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

Abstract

The invention provides a composite current collector, an electrode plate, a secondary battery and an electric device. The composite current collector comprises a polymer supporting layer, a bonding layer and a conductive layer; the bonding layer is arranged on at least one surface of the polymer supporting layer, and the bonding layer comprises polyimide, inorganic particles and a binder; the conductive layer is arranged on the surface, away from the polymer supporting layer, of the bonding layer. The composite current collector provided by the invention has relatively high elongation at break and tensile modulus, and after the composite current collector is coated with the active material layer and dried, the condition that the tab area of the pole piece is wrinkled and shrunk is not easy to occur.

Description

Technical Field

[0001] 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

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

[0003] In recent years, as the application scope of secondary batteries becomes wider and wider, secondary batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles and electric vehicles.

[0004] As secondary batteries have made great progress, higher requirements have been placed on their energy density and safety. 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 problems such as low elongation at break, low tensile modulus, and easy wrinkling and shrinkage, which affect the subsequent process and battery performance.

[0005] 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 technicians in this field. Summary of the invention

[0006] 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 a high elongation at break and tensile modulus and being less prone to wrinkling and shrinkage.

[0007] In order to achieve the above object, the first aspect of the present application provides a composite current collector, comprising:

[0008] a polymer support layer;

[0009] a bonding layer disposed on at least one surface of the polymer support layer, the bonding layer comprising polyimide, inorganic particles and a bonding agent; and

[0010] The conductive layer is disposed on the surface of the adhesive layer facing away from the polymer support layer.

[0011] The above-mentioned composite current collector of the present application is compounded with the conductive layer and the polymer support layer through the bonding layer, and the bonding layer includes polyimide, inorganic particles and a binder; through the mutual cooperation of the polyimide and the inorganic particles in the bonding 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 compounded with the polymer support layer by coating the bonding 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.

[0012] In any embodiment, the mass fraction of the polyimide in the bonding layer 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%. In this way, the composite current collector can have a higher tensile modulus.

[0013] In any embodiment, 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%. In this way, the tensile modulus of the composite current collector can be further improved, and the wrinkling and shrinkage of the tab of the composite current collector can be further alleviated, while at the same time, a greater peeling force can be provided between the conductive layer and the polymer support layer.

[0014] In any embodiment, the thickness of the adhesive layer is 600nm to 2000nm, and can be 800nm ​​to 1500nm. In this way, the tensile modulus of the composite current collector can be better improved, the wrinkling and shrinkage of the tab can be better alleviated, and a greater peeling force can be provided between the conductive layer and the polymer support layer.

[0015] In any embodiment, the bonding layer comprises:

[0016] 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

[0017] 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 a bonding agent.

[0018] 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.

[0019] 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 the binder is 20% to 30%. In this way, the tensile modulus of the composite current collector can be well improved, the wrinkling and shrinkage of the tab can be well alleviated, and the peeling force between the conductive layer and the polymer support layer can be improved.

[0020] In any embodiment, the thickness of the first sub-adhesive layer is 500 nm to 1500 nm, and can be 600 nm to 1200 nm. In this way, the tensile modulus of the composite current collector can be better improved, and the reliability of the tab welding of the composite current collector can be enhanced.

[0021] In any embodiment, the thickness of the second sub-adhesive layer is 300 nm to 700 nm. In this way, the peeling force between the conductive layer and the polymer support layer can be further improved, and the composite current collector can have better tab welding reliability.

[0022] In any embodiment, the inorganic particles include one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide and graphene. In this way, the above-mentioned inorganic particles can cooperate with polyimide to effectively improve the strength of the composite current collector, and these inorganic particles will not react with the electrolyte.

[0023] 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 play a good bonding effect between the polymer support layer and the conductive layer, so that the conductive layer and the polymer support layer have a large peeling force.

[0024] In any embodiment, the composite current collector further comprises a passivation layer, which is disposed between the bonding layer and the conductive layer, so as to provide passivation protection to the interface between the conductive layer and the bonding layer, thereby reducing micro-corrosion of the conductive layer by the electrolyte.

[0025] In any embodiment, the material of the passivation layer includes chromate, dichromate, organic phosphonate, Al 2 O 3 、SiO 2 and Si 3 N 4 One or more of .

[0026] 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 hydroxyethylidene diphosphonic acid, diethylenetriamine pentamethylenephosphonic acid, triethylenetetramine hexamethylenephosphonic acid, and ethylenediamine tetramethylenephosphonic acid. Using 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.

[0027] In any embodiment, the thickness of the passivation layer is 1 nm to 500 nm, and can be optionally 10 nm to 200 nm. In this way, the micro-corrosion of the conductive layer by the electrolyte can be effectively alleviated.

[0028] 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.

[0029] 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.

[0030] In any embodiment, the surface roughness of the conductive layer is Ra, and 0.1 μm < Ra < 2 μm. In this way, not only can the active material layer have good adhesion to the composite current collector, but also the electrode sheet can have a lower resistance.

[0031] The second aspect of the present application also provides an electrode sheet, which includes an active material layer and the composite current collector of the first aspect of the present application, and the active material layer is disposed 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 tab welding reliability of the electrode sheet is good.

[0032] The third aspect of the present application also provides a secondary battery, which includes the composite current collector of the first aspect of the present application or the electrode sheet of the second aspect of the present application.

[0033] The fourth aspect of the present application further provides an electrical device, comprising the secondary battery of the third aspect of the present application.

[0034] 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

[0035] In order to better describe and illustrate the embodiments or examples provided by the present application, reference may be made to one or more drawings. The additional details or examples used to describe the 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 of these applications currently understood. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0036] Figure 1 A schematic diagram of a composite current collector according to an embodiment of the present application;

[0037] Figure 2 A schematic diagram of a composite current collector according to another embodiment of the present application;

[0038] Figure 3 A schematic diagram of an electrode plate according to an embodiment of the present application;

[0039] Figure 4 A schematic diagram of an electrode sheet according to another embodiment of the present application;

[0040] Figure 5 A schematic diagram of a battery cell according to an embodiment of the present application;

[0041] Figure 6 for Figure 5 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0042] Figure 7 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0043] Description of reference numerals:

[0044] 5. Battery cell; 51. Shell; 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

[0045] Below, the embodiments of the composite current collector, electrode plate, secondary battery and electric device of the present application are described in detail with appropriate reference to the 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 structure 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.

