Composite current collector, electrode plate, secondary battery, and electrical apparatus

Abstract

A composite current collector, an electrode plate, a secondary battery, and an electrical apparatus. The composite current collector comprises a polymer support layer, a bonding layer, and a conductive layer. The bonding layer is disposed on at least one surface of the polymer support layer, and the bonding layer comprises polyimide, inorganic particles and a binder. The conductive layer is disposed on a surface of the bonding layer facing away from the polymer support layer. The composite current collector has relatively high elongation at break and tensile modulus; when an active material layer is coated on the composite current collector and dried, a tab region does not easily crack or shrink.

Description

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

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202311587415.9 filed on November 24, 2023, entitled "Composite current collector, electrode plate, secondary battery and electrical device", which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a composite current collector, an electrode plate, 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] In recent years, as the application scope of secondary batteries has become increasingly wider, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0006] As secondary batteries have made significant progress, higher demands have been placed on their energy density and safety. Composite current collectors are more advantageous than conventional current collectors such as copper foil and aluminum foil in improving battery energy density and safety. However, existing composite current collectors suffer from low elongation at break, low tensile modulus, and susceptibility to wrinkling and shrinkage, which impacts subsequent manufacturing processes and battery performance.

[0007] Therefore, seeking a composite current collector with high elongation at break and tensile modulus and not prone to wrinkling and shrinkage is one of the key areas of focus for those skilled in the art.

[0008] Summary of the Invention

[0009] The present application is made in view of the above-mentioned problems, and one of its purposes is to provide a composite current collector having high elongation at break and tensile modulus and being less prone to wrinkling and shrinkage.

[0010] In order to achieve the above objectives, the first aspect of the present application provides a composite current collector, comprising:

[0011] a polymer support layer;

[0012] a bonding layer disposed on at least one surface of the polymer support layer, the bonding layer comprising polyimide, inorganic particles and a binder; and

[0013] The conductive layer is disposed on the surface of the adhesive layer facing away from the polymer support layer.

[0014] The above-mentioned composite current collector of the present application is a composite of a conductive layer and a polymer support layer through an adhesive layer, and the adhesive layer includes polyimide, inorganic particles and a binder; through the mutual cooperation of the polyimide and inorganic particles in the adhesive layer, the tensile modulus of the composite current collector can be effectively improved, and the wrinkling and shrinkage at the pole ear of the composite current collector after the active material layer is coated and dried can be alleviated. In addition, the composite current collector is different from the traditional composite current collector that directly forms a conductive layer on the polymer support layer by evaporation or magnetron sputtering. The conductive layer in the composite current collector can be composited with the polymer support layer by coating the adhesive layer, so there is no problem of large thermal damage to the polymer support layer caused by evaporation or magnetron sputtering, so the composite current collector can have a higher elongation at break.

[0015] In any embodiment, the mass fraction of polyimide in the bonding layer is 30% to 70%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of the binder is 20% to 60%. In this way, the composite current collector can have a higher tensile modulus.

[0016] In any embodiment, the mass fraction of polyimide in the bonding layer is 30% to 55%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of the binder is 35% to 60%. This can further increase the tensile modulus of the composite current collector, further alleviate wrinkling and shrinkage at the tabs of the composite current collector, and at the same time, provide a greater peel force between the conductive layer and the polymer support layer.

[0017] In any embodiment, the thickness of the adhesive layer is 600 nm to 2000 nm, and optionally 800 nm to 1500 nm. This can further improve the tensile modulus of the composite current collector, alleviate wrinkling and shrinkage at the tab, and provide a greater peeling force between the conductive layer and the polymer support layer.

[0018] In any embodiment, the tie layer comprises:

[0019] a first sub-bonding layer, disposed on at least one surface of the polymer support layer, the first sub-bonding layer comprising polyimide, inorganic particles and a binder; and

[0020] The second sub-bonding layer is arranged on the surface of the first sub-bonding layer away from the polymer support layer. The conductive layer is arranged on the surface of the second sub-bonding layer away from the first sub-bonding layer. The second sub-bonding layer includes a binder.

[0021] In this way, the peeling force between the conductive layer and the polymer support layer can be further improved, and the overall tensile modulus of the composite current collector can be further improved, thereby further alleviating the wrinkling and shrinkage at the tab.

[0022] In any embodiment, the mass fraction of polyimide in the first sub-adhesive layer is 60% to 70%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of binder is 20% to 30%. This can significantly improve the tensile modulus of the composite current collector, effectively alleviate wrinkling and shrinkage at the tab, and enhance the peel strength between the conductive layer and the polymer support layer.

[0023] In any embodiment, the thickness of the first sub-adhesive layer is 500 nm to 1500 nm, and can be optionally 600 nm to 1200 nm, so as to better improve the tensile modulus of the composite current collector and enhance the reliability of the tab welding of the composite current collector.

[0024] In any embodiment, the thickness of the second sub-adhesive layer is 300 nm to 700 nm. This can further enhance the peeling force between the conductive layer and the polymer support layer, while also providing the composite current collector with better tab welding reliability.

[0025] In any embodiment, the inorganic particles include one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide, and graphene. Thus, the inorganic particles can cooperate with the polyimide to effectively enhance the strength of the composite current collector, and the inorganic particles do not react with the electrolyte.

[0026] In any embodiment, the binder includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, 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. The above-mentioned binder can provide good bonding between the polymer support layer and the conductive layer, resulting in a strong peeling force between the conductive layer and the polymer support layer.

[0027] In any embodiment, the composite current collector further includes a passivation layer disposed between the adhesive layer and the conductive layer, thereby providing passivation protection at the interface between the conductive layer and the adhesive layer, thereby reducing micro-corrosion of the conductive layer by the electrolyte.

[0028] In any embodiment, the material of the passivation layer includes one or more of chromate, dichromate, organic phosphonate, Al2O3, SiO2 and Si3N4.

[0029] In any embodiment, the chromate includes one or more of sodium chromate, potassium chromate, magnesium chromate, and silver chromate; the dichromate includes one or more of sodium dichromate, potassium dichromate, magnesium dichromate, and silver dichromate; the organic phosphonate includes one or more of hydroxyethane diphosphonic acid, diethylenetriamine pentamethylenephosphonic acid, triethylenetetramine hexamethylenephosphonic acid, and ethylenediamine tetramethylenephosphonic acid. The above passivation materials can play a good passivation and protection role on the conductive layer, effectively alleviating the micro-corrosion of the conductive layer by the electrolyte.

[0030] In any embodiment, the thickness of the passivation layer is 1 nm to 500 nm, and may be selected as 10 nm to 200 nm. In this way, the micro-corrosion of the conductive layer by the electrolyte can be effectively alleviated.

[0031] In any embodiment, the material of the polymer support layer includes one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, and their derivatives, crosslinked products, and copolymers. Using the above materials as the polymer support layer of the composite current collector can effectively improve the safety and energy density of the battery and reduce the cost of the current collector compared with traditional metal foil current collectors such as copper-aluminum and aluminum foil.

[0032] In any embodiment, the material of the conductive layer includes one or more of aluminum, copper, nickel, titanium, silver, aluminum zirconium alloy, graphite, acetylene black, graphene, and carbon nanotubes.

[0033] In any embodiment, the surface roughness of the conductive layer is Ra, where 0.1 μm < Ra < 2 μm. In this way, the active material layer can have good adhesion to the composite current collector, and the electrode sheet can have a lower resistance.

[0034] The second aspect of the present application further provides an electrode sheet, including an active material layer and the composite current collector of the first aspect of the present application, and the active material layer is provided on the surface of the conductive layer facing away from the adhesive layer. In this way, since the composite current collector in the electrode sheet has a high tensile modulus, it is not easy to wrinkle and shrink at the tab during the formation of the active material layer, and the welding reliability of the tab of the electrode sheet is good.

[0035] The third aspect of the present application further provides a secondary battery, including the composite current collector of the first aspect of the present application or the electrode sheet of the second aspect of the present application.

