not penetrate the conductive layer in the thickness direction of the conductive layer. Optionally, the blind vias open toward the substrate layer. Opening the blind vias toward the substrate layer may facilitate embedding other material layers and improve the bonding between the conductive layer and the substrate layer. It is also understood that blind vias can be fabricated in the conductive layer by methods such as laser pore creation, etching pore creation, and hot melt pore creation.

[0069] As some examples of blind via depths, the blind via depth is 30 nanometers (nm) to 500 nm. A blind via depth within this range can provide a good embedding effect, which is beneficial for improving the bonding strength between the conductive layer and the substrate layer. Alternatively, the blind via depth 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.

[0070] As some examples of blind via diameters, the diameter of the blind vias ranges from 5 mm to 50 mm. Within this range, the blind via diameter can provide an appropriate number of blind holes while still providing a good embedding effect. For example, the blind via diameters can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, etc.

[0071] Optionally, the cross-sectional shape of the blind via includes at least one of a circle, an ellipse, and a polygon. It is understood that the cross-sectional shape of the blind via represents a cross-sectional shape perpendicular to the thickness direction of the conductive layer. It is also understood that when the cross-sectional shape of the blind via is a circle, the aperture of the blind via represents the diameter of the circle. When the cross-sectional shape of the blind via is an ellipse, the aperture of the blind via represents the length of the major axis of the ellipse. When the cross-sectional shape of the blind via is a polygon, the aperture of the blind via represents the length of the longest side of the polygon.

[0072] In some embodiments, the percentage of the blind via hole area to the cross-sectional area of ​​the conductive layer is 0.5% to 54.5%. It will be understood that the hole area of ​​the blind via hole represents the area of ​​the cross section of the blind via hole. Alternatively, the percentage of the blind via hole area to 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 blind via hole area to the cross-sectional area of ​​the conductive layer within this range can ensure that the number of blind via holes is appropriate while maintaining relatively stable intrinsic properties of the conductive layer.

[0073] In some embodiments, the pores include through-holes. It is understood that through-holes refer to pores that extend through the conductive layer in the thickness direction of the conductive layer. The provision of through-holes can facilitate the embedding of other material layers to improve the bonding between the conductive layer and the substrate layer. Furthermore, the through-holes can serve as vents, facilitating the removal of gases that may be generated during the preparation of the composite current collector.

[0074] As some examples of through-hole channel pore diameters, the through-hole channel pore diameter is 30 micrometers (μm) to 500 μm. The through-hole channel pore diameter within this range can have an appropriate number of through holes while providing a good embedding effect. For example, the through-hole channel pore diameter 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.

[0075] Optionally, the cross-sectional shape of the through-hole channel includes at least one of a circle, an ellipse, and a polygon. It is understood that the cross-sectional shape of the through-hole channel represents a cross-sectional shape perpendicular to the thickness direction of the conductive layer. It is also understood that when the cross-sectional shape of the through-hole channel is a circle, the aperture of the through-hole channel represents the diameter of the circle. When the cross-sectional shape of the through-hole channel is an ellipse, the aperture of the through-hole channel represents the length of the major axis of the ellipse. When the cross-sectional shape of the through-hole channel is a polygon, the aperture of the through-hole channel represents the length of the longest side of the polygon.

[0076] In some embodiments, the percentage of the hole area of ​​the through-hole channel to the cross-sectional area of ​​the conductive layer is 0.001% to 0.484%. It will be understood that the hole area of ​​the through-hole channel represents the area of ​​the cross-sectional area of ​​the through-hole channel. The percentage of the hole area of ​​the through-hole channel to the cross-sectional area of ​​the conductive layer within this range can make the through-hole channel have an appropriate number while maintaining relatively stable intrinsic properties of the conductive layer. Optionally, the percentage of the hole area of ​​the through-hole channel to 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.