[0046] The "range" disclosed in the present application can be defined in the form of a lower limit and an upper limit, and 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 a particular range. The range defined in this way can be inclusive or exclusive of the end values, and 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 a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is 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 can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0047] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] Reference to "embodiments" herein means 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 the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. The "implementation methods" mentioned herein have a similar understanding.

[0050] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can 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 also include step (c), indicating that step (c) can 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.

[0051] In the present application, in the open technical features or technical solutions described by the words "contain", "include", "comprise", etc., 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 including 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 not only includes a1, a2 and a3, but also includes other members". In the present 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.

[0052] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0053] The weights described in the embodiments of the present application may be μg, mg, g, kg, or other weight units known in the chemical industry.

[0054] 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, and is not prone to wrinkling and shrinkage, which is beneficial to the subsequent process and improves battery performance.

[0055] See also Figure 1 and Figure 2 In some embodiments, the first aspect of the present application provides a composite current collector 10, which includes 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 the bonding layer 12 includes polyimide, inorganic particles and a binder; the conductive layer 13 is disposed on the surface of the bonding layer 12 away from the polymer support layer 11.

[0056] The conventional composite current collector 10 usually forms a conductive layer 13 on the 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, so that the film surface of the composite current collector 10 is easily deformed, and the elongation at break of the composite current collector 10 is reduced. In this regard, the conductive layer 13 can be formed on the polymer support layer 11 by glue coating. 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 pole ear of the composite current collector 10 is easily affected by the drying stress and wrinkled and shrunk, which affects the subsequent process and increases the internal resistance (DCR) of the battery.

[0057] The composite current collector 10 of the present application is compounded with the conductive layer 13 and the polymer support layer 11 through the adhesive layer 12, and the adhesive layer 12 includes polyimide, inorganic particles and a binder; through the mutual cooperation of the polyimide and the inorganic particles in the adhesive layer 12, the tensile modulus of the composite current collector 10 can be effectively improved, and the wrinkling and shrinkage at the pole ear of the composite current collector 10 can be alleviated. In addition, compared with the traditional composite current collector 10 in which the conductive layer 13 is formed by evaporation or magnetron sputtering, the conductive layer 13 of the composite current collector 10 of the present application can be compounded with the polymer support layer 11 by coating the adhesive layer 12, and there is no problem of causing significant thermal damage to the polymer support layer 11, so the composite current collector 10 can have a higher elongation at break.

[0058] 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.

[0059] 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.

[0060] 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 the 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 the binder within the range of 35% to 60%, the tensile modulus of the composite current collector 10 can be further improved, and the wrinkling and shrinkage at the pole ear of the composite current collector 10 can be further alleviated, while at the same time, a greater peeling force can be provided between the conductive layer 13 and the polymer support layer 11.

[0061] 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%.

[0062] In some embodiments, the thickness d1 of the bonding layer 12 is 600nm to 2000nm; optionally, the thickness d1 of the bonding layer 12 is 800nm ​​to 1500nm. Controlling the thickness d1 of the bonding layer 12 within the above range can better improve the tensile modulus of the composite current collector 10 and better alleviate the wrinkling and shrinkage at the pole ear. It can also avoid the situation where the peeling force between the conductive layer 13 and the polymer support layer 11 is too small due to the bonding layer 12 being too thin, resulting in a low welding tensile force and an increase in the DCR of the battery cell; it can also avoid the problem that the risk of pole ear welding failure increases due to the bonding layer 12 being too thick, resulting in cold welding, thereby increasing the 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.

[0063] See also 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 the first sub-bonding layer 121 includes polyimide, inorganic particles and a binder; the second sub-bonding layer 122 is disposed on the surface of the first sub-bonding layer 121 away from the polymer support layer 11, and the conductive layer 13 is disposed on the surface of the second sub-bonding layer 122 away from the first sub-bonding layer 121, and the second sub-bonding layer includes a binder. In other words, in this embodiment, the bonding layer 12 includes a two-layer structure, wherein the first sub-bonding layer 121 close to the polymer support layer 11 includes polyimide, inorganic particles and a binder; the second sub-bonding layer 122 away from the polymer support layer 11 can be a simple binder layer. In this way, the peeling force between the conductive layer 13 and the polymer support layer 11 can be further improved, and the tensile modulus of the composite current collector 10 as a whole can be further improved, thereby further alleviating the wrinkling and shrinkage at the tab.

[0064] 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 well improve the tensile modulus of the composite current collector 10, well alleviate the wrinkling and shrinkage at the pole ear, but also improve the peeling force between the conductive layer 13 and the polymer support layer 11.

[0065] 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%.

[0066] In some embodiments, the thickness d2 of the first sub-bonding layer 121 is 500nm to 1500nm; optionally, the thickness d2 of the first sub-bonding layer 121 is 600nm to 1200nm. Controlling the thickness of the first sub-bonding layer 121 in the bonding layer 12 within the above range can better improve the tensile modulus of the composite current collector 10, improve the reliability of the tab welding of the composite current collector 10, and make the DCR of the battery cell at a normal level. It can be understood that the thickness d2 of the first sub-bonding layer 121 can be, but is not limited to, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, 1250nm, 1300nm, 1350nm, 1400nm, 1450nm, 1500nm.

[0067] In some embodiments, the thickness d3 of the second sub-bonding layer 122 is 300nm to 700nm. The second sub-bonding layer 122 can be a simple adhesive layer, in which polyimide and inorganic particles may not be added. In this way, the peeling force between the conductive layer 13 and the polymer support layer 11 can be further improved, and the composite current collector 10 can have better reliability of the tab welding. It can be understood that the thickness d3 of the second sub-bonding layer 122 can be, but is not limited to, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm.

[0068] In some embodiments, the inorganic particles contained in the bonding layer 12 may be one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide, and graphene. Adding the above inorganic particles to the bonding layer 12 can cooperate with polyimide to effectively improve the strength of the composite current collector 10, and these inorganic particles will not react with the electrolyte. The D50 particle size of the inorganic particles may be 1 nm to 100 nm.

[0069] 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. Optionally, 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 above-mentioned binder can play a good bonding effect 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.

[0070] 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. The present application provides a passivation layer 14 between the bonding layer 12 and the conductive layer 13, which can play a passivation protection role at the interface where the conductive layer 13 contacts the bonding layer 12, thereby reducing the micro-corrosion of the conductive layer 13 by the electrolyte.