[0036] The fourth aspect of the present application further provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0037] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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:

[0039] FIG1 is a schematic diagram of a composite current collector according to one embodiment of the present application;

[0040] FIG2 is a schematic diagram of a composite current collector according to another embodiment of the present application;

[0041] FIG3 is a schematic diagram of an electrode plate according to an embodiment of the present application;

[0042] FIG4 is a schematic diagram of an electrode plate according to another embodiment of the present application;

[0043] FIG5 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0044] FIG6 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG5 ;

[0045] FIG. 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0046] Description of reference numerals:

[0047] 5. Battery cell; 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device; 10. Composite current collector; 11. Polymer support layer; 12. Adhesive layer; 13. Conductive layer; 121. First sub-adhesive layer; 122. Second sub-adhesive layer; 14. Passivation layer; 20. Electrode pole piece; 21. Active material layer. DETAILED DESCRIPTION

[0048] Below, the embodiments of the composite current collector, electrode plate, secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0049] 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.

[0050] 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.

[0051] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0052] 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.

[0053] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, 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 inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. 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 steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0054] In this application, in the open technical features or technical solutions described with words such as "contain", "include", and "include", unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that also include additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or may not include additional members. It 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". 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.

[0055] 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.

[0056] The weights described in the examples of this application may be weight units known in the chemical industry, such as μg, mg, g, and kg.

[0057] At present, due to the great development of secondary batteries, higher requirements are also put forward for the energy density and safety of secondary batteries. Compared with conventional current collectors such as copper foil and aluminum foil, composite current collectors are more conducive to improving the energy density and safety performance of batteries. However, the current composite current collectors have the problems of low elongation at break and low tensile modulus. The composite current collector is prone to wrinkling and shrinkage after coating the active material layer, which affects the subsequent process and battery performance. In this regard, the present application improves the structure of the composite current collector so that it has a higher elongation at break and tensile modulus, is less prone to wrinkling and shrinkage, and is beneficial to the subsequent process and improves battery performance.

[0058] Referring to Figures 1 and 2 , in some embodiments, the first aspect of the present application provides a composite current collector 10, comprising a polymer support layer 11, a bonding layer 12, and a conductive layer 13. The bonding layer 12 is disposed on at least one surface of the polymer support layer 11, and comprises polyimide, inorganic particles, and a binder; the conductive layer 13 is disposed on a surface of the bonding layer 12 facing away from the polymer support layer 11.

[0059] The conventional composite current collector 10 usually forms a conductive layer 13 on a polymer support layer 11 by evaporation or magnetron sputtering. When forming the conductive layer 13, the polymer support layer 11 will be greatly thermally damaged, causing the film surface of the composite current collector 10 to be easily deformed and reducing the elongation at break of the composite current collector 10. To address this issue, a glue coating method can be used to form the conductive layer 13 on the polymer support layer 11. However, the tensile modulus of the composite current collector 10 formed by the glue coating method is low. When the active material layer is formed on the composite current collector 10, the tabs of the composite current collector 10 are easily affected by drying stress and wrinkle and shrink, affecting the subsequent process and increasing the internal resistance (DCR) of the battery.

[0060] The composite current collector 10 of the present application combines the conductive layer 13 with the polymer support layer 11 via an adhesive layer 12, and the adhesive layer 12 includes polyimide, inorganic particles, and a binder. The interaction between the polyimide and the inorganic particles in the adhesive layer 12 effectively improves the tensile modulus of the composite current collector 10, alleviating wrinkling and shrinkage at the tabs of the composite current collector 10. Furthermore, compared to conventional composite current collectors 10 that utilize vapor deposition or magnetron sputtering to form the conductive layer 13, the conductive layer 13 of the composite current collector 10 of the present application can be combined with the polymer support layer 11 by coating the adhesive layer 12, eliminating the problem of significant thermal damage to the polymer support layer 11. Consequently, the composite current collector 10 can exhibit a higher elongation at break.

[0061] It can be understood that the bonding layer 12 can be provided on only one surface of the polymer support layer 11, and accordingly, the conductive layer 13 can be provided on only one surface of the polymer support layer 11; or the bonding layer 12 can be provided on two opposite surfaces of the polymer support layer 11, and accordingly, the conductive layer 13 can be provided on both surfaces of the polymer support layer 11.

[0062] In some embodiments, the mass fraction of polyimide in the bonding layer 12 is 30% to 70%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of binder is 20% to 60%. When the mass fractions of polyimide, inorganic particles, and binder in the bonding layer 12 are within the above ranges, the tensile modulus of the composite current collector can be effectively improved.

[0063] In some embodiments, the mass fraction of polyimide in the bonding layer 12 is 30% to 55%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of binder is 35% to 60%. By controlling the mass fraction of polyimide in the bonding layer 12 within the range of 30% to 55%, the mass fraction of inorganic particles within the range of 5% to 10%, and the mass fraction of binder within the range of 35% to 60%, the tensile modulus of the composite current collector 10 can be further improved, and wrinkling and shrinkage at the tabs of the composite current collector 10 can be further alleviated, while also providing a greater peeling force between the conductive layer 13 and the polymer support layer 11.

[0064] It can be understood that the mass fraction of polyimide in the bonding layer 12 can be but not limited to 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%; the mass fraction of inorganic particles in the bonding layer 12 can be but not limited to 5%, 6%, 7%, 8%, 9%, 10%; the mass fraction of the binder in the bonding layer 12 can be but not limited to 35%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, 50%, 52%, 54%, 55%, 56%, 58%, 60%.

[0065] In some embodiments, the thickness d1 of the adhesive layer 12 is 600 nm to 2000 nm; alternatively, the thickness d1 of the adhesive layer 12 is 800 nm to 1500 nm. Controlling the thickness d1 of the adhesive layer 12 within the above range can better improve the tensile modulus of the composite current collector 10 and better alleviate wrinkling and shrinkage at the tab. This can also avoid situations where the peel force between the conductive layer 13 and the polymer support layer 11 is too low due to a too thin adhesive layer 12, resulting in low welding tension and an increased DCR of the battery cell. It can also avoid problems where an overly thick adhesive layer 12 increases the risk of tab welding failure, leading to cold solder joints and thus an increased DCR of the battery cell. It can be understood that the thickness d1 of the bonding layer 12 can be, but is not limited to, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, or 2000 nm.

[0066] Referring to Figure 2 , in some embodiments, the bonding layer 12 includes a first sub-bonding layer 121 and a second sub-bonding layer 122. The first sub-bonding layer 121 is disposed on at least one surface of the polymer support layer 11 and comprises polyimide, inorganic particles, and a binder. The second sub-bonding layer 122 is disposed on the surface of the first sub-bonding layer 121 facing away from the polymer support layer 11. The conductive layer 13 is disposed on the surface of the second sub-bonding layer 122 facing away from the first sub-bonding layer 121 and comprises a binder. In other words, in this embodiment, the bonding layer 12 comprises a two-layer structure: the first sub-bonding layer 121, which is closer to the polymer support layer 11, comprises polyimide, inorganic particles, and a binder; the second sub-bonding layer 122, which is further away from the polymer support layer 11, can be a simple binder layer. This can further enhance the peel force between the conductive layer 13 and the polymer support layer 11, and further improve the overall tensile modulus of the composite current collector 10, thereby further alleviating wrinkling and shrinkage at the tab.

[0067] In some embodiments, the mass fraction of polyimide in the first sub-bonding layer 121 is 60% to 70%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of binder is 20% to 30%. Controlling the mass fraction of polyimide in the first sub-bonding layer 121 within the range of 60% to 70%, the mass fraction of inorganic particles within the range of 5% to 10%, and the mass fraction of binder within the range of 20% to 30% can not only effectively improve the tensile modulus of the composite current collector 10 and effectively alleviate wrinkling and shrinkage at the tab, but also improve the peeling force between the conductive layer 13 and the polymer support layer 11.

[0068] It can be understood that the mass fraction of polyimide in the first sub-bonding layer 121 can be but not limited to 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%; the mass fraction of inorganic particles can be but not limited to 5%, 6%, 7%, 8%, 9%, 10%; the mass fraction of the binder can be but not limited to 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%.

[0069] In some embodiments, the thickness d2 of the first sub-adhesive layer 121 is 500 nm to 1500 nm. Optionally, the thickness d2 of the first sub-adhesive layer 121 is 600 nm to 1200 nm. Controlling the thickness of the first sub-adhesive layer 121 in the adhesive layer 12 within the above range can better improve the tensile modulus of the composite current collector 10, enhance the tab welding reliability of the composite current collector 10, and maintain a normal DCR of the battery cell. It is understood that the thickness d2 of the first sub-adhesive layer 121 can be, but is not limited to, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, 1250 nm, 1300 nm, 1350 nm, 1400 nm, 1450 nm, or 1500 nm.

