Composite current collector and preparation method therefor, and electrode sheet, battery and electric apparatus

Abstract

A composite current collector and a preparation method therefor, and an electrode sheet, a battery and an electric apparatus. The composite current collector comprises a support layer, and a bonding layer, a first conductive layer and a second conductive layer, which are sequentially arranged in a stacked manner on at least one surface of the support layer, wherein the first conductive layer contains a first metal material, the second conductive layer contains a second metal material, and the grain size of the second metal material is smaller than that of the first metal material. Thus, the fracture strength and tensile modulus of the composite current collector are effectively improved, and the problems of wrinkling and shrinkage existing in a tab area of the composite current collector are ameliorated.

Description

Composite current collector and preparation method thereof, electrode sheet, battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202311606674.1 filed on November 27, 2023, entitled "Composite current collector and its preparation method, electrode plate, battery and electrical device", which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a composite current collector and a preparation method thereof, an electrode plate, a battery, and an electrical device. Background Art

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

[0005] Secondary batteries are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power stations, as well as in various fields such as electric vehicles and consumer electronics, due to their advantages such as high energy density, high output power, long cycle life, and low environmental pollution. Compared with traditional pure metal foil current collectors, composite current collectors with a polymer layer in the middle and conductive layers on both sides can reduce the overall weight of the current collector, thereby increasing the energy density of secondary batteries. Providing an adhesive layer between the support layer and the conductive layer can improve the elongation and adhesion of traditional composite current collectors, but their overall fracture strength and tensile modulus are low, and there is a problem of wrinkling and shrinkage in the tab area.

[0006] Summary of the Invention

[0007] The present application provides a composite current collector and its preparation method, electrode plate, battery and electrical device, aiming to improve the fracture strength and tensile modulus of the composite current collector, while alleviating the wrinkling and shrinkage problem in the tab area of ​​the composite current collector.

[0008] In a first aspect of the present application, a composite current collector is provided, comprising a support layer and a bonding layer, a first conductive layer, and a second conductive layer stacked in sequence on at least one surface of the support layer, wherein the first conductive layer comprises a first metal material, and the second conductive layer comprises a second metal material, and the grain size of the second metal material is smaller than the grain size of the first metal material.

[0009] In the above-mentioned composite current collector, the grain size of the second metal material is smaller than the grain size of the first metal material, so that the second conductive layer has more grain boundaries than the first conductive layer, thereby greatly improving the fracture strength and tensile modulus of the composite current collector; and the increase in the grain boundaries of the second conductive layer can improve the thermal conductivity of the composite current collector, thereby alleviating the wrinkling and shrinkage problem of the tab area of ​​the composite current collector caused by the drying stress during coating, improving the reliability of the tab welding, and reducing the DC internal resistance of the battery.

[0010] In some embodiments, the ratio of the grain size of the first metal material to the grain size of the second metal material is 2-50, and can be optionally 2.5-40.

[0011] In some embodiments, the difference between the grain size of the first metal material and the grain size of the second metal material is 200 nm to 3300 nm, and can be optionally 300 nm to 3100 nm.

[0012] In some embodiments, the grain size of the second metal material is 50 nm to 300 nm.

[0013] In some embodiments, the grain size of the first metal material is 500 nm to 3000 nm.

[0014] In some embodiments, the first metal material and the second metal material each independently include one or more of aluminum metal and aluminum alloy.

[0015] In some embodiments, the ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is 1 to 10, and can be optionally 1.5 to 8.

[0016] In some embodiments, the thickness of the first conductive layer is 500 nm to 1500 nm, and can be optionally 600 nm to 1200 nm.

[0017] In some embodiments, the thickness of the second conductive layer is 100 nm to 700 nm, and can be optionally 200 nm to 500 nm.

[0018] In some embodiments, the density of the composite current collector is ≥90%.

[0019] In some embodiments, the density of the first conductive layer is ≥60%.

[0020] In some embodiments, the composite current collector has a tensile modulus of 5 GPa to 12 GPa.

[0021] In some embodiments, the composite current collector has a fracture strength of ≥160 MPa.

[0022] In some embodiments, the composite current collector further includes a passivation layer, and the passivation layer is disposed between the bonding layer and the first conductive layer.

[0023] In some embodiments, the passivation layer has a thickness of 10 nm to 200 nm.

[0024] In some embodiments, the passivation layer comprises a passivating agent including one or more of an organic phosphate, a chromate, a dichromate, Al2O3, SiO2, and Si3N4.

[0025] In some embodiments, the organic phosphate 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.

[0026] In some embodiments, the chromate includes one or more of sodium chromate, potassium chromate, magnesium chromate, and silver chromate.

[0027] In some embodiments, the dichromate includes one or more of ammonium dichromate, potassium dichromate, sodium dichromate, and magnesium dichromate.

[0028] In some embodiments, the thickness of the adhesive layer is 300 nm to 700 nm.

[0029] In some embodiments, the bonding layer comprises a bonding agent, and the bonding agent includes one or more of a bonding composition, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide, and the bonding composition includes isocyanate and polyester polyol.