[0071] In some embodiments, the material of the passivation layer 14 includes chromate, dichromate, organic phosphonate, Al 2 O 3 、SiO 2 and Si 3 N 4 One or more of. 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), triethylenetetraamine hexa (methylene phosphonic acid) (TETHMP) and ethylenediaminetetra (methylene phosphonic acid) (EDTMP). The above-mentioned materials are used to form a passivation layer 14 at the interface where the conductive layer 13 contacts the bonding layer 12, which can play a good passivation protection role on the conductive layer 13 and effectively alleviate the micro-corrosion of the electrolyte to the conductive layer 13.

[0072] In some embodiments, the thickness of the passivation layer 14 is 1 nm to 500 nm; optionally, 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 the micro-corrosion of the electrolyte on the conductive layer 13. It can be 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, 500 nm.

[0073] 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, 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, crosslinks, 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.

[0074] 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 above-mentioned inorganic insulating material to the material of the polymer support layer 11, the strength of the composite current collector 10 may be further improved.

[0075] In some embodiments, the thickness of the polymer support layer 11 is 2 μm to 40 μm; optionally, the thickness of the polymer support layer 11 is 3 μm to 8 μm. By controlling the thickness of the polymer support layer 11 within the above range, the battery using the composite current collector 10 can 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.

[0076] 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 is understood that the composite current collector 10 can be a positive electrode current collector or a negative electrode current collector according to the type of material of the conductive layer 13. For example, when the material of the conductive layer 13 is aluminum, the composite current collector 10 is a positive electrode current collector; when the material of the conductive layer 13 is copper, the composite current collector 10 is a negative electrode current collector.

[0077] In some embodiments, the thickness of the conductive layer 13 is 800nm ​​to 2000nm. Controlling the thickness of the conductive layer 13 within the above range can play a good role in collecting current and make the battery have better safety. It can be understood that the thickness of the conductive layer 13 can be but not limited to 800nm, 850nm, 900nm, 950nm, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm.

[0078] 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.

[0079] In some embodiments, the composite current collector 10 of the first aspect of the present application can be prepared by the following method:

[0080] Provide a polymer support layer 11 and a conductive layer 13;

[0081] Bond the polymer support layer 11 and the conductive layer 13 together through a bonding paste; and

[0082] Cure the bonding paste to form a bonding layer 12 between the polymer support layer 11 and the conductive layer 13. The bonding paste includes polyimide, inorganic particles, and a binder.

[0083] The conductive layer 13 is composite 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 traditional composite current collector 10 formed by evaporation coating or magnetron sputtering to form the conductive layer 13, the composite current collector 10 prepared by the above method will 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.

[0084] 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.

[0085] 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 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, and the composite current collector is matured to make the adhesive fully adhered, and then the metal foil can be thinned by corrosion thinning process according to design requirements to obtain a suitable thickness. In addition, before the composite, a metal layer can be formed as the conductive layer 13 on a thick carrier by evaporation or electrolysis, 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 the adhesive slurry to form a composite current collector 10.

[0086] In some embodiments, the bonding layer 12 is 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, and the second sub-bonding layer 122 may only include a binder.

[0087] The bonding slurry forming the first sub-bonding layer 121 can be prepared by the following method: polyimide liquid, inorganic particles and bonding agent are mixed in proportion and added into 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 bonding agent is 20% to 30%; a certain amount of N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred to a viscosity of 500cps to 10000cps to obtain the bonding slurry.

[0088] In some embodiments, when the bonding 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 bonding slurry of the first sub-bonding layer 121 on the metal foil as the conductive layer 13, baking the metal foil coated with the bonding slurry in an oven at 80°C to 110°C, and then thermally composite the baked metal foil with the bonding slurry coated side with the polymer support layer 11, and the composite current collector is matured to make the adhesive fully adhered, and then the metal foil can be thinned by corrosion thinning process according to design requirements to obtain a suitable thickness. 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 bonding slurry is coated to composite the metal layer with the polymer support layer 11 to form a composite current collector 10.

[0089] In some embodiments, before gravure coating the bonding slurry on the conductive layer 13, the surface of the conductive layer 13 coated with the bonding slurry may be first passivated to form a passivation layer 14. Specifically, the passivation layer 14 may be formed by compounding a passivation material on the conductive layer 13 by gravure printing, evaporation or magnetron sputtering, and then gravure coating the bonding slurry on the passivation layer 14.

[0090] See also Figure 3 and Figure 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 a 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 away from the bonding layer 12. In this way, the electrode plate 20 adopts the composite current collector 10 of the first aspect of the present application. Since the composite current collector 10 has a high tensile modulus, the tabs are not easily wrinkled and shrunk when the active material layer 21 is formed, and the tab welding reliability of the electrode plate 20 is good.

[0091] 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. As an example, when the active material in the active material layer 21 is a positive electrode active material and the conductive layer 13 is an 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 a copper foil, the electrode plate 20 is a negative electrode plate.

[0092] It can be understood that no matter the electrode plate 20 is a positive electrode plate or a negative electrode plate, the composite current collector 10 can be made of Figure 1 The bonding layer 12 shown is a composite current collector 10 with a single-layer structure. The electrode plate 20 has a structure as shown in FIG. Figure 3 As shown; you can also use Figure 2 The bonding layer 12 shown is a composite current collector 10 with a double-layer structure. The electrode plate 20 has a structure as shown in FIG. Figure 4 shown.

[0093] 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 includes the electrode plate 20 of the second aspect of the present application. It can be understood that in the secondary battery, only the positive electrode plate can use the electrode plate 20 of the second aspect of the present application, and only the negative electrode plate can use the electrode plate 20 of the second aspect of the present application, or both the positive electrode plate and the negative electrode plate can use the electrode plate 20 of the second aspect of the present application.

[0094] 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.

[0095] The secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0096] 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.

[0097] In one embodiment of the present application, a secondary battery is provided.

[0098] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0099] Positive electrode

[0100] 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.

[0101] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0102] In some embodiments, the positive electrode current collector may be the composite current collector of the first aspect of the present application.

[0103] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0104] 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 positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO 2 Non-limiting examples of lithium nickel oxides may include LiNiO 2 Non-limiting examples of lithium manganese oxides may include LiMnO 2 、LiMn 2 O 4 etc.; Non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (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 O 2 .

[0105] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charging and discharging 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 content of Li 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 content of Li in the positive electrode material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li 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 the new material obtained by appropriate modification on the basis of the listed positive electrode materials is also within the scope of the positive electrode material. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode material, and non-limiting examples include coating modification.