[0070] In some embodiments, the thickness d3 of the second sub-bonding layer 122 is 300 nm to 700 nm. The second sub-bonding layer 122 can be a simple adhesive layer, to which polyimide and inorganic particles may not be added. This can further enhance the peeling force between the conductive layer 13 and the polymer support layer 11, while also providing the composite current collector 10 with better tab welding reliability. It is understood that the thickness d3 of the second sub-bonding layer 122 can be, but is not limited to, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, or 700 nm.

[0071] In some embodiments, the inorganic particles contained in the bonding layer 12 can be one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide, and graphene. Adding these inorganic particles to the bonding layer 12 can effectively enhance the strength of the composite current collector 10 by interacting with the polyimide. Furthermore, these inorganic particles do not react with the electrolyte. The D50 particle size of the inorganic particles can range from 1 nm to 100 nm.

[0072] In some embodiments, the binder in the bonding layer 12 includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, 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. Alternatively, the binder includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound and polyurethane. In some specific examples, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane. The use of the above-mentioned binder can play a good bonding role between the polymer support layer 11 and the conductive layer 13, so that the conductive layer 13 and the polymer support layer 11 have a large peeling force.

[0073] In some embodiments, the composite current collector 10 further includes a passivation layer 14, which is disposed between the bonding layer 12 and the conductive layer 13. The conductive layer 13 of the composite current collector 10 and the polymer support layer 11 are bonded together by the bonding layer 12 containing a binder. When the composite current collector 10 is used in a battery, the electrolyte may penetrate between the bonding layer 12 and the conductive layer 13, thereby causing micro-corrosion to the conductive layer 13. By disposing the passivation layer 14 between the bonding layer 12 and the conductive layer 13, the present application can provide a passivation protection at the interface where the conductive layer 13 contacts the bonding layer 12, thereby reducing micro-corrosion of the conductive layer 13 by the electrolyte.

[0074] In some embodiments, the material of the passivation layer 14 includes one or more of chromate, dichromate, organic phosphonate, Al2O3, SiO2 and Si3N4. Among them, chromate includes one or more of sodium chromate, potassium chromate, magnesium chromate, silver chromate and ammonium dichromate; dichromate includes one or more of sodium dichromate, potassium dichromate, magnesium dichromate and silver dichromate; organic phosphonate includes one or more of hydroxyethylidene diphosphonic acid (HEDP), diethylenetriamine penta (methylene phosphonic acid) (DETPMP), triethylenetetramine hexa (methylene phosphonic acid) (TETHMP) and ethylenediamine tetra (methylene phosphonic acid) (EDTMP). The above-mentioned materials are used to form the passivation layer 14 at the interface where the conductive layer 13 contacts the bonding layer 12, which can provide good passivation protection for the conductive layer 13 and effectively alleviate the micro-corrosion of the conductive layer 13 by the electrolyte.

[0075] In some embodiments, the thickness of the passivation layer 14 is 1 nm to 500 nm; alternatively, the thickness of the passivation layer 14 is 10 nm to 200 nm. Controlling the thickness of the passivation layer 14 within the above range can effectively alleviate micro-corrosion of the conductive layer 13 by the electrolyte. It is understood that the thickness of the passivation layer 14 can be, but is not limited to, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, 150 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 250 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 350 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, 450 nm, 460 nm, 480 nm, or 500 nm.

[0076] In some embodiments, the material of the polymer support layer 11 includes 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, polyoxymethylene, polyphenylene oxide, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, and their derivatives, crosslinked products, and copolymers. Using the above materials as the polymer support layer 11 of the composite current collector 10 can effectively improve the safety and energy density of the battery and reduce the cost of the current collector compared to traditional metal foil current collectors such as copper, aluminum, and aluminum foil.

[0077] In some embodiments, the material of the polymer support layer 11 may also include one or more of a metal material and an inorganic insulating material. The inorganic insulating material may include one or more of aluminum oxide, silicon carbide, and silicon dioxide. By adding the aforementioned inorganic insulating materials to the material of the polymer support layer 11, the strength of the composite current collector 10 can be further improved.

[0078] In some embodiments, the thickness of the polymer support layer 11 is 2 μm to 40 μm; alternatively, the thickness of the polymer support layer 11 is 3 μm to 8 μm. Controlling the thickness of the polymer support layer 11 within the aforementioned range can enable a battery using the composite current collector 10 to have a higher energy density and better safety. It can be understood that the thickness of the polymer support layer 11 can be but is not limited to 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm.

[0079] In some embodiments, the material of the conductive layer 13 includes one or more of aluminum, copper, nickel, titanium, silver, aluminum-zirconium alloy, graphite, acetylene black, graphene, and carbon nanotubes. It will be appreciated that, depending on the material of the conductive layer 13, the composite current collector 10 can be a positive electrode current collector or a negative electrode current collector. For example, when the conductive layer 13 is made of aluminum, the composite current collector 10 is a positive electrode current collector; when the conductive layer 13 is made of copper, the composite current collector 10 is a negative electrode current collector.

[0080] In some embodiments, the thickness of the conductive layer 13 is 800 nm to 2000 nm. Controlling the thickness of the conductive layer 13 within the above range can play a good role in current collection and make the battery have better safety. It is understandable that the thickness of the conductive layer 13 can be, but is not limited to, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, and 2000 nm.

[0081] In some of these embodiments, the surface roughness of the conductive layer 13 is Ra, where 0.1 μm < Ra < 2 μm. The surface roughness of the conductive layer 13 of the composite current collector 10 affects the adhesion of the active material layer to the composite current collector 10 and the resistance of the electrode sheet. Controlling the surface roughness Ra of the conductive layer 13 within the range of 0.1 μm < Ra < 2 μm can not only provide good adhesion between the active material layer and the composite current collector but also result in a lower resistance for the electrode sheet. It can be understood that the surface roughness Ra of the conductive layer 13 can be, but is not limited to, 0.11 μm, 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm.

[0082] In some embodiments, the composite current collector 10 of the first aspect of the present application can be prepared by the following method:

[0083] Provide a polymer support layer 11 and a conductive layer 13;

[0084] Bond the polymer support layer 11 and the conductive layer 13 together through a bonding paste; and

[0085] Cure the bonding paste to form a bonding layer 12 between the polymer support layer 11 and the conductive layer 13, and the bonding paste includes polyimide, inorganic particles, and a binder.

[0086] Composite the conductive layer 13 with the polymer support layer 11 through the bonding layer 12, and the bonding layer 12 includes polyimide, inorganic particles, and a binder; compared with the conventional composite current collector 10 formed by vapor deposition or magnetron sputtering to form the conductive layer 13, the composite current collector 10 prepared by the above method does not cause significant thermal damage to the polymer support layer 11, and can endow the composite current collector 10 with a high elongation at break; and through the mutual cooperation of polyimide and inorganic particles in the bonding layer 12, the tensile modulus of the prepared composite current collector 10 can be effectively improved, and the wrinkling and shrinkage at the tab of the composite current collector 10 can be alleviated.

[0087] In some of these embodiments, the bonding layer 12 is a single-layer structure, and the bonding paste for forming the bonding layer 12 can be prepared by the following method: Mix polyimide liquid, inorganic particles, and a binder in proportion and add them to a stirring tank, where the mass fraction of polyimide is 30% - 55%, the mass fraction of inorganic particles is 5% - 10%, and the mass fraction of the binder is 35% - 60%; add a certain amount of N-methylpyrrolidone (NMP) as a solvent and stir and mix until the viscosity is 2000 cps - 20000 cps to obtain the bonding paste.

[0088] In some embodiments, when the adhesive layer 12 is a single-layer structure, the polymer support layer 11 and the conductive layer 13 can be composited by the following method: gravure coating the above-mentioned adhesive slurry on the metal foil serving as the conductive layer 13, baking the metal foil coated with the adhesive slurry in an oven at 80°C to 110°C, and then thermally composite the baked metal foil with the adhesive slurry coated side with the polymer support layer 11. After the composite current collector is matured to allow the adhesive to fully adhere, the metal foil can then be thinned by a corrosion thinning process to obtain a suitable thickness according to design requirements. In addition, a metal layer can be formed as the conductive layer 13 on a thick carrier by evaporation or electrolysis before composite, the metal layer can be peeled off from the thick carrier, and then the metal layer and the polymer support layer 11 can be composited by coating with adhesive slurry to form a composite current collector 10.