[0030] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0031] In some embodiments, the thickness of the support layer is 2 μm to 10 μm.

[0032] In some embodiments, the support layer includes one or more of a polymer material and a polymer-based composite material.

[0033] In some embodiments, the polymer material 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, their derivatives, their cross-linked products and their copolymers.

[0034] In some embodiments, the polymer-based composite material includes the polymer material and an additive, and the additive includes one or more of a third metal material and an inorganic non-metallic material.

[0035] In some embodiments, the third metal material includes one or more of aluminum, copper, nickel, iron, silver, titanium, and alloys thereof.

[0036] In some embodiments, the inorganic non-metallic material includes one or more of graphite, conductive carbon, aluminum oxide, silicon oxide, silicon carbide, and silicon dioxide.

[0037] In a second aspect of the present application, a method for preparing a composite current collector is provided, comprising the following steps:

[0038] An adhesive layer, a first conductive layer, and a second conductive layer are sequentially stacked on at least one surface of the supporting layer; the first conductive layer comprises a first metal material, the second conductive layer comprises a second metal material, and the grain size of the second metal material is smaller than the grain size of the first metal material.

[0039] The above preparation method is relatively simple and suitable for batch production of composite current collectors.

[0040] In some embodiments, the step of forming the second conductive layer includes: disposing the second conductive layer on the surface of the first conductive layer by using an evaporation method and / or a magnetron sputtering method.

[0041] In some embodiments, the step of forming the bonding layer and the first conductive layer stacked in sequence on at least one surface of the supporting layer includes: setting a first slurry containing a binder on the surface of at least one of the supporting layer and the first conductive layer, and solidifying the first slurry to form the bonding layer.

[0042] In some embodiments, the method for preparing the composite current collector further includes: forming a passivation layer between the bonding layer and the first conductive layer.

[0043] In some embodiments, the step of forming the passivation layer includes: disposing a second slurry containing a passivator on one surface of the first conductive layer, and curing the second slurry to form the passivation layer.

[0044] The third aspect of the present application provides an electrode plate, comprising at least one of the composite current collector described in the first aspect of the present application and the composite current collector prepared by the preparation method described in the second aspect of the present application.

[0045] The electrode plate of the present application includes at least one of the composite current collector provided in the present application and the composite current collector prepared by the preparation method provided in the present application, and thus has at least the same advantages as the composite current collector or the composite current collector prepared by the preparation method.

[0046] The fourth aspect of the present application provides a battery, comprising at least one of the composite current collector described in the first aspect of the present application, the composite current collector prepared by the preparation method described in the second aspect of the present application, and the electrode plate described in the third aspect of the present application.

[0047] The battery of the present application includes at least one of the composite current collector provided in the present application, the composite current collector prepared by the preparation method provided in the present application, and the electrode plate provided in the present application, and thus has at least the same advantages as the composite current collector, the composite current collector prepared by the preparation method, or the electrode plate.

[0048] In a fifth aspect of the present application, an electrical device is provided, comprising the battery described in the fourth aspect of the present application.

[0049] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery.

[0050] 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

[0051] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0052] FIG1 is a schematic diagram of a composite current collector according to one embodiment of the present application.

[0053] FIG2 is a schematic diagram of a composite current collector according to another embodiment of the present application.

[0054] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0055] FIG. 4 is an exploded view of the battery cell shown in FIG. 3 according to an embodiment of the present application.

[0056] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0057] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0058] FIG. 7 is an exploded view of the battery pack shown in FIG. 6 according to an embodiment of the present application.

[0059] FIG8 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0060] Explanation of the accompanying drawings: 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 cover plate; 6 electrical device; 7 composite current collector; 71 support layer; 72 adhesive layer; 73 first conductive layer; 74 second conductive layer; 75 passivation layer. DETAILED DESCRIPTION

[0061] Below, some embodiments of the composite current collector and its preparation method, electrode plate, battery and electrical 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.

[0062] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0063] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0064] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0065] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0066] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0067] In this application, in the open technical features or technical solutions described with words such as "contain", "include", and "include", unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that also include additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members". In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0068] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0069] The supporting layer material of traditional composite current collectors is mainly PET (polyethylene terephthalate) or PP (polypropylene). Although the adhesive layer provided between the supporting layer and the conductive layer can improve the elongation and adhesion of the traditional composite current collector, its overall breaking strength and tensile modulus are low. In addition, during the coating stage, the tab area is easily affected by drying stress and wrinkles and shrinks, affecting the welding of the tab and the DC internal resistance (DCR) of the battery.

[0070] In view of this, the present application provides a composite current collector comprising a support layer, and an adhesive layer, a first conductive layer, and a second conductive layer sequentially stacked on at least one surface of the support layer. The first conductive layer comprises a first metal material, and the second conductive layer comprises a second metal material, wherein the grain size of the second metal material is smaller than that of the first metal material. The grain size of the second metal material is smaller than that of the first metal material, resulting in a greater number of grain boundaries in the second conductive layer than in the first conductive layer, thereby significantly improving the fracture strength and tensile modulus of the composite current collector. Furthermore, the increased number of grain boundaries in the second conductive layer can enhance the thermal conductivity of the composite current collector, thereby alleviating the wrinkling and shrinkage problem of the tab region of the composite current collector caused by drying stress during coating, improving the reliability of tab welding, and reducing the direct current resistance (DCR) of the battery.