[0077] Please refer to Figure 1, which shows a schematic structure of the composite current collector 3 in one embodiment of the present application. The composite current collector 3 includes a substrate layer 31 and a conductive layer 32. The substrate layer 31 has a first surface and a second surface relative to each other. A conductive layer 32 is provided on both the first surface and the second surface. A pore is provided inside the conductive layer 32. Furthermore, the pore includes a blind hole 321 and a through hole 322. The opening of the blind hole 321 faces the substrate layer 31. After the composite current collector 3 in this embodiment is applied to the battery, when the battery is in an abnormal operating condition and the composite current collector is subjected to abnormal force, the conductive layer is likely to break in time near the pore, weakening the current transmission inside the current collector and reducing the risk of continuous electrochemical reactions inside the battery under abnormal operating conditions. This is conducive to reducing the risk of thermal runaway such as fire and explosion in the battery, thereby improving the safety performance of the battery.

[0078] In some embodiments, the through-hole channels include a first through-hole channel and a second through-hole channel, wherein 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 propagation of fractures in the conductive layer from the first through-hole channel to the surrounding area when the battery is in abnormal operating conditions, thereby increasing the fracture rate of the conductive layer and more promptly reducing current transmission within the current collector. The smaller aperture of the second through-hole channel provides a greater number of through-hole channels per unit area of ​​the conductive layer, further facilitating the discharge of gases that may be generated during the preparation of the composite current collector.

[0079] In some embodiments, the ratio of the number of the first through-hole channels to the second through-hole channels is (20-40):(60-80). Within this range, the number of the first through-hole channels to the second through-hole channels can be better adapted to the number of the first through-hole channels with larger pore diameters and the second through-hole channels with smaller pore diameters, which is beneficial to further promote the effect of breaking the conductive layer and venting. Optionally, the ratio of the number of the first through-hole channels to the second through-hole channels can be 20:80, 25:75, 30:70, 35:65, 40:60, etc.

[0080] In some embodiments, the pore size of the first through-hole channel is 300 μm to 500 μm. Alternatively, the pore size of the first through-hole channel can be 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 420 μm, 450 μm, 480 μm, 500 μm, etc.

[0081] In some embodiments, the pore size of the second through hole channel is 30 μm to 300 μm. Alternatively, the pore size of the second through hole channel can be 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, etc.

[0082] In some embodiments, the composite current collector further comprises a bonding layer, which is positioned between the substrate layer and the conductive layer. The provision of the bonding layer can improve the bonding strength between the substrate layer and the conductive layer, thereby facilitating a more stable structure of the composite current collector. It is understood that the bonding layer can be prepared by applying a bonding slurry and then curing it.

[0083] In some embodiments, the adhesive layer includes a main body and a protruding portion, wherein the protruding portion protrudes from the main body and is embedded in the pores. By embedding the protruding portion in the pores of the conductive layer, the contact area between the adhesive layer and the conductive layer can be increased, thereby forming a more stable bonding effect between the adhesive layer and the conductive layer, further improving the bonding force between the conductive layer and the adhesive layer, and further improving the bonding force between the substrate layer and the conductive layer, thereby promoting the improvement of the structural stability of the composite current collector.

[0084] It is understandable that the main body and the protrusion can be made of the same material. It is also understandable that the main body and the protrusion can be an integrally formed structure.

[0085] In some embodiments, the thickness of the main body is 0.5 μm to 5 μm. This thickness allows the adhesive layer to perform well while maintaining a suitable overall thickness for the composite current collector. Alternatively, the thickness of the main body 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.

[0086] In some embodiments, the protrusions correspond to the pores of the conductive layer one by one, and the protrusions completely fill the pores of the conductive layer.

[0087] 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.

[0088] In some embodiments, the bonding layer contains filler particles. Introducing filler particles into the bonding layer can improve the elastic modulus of the composite current collector, potentially mitigating wrinkling issues during electrode processing. It is understood that the filler particles are dispersed throughout the main portion and protrusions of the bonding layer.

[0089] Optionally, the mass percentage of the filler particles in the bonding layer is 10% to 20%. Within this range, the mass percentage of the filler particles in the bonding layer can provide the bonding layer with suitable bonding properties and a suitable elastic modulus. Further, optionally, the mass percentage of the filler particles in the bonding layer can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0090] Optionally, the filler particles have a Dv50 of 30 nm to 500 nm. Filler particles with a particle size distribution within this range can be more evenly dispersed in the adhesive layer, promoting further improvement in the elastic modulus of the composite current collector. Further optionally, the filler particles can have a Dv50 of 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.