[0089] In some embodiments, the bonding layer 12 has a double-layer structure, including a first sub-bonding layer 121 and a second sub-bonding layer 122. The first sub-bonding layer 121 is disposed on a side close to the polymer support layer 11, and the second sub-bonding layer 122 is disposed on a side away from the polymer support layer 11. The first sub-bonding layer 121 includes polyimide, inorganic particles, and a binder, while the second sub-bonding layer 122 may include only a binder.

[0090] The bonding slurry forming the first sub-bonding layer 121 can be prepared by the following method: polyimide liquid, inorganic particles and adhesive are mixed in proportion and added to a stirring tank, wherein the mass fraction of polyimide is 60% to 70%, the mass fraction of inorganic particles is 5% to 10%, and the mass fraction of adhesive is 20% to 30%; a certain amount of N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred and mixed until the viscosity is 500cps to 10000cps to obtain the bonding slurry.

[0091] In some embodiments, when the adhesive layer 12 is a double-layer structure, the polymer support layer 11 and the conductive layer 13 can be composited by the following method: gravure coating the adhesive slurry of the first sub-adhesive layer 121 on the metal foil serving as the conductive layer 13, baking the metal foil coated with the adhesive slurry in an oven at 80°C to 110°C, and then thermally composite the baked metal foil with the adhesive slurry coated side with the polymer support layer 11. After the composite current collector is aged to allow the adhesive to fully adhere, the metal foil can then be thinned by etching and thinning to obtain a suitable thickness according to design requirements. In addition, a metal layer can be formed as the conductive layer 13 on a thick carrier by evaporation or electrolysis before composite, the metal layer can be peeled off from the thick carrier, and then the metal layer and the polymer support layer 11 can be composited by coating with adhesive slurry to form a composite current collector 10.

[0092] In some embodiments, before gravure coating the adhesive slurry on the conductive layer 13, the surface of the conductive layer 13 coated with the adhesive slurry may be passivated to form a passivation layer 14. Specifically, the passivation layer 14 may be formed by compositely coating the passivation material on the conductive layer 13 using gravure printing, evaporation, or magnetron sputtering; then, gravure coating the adhesive slurry on the passivation layer 14.

[0093] Referring to Figures 3 and 4, in some embodiments, the second aspect of the present application further provides an electrode plate 20, which includes an active material layer 21 and the composite current collector 10 of the first aspect of the present application. The active material layer 21 is disposed on the surface of the conductive layer 13 of the composite current collector 10 facing away from the adhesive layer 12. Thus, the electrode plate 20 employs the composite current collector 10 of the first aspect of the present application. Because the composite current collector 10 has a high tensile modulus, its tabs are less susceptible to wrinkling and shrinkage when the active material layer 21 is formed, and the tab welding reliability of the electrode plate 20 is good.

[0094] In some embodiments, the electrode plate 20 may be a positive electrode plate or a negative electrode plate, depending on the material of the active material layer 21 and the material of the conductive layer 13. For example, when the active material in the active material layer 21 is a positive electrode active material and the conductive layer 13 is aluminum foil, the electrode plate 20 is a positive electrode plate; when the active material in the active material layer 21 is a negative electrode active material and the conductive layer 13 is copper foil, the electrode plate 20 is a negative electrode plate.

[0095] It can be understood that regardless of whether the electrode plate 20 is a positive electrode plate or a negative electrode plate, its composite current collector 10 can adopt a composite current collector 10 with a single-layer structure of the bonding layer 12 as shown in Figure 1, and the structure of the electrode plate 20 at this time is shown in Figure 3; it can also adopt a composite current collector 10 with a double-layer structure of the bonding layer 12 as shown in Figure 2, and the structure of the electrode plate 20 at this time is shown in Figure 4.

[0096] In some embodiments, the third aspect of the present application further provides a secondary battery, which includes the composite current collector 10 of the first aspect of the present application or the electrode plate 20 of the second aspect of the present application. It is understood that in the secondary battery, only the positive electrode plate may adopt the electrode plate 20 of the second aspect of the present application, or only the negative electrode plate may adopt the electrode plate 20 of the second aspect of the present application, or both the positive electrode plate and the negative electrode plate may adopt the electrode plate 20 of the second aspect of the present application.

[0097] In some embodiments, the fourth aspect of the present application further provides an electrical device, which includes the secondary battery of the third aspect of the present application.

[0098] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0099] Unless otherwise specified, the components, material types, or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.

[0100] In one embodiment of the present application, a secondary battery is provided.

[0101] 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.

[0102] Positive electrode

[0103] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0104] 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.

[0105] In some embodiments, the positive electrode current collector may be the composite current collector of the first aspect of the present application.

[0106] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0107] As a non-limiting example, the positive electrode active material of the lithium-ion secondary battery may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other 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. Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure 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 manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide 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 0.85 Co 0.1 Al 0.05 O2.

[0108] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0109] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0110] As non-limiting examples, the positive electrode active material of a sodium ion secondary battery may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0111] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0112] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be one or more of P, S and Si; n represents (YO4) n- valence.

[0113] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0114] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0115] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y One or more of (0≤y≤1).

[0116] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ) compounds. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0117] The weight ratio of the positive electrode active material in the positive electrode active material layer is 80 wt % to 100 wt % based on the total weight of the positive electrode active material layer.

[0118] In some embodiments, the positive electrode active material layer may further optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode active material layer is 0% to 20% by weight, based on the total weight of the positive electrode active material layer.

[0119] 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. The weight ratio of the conductive agent in the positive electrode active material layer is 0% to 20% by weight, based on the total weight of the positive electrode active material layer.

[0120] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, the positive electrode sheet is formed by cold rolling; the positive electrode powder coating unit area density is 150mg / m 2 ~350 mg / m 2 The compaction density of the positive electrode is 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0121] The calculation formula of the compacted density is:

[0122] Compaction density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0123] The mass M of the positive electrode active material per unit area of ​​the positive electrode membrane can be obtained by weighing using a standard balance.

[0124] The thickness T of the positive electrode film can be measured using a micrometer, for example, a Mitutoyo 293-100 with an accuracy of 0.1 μm. It should be noted that the thickness of the positive electrode film described in this application refers to the thickness of the positive electrode film in the positive electrode sheet after cold pressing and used in battery assembly.

[0125] Negative electrode

[0126] 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.

[0127] 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.

[0128] In some embodiments, the negative electrode current collector may be the composite current collector of the first aspect of the present application.

[0129] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art.

[0130] As a non-limiting example, the negative electrode active material of the lithium-ion secondary battery may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. 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.

[0131] As a non-limiting example, the negative active material of the sodium ion secondary battery is generally a hard carbon material, a two-dimensional metal carbide or a nitride. Preferably, the negative active material of the sodium ion secondary battery is generally a hard carbon material.

[0132] In some embodiments, the negative electrode active material layer may further optionally 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).

[0133] 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.

[0134] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0135] 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 on both 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 75g / m 2 ~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0136] electrolytes

[0137] 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.

[0138] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0139] In some embodiments, the electrolyte salt of the lithium ion secondary battery 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 difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0140] In some embodiments, the solvent may include one or more of fluoroethylene carbonate (FEC), 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 (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0141] 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.

[0142] 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.

[0143] Isolation film

[0144] 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.

[0145] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0146] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0147] 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.

[0148] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0149] 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.

[0150] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0151] 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.

[0152] 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, FIG5 shows a battery cell 5 with a square structure as an example.

[0153] In some embodiments, referring to Figure 6, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 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 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0154] In some embodiments, the battery cells 5 can be assembled into a battery module. The number of battery cells 5 contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0155] In the battery module, the plurality of battery cells 5 can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, the plurality of battery cells 5 can be fixed by fasteners.

[0156] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0157] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0158] 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.

[0159] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0160] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0161] FIG7 shows an example of an electric device 6. 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 may be used.

[0162] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0163] The following are some examples.

[0164] 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.

[0165] 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.