[0071] One embodiment of the present application provides a composite current collector, comprising a support layer and an adhesive layer, a first conductive layer, and a second conductive layer stacked in sequence on at least one surface of the support layer, wherein the first conductive layer comprises a first metal material, and the second conductive layer comprises a second metal material, and the grain size of the second metal material is smaller than the grain size of the first metal material.

[0072] In the above-mentioned composite current collector, the grain size of the second metal material is smaller than the grain size of the first metal material, so that the second conductive layer has more grain boundaries than the first conductive layer, thereby greatly improving the fracture strength and tensile modulus of the composite current collector; and the increase in the grain boundaries of the second conductive layer can improve the thermal conductivity of the composite current collector, thereby alleviating the wrinkling and shrinkage problem of the tab area of ​​the composite current collector caused by the drying stress during coating, improving the reliability of the tab welding, and reducing the DC internal resistance (DCR) of the battery.

[0073] In some embodiments, in conjunction with Figure 1, the composite current collector 7 includes a support layer 71, an adhesive layer 72, a first conductive layer 73 and a second conductive layer 74. On two opposite surfaces of the support layer 71 and in a direction away from the support layer 71, the adhesive layer 72, the first conductive layer 73 and the second conductive layer 74 are stacked in sequence. The first conductive layer 73 includes a first metal material, and the second conductive layer 74 includes a second metal material. The grain size of the second metal material is smaller than the grain size of the first metal material.

[0074] In some embodiments, the ratio of the grain size of the first metal material to the grain size of the second metal material is 2 to 50. This can further improve the fracture strength and tensile modulus of the composite current collector, while also further alleviating the wrinkling and shrinkage problem in the tab region of the composite current collector caused by drying stress during coating. In some embodiments, the ratio of the grain size of the first metal material to the grain size of the second metal material is 2.5 to 40.

[0075] In some embodiments, the difference between the grain size of the first metal material and the grain size of the second metal material is 200 nm to 3300 nm. This can further improve the fracture strength and tensile modulus of the composite current collector, while also further alleviating the problem of wrinkling and shrinkage in the tab area of ​​the composite current collector caused by drying stress during coating. In some embodiments, the difference between the grain size of the first metal material and the grain size of the second metal material is 300 nm to 3100 nm.

[0076] In this application, the unit "nm" refers to nanometers.

[0077] In some embodiments, the second metal material has a grain size of 50 nm to 300 nm. A grain size within this range increases the number of grain boundaries in the second conductive layer, further improving the composite current collector's fracture strength and tensile modulus while mitigating wrinkling and shrinkage in the tab region of the composite current collector caused by drying stress during coating. The grain size of the second metal material includes, but is not limited to, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, and 300 nm.

[0078] In some embodiments, the grain size of the first metal material is 500 nm to 3000 nm. A grain size of the first metal material within this range can further improve the composite current collector's fracture strength and tensile modulus, and further alleviate wrinkling and shrinkage in the tab region of the composite current collector caused by drying stress during coating. It is understood that the grain size of the first metal material includes, but is not limited to, 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, and 3000 nm.

[0079] In some embodiments, the first metal material and the second metal material each independently include one or more of aluminum metal and an aluminum alloy.

[0080] In some embodiments, the ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is 1 to 10. This improves the fracture strength and tensile modulus of the composite current collector without adding additional void defects. It also minimizes thickness fluctuations between the first and second conductive layers, retaining the high adhesion and high ductility characteristics of the composite current collector. This meets battery manufacturing requirements, reduces the risk of cracking in the first and second conductive layers, and maintains the battery's DCR within a reasonable range. In some embodiments, the ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is 1.5 to 8.

[0081] In some embodiments, the thickness of the first conductive layer is 500nm to 1500nm. As a result, the fracture strength and tensile modulus of the composite current collector are improved without adding additional hole defects. At the same time, the thickness fluctuation of the first conductive layer is relatively small, retaining the high adhesion and high ductility characteristics of the composite current collector, meeting the battery manufacturing requirements, reducing the risk of cracking of the first conductive layer, and maintaining the DCR of the battery within a reasonable range. It is understood that the thickness of the first conductive layer includes but is not limited to: 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm. In some embodiments, the thickness of the first conductive layer is 600nm to 1200nm.

[0082] In some embodiments, the thickness of the second conductive layer is 100nm to 700nm. As a result, the fracture strength and tensile modulus of the composite current collector are improved without adding additional hole defects. At the same time, the thickness fluctuation of the second conductive layer is relatively small, retaining the high adhesion and high ductility characteristics of the composite current collector, meeting the battery manufacturing requirements, reducing the risk of cracking of the second conductive layer, and maintaining the DCR of the battery within a reasonable range. It is understood that the thickness of the second conductive layer includes but is not limited to: 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm. In some embodiments, the thickness of the second conductive layer is 200nm to 500nm.