[0091] 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.

[0092] In some embodiments, the filler particles include insulating filler particles. The use of insulating filler particles can reduce the risk of the introduction of filler particles adversely affecting the conductive properties of the composite current collector, thereby helping the composite current collector maintain relatively suitable and stable conductive properties.

[0093] In some embodiments, the filler particles include inorganic filler particles. Alternatively, the filler particles include 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, and boron carbide.

[0094] In some embodiments, the filler particles include first filler particles, one end of the first filler particles extends into the main body, and the other end extends into the raised portion. In this case, a portion of the first filler particles is located in the main body of the bonding layer, and the other portion is located in the raised portion of the bonding layer. This can provide a support site between the conductive layer and the bonding layer, which is beneficial for improving the support force of the bonding layer on the conductive layer and further improving the elastic modulus of the composite current collector. Optionally, the Dv50 of the first filler particles is 200nm to 500nm. For example, the Dv50 of the first filler particles can be 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 380nm, 400nm, 420nm, 450nm, 480nm, 500nm, etc.

[0095] In some embodiments, the filler particles further include second filler particles, and the Dv50 of the second filler particles is smaller than the Dv50 of the first filler particles. The second filler particles have a smaller particle size distribution and can be more evenly dispersed in the bonding layer, further promoting the improvement of the elastic modulus of the composite current collector. In addition, the second filler particles with a smaller particle size distribution can be better dispersed in the protrusions of the bonding layer, that is, the second filler particles can be better dispersed in the pores of the conductive layer, which is beneficial to improve the mutual support between the bonding layer and the conductive layer and enhance the elastic modulus of the composite current collector. Optionally, the Dv50 of the second filler particles is 30nm to 200nm. Further optionally, the Dv50 of the second filler particles can be 30nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, etc.

[0096] In some embodiments, the mass ratio of the second filler particles to the first filler particles is (30-50):(50-70). Within this range, the mass ratio of the second filler particles to the first filler particles can better match the second filler particles and further improve the elastic modulus of the composite current collector.

[0097] In some embodiments, the adhesive layer contains a flame retardant. The inclusion of the flame retardant can improve the flame retardancy of the composite current collector, further reducing the risk of thermal runaway, such as fire or explosion, in the battery under abnormal operating conditions. It is understood that the flame retardant is dispersed throughout the main body and raised portions of the adhesive layer.

[0098] Optionally, the mass percentage of the flame retardant in the bonding layer is 20% to 40%. Within this mass percentage range, the composite current collector exhibits a good flame retardant effect while also providing the bonding layer with good bonding properties. Furthermore, the mass percentage of the flame retardant in the bonding layer can be 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0099] In some embodiments, the flame retardant includes a granular flame retardant. The granular flame retardant can not only play a flame retardant role, but also play a corresponding supporting role for the adhesive layer, which is beneficial to improving the elastic modulus of the composite current collector.

[0100] 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.

[0101] In some embodiments, the flame retardant includes an organic flame retardant and an inorganic flame retardant. The organic flame retardant can be better mixed with the adhesive layer based on the principle of like dissolves like. The inorganic flame retardant can provide flame retardancy while also providing support for the adhesive layer. Optionally, the organic flame retardant accounts for 10% to 20% by weight of the adhesive layer, and the inorganic flame retardant accounts for 10% to 20% by weight of the adhesive layer. Furthermore, the organic flame retardant can account for 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or the like by weight of the adhesive layer. Furthermore, the inorganic flame retardant can account for 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or the like by weight of the adhesive layer.