[0106] In the list of positive electrode materials in this application, the content of oxygen (O) is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be measured by molar content, but is not limited to this.

[0107] As a non-limiting example, the positive electrode active material of the sodium ion secondary battery may include one or more of the following materials: one or more of 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.

[0108] 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 MO 2 , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0109] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO 4 ) 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 (YO 4 ) n- valence state.

[0110] The polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO 4 )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 (YO 4 ) n- valence state; the halogen can be one or more of F, Cl and Br.

[0111] The polyanionic compound can also be a compound having sodium ions, tetrahedral (YO 4 ) n- Anion unit, polyhedral unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO 4 ) n- valence state; Z represents a transition metal, which may 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.

[0112] Polyanionic compounds are, for example, NaFePO 4 、Na 3 V 2 (PO 4 ) 3 (Sodium vanadium phosphate, referred to as NVP), Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), NaM'PO 4 F (M' is one or more of V, Fe, Mn and Ni) and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y One or more of (0≤y≤1).

[0113] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ) compounds. The transition metal may 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.

[0114] 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.

[0115] In some embodiments, the positive electrode active material layer may also 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 wt % to 20 wt %, based on the total weight of the positive electrode active material layer.

[0116] In some embodiments, the positive electrode active material layer may further include a conductive agent. As a non-limiting example, 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 wt % to 20 wt %, based on the total weight of the positive electrode active material layer.

[0117] 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, and 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 surface 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 .

[0118] The calculation formula of the compacted density is:

[0119] Compacted density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0120] The mass M of the positive electrode active material per unit area of ​​the positive electrode film can be obtained by weighing using a standard balance.

[0121] The thickness T of the positive electrode film can be measured by using a micrometer, for example, a Mitutoyo 293-100 micrometer 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 used for assembling the battery after cold pressing.

[0122] Negative electrode

[0123] 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.

[0124] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0125] In some embodiments, the negative electrode current collector may be the composite current collector of the first aspect of the present application.

[0126] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery known in the art.

[0127] 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, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, 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.

[0128] As a non-limiting example, the negative electrode 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 electrode active material of the sodium ion secondary battery is generally a hard carbon material.

[0129] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0130] 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.

[0131] 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)).

[0132] 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 surface of the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode collector coated with the negative electrode slurry can be on a single surface of the negative electrode collector or on both surfaces of the negative electrode 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 the negative electrode slurry is coated, 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 sheet can be 1.0g / cm 3 ~1.8g / cm 3 .

[0133] Electrolytes

[0134] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0135] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0136] In some embodiments, the electrolyte salt of the lithium ion secondary battery may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F2 ), one or more of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0137] 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), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0138] In some embodiments, the electrolyte may further include additives, such as 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, additives that improve battery high or low temperature performance, etc.

[0139] 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.

[0140] Isolation film

[0141] 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 stability and mechanical stability can be selected.

[0142] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0143] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may be 12 μm to 20 μm.

[0144] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0145] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0146] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0147] The secondary battery includes at least one battery cell. The secondary battery may include one or more battery cells.

[0148] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0149] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 5 The battery cell 5 is a square structure as an example.

[0150] In some embodiments, reference Figure 6 , the outer packaging may include a shell 51 and a cover plate 53. Among them, 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 form 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.

[0151] 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, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0152] In the battery module, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0153] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0154] 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 according to the application and capacity of the battery pack.

[0155] The battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0156] In addition, the present application also provides an electrical 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 electrical device, and can also be used as an energy storage unit for the electrical device. The electrical 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 are not limited thereto.

[0157] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0158] Figure 7 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module can be used.

[0159] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0160] The following are some examples.

[0161] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0162] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0163] 1. Implementation

[0164] Embodiment 1:

[0165] 1) Preparation of positive electrode

[0166] 1.1) Preparation of positive electrode adhesive slurry

[0167] The polyimide liquid, boehmite powder and PU682 polyurethane adhesive are mixed and added into 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 rotation speed of 2000 rpm for 1 hour to obtain a positive electrode bonding slurry.

[0168] 1.2) Preparation of positive electrode composite current collector

[0169] A metal aluminum foil is selected as the material of the conductive layer. The passivation liquid potassium dichromate is evenly coated on the surface of the metal aluminum foil by gravure printing to form a passivation layer, and the thickness of the passivation layer is 100nm; the above-mentioned positive electrode bonding slurry is gravure coated on the passivation surface of the passivated metal aluminum foil; the coated metal aluminum foil is baked in an oven and then thermally composited with the polymer support layer to complete single-sided bonding. The metal aluminum foil is composited on the other side of the polymer support layer in the same way. After the composite metal aluminum foil is aged, the adhesive is fully adhered; then the metal aluminum foil is subjected to corrosion thinning treatment to obtain a conductive layer with a thickness of 1000nm, thereby obtaining a composite current collector. The bonding slurry in the composite current collector is thermally composited and aged to form a bonding layer with a thickness of 1000nm; the thickness of the polymer support layer is 6μm; the surface roughness Ra of the conductive layer is 0.6μm.

[0170] 1.3) Preparation of positive electrode active material layer

[0171] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR styrene butadiene latex are mixed evenly 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 is coated on the conductive layers on both sides of the positive electrode composite current collector, and the positive electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The positive electrode compaction density is 3.4g / cm 3 .

[0172] 2) Negative electrode sheet preparation

[0173] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose CMC are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 98:1:1 to obtain a negative electrode slurry. The above negative electrode slurry is coated on both sides of the negative electrode current collector copper foil, and the negative electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The negative electrode compaction density is 1.6g / cm 3 .

[0174] 3) Preparation of electrolyte

[0175] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an organic solvent. 6 Dissolve in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0176] 4) Isolation film

[0177] A polypropylene / polyethylene / polypropylene (PP / PE / PP) composite diaphragm is used as the isolation membrane.

[0178] 5) Cell preparation

[0179] The positive electrode sheet, the isolation film and the negative electrode sheet are wound together into a bare battery cell, and the isolation film 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 pole ears; the battery cell with the pole ears welded is placed in a battery casing, the above-mentioned electrolyte is injected, and sealing, formation and other processes are carried out to obtain a lithium-ion secondary battery.

[0180] Embodiment 2:

[0181] This embodiment is basically the same as the embodiment 1, except that in step 1.1), the mass fraction of the polyimide in the bonding layer is 30%, the mass fraction of the boehmite is 10%, and the mass fraction of the polyurethane adhesive is 60%.