[0083] In some embodiments, the density of the composite current collector is ≥90%. The density of the composite current collector within the above range is conducive to further improving the fracture strength and tensile modulus of the composite current collector.

[0084] In this application, compactness refers to the uniformity of the conductive layer and also represents density. Generally, poor compactness of the composite current collector will cause light leakage under dark field conditions of the backlight screen. At the same time, too poor compactness will affect the mechanical strength of the composite current collector. The conductive layer refers to at least one of the first conductive layer and the second conductive layer.

[0085] In some embodiments, the density of the first conductive layer is ≥60%, which is beneficial for further improving the fracture strength and tensile modulus of the composite current collector.

[0086] In some embodiments, the tensile modulus of the composite current collector is 5 GPa to 12 GPa. It is understood that the tensile modulus of the composite current collector includes but is not limited to: 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 11 GPa, 12 GPa.

[0087] In this application, the unit "GPa" refers to gigapascals.

[0088] In some embodiments, the composite current collector has a fracture strength of ≥ 160 megapascals (MPa).

[0089] In some embodiments, the composite current collector further includes a passivation layer disposed between the adhesive layer and the first conductive layer, thereby inhibiting electrolyte corrosion of the first conductive layer and improving the peeling force between the support layer and the first conductive layer.

[0090] In some embodiments, referring to FIG2 , the composite current collector 7 further includes a passivation layer 75 disposed between the bonding layer 72 and the first conductive layer 73. That is, the composite current collector 7 includes a support layer 71 and, on at least one surface of the support layer 71, a bonding layer 72, a passivation layer 75, a first conductive layer 73, and a second conductive layer 74 stacked in sequence. This prevents the electrolyte from corroding the first conductive layer 73, thereby improving the peeling force between the support layer 71 and the first conductive layer 73.

[0091] In some embodiments, the composite current collector includes a support layer, an adhesive layer, a passivation layer, a first conductive layer, and a second conductive layer. The adhesive layer, the passivation layer, the first conductive layer, and the second conductive layer are stacked in sequence on two opposite surfaces of the support layer and in a direction away from the support layer.

[0092] In some embodiments, the thickness of the passivation layer is 10 nm to 200 nm. It is understood that the thickness of the passivation layer includes but is not limited to: 10 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, and 200 nm.

[0093] In some embodiments, the passivation layer comprises a passivator, and the passivator comprises one or more of an organic phosphate, a chromate, a dichromate, Al2O3, SiO2, and Si3N4. Thus, it is possible to further inhibit the electrolyte from corroding the first conductive layer, thereby further improving the peeling force between the support layer and the first conductive layer. In some embodiments, the organic phosphate comprises one or more of hydroxyethylidene diphosphonic acid, diethylenetriamine penta (methylene phosphonic acid), triethylenetetraamine hexa (methylene phosphonic acid), and ethylenediamine tetra (methylene phosphonic acid). In some embodiments, the chromate comprises one or more of sodium chromate, potassium chromate, magnesium chromate, and silver chromate. In some embodiments, the dichromate comprises one or more of ammonium dichromate, potassium dichromate, sodium dichromate, and magnesium dichromate.

[0094] In some embodiments, the thickness of the adhesive layer is 300 nm to 700 nm. It is understood that the thickness of the adhesive layer includes but is not limited to: 300 nm, 400 nm, 500 nm, 600 nm, and 700 nm.

[0095] In some embodiments, the adhesive layer comprises an adhesive, and the adhesive comprises one or more of an adhesive composition, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide, and the adhesive composition comprises isocyanate and polyester polyol. In some embodiments, the polyurethane comprises one or more of thermoplastic polyurethane and reactive polyurethane.

[0096] In some embodiments, the thickness of the support layer is 2 μm to 10 μm. It is understood that the thickness of the support layer includes but is not limited to: 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm.

[0097] In this application, the unit "μm" means micrometer.

[0098] In some embodiments, the support layer comprises one or more of a polymer material and a polymer-based composite material.

[0099] In some embodiments, the polymer material 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, their derivatives, their cross-linked products and their copolymers.

[0100] In some embodiments, the polymer-based composite material includes a polymer material and an additive, wherein the additive includes one or more of a third metal material and an inorganic non-metallic material. In some embodiments, the third metal material includes one or more of aluminum, copper, nickel, iron, silver, titanium, and alloys thereof. In some embodiments, the inorganic non-metallic material includes one or more of graphite, conductive carbon, aluminum oxide, silicon oxide, silicon carbide, and silicon dioxide.

[0101] Another embodiment of the present application provides a method for preparing the composite current collector, comprising the following steps:

[0102] An adhesive layer, a first conductive layer and a second conductive layer are sequentially stacked on at least one surface of the support layer.

[0103] The above preparation method is relatively simple and suitable for mass production of composite current collectors. It can be understood that the above adhesive layer is used to connect the support layer and the first conductive layer.

[0104] In some embodiments, the step of forming the second conductive layer includes: disposing the second conductive layer on the surface of the first conductive layer by using an evaporation method and / or a magnetron sputtering method.