[0166] 1. Implementation

[0167] Example 1:

[0168] 1) Preparation of positive electrode sheet

[0169] 1.1) Preparation of positive electrode adhesive slurry

[0170] Polyimide liquid, boehmite powder and PU682 polyurethane adhesive are mixed and added to a stirring tank; the mass fraction of polyimide is 43%, the mass fraction of boehmite is 7%, and the mass fraction of PU682 polyurethane adhesive is 50%; N-methylpyrrolidone (NMP) is added as a solvent, and stirred at a speed of 2000 rpm for 1 hour to obtain a positive electrode bonding slurry.

[0171] 1.2) Preparation of positive electrode composite current collector

[0172] Aluminum foil was selected as the conductive layer material. A passivation solution, potassium dichromate, was evenly applied to the surface of the aluminum foil via gravure printing to form a 100 nm thick passivation layer. The positive electrode adhesive slurry was then gravure-coated onto the passivated surface of the aluminum foil. The coated aluminum foil was then oven-baked and thermally laminated with a polymer support layer to complete single-sided lamination. The aluminum foil was laminated to the other side of the polymer support layer using the same method. The laminated aluminum foil was then aged to ensure sufficient adhesion of the adhesive. The aluminum foil was then thinned by etching to form a 1000 nm thick conductive layer, thus forming a composite current collector. The adhesive slurry in the composite current collector was thermally laminated and aged to form a 1000 nm thick adhesive layer. The polymer support layer was 6 μm thick, and the surface roughness Ra of the conductive layer was 0.6 μm.

[0173] 1.3) Preparation of positive electrode active material layer

[0174] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR styrene-butadiene latex were mixed uniformly in the solvent N-methylpyrrolidone at a mass ratio of 97:1.2:1.8 to obtain a positive electrode slurry. The above positive electrode slurry was applied to the conductive layer on both sides of the positive electrode composite current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The positive electrode compaction density was 3.4g / cm 3 .

[0175] 2) Preparation of negative electrode sheet

[0176] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose (CMC) were mixed uniformly in a suitable amount of deionized water at a mass ratio of 98:1:1 to obtain a negative electrode slurry. The negative electrode slurry was applied to both sides of the negative electrode current collector copper foil. The negative electrode sheet was obtained through drying, cold pressing, slitting, and cutting. The negative electrode compaction density was 1.6 g / cm 3 .

[0177] 3) Electrolyte preparation

[0178] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an organic solvent, and fully dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0179] 4) Isolation film

[0180] Polypropylene / polyethylene / polypropylene (PP / PE / PP) composite diaphragm is used as the isolation membrane.

[0181] 5) Cell preparation

[0182] The above-mentioned positive electrode sheet, separator and negative electrode sheet are wound together into a bare battery cell, and the separator is located between the positive electrode sheet and the negative electrode sheet to play an isolating role; double-sided metal edging is used for roller welding and transfer welding to form tabs; the battery cell with the tabs welded is placed in a battery casing, and the above-mentioned electrolyte is injected, and sealing, formation and other processes are carried out to obtain a lithium-ion secondary battery.

[0183] Example 2:

[0184] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the bonding layer are 30%, 10%, and 60%.

[0185] Example 3:

[0186] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 35%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 55%.

[0187] Example 4:

[0188] This embodiment is basically the same as embodiment 1, except that in step 1.1), the mass fraction of polyimide in the bonding layer is 40%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 50%.

[0189] Example 5:

[0190] This embodiment is basically the same as embodiment 1, except that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 40%.

[0191] Example 6:

[0192] This embodiment is basically the same as embodiment 1, except that in step 1.1), the mass fraction of polyimide in the bonding layer is 55%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 35%.

[0193] Example 7:

[0194] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 25%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 65%.

[0195] Example 8:

[0196] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 60%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 30%.

[0197] Example 9:

[0198] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 5%, and the mass fraction of polyurethane adhesive is 45%.

[0199] Example 10:

[0200] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 6%, and the mass fraction of the polyurethane adhesive is 44%.

[0201] Example 11:

[0202] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 7%, and the mass fraction of the polyurethane adhesive is 43%.

[0203] Example 12:

[0204] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 8%, and the mass fraction of polyurethane adhesive is 42%.

[0205] Example 13:

[0206] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 9%, and the mass fraction of polyurethane adhesive is 41%.

[0207] Example 14:

[0208] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 4%, and the mass fraction of the polyurethane adhesive is 46%.

[0209] Example 15:

[0210] This embodiment is basically the same as embodiment 1, except that in step 1.1), the mass fraction of polyimide in the bonding layer is 50%, the mass fraction of boehmite is 11%, and the mass fraction of polyurethane adhesive is 39%.

[0211] Example 16:

[0212] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 600 nm.

[0213] Example 17:

[0214] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 800 nm.

[0215] Example 18:

[0216] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 1500 nm.

[0217] Example 19:

[0218] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 2000 nm.

[0219] Example 20:

[0220] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 500 nm.

[0221] Example 21:

[0222] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the bonding layer is 2100 nm.

[0223] Example 22:

[0224] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the inorganic particles are silicon carbide.

[0225] Example 23:

[0226] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the material of the passivation layer is hydroxyethylidene diphosphonic acid; accordingly, the formed passivation layer is a phosphate passivation layer.

[0227] Example 24:

[0228] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the thickness of the passivation layer is 200 nm.

[0229] Example 25:

[0230] This embodiment is basically the same as embodiment 1, with the only difference being that in step 1.2), the surface roughness Ra of the conductive layer is 1.5 μm.

[0231] Example 26:

[0232] 1) Preparation of positive electrode sheet

[0233] 1.1) Preparation of positive electrode first sub-bonding layer slurry

[0234] Polyimide liquid, boehmite powder and PU682 polyurethane adhesive were mixed and added to a stirring tank; the mass fraction of polyimide was 65%, the mass fraction of boehmite was 7%, and the mass fraction of PU682 polyurethane adhesive was 28%; N-methylpyrrolidone was added as a solvent, and stirred at a speed of 2000 rpm for 1 hour to obtain the positive electrode first sub-bonding layer slurry.

[0235] 1.2) Preparation of positive electrode composite current collector

[0236] Aluminum foil was selected as the conductive layer material. A passivation solution, potassium dichromate, was evenly applied to the surface of the aluminum foil via gravure printing to form a 100 nm thick passivation layer. The aforementioned positive electrode first sub-bonding layer slurry was gravure-coated onto the surface of the polymer support layer, oven-dried, and then rolled up for later use. A PU682 polyurethane adhesive layer was gravure-coated onto the passivated surface of the passivated aluminum foil. The coated aluminum foil was oven-baked, and the polyurethane adhesive layer-coated side of the aluminum foil was thermally laminated to the polymer support layer-coated side of the positive electrode first sub-bonding layer slurry, completing single-sided lamination. The aluminum foil was laminated to the other side of the polymer support layer using the same method. After lamination, the aluminum foil was aged to ensure sufficient adhesive adhesion. The aluminum foil was then thinned by etching to obtain a 1000 nm thick conductive layer, thus forming a composite current collector. The positive electrode first sub-bonding layer slurry and polyurethane layer in the composite current collector were thermally combined and aged to form the positive electrode first and second sub-bonding layers, respectively. The thickness of the positive electrode first sub-bonding layer was 800 nm, the thickness of the positive electrode second sub-bonding layer was 600 nm, and the thickness of the polymer support layer was 6 μm. The surface roughness Ra of the conductive layer was 0.6 μm.

[0237] 1.3) Preparation of positive electrode active material layer

[0238] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR styrene-butadiene latex were mixed uniformly in the solvent N-methylpyrrolidone at a mass ratio of 97:1.2:1.8 to obtain a positive electrode slurry. The above positive electrode slurry was applied to the conductive layer on both sides of the positive electrode composite current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The positive electrode compaction density was 3.4g / cm 3 .

[0239] The steps for preparing the negative electrode sheet, electrolyte, separator and battery cell are the same as those in Example 1.

[0240] Example 27:

[0241] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first sub-adhesive layer of the positive electrode is 60%, 10%, and 30%.

[0242] Example 28:

[0243] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide in the first sub-adhesive layer of the positive electrode is 63%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 27%.

[0244] Example 29:

[0245] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 68%, 10%, and 22%.

[0246] Example 30:

[0247] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 70%, 10%, and 20%.