[0182] Embodiment 3:

[0183] This embodiment is basically the same as the embodiment 1, except that in step 1.1), the mass fraction of the polyimide in the bonding layer is 35%, the mass fraction of the boehmite is 10%, and the mass fraction of the polyurethane adhesive is 55%.

[0184] Embodiment 4:

[0185] 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%.

[0186] Embodiment 5:

[0187] 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%.

[0188] Embodiment 6:

[0189] 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%.

[0190] Embodiment 7:

[0191] 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 25%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 65%.

[0192] Embodiment 8:

[0193] 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 60%, the mass fraction of boehmite is 10%, and the mass fraction of polyurethane adhesive is 30%.

[0194] Embodiment 9:

[0195] 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 5%, and the mass fraction of polyurethane adhesive is 45%.

[0196] Embodiment 10:

[0197] 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 6%, and the mass fraction of polyurethane adhesive is 44%.

[0198] Embodiment 11:

[0199] 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 7%, and the mass fraction of polyurethane adhesive is 43%.

[0200] Embodiment 12:

[0201] 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 8%, and the mass fraction of polyurethane adhesive is 42%.

[0202] Embodiment 13:

[0203] 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 9%, and the mass fraction of polyurethane adhesive is 41%.

[0204] Embodiment 14:

[0205] This embodiment is basically the same as the embodiment 1, except that in step 1.1), the mass fraction of the polyimide in the bonding layer is 50%, the mass fraction of the boehmite is 4%, and the mass fraction of the polyurethane adhesive is 46%.

[0206] Embodiment 15:

[0207] 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%.

[0208] Embodiment 16:

[0209] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 600 nm.

[0210] Embodiment 17:

[0211] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 800 nm.

[0212] Embodiment 18:

[0213] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 1500 nm.

[0214] Embodiment 19:

[0215] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 2000 nm.

[0216] Embodiment 20:

[0217] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 500 nm.

[0218] Embodiment 21:

[0219] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the bonding layer is 2100 nm.

[0220] Embodiment 22:

[0221] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the inorganic particles are silicon carbide.

[0222] Embodiment 23:

[0223] This embodiment is basically the same as the embodiment 1, and the only difference is 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.

[0224] Embodiment 24:

[0225] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the thickness of the passivation layer is 200 nm.

[0226] Embodiment 25:

[0227] This embodiment is basically the same as Embodiment 1, except that in step 1.2), the surface roughness Ra of the conductive layer is 1.5 μm.

[0228] Embodiment 26:

[0229] 1) Preparation of positive electrode

[0230] 1.1) Preparation of positive electrode first sub-bonding layer slurry

[0231] The polyimide liquid, boehmite powder and PU682 polyurethane adhesive are mixed and added into a stirring tank; wherein the mass fraction of polyimide is 65%, the mass fraction of boehmite is 7%, and the mass fraction of PU682 polyurethane adhesive is 28%; N-methylpyrrolidone is added as a solvent, and stirred at a rotation speed of 2000 rpm for 1 hour to obtain the positive electrode first sub-bonding layer slurry.

[0232] 1.2) Preparation of positive electrode composite current collector

[0233] A metal aluminum foil is selected as the material of the conductive layer. The passivation liquid potassium dichromate is evenly coated on the surface of the metal aluminum foil by gravure printing to passivate and form a passivation layer. The thickness of the passivation layer is 100nm. The above-mentioned positive electrode first sub-bonding layer slurry is coated on the surface of the polymer support layer by gravure printing, and the positive electrode first sub-bonding layer slurry is rolled up for standby use after drying in an oven. A PU682 type polyurethane adhesive layer is gravure coated on the passivated surface of the passivated metal aluminum foil. The coated metal aluminum foil is baked in an oven, and the side of the metal aluminum foil coated with the polyurethane adhesive layer and the side of the polymer support layer coated with the positive electrode first sub-bonding layer slurry are thermally composited to complete single-sided lamination. The metal aluminum foil is composited on the other side of the polymer support layer by the same method. After the composite metal aluminum foil is aged, the adhesive is fully adhered; then the metal aluminum foil is subjected to corrosion thinning treatment to obtain a conductive layer with a thickness of 1000nm, thereby obtaining a composite current collector. The positive electrode first sub-bonding layer slurry and the polyurethane layer in the composite current collector are thermally compounded and aged to form the positive electrode first sub-bonding layer and the positive electrode second sub-bonding layer respectively. The thickness of the positive electrode first sub-bonding layer is 800nm, the thickness of the positive electrode second sub-bonding layer is 600nm, and the thickness of the polymer support layer is 6μm; the surface roughness Ra of the conductive layer is 0.6μm.

[0234] 1.3) Preparation of positive electrode active material layer

[0235] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR styrene butadiene latex are mixed evenly 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 is coated on the conductive layers on both sides of the positive electrode composite current collector, and the positive electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The positive electrode compaction density is 3.4g / cm 3 .

[0236] The steps of preparing the negative electrode sheet, electrolyte, isolation membrane and battery cell are the same as those in Example 1.

[0237] Embodiment 27:

[0238] This embodiment is basically the same as Embodiment 26, except 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%.

[0239] Embodiment 28:

[0240] This embodiment is basically the same as Embodiment 26, except 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 63%, 10%, and 27%.

[0241] Embodiment 29:

[0242] This embodiment is basically the same as Embodiment 26, except that the mass fraction of polyimide in the first sub-bonding layer of the positive electrode is 68%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 22%.

[0243] Embodiment 30:

[0244] This embodiment is basically the same as Embodiment 26, except 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 70%, 10%, and 20%.

[0245] Embodiment 31:

[0246] This embodiment is basically the same as Embodiment 26, except 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%.

[0247] Embodiment 32:

[0248] This embodiment is basically the same as Embodiment 26, except that the mass fraction of polyimide, the mass fraction of boehmite, and the mass fraction of polyurethane adhesive in the first sub-bonding layer of the positive electrode is 75%, 10%, and 15%.

[0249] Embodiment 33:

[0250] This embodiment is basically the same as Embodiment 26, except that the mass fraction of polyimide in the first sub-bonding layer of the positive electrode is 65%, the mass fraction of boehmite is 5%, and the mass fraction of the polyurethane adhesive is 30%.

[0251] Embodiment 34:

[0252] This embodiment is basically the same as Embodiment 26, except 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%, 6%, and 29%.

[0253] Embodiment 35:

[0254] This embodiment is basically the same as Embodiment 26, except 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%.