[0105] In some embodiments, the step of forming the first conductive layer includes thinning the conductive layer comprising the first metal material to form the first conductive layer. The conductive layer may be thinned to a suitable thickness by at least one of physical etching and chemical etching (chemical corrosion), thereby forming the first conductive layer.

[0106] In some embodiments, the step of forming a sequentially stacked adhesive layer and a first conductive layer on at least one surface of the support layer includes: applying a first slurry containing an adhesive on a surface of at least one of the support layer and the first conductive layer, and curing the first slurry to form the adhesive layer. It is understood that the first slurry containing an adhesive may be applied on the surface of the support layer or the first conductive layer, or may be applied on both the support layer and the first conductive layer.

[0107] In some embodiments, the method for preparing the composite current collector further includes forming a passivation layer between the adhesive layer and the first conductive layer. The passivation layer can inhibit the electrolyte from corroding the first conductive layer, thereby improving the peeling force between the support layer and the first conductive layer.

[0108] In some embodiments, the step of forming the passivation layer includes: disposing a second slurry containing a passivator on one surface of the first conductive layer, and curing the second slurry to form the passivation layer.

[0109] In some embodiments, the step of forming a bonding layer and a passivation layer stacked in sequence on at least one surface of the support layer includes: disposing a first slurry containing a bonding agent on the surface of at least one of the support layer and the passivation layer, and curing the first slurry to form the bonding layer.

[0110] Yet another embodiment of the present application provides an electrode plate comprising the composite current collector described above. The electrode plate comprises the composite current collector described above, and thus the electrode plate has at least the same advantages as the composite current collector described above. In some embodiments, the electrode plate can be at least one of a positive electrode plate and a negative electrode plate.

[0111] Yet another embodiment of the present application provides a battery comprising the aforementioned composite current collector or electrode plate. This battery comprises the aforementioned composite current collector or electrode plate, and thus has at least the same advantages as the aforementioned composite current collector or electrode plate. This battery comprises a secondary battery and a primary battery; the secondary battery includes, but is not limited to, at least one of a lithium-ion battery, a sodium-ion battery, and a magnesium-ion battery; and the primary battery includes, but is not limited to, a lithium primary battery.

[0112] Another embodiment of the present application further provides an electrical device comprising the above-mentioned battery. The electrical device comprises the above-mentioned battery, and thus the electrical device has at least the same advantages as the above-mentioned battery.

[0113] In addition, the battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0114] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0115] Positive electrode

[0116] 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, wherein the positive electrode active material layer includes a positive electrode active material.

[0117] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0118] In some embodiments, the positive electrode current collector may be the composite current collector described above in this application.

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

[0120] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, unless otherwise specified, the content of Li is the initial state of the material. The positive electrode active 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 active material contained in the plate will usually change. 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 new materials obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials, and non-limiting examples include coating modification.

[0121] In the examples of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0122] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0123] The positive electrode active material includes a sodium ion active material.

[0124] As an example, the sodium ion active material may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0125] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides may be Na x MO2, wherein M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0126] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4) n- valence.

[0127] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0128] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0129] Polyanionic compounds may include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) wherein M′ in NaM′PO4F may include one or more of V, Fe, Mn and Ni.

[0130] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may include Na a Me b Me' c (CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0131] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0132] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side of a positive electrode current collector, and performing drying, cold pressing, and other processes to obtain a positive electrode sheet. The type of solvent can be selected from, but not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm 2 -35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 -3.6g / cm 3 , optional 3.3g / cm 3 -3.5g / cm 3 .

[0134] In this application, the unit "mPa·s" refers to millipascal·second, and the unit "mg / cm 2 " refers to milligrams per square centimeter, the unit is "g / cm 3 ” refers to grams per cubic centimeter.

[0135] Negative electrode

[0136] 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.

[0137] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0138] In some embodiments, the negative electrode current collector may be the composite current collector described above.

[0139] In some embodiments, the negative electrode current collector may be a metal foil or other composite current collector. For example, copper foil may be used as the metal foil. Other composite current collectors may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. Other composite current collectors can be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0140] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0141] 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).

[0142] 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.

[0143] 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)).

[0144] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 -220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 -1.8g / cm 3 .

[0145] In this application, the unit "g / m 2 ” refers to grams per square meter.

[0146] In some embodiments, the positive electrode current collector and / or the negative electrode current collector adopts the composite current collector described above in this application. It is understood that only the positive electrode current collector can adopt the composite current collector described above in this application, or only the negative electrode current collector can adopt the composite current collector described above in this application. Of course, both the positive electrode current collector and the negative electrode current collector can also adopt the composite current collector described above in this application.

[0147] electrolytes

[0148] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0149] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0150] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0151] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0152] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0153] 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.

[0154] Isolation film

[0155] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0156] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0157] In some embodiments, the isolation film has a thickness of 6 μm-40 μm, and optionally 12 μm-20 μm.

[0158] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0159] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0160] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0162] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0163] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 5 with a square structure as an example.

[0164] In some embodiments, referring to Figure 4, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0165] The secondary battery may be a battery module 4 or a battery pack 1 .