[0248] Example 31:

[0249] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 55%, 10%, and 35%.

[0250] Example 32:

[0251] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 75%, 10%, and 15%.

[0252] Example 33:

[0253] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide in the first sub-adhesive layer of the positive electrode is 65%, the mass fraction of boehmite is 5%, and the mass fraction of the polyurethane adhesive is 30%.

[0254] Example 34:

[0255] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide in the first sub-adhesive layer of the positive electrode is 65%, the mass fraction of boehmite is 6%, and the mass fraction of the polyurethane adhesive is 29%.

[0256] Example 35:

[0257] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 65%, 7%, and 28%.

[0258] Example 36:

[0259] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 65%, 8%, and 27%.

[0260] Example 37:

[0261] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first positive electrode bonding layer is 65%, 9%, and 26%.

[0262] Example 38:

[0263] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide in the first sub-adhesive layer of the positive electrode is 65%, the mass fraction of boehmite is 4%, and the mass fraction of the polyurethane adhesive is 31%.

[0264] Example 39:

[0265] This embodiment is basically the same as embodiment 26, with the only difference being that the mass fraction of polyimide in the first sub-adhesive layer of the positive electrode is 65%, the mass fraction of boehmite is 11%, and the mass fraction of the polyurethane adhesive is 24%.

[0266] Example 40:

[0267] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 500 nm.

[0268] Example 41:

[0269] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 600 nm.

[0270] Example 42:

[0271] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 1000 nm.

[0272] Example 43:

[0273] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 1200 nm.

[0274] Example 44:

[0275] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 1500 nm.

[0276] Example 45:

[0277] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 400 nm.

[0278] Example 46:

[0279] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the first sub-bonding layer of the positive electrode is 1600 nm.

[0280] Example 47:

[0281] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the second sub-bonding layer of the positive electrode is 300 nm.

[0282] Example 48:

[0283] This embodiment is basically the same as embodiment 26, with the only difference being that the thickness of the second sub-bonding layer of the positive electrode is 700 nm.

[0284] Example 49:

[0285] 1) Preparation of positive electrode sheet

[0286] The positive electrode active material NCM811, conductive carbon black, and binder SBR styrene-butadiene latex were mixed uniformly in a solvent N-methylpyrrolidone at a mass ratio of 97:1.2:1.8 to obtain a positive electrode slurry. The positive electrode slurry was applied to both sides of the positive electrode current collector aluminum foil. The positive electrode sheets were obtained through drying, cold pressing, slitting, and cutting. The positive electrode compaction density was 3.4g / cm 3 .

[0287] 2) Preparation of negative electrode sheet

[0288] 2.1) Preparation of negative electrode adhesive slurry

[0289] Polyimide liquid, boehmite powder and PU682 polyurethane adhesive were mixed and added to a stirring tank; the mass fraction of polyimide was 43%, the mass fraction of boehmite was 7%, and the mass fraction of PU682 polyurethane adhesive was 50%; N-methylpyrrolidone was added as a solvent, and the mixture was stirred at a speed of 2000 rpm for 1 hour to obtain a negative electrode bonding slurry.

[0290] 2.2) Preparation of negative electrode composite current collector

[0291] A copper foil was selected as the conductive layer material. A passivation treatment using potassium dichromate as a passivation solution was evenly applied to the surface of the copper foil via gravure printing to form a 100 nm thick passivation layer. The negative electrode adhesive slurry was then gravure-coated onto the passivated surface of the copper foil. The coated copper foil was then oven-baked and thermally laminated with a polymer support layer to complete single-sided lamination. The copper foil was laminated to the other side of the polymer support layer using the same method. After lamination, the copper foil was aged to ensure sufficient adhesion of the adhesive. The copper foil was then thinned by etching to obtain a 1000 nm thick conductive layer, thus forming a composite current collector. The adhesive slurry in the composite current collector was thermally laminated and aged to form a 1000 nm thick adhesive layer. The polymer support layer was 6 μm thick, and the surface roughness Ra of the conductive layer was 0.6 μm.

[0292] 2.3) Preparation of negative electrode active material layer

[0293] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose (CMC) were mixed uniformly in a suitable amount of deionized water in a mass ratio of 98:1:1 to obtain a negative electrode slurry. The above negative electrode slurry was applied to the conductive layer on both sides of the negative electrode composite current collector. After drying, cold pressing, slitting, and cutting, the negative electrode sheet was obtained. The negative electrode compaction density was 1.6g / cm 3 .

[0294] The steps for preparing the electrolyte, isolation membrane and battery cell are the same as those in Example 1.

[0295] Example 50:

[0296] This embodiment is basically the same as Example 49, with the only difference being that in step 2.1), the mass fraction of polyimide in the bonding layer is 30%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 60%.

[0297] Example 51:

[0298] This embodiment is basically the same as Example 49, with the only difference being that in step 2.1), the mass fraction of polyimide in the bonding layer is 55%, the mass fraction of boehmite is 5%, and the mass fraction of the polyurethane adhesive is 40%.

[0299] Example 52:

[0300] This embodiment is basically the same as Example 49, with the only difference being that in step 2.2), the thickness of the bonding layer is 600 nm.

[0301] Example 53:

[0302] This embodiment is basically the same as Example 49, with the only difference being that in step 2.2), the thickness of the bonding layer is 2000 nm.

[0303] Example 54:

[0304] 1) Preparation of positive electrode sheet

[0305] The positive electrode active material NCM811, conductive carbon black, and binder SBR styrene-butadiene latex were mixed uniformly in a solvent N-methylpyrrolidone at a mass ratio of 97:1.2:1.8 to obtain a positive electrode slurry. The positive electrode slurry was applied to both sides of the positive electrode current collector aluminum foil. The positive electrode sheets were obtained through drying, cold pressing, slitting, and cutting. The positive electrode compaction density was 3.4g / cm 3 .

[0306] 2) Preparation of negative electrode sheet

[0307] 2.1) Preparation of negative electrode first sub-bonding layer slurry

[0308] Polyimide liquid, boehmite powder and PU682 polyurethane adhesive were mixed and added to a stirring tank; the mass fraction of polyimide was 65%, the mass fraction of boehmite was 7%, and the mass fraction of PU682 polyurethane adhesive was 28%; N-methylpyrrolidone was added as a solvent, and stirred at a speed of 2000 rpm for 1 hour to obtain the negative electrode first sub-bonding layer slurry.

[0309] 2.2) Preparation of negative electrode composite current collector

[0310] A copper foil was selected as the conductive layer material. A chromium-containing passivation treatment was applied to the surface of the copper foil via gravure printing to form a 100 nm thick passivation layer. The aforementioned negative electrode first sub-bonding layer slurry was gravure-coated onto the surface of the polymer support layer, oven-dried, and then rolled up for later use. A PU682 polyurethane adhesive layer was gravure-coated onto the passivated surface of the copper foil. The coated copper foil was then oven-baked, and the side of the copper foil coated with the polyurethane adhesive layer was thermally laminated to the side of the polymer support layer coated with the negative electrode first sub-bonding layer slurry, completing single-sided lamination. The copper foil was laminated to the other side of the polymer support layer using the same method. After lamination, the copper foil was aged to ensure sufficient adhesive adhesion. The copper foil was then thinned by etching to obtain a 1000 nm thick conductive layer, thus forming a composite current collector. The negative electrode first sub-bonding layer slurry and the polyurethane binder layer in the composite current collector were thermally combined and aged to form the negative electrode first and second sub-bonding layers, respectively. The thickness of the negative electrode first sub-bonding layer was 800 nm, the thickness of the negative electrode second sub-bonding layer was 600 nm, and the thickness of the polymer support layer was 6 μm. The surface roughness Ra of the conductive layer was 0.6 μm.

[0311] 2.3) Preparation of negative electrode active material layer

[0312] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose (CMC) were mixed uniformly in a suitable amount of deionized water in a mass ratio of 98:1:1 to obtain a negative electrode slurry. The above negative electrode slurry was applied to the conductive layer on both sides of the negative electrode composite current collector. After drying, cold pressing, slitting, and cutting, the negative electrode sheet was obtained. The negative electrode compaction density was 1.6g / cm 3 .

[0313] The steps for preparing the electrolyte, isolation membrane and battery cell are the same as those in Example 49.