[0255] Embodiment 36:

[0256] This embodiment is basically the same as Embodiment 26, except 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%.

[0257] Embodiment 37:

[0258] This embodiment is basically the same as Embodiment 26, except 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%.

[0259] Embodiment 38:

[0260] This embodiment is basically the same as Embodiment 26, except 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%.

[0261] Embodiment 39:

[0262] This embodiment is basically the same as Embodiment 26, except 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%, 11%, and 24%.

[0263] Embodiment 40:

[0264] This embodiment is basically the same as Embodiment 26, except that the thickness of the first sub-bonding layer of the positive electrode is 500 nm.

[0265] Embodiment 41:

[0266] This embodiment is basically the same as Embodiment 26, except that the thickness of the first sub-bonding layer of the positive electrode is 600 nm.

[0267] Embodiment 42:

[0268] 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.

[0269] Embodiment 43:

[0270] This embodiment is basically the same as Embodiment 26, except that the thickness of the first sub-bonding layer of the positive electrode is 1200 nm.

[0271] Embodiment 44:

[0272] This embodiment is basically the same as Embodiment 26, except that the thickness of the first sub-bonding layer of the positive electrode is 1500 nm.

[0273] Embodiment 45:

[0274] This embodiment is basically the same as Embodiment 26, except that the thickness of the first sub-bonding layer of the positive electrode is 400 nm.

[0275] Embodiment 46:

[0276] 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.

[0277] Embodiment 47:

[0278] 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.

[0279] Embodiment 48:

[0280] This embodiment is basically the same as Embodiment 26, except that the thickness of the second sub-bonding layer of the positive electrode is 700 nm.

[0281] Embodiment 49:

[0282] 1) Preparation of positive electrode

[0283] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR styrene butadiene latex are mixed in a mass ratio of 97:1.2:

[0284] 1.8 Mix evenly in solvent N-methylpyrrolidone to obtain positive electrode slurry. Coat the positive electrode slurry on both sides of the positive electrode current collector aluminum foil, and obtain positive electrode sheets through drying, cold pressing, slitting and cutting. The positive electrode compaction density is 3.4g / cm 3 .

[0285] 2) Negative electrode sheet preparation

[0286] 2.1) Preparation of negative electrode adhesive slurry

[0287] The polyimide liquid, boehmite powder and PU682 polyurethane adhesive are mixed and added into 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 is added as a solvent, and the mixture is stirred at a rotation speed of 2000 rpm for 1 hour to obtain a negative electrode bonding slurry.

[0288] 2.2) Preparation of negative electrode composite current collector

[0289] A metal copper foil is selected as the material of the conductive layer. The passivation liquid potassium dichromate is evenly coated on the surface of the metal copper foil by gravure printing to form a passivation layer. The thickness of the passivation layer is 100nm. The above-mentioned negative electrode adhesive slurry is gravure coated on the passivation surface of the passivated metal copper foil. The coated metal copper foil is baked in an oven and then thermally composited with the polymer support layer to complete single-sided lamination. The metal copper foil is composited on the other side of the polymer support layer in the same way. After the composite metal copper foil is aged, the adhesive is fully adhered. Then the metal copper foil is subjected to corrosion thinning treatment to obtain a conductive layer with a thickness of 1000nm, thereby obtaining a composite current collector. The adhesive slurry in the composite current collector is thermally composited and aged to form an adhesive layer with a thickness of 1000nm; the thickness of the polymer support layer is 6μm; the surface roughness Ra of the conductive layer is 0.6μm.

[0290] 2.3) Preparation of negative electrode active material layer

[0291] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose CMC are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 98:1:1 to obtain a negative electrode slurry. The above negative electrode slurry is coated on the conductive layers on both sides of the negative electrode composite current collector, and the negative electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The negative electrode compaction density is 1.6g / cm 3 .

[0292] The steps for preparing the electrolyte, isolation membrane and battery cell are the same as those in Example 1.

[0293] Embodiment 50:

[0294] This embodiment is basically the same as Embodiment 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%.

[0295] Embodiment 51:

[0296] This embodiment is basically the same as Embodiment 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%.

[0297] Embodiment 52:

[0298] This embodiment is basically the same as Embodiment 49, with the only difference being that in step 2.2), the thickness of the bonding layer is 600 nm.

[0299] Embodiment 53:

[0300] This embodiment is basically the same as Embodiment 49, with the only difference being that in step 2.2), the thickness of the bonding layer is 2000 nm.

[0301] Embodiment 54:

[0302] 1) Preparation of positive electrode

[0303] The positive electrode active material NCM811, the conductive agent conductive carbon black, and the binder SBR butadiene latex are mixed 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 is coated on both sides of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The positive electrode compaction density is 3.4g / cm 3 .

[0304] 2) Negative electrode sheet preparation

[0305] 2.1) Preparation of negative electrode first sub-bonding layer slurry

[0306] The polyimide liquid, boehmite powder and PU682 polyurethane adhesive are mixed and added into a stirring tank; wherein the mass fraction of polyimide is 65%, the mass fraction of boehmite is 7%, and the mass fraction of PU682 polyurethane adhesive is 28%; N-methylpyrrolidone is added as a solvent, and stirred at a rotation speed of 2000 rpm for 1 hour to obtain the negative electrode first sub-bonding layer slurry.

[0307] 2.2) Preparation of negative electrode composite current collector

[0308] A metal copper foil is selected as the material of the conductive layer, and a chromium-containing passivation treatment is performed on the surface of the metal copper foil by gravure printing to form a passivation layer, and the thickness of the passivation layer is 100 nm; the above-mentioned negative electrode first sub-bonding layer slurry is coated on the surface of the polymer support layer by gravure printing, and the negative electrode first sub-bonding layer slurry is rolled up for standby use after drying in an oven; a PU682 type polyurethane adhesive layer is gravure coated on the passivated surface of the passivated metal copper foil; the coated metal copper foil is baked in an oven, and the side of the metal copper foil coated with the polyurethane adhesive layer and the side of the polymer support layer coated with the negative electrode first sub-bonding layer slurry are thermally composited to complete single-sided lamination. The metal copper foil is composited on the other side of the polymer support layer by the same method. After the composite metal copper foil is aged, the adhesive is fully adhered; then the metal copper foil is subjected to corrosion thinning treatment to obtain a conductive layer with a thickness of 1000 nm, thereby obtaining a composite current collector. The negative electrode first sub-bonding layer slurry and the polyurethane binder layer in the composite current collector are thermally compounded and aged to form the negative electrode first sub-bonding layer and the negative electrode second sub-bonding layer respectively. The thickness of the negative electrode first sub-bonding layer is 800nm, the thickness of the negative electrode second sub-bonding layer is 600nm, and the thickness of the polymer support layer is 6μm; the surface roughness Ra of the conductive layer is 0.6μm.