[0102] Please refer to Figure 2, which shows a schematic structure of a composite current collector 3 according to one embodiment of the present application. The composite current collector 3 includes a substrate layer 31 and a conductive layer 32. The substrate layer 31 has a first surface and a second surface facing each other. A conductive layer 32 is provided on both the first and second surfaces. The conductive layer 32 has channels disposed within it. There are multiple channels, spaced apart. These channels include blind channels and through channels. The composite current collector 3 also includes an adhesive layer 33, which is positioned between the substrate layer 31 and the conductive layer 32. The adhesive layer 33 includes a main portion 331 and a protrusion 332, which protrudes from the main portion 331 and is embedded within the channels. The adhesive layer 33 contains filler particles. The filler particles are dispersed in the main portion 331 and the protrusion 332 of the adhesive layer 33. The filler particles include first filler particles 34, one end of which extends into the main portion 331 and the other end into the protrusion 332. The filler particles further include second filler particles 35 , wherein the Dv50 of the second filler particles 35 is smaller than the Dv50 of the first filler particles 34 . The bonding layer includes a flame retardant 36 . The flame retardant 36 is dispersed in the main body portion 331 and the raised portion 332 of the bonding layer 33 .

[0103] In some embodiments, the surface of the conductive layer further includes a passivation 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, reducing electrolyte corrosion on the conductive layer, and thus improving 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 bond between the conductive layer and the bonding layer after the composite current collector is infiltrated with the electrolyte.

[0104] In some embodiments, the conductive layer comprises a metal material. Optionally, the metal material comprises at least one of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium, and tin.

[0105] In some embodiments, 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.

[0106] Another embodiment of the present application provides a pole piece, which includes the composite current collector.

[0107] Another embodiment of the present application provides a secondary battery. The secondary battery includes the above-mentioned electrode.

[0108] 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.

[0109] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0110] 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.

[0111] Positive electrode

[0112] 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.

[0113] 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.

[0114] 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 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 may 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.

[0115] 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 Co0.2 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.

[0116] 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.

[0117] 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.

[0118] 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 .

[0119] Negative electrode

[0120] 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.

[0121] 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.

[0122] 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 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 may 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.

[0123] 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.

[0124] 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).

[0125] 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.

[0126] 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)).

[0127] 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 .

[0128] electrolytes

[0129] 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.

[0130] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0131] 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).

[0132] 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.

[0133] 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.

[0134] 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.

[0135] Isolation film

[0136] 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.

[0137] 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.

[0138] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0139] 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.

[0140] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0141] 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.

[0142] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] The secondary battery may be a battery module or a battery pack.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] Example 1

[0159] The preparation method of the composite current collector in this embodiment includes:

[0160] S101: etching holes on the surface of the aluminum foil to form blind holes and through holes, and passivating the aluminum foil.

[0161] S102: Casting PET onto the etched surface of the aluminum foil.

[0162] S103: etching another aluminum foil surface to form blind holes and through holes, passivating the aluminum foil, and covering the aluminum foil on the PET surface so that the etched surface of the aluminum foil contacts the PET.

[0163] S104: hot pressing the product obtained in S103 to form a composite structure of aluminum foil and PET substrate layer, and then aging for 72 hours (h).

[0164] S105: etching and thinning the aluminum foil.

[0165] Example 2

[0166] The preparation method of the composite current collector in this embodiment includes:

[0167] S101: etching holes on the surface of the aluminum foil to form blind holes and through holes, and passivating the aluminum foil.

[0168] S102: Applying a bonding slurry to the surface of the aluminum foil, drying it, and then laminating the PET substrate layer to the surface of the bonding slurry. The bonding slurry includes a binder, filler particles, and a flame retardant.

[0169] S103: hot pressing the product obtained in S102 to form a composite structure of aluminum foil, adhesive layer and PET substrate layer, and then aging for 72 hours.

[0170] S104: etching the surface of another piece of aluminum foil to form blind holes and through holes, and passivating the aluminum foil.

[0171] S105: Applying a bonding slurry to the surface of the aluminum foil, drying it, and then laminating the product obtained in S103 to the surface of the bonding slurry so that the PET substrate layer is in contact with the bonding slurry. The bonding slurry includes a binder modified polypropylene, filler particles of aluminum oxide, and a flame retardant decabromodiphenyl ether.

[0172] S106: hot pressing the product obtained in S105 to form a composite structure of aluminum foil, adhesive layer and PET substrate layer, and then aging for 72 hours.

[0173] S107: etching and thinning the aluminum foil.

[0174] Example 3 to Example 24

[0175] Compared with Example 2, the differences between Examples 3 to 24 are that the blind vias, through vias, filling particles, and flame retardants are different, as shown in Table 1.