[0166] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0167] FIG5 shows an example battery module 4. Referring to FIG5 , in the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0168] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0169] 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. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0170] Figures 6 and 7 illustrate an example battery pack 1. Referring to Figures 6 and 7 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0171] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0172] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0173] FIG8 shows an example of an electric device 6. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0174] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0175] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0176] Example 1

[0177] (1) The preparation method of the composite current collector comprises the following steps:

[0178] (1.1) preparing an aluminum foil intermediate having a thickness of 3 μm to 5 μm and a grain size of 2000 nm by cold rolling the aluminum foil and controlling the annealing process of the aluminum foil;

[0179] (1.2) preparing a passivation slurry using potassium dichromate as a passivation agent, and evenly coating the passivation slurry on the surface of the aluminum foil intermediate by gravure coating to form a passivation layer with a thickness of 100 nm;

[0180] (1.3) gravure coating a polyurethane adhesive slurry on the surface of the passivation layer away from the aluminum foil intermediate to form an adhesive layer with a thickness of 500 nm;

[0181] (1.4) The aluminum foil intermediate with the adhesive layer obtained in step (1.3) was baked in an oven at 110 degrees Celsius (°C), and then laminated to two surfaces of the support layer in the thickness direction, and aged at 80°C for 72 hours (h) to obtain a first semi-finished product, wherein the support layer had a thickness of 6 μm and was made of PET;

[0182] (1.5) The aluminum foil intermediate in the first semi-finished product is corroded and thinned using a 60 g / L sodium hydroxide solution to form a first conductive layer with a thickness of 800 nm. The grain size of the aluminum (first metal material) in the first conductive layer is 2000 nm. After etching to the designed thickness, the foil is washed with water and then polished with 68% nitric acid. After cleaning, it is sprayed with water and squeezed with a squeeze roller to remove any residual moisture. Finally, it is dried in an 80°C oven and rolled to obtain a second semi-finished product.

[0183] (1.6) Place the second semi-finished product after step (1.5) in the vacuum coating chamber and evacuate to 10 -2Pa (Pa), high-purity aluminum filaments are melted and evaporated in a metal evaporation chamber at a temperature of 1200°C to 2000°C. The evaporated metal passes through a cooling system in a vacuum plating chamber and is finally deposited on the surface of the first conductive layer to form a second conductive layer. The grain size of the aluminum (second metal material) in the second conductive layer is 200nm. The resulting composite current collector includes a support layer, an adhesive layer, a passivation layer, a first conductive layer, and a second conductive layer. The adhesive layer, passivation layer, first conductive layer, and second conductive layer are stacked in sequence on both surfaces of the support layer in the thickness direction and in a direction away from the support layer.

[0184] (2) The method for preparing a secondary battery comprises the following steps:

[0185] (2.1) Preparation of positive electrode sheet

[0186] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black SP and binder PVDF were dispersed in solvent NMP in a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the double-sided surface of the composite current collector prepared in the above step (1), and after drying and cold pressing, a positive electrode sheet was obtained. The compaction density of the positive electrode sheet was 3.4 g / cm 3 .

[0187] (2.2) Preparation of negative electrode sheet

[0188] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then super-cold pressed and cut to obtain a negative electrode sheet. The compaction density of the negative electrode sheet was 1.6 g / cm 3 .

[0189] (2.3) Isolation membrane

[0190] Use a separator with PP laminated on both sides of PE (PP / PE / PP).

[0191] (2.4) Preparation of electrolyte

[0192] The organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), with a volume ratio of 30:70. In an argon atmosphere glove box with a water content of <10 ppm, thoroughly dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte solution. The concentration of the lithium salt is 1 mol / L.

[0193] (2.5) Preparation of batteries

[0194] The positive electrode sheet, separator and negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role. After winding into a bare battery cell, the double-sided metal edging method is used to roller weld the electrode ears, and then fill them with aluminum-plastic film. After baking at 80°C to remove water, non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, the finished battery is obtained.

[0195] Example 2-32

[0196] The method is basically the same as Example 1, except that: the preparation method of the composite current collector in step (1) is different; specifically, the thickness of the first conductive layer, the thickness of the second conductive layer, the grain size of the first metal material, and the grain size of the second metal material are changed.

[0197] Comparative Example 1

[0198] The method is basically the same as Example 1, except that the preparation method of the composite current collector in step (1) is different; specifically, step (1.6) is omitted, that is, the composite current collector does not have a second conductive layer.

[0199] The product parameters of the composite current collectors prepared in Examples 1-32 and Comparative Example 1 are shown in Table 1.

[0200] Performance Testing

[0201] (1) Test method for thickness of the first conductive layer, the second conductive layer, the passivation layer, the bonding layer, and the support layer, as well as thickness fluctuation of the first conductive layer and the second conductive layer

[0202] The cross-section sample of the composite current collector is prepared by liquid nitrogen quenching or argon ion etching. The secondary electron phase morphology of the cross-section of the sample is observed by scanning electron microscopy (SEM) at a magnification of 1000 to 30000 times. The thickness of the first conductive layer, the second conductive layer, the passivation layer, the bonding layer or the support layer can be measured with a minimum resolution of nanometers.