[0309] 2.3) Preparation of negative electrode active material layer

[0310] The negative electrode active material graphite, conductive agent conductive carbon black, and binder carboxymethyl cellulose CMC are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 98:1:1 to obtain a negative electrode slurry. The above negative electrode slurry is coated on the conductive layers on both sides of the negative electrode composite current collector, and the negative electrode sheet is obtained through drying, cold pressing, striping, and cutting processes. The negative electrode compaction density is 1.6g / cm 3 .

[0311] The steps for preparing the electrolyte, isolation membrane and battery cell are the same as those in Example 49.

[0312] Embodiment 55:

[0313] This embodiment is basically the same as Embodiment 54, except that in step 2.2), the mass fraction of polyimide in the first sub-bonding layer of the negative electrode is 60%, the mass fraction of boehmite is 10%, and the mass fraction of the polyurethane adhesive is 30%.

[0314] Embodiment 56:

[0315] This embodiment is basically the same as Embodiment 54, except that in step 2.2), the mass fraction of polyimide in the first sub-bonding layer of the negative electrode is 70%, the mass fraction of boehmite is 5%, and the mass fraction of the polyurethane adhesive is 25%.

[0316] Embodiment 57:

[0317] 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.

[0318] Embodiment 58:

[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 1500 nm.

[0320] 2. Comparison

[0321] Comparative Example 1:

[0322] This comparative example is basically the same as Example 20, except that in step 1.1), the positive electrode adhesive slurry does not contain polyimide and inorganic particles.

[0323] Comparative Example 2:

[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.

[0325] Comparative Example 3:

[0326] 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.

[0327] Comparative Example 4:

[0328] 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.

[0329] Comparative Example 5:

[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.

[0331] Comparative Example 6:

[0332] This comparative example is basically the same as Example 49, with the only difference being that in step 2.1), the negative electrode bonding slurry does not contain inorganic particles.

[0333] 3. Test Method

[0334] 1) Thickness test of each layer in the composite current collector

[0335] The cross-section samples of the current collector are prepared by liquid nitrogen quenching or argon ion etching, and the secondary electron phase morphology of the cross-section of the sample is observed by scanning electron microscopy (1000-30000 times), and the thickness of the polymer support layer, bonding layer, first sub-bonding layer, second sub-bonding layer, passivation layer and conductive layer are measured. The minimum resolution can reach the nanometer level.

[0336] 2) Polyimide, inorganic particles, and binder content test

[0337] The content of polyimide, inorganic particles and binder in the bonding layer can be tested by conventional methods in the art, for example, by combining infrared testing with XRD.

[0338] 3) Conductive layer roughness test

[0339] The surface of the conductive layer of the composite current collector is tested using a roughness tester to obtain the Ra value.

[0340] Ra average = sum of Ra values ​​of 10 test points / 10.

[0341] 4) Composite current collector fracture elongation test

[0342] MD (longitudinal) tensile elongation at break test: Use a standard sampler to cut the sample into 10 samples of 15mm width and 15cm length along the MD direction; fix the sample on the clamp of the tensile machine, set the speed to 50mm / min, the gauge length between the clamps to 50mm, and perform the tensile test, and take the elongation at break. MD elongation at break = the sum of the elongations at break of 10 test samples / 10; the unit is %.

[0343] TD (transverse) tensile modulus test: Use a standard sampler to cut the sample into 10 samples of 15mm width and 15cm length along the TD direction; fix the sample on the clamp of the tensile machine, set the speed to 50mm / min, the gauge length between the clamps to 50mm, and perform the tensile test, and take the elongation at break. TD elongation at break = the sum of the elongations at break of 10 test samples / 10; the unit is %.

[0344] 5) Composite current collector tensile modulus test

[0345] MD (longitudinal) tensile modulus test: Use a standard sampler to cut the sample into 10 samples of 15mm width and 15cm length along the MD direction; fix the sample on the clamp of the tensile machine, set the speed to 50mm / min, and the gauge length between the clamps to 50mm, and perform the tensile test. Take the strength corresponding to 1% elongation for modulus calculation. MD tensile modulus = (strength / 1%) / 1000; MD tensile modulus average = the sum of the moduli of 10 test samples / 10; the unit is GPa.

[0346] TD (transverse) tensile modulus test: Use a standard sampler to cut the sample into 10 samples of 15mm width and 15cm length along the TD direction; fix the sample on the clamp of the tensile machine, set the speed to 50mm / min, and the gauge length between the clamps to 50mm, and perform the tensile test. Take the strength corresponding to 1% elongation for modulus calculation. TD tensile modulus = (strength / 1%) / 1000; TD tensile modulus average = the sum of the moduli of 10 test samples / 10; the unit is GPa.

[0347] 6) Conductive layer peeling force test

[0348] After laminating the sample with the non-corona surface of the ethylene-acrylic acid copolymer (EAA) film, cover the EAA film with 12μm thick PET, place it on a heat sealer, and laminat it at a temperature of 120℃ and a pressure of 0.2MPa. Cut the laminated sample into 100mm long and 20mm wide samples, and use 3M double-sided tape to stick the non-laminated surface of the conductive layer on the steel plate; clamp the sample on the fixture of the tensile machine, with a spacing of 50mm and a speed of 300mm / min to perform a 180℃ peel test, read the peel force, convert it into N / m units, and take the average peel force of 5 parallel samples; the average peel force = the sum of the peel forces of 5 test samples / 5.

[0349] 7) Tab shrinkage test

[0350] Before coating 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 coating 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 coating the active material layer and drying it with the original tab width before coating to calculate the shrinkage rate;

[0351] Tab shrinkage rate = (original tab width - tab width after coating) / original tab width) * 100%;

[0352] The average value of the lug shrinkage rate = the sum of the shrinkage rates of 10 lugs / 10; the lug shrinkage rate requirement is ≤5%;

[0353] 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.

[0354] 8) Pole shear force test

[0355] Stick a special shear force test tape on the steel plate with a width of 4 mm and a length of 5 mm. Stick the electrode on the tape and use a high-speed rail tensile tester to measure the bonding force between the active material layer and the conductive layer (shear force specification ≥ 0.3 MPa);

[0356] Shear force mean = sum of shear force values ​​of 10 samples / 10;

[0357] 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.