[0176] Comparative Example 1

[0177] Compared with Example 1, the difference of this comparative example is that the aluminum foil is not subjected to etching and pore-forming treatment.

[0178] Comparative Example 2

[0179] Compared with Example 2, the difference of this comparative example is that the aluminum foil is not pore-formed, and the bonding slurry does not contain filler particles and flame retardant particles.

[0180] Table 1

[0181] In Table 1, the unit of the blind via hole diameter is mm. The unit of the blind via hole depth is nm. The unit of the blind via hole spacing is mm. The unit of the second through hole hole diameter is μm. The unit of the first through hole hole diameter is μm. The unit of the through hole hole spacing is mm. The unit of the Dv50 of the second filler particle is nm. The unit of the Dv50 of the first filler particle is nm.

[0182] Battery preparation

[0183] (1) Preparation of positive electrode sheets.

[0184] LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.5 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.

[0185] (2) Preparation of negative electrode sheets.

[0186] 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.

[0187] (3) The isolation film is made of polypropylene isolation film.

[0188] (4) Preparation of electrolyte.

[0189] 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%.

[0190] Test Case

[0191] (1) The elastic modulus of the composite current collector was tested. The test method was as follows: the current collector was cut into 15 mm × 150 mm strips and subjected to a tensile test using a universal tensile testing machine with a gauge length of 50 mm and a tensile speed of 50 mm / min until the test fracture. The chord slope method was used to calculate the chord slope corresponding to a strain of 0.1% to 1%; E = (σ2 - σ1) / (ε2 - ε1), where E is the elastic modulus, σ1 is the stress measured at a strain value of ε1 = 0.001 (0.1%), in gigapascals (GPa), and σ2 is the stress measured at a strain value of ε2 = 0.01 (1%), in GPa. The results are shown in Table 2.

[0192] (2) The peel strength of the conductive layer in the composite current collector was tested. The test method was as follows: After laminating the sample to the non-corona surface of the ethylene-acrylic acid copolymer (EAA) film, a 12 μm thick PET film was covered on the EAA film. The film was placed on a heat sealer and laminated at a temperature of 120°C and a pressure of 0.2 MPa. The laminated sample was cut into 100 mm long and 20 mm wide samples. The non-laminated surface of the conductive layer was attached to a steel plate using 3M double-sided tape. The sample was clamped in the fixture of a tensile testing machine with a spacing of 50 mm and a speed of 300 mm / min. A 180° peel test was performed. The peel force was read and converted into Newtons per meter (N / m). Five parallel samples were tested and the average peel force was 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.

[0193] (3) Testing the coating for wrinkles: Using a one-out-four coating design, observe the coating process to see if the tabs are wrinkled and if the tabs bulge during winding. Wrinkles are considered if the bulge exceeds 1 mm. The results are shown in Table 2.

[0194] (4) 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 broken after the nail penetration, it was judged as a failure. If there was no smoke, fire, or explosion-proof valve breaking 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.

[0195] (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, charging at a rate of 1 Coulomb (C) and discharging at a rate of 1C, 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.

[0196] (6) The battery was subjected to a DCR test. The test method was as follows: a battery cell was adjusted to a 50% SOC state, discharged at a rate of 4C (corresponding to a discharge current of I) for 30 seconds, and 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, and the DCR data for each battery cell was obtained. The results are shown in Table 2.

[0197] Table 2

[0198] In Table 2, the unit of the current collector elastic modulus is GPa. The unit of the conductive layer peel strength is N / m. The unit of the number of cycles is cycles. The unit of DCR is milliohm (mΩ).

[0199] As can be seen from Tables 1 and 2, the needle penetration rates of the batteries in Examples 1 to 24 are higher than those of the batteries in Comparative Examples 1 and 2. This indicates that the provision of pores within the conductive layer of the composite current collector can improve battery safety.