[0314] Example 55:

[0315] This embodiment is basically the same as embodiment 54, with the only difference being that in step 2.2), the mass fraction of polyimide in the first sub-adhesive layer of the negative electrode is 60%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 30%.

[0316] Example 56:

[0317] This embodiment is basically the same as Example 54, with the only difference being that in step 2.2), the mass fraction of polyimide in the first sub-adhesive layer of the negative electrode is 70%, the mass fraction of boehmite is 5%, and the mass fraction of the polyurethane adhesive is 25%.

[0318] Example 57:

[0319] This embodiment is basically the same as embodiment 54, with the only difference being that in step 2.2), the thickness of the first sub-bonding layer of the negative electrode is 500 nm.

[0320] Example 58:

[0321] This embodiment is basically the same as embodiment 54, with the only difference being that in step 2.2), the thickness of the first sub-bonding layer of the negative electrode is 1500 nm.

[0322] 2. Comparative Example

[0323] Comparative Example 1:

[0324] This comparative example is basically the same as Example 20, with the only difference being that in step 1.1), the positive electrode adhesive slurry does not contain polyimide and inorganic particles.

[0325] Comparative Example 2:

[0326] This comparative example is basically the same as Example 20, with the only difference being that in step 1.1), the positive electrode adhesive slurry does not contain polyimide.

[0327] Comparative Example 3:

[0328] This comparative example is basically the same as Example 20, with the only difference being that in step 1.1), the positive electrode bonding slurry does not contain inorganic particles.

[0329] Comparative Example 4:

[0330] This comparative example is basically the same as Example 49, except that in step 2.1), the negative electrode adhesive slurry does not contain polyimide and inorganic particles.

[0331] Comparative Example 5:

[0332] This comparative example is basically the same as Example 49, except that in step 2.1), the negative electrode adhesive slurry does not contain polyimide.

[0333] Comparative Example 6:

[0334] This comparative example is basically the same as Example 49, except that in step 2.1), the negative electrode adhesive slurry does not contain inorganic particles.

[0335] 3. Test Method

[0336] 1) Thickness test of each layer in the composite current collector

[0337] The current collector cross-section samples were prepared using liquid nitrogen quenching or argon ion etching. The secondary electron phase morphology of the sample cross-section was observed using a scanning electron microscope at magnification (1,000 to 30,000 times). The thickness of the polymer support layer, bonding layer, first sub-bonding layer, second sub-bonding layer, passivation layer, and conductive layer were measured. The minimum resolution can reach the nanometer level.

[0338] 2) Polyimide, inorganic particles, and binder content test

[0339] The content of polyimide, inorganic particles and binder in the adhesive layer can be tested by conventional methods in the art, for example, by combining infrared testing with XRD.

[0340] 3) Conductive layer roughness test

[0341] The surface of the conductive layer of the composite current collector is tested using a roughness tester to obtain the Ra value.

[0342] Average Ra value = sum of Ra values ​​of 10 test points / 10.

[0343] 4) Composite current collector fracture elongation test

[0344] MD (Machine Direction) Tensile Elongation at Break Test: Use a standard sampler to cut the sample along the MD into 10 strips, each 15 mm wide and 15 cm long. Secure the sample to the clamps of a tensile testing machine at a speed of 50 mm / min and a gauge length of 50 mm between the clamps. Tensile testing is performed, and the elongation at break is calculated. MD elongation at break = the sum of the elongations at break of the 10 test samples / 10; units are %.

[0345] TD (Transverse Directional) Tensile Modulus Test: Use a standard sampler to cut the sample along the TD direction into 10 strips, each 15 mm wide and 15 cm long. Secure the sample to the clamps of a tensile testing machine at a speed of 50 mm / min and a gauge distance of 50 mm between the clamps. Tensile testing is performed, and the elongation at break is calculated. TD elongation at break = the sum of the elongations at break of the 10 test samples / 10; units are %.

[0346] 5) Composite current collector tensile modulus test

[0347] MD (Machine Direction) Tensile Modulus Test: Use a standard sampler to cut the sample along the MD into 10 strips, each 15 mm wide and 15 cm long. Secure the sample to the clamps of a tensile testing machine at a speed of 50 mm / min and a gauge distance of 50 mm between clamps. Tensile testing is performed, and the modulus is calculated using the strength corresponding to 1% elongation. MD tensile modulus = (strength / 1%) / 1000; average MD tensile modulus = sum of the moduli of the 10 test samples / 10. Units are GPa.

[0348] TD (Transverse Directional) Tensile Modulus Test: Use a standard sampler to cut the sample along the TD direction into 10 strips, each 15 mm wide and 15 cm long. Secure the sample to the clamps of a tensile testing machine at a speed of 50 mm / min and a gauge distance of 50 mm between the clamps. Tensile testing is performed, and the modulus is calculated using the strength corresponding to 1% elongation. TD tensile modulus = (strength / 1%) / 1000; average TD tensile modulus = sum of the moduli of the 10 test samples / 10. Units are GPa.

[0349] 6) Conductive layer peeling force test

[0350] After laminating the sample to the non-corona surface of ethylene-acrylic acid copolymer (EAA) film, 12μm-thick PET was then placed on the EAA film and placed on a heat sealer for lamination at 120°C and 0.2MPa. The laminated sample was cut into 100mm long and 20mm wide specimens, and 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 50mm and a speed of 300mm / min. A 180°C peel test was performed. The peel force was read and converted to N / m. Five parallel samples were tested, and the average peel force was calculated. The average peel force = the sum of the peel forces of the five test samples / 5.

[0351] 7) Tab shrinkage test

[0352] Before applying the active material layer on the composite current collector, align the film ruler with the tab area of ​​the composite current collector and measure the tab width every 50 meters; after applying the active material layer on the composite current collector and drying it, align the film ruler with the tab area of ​​the composite current collector again and measure the tab width every 50 meters; compare the tab width measured after applying the active material layer and drying it with the original tab width before coating to calculate the shrinkage rate;

[0353] Tab shrinkage rate = (original tab width - tab width after coating) / original tab width) * 100%;

[0354] The average shrinkage rate of the tab = the sum of the shrinkage rates of 10 tabs / 10; the tab shrinkage rate requirement is ≤ 5%;

[0355] Through the above-mentioned tab shrinkage test data, it is possible to evaluate whether the tab is wrinkled and shrunk after coating the active material layer and drying, and the degree of wrinkling and shrinkage.

[0356] 8) Pole shear force test

[0357] Attach a shear force test tape to a steel plate with a width of 4 mm and a length of 5 mm. Attach the electrode to the tape and use a high-speed rail tensile tester to measure the bonding strength between the active material layer and the conductive layer (shear force specification ≥ 0.3 MPa).

[0358] Shear force mean = sum of shear force values ​​of 10 samples / 10;

[0359] The bonding force between the active material layer and the conductive layer of the electrode can be evaluated through the above-mentioned electrode shear force test data.

[0360] 9) Tab welding tensile test

[0361] Through the conventional battery manufacturing process, the positive electrode sheet, the separator and the negative electrode sheet are wound together into a bare battery cell, and the double-sided metal edging method is used to roll weld and transfer welding to form the tab; the welding tension after welding of the single-layer tab is measured using a high-speed rail tensile test machine. The welding area of ​​the electrode sheet (tab, weld mark and active material layer) is selected and cut into samples with a width of 50mm and a length of 60mm, where the weld mark area is located in the middle of the sample. The sample is stretched at a speed of 5mm / min, and the maximum force value when the weld breaks is read. 10 samples were selected for testing, with one sample taken at intervals of 1m. The mechanical bonding effect of the welding is evaluated by the mean and standard deviation of the welding tension of the samples. Among them, the mean welding tension = the sum of the welding tension values ​​of 10 samples / 10.

[0362] 10) U-shaped resistance test after electrode roller welding

[0363] Cut the welded electrode into samples of the same size as the battery cell, and use an internal resistance meter to measure the resistance between the two tabs.

[0364] The average value of the U-shaped resistance is the sum of the U-shaped resistance values ​​of the 10 samples / 10.