[0203] Thickness fluctuation of the first conductive layer and the second conductive layer (%) = (H2-H1) / H1*100%;

[0204] Wherein, H1 represents the designed value of the total thickness of the first conductive layer and the second conductive layer, and H2 represents the actual measured value of the total thickness of the first conductive layer and the second conductive layer in the cross-sectional sample of the composite current collector.

[0205] (2) Testing method for grain size of the first metal material and the second metal material

[0206] Use SEM to magnify the first conductive layer or the second conductive layer 10,000 to 30,000 times, observe the grain size on the surface, and randomly measure the size of 300 grains and take the average value, with a minimum resolution of nanometers;

[0207] The grain size of the first metal material = the sum of the grain sizes of 300 first metal materials / 300;

[0208] The grain size of the second metal material=the sum of the grain sizes of 300 second metal materials / 300.

[0209] (3) Testing method for tensile modulus of composite current collector

[0210] Using a standard sampler, cut the composite current collector into 10 samples, each 15 mm wide and 15 cm long, along the MD or TD directions. The samples were secured to the clamps of a tensile testing machine at a set speed of 50 mm / min and a gauge length of 50 mm between clamps. Tension testing was performed, and the modulus was calculated using the strength corresponding to 1% elongation. The tensile modulus (GPa) is calculated as (strength / 1%) / 1000, with the tensile modulus of the composite current collector being the average of the tensile moduli of the 10 test samples. The MD direction of the composite current collector refers to the machine direction, or longitudinal direction, of the composite current collector, while the TD direction of the composite current collector refers to the direction perpendicular to the MD direction, i.e., the transverse direction of the composite current collector.

[0211] (4) Test method for fracture strength of composite current collector

[0212] Use a standard sampler to cut the composite current collector into 10 samples of 15 mm width and 15 cm length along the MD direction or TD direction; fix the sample to the clamp of the tensile testing machine, set the speed to 50 mm / min, and the gauge length between the clamps to 50 mm, and perform a tensile test, and measure the corresponding maximum strength and elongation at break;

[0213] The breaking strength of the composite current collector (MPa) = the sum of the maximum tensile strengths of 10 samples / 10.

[0214] (5) Test method for the density of the composite current collector and the density of the first conductive layer

[0215] Place a flat second semi-finished product sample or composite current collector sample on the CCD optical microscope operating table. Turn on the light source on the back of the operating table, turn off the light source of the microscope, and take dark field photos of the sample in three areas. Use ImageJ image processing software to select the image saved by the CCD and calculate the density percentage M value.

[0216] M mean = sum of M values ​​of 3 test areas / 3;

[0217] The density measured using the second semi-finished product is the density of the first conductive layer, and the density measured using the composite current collector is the density of the composite current collector.

[0218] (6) Testing method for the shrinkage rate of the tab

[0219] The positive electrode tab size needs to be measured at intervals of 50 meters to calculate the tab shrinkage rate. The measurement method is to use a film ruler to align the tab area after coating and drying, measure the width size and then compare it with the original tab size to calculate the shrinkage rate. Shrinkage rate = (original tab size - tab width size) / original tab size) * 100%;

[0220] The shrinkage rate of the tab = the sum of the shrinkage rates of 10 tabs / 10.

[0221] (7) Testing method for welding tensile strength of tabs

[0222] Use a high-speed rail tensile testing machine to measure the welding tension after the tab is welded. The welding area of ​​the positive electrode (tab, weld mark and active material layer) is selected and cut into samples with a width of 50mm and a length of 60mm, where the weld mark area is located in the middle of the sample. The sample is stretched at a speed of 5mm / min. The welding tension specification requires ≥25 Newtons (N), and the maximum force value when the weld breaks is read. One sample is taken at every 1 meter interval, and a total of 10 samples are selected for testing. Finally, the average value of the welding tension of the 10 samples is taken.

[0223] (8) Testing method of U-shaped resistor after electrode roller welding

[0224] Cut the welded electrode into samples of the same size as the battery cell, and measure the resistance between the two positive electrode tabs with an internal resistance meter;

[0225] The U-shaped resistance after the electrode roll welding = the sum of the U-shaped resistance values ​​of 10 samples / 10.

[0226] (9)DCR test method

[0227] A DCR test was performed using a battery tester. The specific test method was as follows: the battery capacity was adjusted to 50% SOC, the voltage V1 was recorded, and then the battery was discharged at 4C for 30 seconds to obtain the voltage V2. DCR = (V1 - V2) / 4C, where 4C is the discharge current.

[0228] The DCR value of a battery = the sum of the DCR values ​​of 10 samples / 10.

[0229] The performance test results of the composite current collectors prepared in Examples 1-32 and Comparative Example 1 are shown in Table 2.

[0230] Table 1

[0231]

[0232] Table 2

[0233] In Table 2, the unit "mΩ" refers to milliohm.