[0200] As can be seen from Examples 2 to 16, when the blind via diameter, blind via depth, blind via spacing, second through-hole diameter, first through-hole diameter, through-hole spacing, second through-hole to first through-hole ratio, Dv50 of the second filler particles, Dv50 of the first filler particles, mass ratio of the second filler particles to the first filler particles, mass percentage of the filler particles in the adhesive layer, mass percentage of the organic flame retardant in the adhesive layer, and mass percentage of the inorganic flame retardant in the adhesive layer are within the corresponding appropriate ranges, the corresponding tests can produce good results. For example, the composite current collector has a high elastic modulus, a high peel strength of the conductive layer, no wrinkling during coating, a high needle penetration rate of the battery, a large number of cycles, and a low DCR.

[0201] Comparing Example 17 with Example 3 shows that when the conductive layer lacks through-holes, the elastic modulus of the current collector decreases. This is likely due to the reduced support between the conductive layer and the adhesive layer, which reduces the elastic modulus. The peel strength of the conductive layer decreases, which is likely due to the difficulty of gases generated during the composite current collector preparation being discharged through the through-holes in a timely manner. The needle penetration rate decreases, which is likely due to the reduced trigger points for the conductive layer to break, making it difficult for the conductive layer to break in time, thus reducing the needle penetration rate.

[0202] Comparing Example 18 with Example 3 shows that when the conductive layer lacks blind vias, the elastic modulus of the current collector decreases, likely due to the reduced support between the conductive layer and the adhesive layer. The peel strength of the conductive layer decreases, likely due to the reduced contact area between the adhesive layer and the conductive layer. The needle penetration rate decreases, likely due to the reduced number of fracture sites in the conductive layer, making it difficult for the conductive layer to rupture in time, resulting in a lower needle penetration rate.

[0203] It can be seen from Example 19 and Example 3 that when the depth of the blind via is large, the conductivity of the conductive layer may decrease, thereby resulting in a decrease in the number of cycles and an increase in DCR.

[0204] As can be seen from Examples 20 and 3, a larger pore size of the first through-hole channel may reduce the mechanical properties of the conductive layer, leading to wrinkling during coating. Furthermore, a larger pore size of the first through-hole channel may reduce the conductivity of the conductive layer, resulting in a reduced number of cycles and an increased DCR.

[0205] It can be seen from Example 21 and Example 3 that when the spacing between the through-hole channels is large, the through-hole channels are arranged more sparsely, which reduces the trigger points for the conductive layer to break, thereby reducing the needle penetration rate.

[0206] It can be seen from Example 22 and Example 3 that when the pitch of the through-hole channels is small, the through-hole channels are arranged more densely, which may affect the conductive performance of the conductive layer, thereby reducing the number of cycles and increasing the DCR.

[0207] As can be seen from Examples 23, 24, and 3, when the first or second filler particles are absent, the elastic modulus decreases, the coating wrinkles, and the needle punch pass rate decreases. This is likely due to insufficient filling by the filler particles, resulting in a reduced elastic modulus and wrinkling. Furthermore, insufficient filling by the filler particles may reduce the flame retardant effect, leading to a decrease in the needle punch pass rate.

[0208] 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.

[0209] 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 and a conductive layer; the substrate layer has a first surface and a second surface opposite to each other; the conductive layer is arranged on the first surface and / or the second surface; and a pore is arranged inside the conductive layer.

2. The composite current collector according to claim 1, wherein: There are multiple channels, and the multiple channels are arranged at intervals.

3. The composite current collector according to claim 2, wherein: The spacing between adjacent channels is 5 mm to 60 mm.

4. The composite current collector according to any one of claims 1 to 3, wherein The channels include blind channels.

5. The composite current collector according to claim 4, wherein: The opening of the blind via is toward the substrate layer.

6. The composite current collector according to claim 4 or 5, wherein: The depth of the blind hole is 30nm to 500nm.

7. The composite current collector according to any one of claims 4 to 6, wherein: The blind hole has a diameter of 5 mm to 50 mm.

8. The composite current collector according to any one of claims 4 to 7, wherein: The percentage of the hole area of ​​the blind via to the cross-sectional area of ​​the conductive layer is 0.5% to 54.5%.

9. The composite current collector according to any one of claims 4 to 8, wherein The cross-section of the blind hole includes at least one of a circular shape, an elliptical shape and a polygonal shape.