[0365] The parameters of the electrodes in the secondary batteries of the above-mentioned embodiments and comparative examples of the present application are shown in Tables 1 and 2, and the performance data of the electrodes are shown in Tables 3 and 4. In Tables 1 to 4, "S" represents an embodiment, and "D" represents a comparative example. For example, S1 represents Example 1, S2 represents Example 2, and so on; similarly, D1 represents Comparative Example 1, D2 represents Comparative Example 2, and so on. In Tables 1 and 2, the three data separated by "," in the "Bonding Layer Composition" and "First Sub-Bonding Layer Composition" parameters represent, from left to right, the mass fractions of polyimide, inorganic particles, and binder, respectively. For example, "43, 7, 50" in Example 1 indicates that the mass fractions of polyimide, inorganic particles, and binder in the bonding layer are 43%, 7%, and 50%, respectively; similarly, the other embodiments and comparative examples are similar. " / " in Tables 1 and 2 indicates not present, and " / " in Tables 3 and 4 indicates not tested.

[0366] Table 1

[0367] Table 2

[0368] Table 3

[0369] Table 4

[0370] It can be seen from the above Examples 1 to 58 that the composite current collector of the present application has a larger tensile modulus and elongation at break, and the electrode using the composite current collector of the present application has a smaller tab shrinkage rate, a larger electrode welding tensile force and a smaller U-shaped resistance.

[0371] By comparing Examples 1 to 7 and Example 8, it can be seen that by controlling the content of polyimide in the bonding layer to 30% to 55% and the content of the binder to 35% to 60%, the composite current collector can have a larger tensile modulus while further improving the welding tension of the electrode, reducing the U-shaped resistance of the electrode, and making the electrode have a higher elongation at break.

[0372] By comparing Examples 9 to 15, it can be seen that controlling the content of inorganic particles in the bonding layer to 5% to 10% can enable the composite current collector to have a larger tensile modulus and elongation at break, while enabling the electrode to have a smaller tab shrinkage rate, a larger electrode welding tensile force and a smaller U-shaped resistance, and its overall performance is better.

[0373] Comparison of Examples 16 to 21 shows that controlling the adhesive layer thickness within the range of 600nm to 2000nm can result in a composite current collector having a higher tensile modulus and elongation at break, while also enabling the electrode to have a lower tab shrinkage, a higher electrode welding tensile force, and a lower U-shaped resistance, resulting in excellent overall performance. Furthermore, controlling the adhesive layer thickness within the range of 800nm ​​to 1500nm can further improve overall performance.

[0374] By comparing Examples 26 to 32, it can be seen that when the bonding layer adopts a double-layer structure, controlling the content of polyimide in the first sub-bonding layer within the range of 60% to 70%, and controlling the content of the binder within the range of 20% to 30%, can enable the composite current collector to have a larger tensile modulus and elongation at break, while enabling the electrode to have a smaller tab shrinkage rate, a larger electrode welding tensile force and a smaller U-shaped resistance, thereby having more excellent comprehensive performance.

[0375] By comparing Examples 33 to 39, it can be seen that when the bonding layer adopts a double-layer structure, controlling the content of inorganic particles in the first sub-bonding layer to 5% to 10% can enable the composite current collector to have a larger tensile modulus and elongation at break, while at the same time enabling the electrode to have a smaller tab shrinkage rate, a larger electrode welding tensile force and a smaller U-shaped resistance, thereby having more excellent overall performance.

[0376] By comparing Examples 40 to 46, it can be seen that when the bonding layer adopts a double-layer structure and the thickness of the first sub-bonding layer is controlled within the range of 500nm to 1500nm, the composite current collector can have a larger tensile modulus and elongation at break, while the electrode can have a smaller tab shrinkage rate, a larger electrode welding tensile force and a smaller U-shaped resistance, thereby having more excellent comprehensive performance.

[0377] By comparing Comparative Examples 1 to 3 with Example 20, and comparing Comparative Examples 4 to 6 with Example 49, it can be seen that: when polyimide and / or inorganic particles are not used in the bonding layer, the tensile modulus of the composite current collector is significantly reduced, the pole tab shrinkage rate is increased, the pole piece welding tension is reduced, the U-shaped resistance is increased, and its overall performance is significantly reduced.

[0378] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0379] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector comprising: a polymer support layer; A bonding layer, disposed on at least one surface of the polymer support layer, wherein the bonding layer comprises polyimide, inorganic particles and a bonding agent; as well as The conductive layer is disposed on the surface of the bonding layer facing away from the polymer support layer.

2. The composite current collector according to claim 1, wherein: In the bonding layer, the mass fraction of the polyimide is 30% to 70%, the mass fraction of the inorganic particles is 5% to 10%, and the mass fraction of the binder is 20% to 60%.

3. The composite current collector according to claim 1 or 2, wherein: The mass fraction of the polyimide in the bonding layer is 30% to 55%, the mass fraction of the inorganic particles is 5% to 10%, and the mass fraction of the binder is 35% to 60%.

4. The composite current collector according to any one of claims 1 to 3, wherein The thickness of the bonding layer is 600nm-2000nm.

5. The composite current collector according to claim 4, wherein: The thickness of the bonding layer is 800nm-1500nm.

6. The composite current collector according to claim 1, wherein: The bonding layer comprises: A first sub-bonding layer, disposed on at least one surface of the polymer support layer, wherein the first sub-bonding layer comprises the polyimide, the inorganic particles and the binder; and The second sub-bonding layer is arranged on the surface of the first sub-bonding layer away from the polymer support layer, the conductive layer is arranged on the surface of the second sub-bonding layer away from the first sub-bonding layer, and the second sub-bonding layer includes the adhesive.

7. The composite current collector according to claim 6, wherein: In the first sub-bonding layer, the mass fraction of the polyimide is 60% to 70%, the mass fraction of the inorganic particles is 5% to 10%, and the mass fraction of the binder is 20% to 30%.

8. The composite current collector according to claim 6 or 7, wherein: The thickness of the first sub-adhesive layer is 500 nm to 1500 nm.

9. The composite current collector according to claim 8, wherein: The thickness of the first sub-adhesive layer is 600 nm to 1200 nm.

10. The composite current collector according to any one of claims 6 to 9, wherein: The thickness of the second sub-adhesive layer is 300 nm to 700 nm.

11. The composite current collector according to any one of claims 1 to 10, wherein: The inorganic particles include one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide and graphene.

12. The composite current collector according to any one of claims 1 to 11, wherein: The binder includes one or more of a composition containing multifunctional isocyanate and polyester polyol compounds, 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.

13. The composite current collector according to any one of claims 1 to 12, wherein: Also includes: The passivation layer is disposed between the bonding layer and the conductive layer.

14. The composite current collector according to claim 13, wherein: The material of the passivation layer includes one or more of chromate, dichromate, organic phosphonate, Al2O3, SiO2 and Si3N4.

15. The composite current collector according to claim 14, wherein: The chromate includes one or more of sodium chromate, potassium chromate, magnesium chromate and silver chromate.

16. The composite current collector according to claim 14 or 15, wherein: The dichromate includes one or more of sodium dichromate, potassium dichromate, magnesium dichromate and silver dichromate.

17. The composite current collector according to any one of claims 14 to 16, wherein: The organic phosphonate includes one or more of hydroxyethylidene diphosphonic acid, diethylene triamine penta methylene phosphonic acid, triethylene tetraamine hexa methylene phosphonic acid and ethylene diamine tetra methylene phosphonic acid.

18. The composite current collector according to any one of claims 13 to 17, wherein: The thickness of the passivation layer is 1 nm to 500 nm.

19. The composite current collector according to claim 18, wherein: The thickness of the passivation layer is 10nm-200nm.

20. The composite current collector according to any one of claims 1 to 19, wherein The material of the polymer support layer includes 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 and their derivatives, crosslinked products and copolymers.

21. The composite current collector according to any one of claims 1 to 20, wherein: The material of the conductive layer includes one or more of aluminum, copper, nickel, titanium, silver, aluminum-zirconium alloy, graphite, acetylene black, graphene and carbon nanotubes.

22. The composite current collector according to any one of claims 1 to 21, wherein The surface roughness of the conductive layer is Ra, 0.1 μm <Ra<2μm。 23. An electrode plate, comprising an active material layer and the composite current collector according to any one of claims 1 to 22, wherein the active material layer is disposed on a surface of the conductive layer away from the bonding layer.

24. A secondary battery comprising the composite current collector according to any one of claims 1 to 22 or the electrode sheet according to claim 23.

25. An electrical device comprising the secondary battery according to claim 24.

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