[0358] 9) Tab welding tensile test

[0359] Through the conventional battery manufacturing process, the positive electrode sheet, the isolation film 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 into the pole ear; the welding tension after welding of the single-layer pole ear is measured using a high-speed rail tensile test machine. The welding area of ​​the pole sheet (pole ear, 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 an interval 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.

[0360] 10) U-shaped resistance test after pole piece roller welding

[0361] The welded electrode pieces are cut into samples of the same size as the battery cells, and the resistance between the two electrode ears is measured with an internal resistance meter.

[0362] The average U-shaped resistance value = the sum of the U-shaped resistance values ​​of 10 samples / 10.

[0363] The parameters of the pole pieces 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 pole pieces 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 embodiment 1, S2 represents embodiment 2, and so on; similarly, D1 represents comparative example 1, D2 represents comparative example 2, and so on. The three data separated by "," in the parameters of "bonding layer composition" and "first sub-bonding layer composition" in Tables 1 and 2 represent the mass fractions of polyimide, inorganic particles and binder from left to right, respectively. For example, "43, 7, 50" in Example 1 means that the mass fractions of polyimide, inorganic particles and binder in the bonding layer are 43%, 7%, and 50%, respectively; other embodiments and comparative examples are similar. " / " in Tables 1 and 2 means that it does not exist, and " / " in Tables 3 and 4 means that it has not been tested.

[0364] Table 1

[0365]

[0366]

[0367]

[0368] Table 2

[0369]

[0370]

[0371]

[0372] Table 3

[0373]

[0374]

[0375]

[0376] Table 4

[0377]

[0378]

[0379]

[0380]

[0381] 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 pole piece using the composite current collector of the present application has a smaller pole lug shrinkage rate, a larger pole piece welding tensile force and a smaller U-shaped resistance.

[0382] 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 tensile force of the pole piece, reducing the U-shaped resistance of the pole piece, and making the pole piece have a higher elongation at break.

[0383] 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 pole piece to have a smaller tab shrinkage rate, a larger pole piece welding tensile force and a smaller U-shaped resistance, and its overall performance is better.

[0384] By comparing Examples 16 to 21, it can be seen that controlling the thickness of the adhesive layer within the range of 600nm to 2000nm can make the composite current collector have a larger tensile modulus and elongation at break, while making the pole piece have a smaller tab shrinkage, a larger pole piece welding tension and a smaller U-shaped resistance, and has excellent comprehensive performance. Furthermore, controlling the thickness of the adhesive layer within the range of 800nm ​​to 1500nm can further improve the comprehensive performance.

[0385] By comparing Examples 26 to 32, it can be seen that when the bonding layer adopts a double-layer structure, the content of polyimide in the first sub-bonding layer is controlled within the range of 60% to 70%, and the content of the binder is controlled within the range of 20% to 30%. This can enable the composite current collector to have a larger tensile modulus and elongation at break, while allowing the pole piece to have a smaller pole ear shrinkage rate, a larger pole piece welding tensile force and a smaller U-shaped resistance, thereby having more excellent comprehensive performance.

[0386] 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 pole piece to have a smaller pole ear shrinkage rate, a larger pole piece welding tensile force and a smaller U-shaped resistance, thereby having more excellent overall performance.

[0387] 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 pole piece can have a smaller pole lug shrinkage rate, a larger pole piece welding tensile force and a smaller U-shaped resistance, thereby having more excellent overall performance.

[0388] By comparing Comparative Examples 1 to 3 with Example 20, and 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 ear shrinkage rate is increased, the pole piece welding tension is reduced, the U-type resistance is increased, and its comprehensive performance is significantly reduced.

[0389] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0390] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector, It is characterized in that include: 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, It is characterized in that 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, It is characterized in that 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 claim 2, It is characterized in that The thickness of the bonding layer is 600nm to 2000nm, and can be optionally 800nm ​​to 1500nm.

5. The composite current collector according to claim 1, It is characterized in that 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.

6. The composite current collector according to claim 5, It is characterized in that 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%.

7. The composite current collector according to claim 5, It is characterized in that The thickness of the first sub-adhesive layer is 500nm-1500nm, and can be optionally 600nm-1200nm.

8. The composite current collector according to claim 5, It is characterized in that The thickness of the second sub-adhesive layer is 300 nm to 700 nm.

9. The composite current collector according to any one of claims 1 to 8, It is characterized in that The inorganic particles include one or more of boehmite, silicon carbide, silicon oxide, aluminum oxide, calcium carbonate, titanium oxide and graphene.

10. The composite current collector according to any one of claims 1 to 8, It is characterized in that 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.

11. The composite current collector according to any one of claims 1 to 8, It is characterized in that Also includes: The passivation layer is disposed between the bonding layer and the conductive layer.

12. The composite current collector according to claim 11, It is characterized in that The materials of the passivation layer include chromate, dichromate, organic phosphonate, Al 2 O 3 、SiO 2 and Si 3 N 4 One or more of .

13. The composite current collector according to claim 12, It is characterized in that Satisfy at least one of the following (1) to (3): (1) The chromate includes one or more of sodium chromate, potassium chromate, magnesium chromate and silver chromate; (2) The dichromate includes one or more of sodium dichromate, potassium dichromate, magnesium dichromate and silver dichromate; (3) 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).

14. The composite current collector according to claim 12 or 13, It is characterized in that The thickness of the passivation layer is 1 nm to 500 nm, and can be optionally 10 nm to 200 nm.

15. The composite current collector according to any one of claims 1 to 8, 12 and 13, It is characterized in that 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.

16. The composite current collector according to any one of claims 1 to 8, 12 and 13, It is characterized in that 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.

17. The composite current collector according to any one of claims 1 to 8, 12 and 13, It is characterized in that The surface roughness of the conductive layer is Ra, 0.1 μm <Ra<2μm。 18. An electrode plate, It is characterized in that The composite current collector comprises an active material layer and the composite current collector according to any one of claims 1 to 17, wherein the active material layer is arranged on a surface of the conductive layer away from the bonding layer.

19. A secondary battery, It is characterized in that It comprises the composite current collector according to any one of claims 1 to 17 or the electrode sheet according to claim 18.

20. An electrical device, It is characterized in that Includes the secondary battery as claimed in claim 19.

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