10. The composite current collector according to any one of claims 1 to 9, wherein: The channels include through-hole channels.

11. The composite current collector according to claim 10, wherein: The pore diameter of the through hole is 30 μm to 500 μm.

12. The composite current collector according to claim 10 or 11, wherein: The percentage of the hole area of ​​the through hole channel to the cross-sectional area of ​​the conductive layer is 0.001% to 0.484%.

13. The composite current collector according to any one of claims 10 to 12, wherein: The cross-sectional shape of the through hole includes at least one of a circle, an ellipse and a polygon.

14. The composite current collector according to any one of claims 10 to 13, wherein: The through-hole channel comprises a first through-hole channel and a second through-hole channel, and the aperture of the first through-hole channel is larger than the aperture of the second through-hole channel.

15. The composite current collector according to claim 14, wherein: The ratio of the number of the first through-hole channels to the number of the second through-hole channels is (20-40):(60-80).

16. The composite current collector according to claim 14 or 15, wherein: The aperture of the first through hole is 300 μm to 500 μm.

17. The composite current collector according to any one of claims 14 to 16, wherein: The pore size of the second through hole is 30 μm to 300 μm.

18. The composite current collector according to any one of claims 1 to 17, wherein: The composite current collector further includes a bonding layer, and the bonding layer is located between the substrate layer and the conductive layer.

19. The composite current collector according to claim 18, wherein: The bonding layer includes a main body and a protruding portion, wherein the protruding portion protrudes from the main body and is embedded in the hole.

20. The composite current collector according to claim 19, wherein: The thickness of the main body is 0.5 μm to 5 μm.

21. The composite current collector according to any one of claims 18 to 20, wherein: The adhesive layer includes an adhesive.

22. The composite current collector according to claim 21, 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.

23. The composite current collector according to any one of claims 18 to 22, wherein: The tie layer comprises filler particles.

24. The composite current collector according to claim 23, wherein: The mass percentage of the filler particles in the bonding layer is 10% to 20%.

25. The composite current collector according to claim 23 or 24, wherein: The Dv50 of the filler particles is 30nm to 500nm.

26. The composite current collector according to any one of claims 23 to 25, wherein: The filler particles include insulating filler particles.

27. The composite current collector according to any one of claims 23 to 26, wherein: The filler particles include 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, and boron carbide.

28. The composite current collector according to any one of claims 23 to 27, 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 of the first filler particles extends into the protrusion portion.

29. The composite current collector according to claim 28, wherein: The Dv50 of the first filler particles is 200nm to 500nm.

30. The composite current collector according to claim 28 or 29, wherein: The filler particles further include second filler particles, the Dv50 of the second filler particles being smaller than the Dv50 of the first filler particles.

31. The composite current collector according to claim 30, wherein: The Dv50 of the second filler particles is 30 nm to 200 nm.

32. The composite current collector according to claim 30 or 31, wherein: The mass ratio of the second filler particles to the first filler particles is (30-50):(50-70).

33. The composite current collector according to any one of claims 18 to 32, wherein: The tie layer includes a flame retardant.

34. The composite current collector according to claim 33, wherein: The mass percentage of the flame retardant in the bonding layer is 20% to 40%.

35. The composite current collector according to claim 33 or 34, wherein: 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.

36. The composite current collector according to any one of claims 33 to 35, wherein: The flame retardant comprises an organic flame retardant and an inorganic flame retardant, the mass percentage of the organic flame retardant in the bonding layer is 10% to 20%, and the mass percentage of the inorganic flame retardant in the bonding layer is 10% to 20%.

37. The composite current collector according to any one of claims 1 to 36, wherein: The surface of the conductive layer also includes a passivation layer.

38. The composite current collector according to claim 37, wherein: The passivation layer includes at least one of chromate, phosphate, aluminum oxide, silicon dioxide and silicon nitride.

39. A pole piece comprising the composite current collector according to any one of claims 1 to 38.

40. A secondary battery comprising the electrode sheet according to claim 39.

41. An electrical device comprising at least one of the composite current collector according to any one of claims 1 to 38, the pole piece according to claim 39, and the secondary battery according to claim 40.

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