[0234] From Table 1 and Table 2, we can see the following:

[0235] Comparative Example 1 does not set the second conductive layer. Compared with Comparative Example 1, the fracture strength and tensile modulus of the composite current collector of Example 1-32 and the welding tensile force of the pole tab are significantly higher, and the pole tab shrinkage rate, U-shaped resistance after pole piece roller welding, and DCR value of the composite current collector of Example 1-32 are significantly lower, indicating that the present application effectively improves the fracture strength and tensile modulus of the composite current collector by setting the second conductive layer and making the grain size of the second metal material in the second conductive layer smaller than the grain size of the first metal material in the first conductive layer, while alleviating the wrinkling and shrinkage problem in the pole tab area of ​​the composite current collector.

[0236] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0237] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector comprising a support layer and an adhesive layer, a first conductive layer, and a second conductive layer stacked in sequence on at least one surface of the support layer, wherein the first conductive layer comprises a first metal material, and the second conductive layer comprises a second metal material, wherein the grain size of the second metal material is smaller than the grain size of the first metal material.

2. The composite current collector according to claim 1, wherein The ratio of the grain size of the first metal material to the grain size of the second metal material is 2-50.

3. The composite current collector according to claim 1 or 2, wherein: The ratio of the grain size of the first metal material to the grain size of the second metal material is 2.5-40.

4. The composite current collector according to any one of claims 1 to 3, wherein: The difference between the grain size of the first metal material and the grain size of the second metal material is 200 nm to 3300 nm.

5. The composite current collector according to any one of claims 1 to 4, wherein: The difference between the grain size of the first metal material and the grain size of the second metal material is 300 nm to 3100 nm.

6. The composite current collector according to any one of claims 1 to 5, wherein: The grain size of the second metal material is 50 nm to 300 nm.

7. The composite current collector according to any one of claims 1 to 6, wherein: The grain size of the first metal material is 500nm to 3000nm.

8. The composite current collector according to any one of claims 1 to 7, wherein: The first metal material and the second metal material each independently include one or more of aluminum metal and aluminum alloy.

9. The composite current collector according to any one of claims 1 to 8, wherein: The composite current collector has one or more of the following characteristics: (a) a ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is 1 to 10; (b) the thickness of the first conductive layer is 500 nm to 1500 nm; (c) The thickness of the second conductive layer is 100 nm to 700 nm.

10. The composite current collector according to any one of claims 1 to 9, wherein: The ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is 1.5-8.

11. The composite current collector according to any one of claims 1 to 10, wherein: The density of the composite current collector is ≥90%.

12. The composite current collector according to any one of claims 1 to 11, wherein: The density of the first conductive layer is ≥60%.

13. The composite current collector according to any one of claims 1 to 12, wherein: The tensile modulus of the composite current collector is 5 GPa to 12 GPa.

14. The composite current collector according to any one of claims 1 to 13, wherein: The fracture strength of the composite current collector is ≥160 MPa.

15. The composite current collector according to any one of claims 1 to 14, wherein: The composite current collector further includes a passivation layer, and the passivation layer is disposed between the bonding layer and the first conductive layer. The composite current collector according to claim 15 , wherein: The passivation layer contains a passivating agent, and the passivating agent includes one or more of organic phosphate, chromate, dichromate, Al2O3, SiO2 and Si3N4.

17. The composite current collector according to any one of claims 1 to 16, wherein: The thickness of the bonding layer is 300nm to 700nm.

18. The composite current collector according to any one of claims 1 to 17, wherein: The thickness of the support layer is 2 μm to 10 μm.

19. The composite current collector according to any one of claims 1 to 18, wherein: The support layer includes one or more of a polymer material and a polymer-based composite material.

20. A method for preparing a composite current collector, comprising the following steps: An adhesive layer, a first conductive layer, and a second conductive layer are sequentially stacked on at least one surface of the supporting layer; the first conductive layer comprises a first metal material, the second conductive layer comprises a second metal material, and the grain size of the second metal material is smaller than the grain size of the first metal material.

21. The preparation method according to claim 20, wherein The step of forming the second conductive layer includes: arranging the second conductive layer on the surface of the first conductive layer by using an evaporation method and / or a magnetron sputtering method.

22. The preparation method according to claim 20 or 21, wherein The step of forming the bonding layer and the first conductive layer stacked in sequence on at least one surface of the support layer includes: disposing a first slurry containing a binder on the surface of at least one of the support layer and the first conductive layer, and curing the first slurry to form the bonding layer.

23. The preparation method according to any one of claims 20 to 22, wherein: The method further comprises the steps of forming a passivation layer between the bonding layer and the first conductive layer; The step of forming the passivation layer includes: disposing a second slurry containing a passivator on one surface of the first conductive layer, and curing the second slurry to form the passivation layer.

24. An electrode plate comprising at least one of the composite current collector according to any one of claims 1 to 19 and the composite current collector prepared by the preparation method according to any one of claims 20 to 23.

25. A battery comprising at least one of the composite current collector according to any one of claims 1 to 19, the composite current collector prepared by the preparation method according to any one of claims 20 to 23, and the electrode sheet according to claim 24.

26. An electrical device comprising the battery according to claim 25.

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