Composite current collector and preparation method thereof, pole piece, battery and electric device

Abstract

The invention discloses a composite current collector and a preparation method thereof, a pole piece, a battery and an electric device. The composite current collector comprises a polymer-based film layer, the conductive layer is arranged on at least one part of the surface of the polymer-based film layer, and the elastic modulus of the composite current collector is not less than 0.5 GPa.

Description

Composite current collector and preparation method thereof, pole piece, battery and electrical device Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a composite current collector and a preparation method thereof, a pole piece, a battery, and an electrical device. Background Art

[0002] Composite current collectors are a new type of current collector material for power batteries. They typically use a polymer material as a matrix support layer, and a conductive layer is formed by metallizing the surface of the support layer. This can form a sandwich-like structure. Compared to traditional current collectors such as copper foil or aluminum foil, composite current collectors can achieve certain improvements in safety, energy density, and service life. However, in conventional composite current collectors, since the polymer matrix acts as an energy absorber, it is difficult to directly weld the composite current collector and the tab when the composite current collector is used in the battery field. Subsequent production can only be carried out by subsequently grafting a pure metal current collector. This not only requires additional production processes and costs, but also affects production reliability.

[0003] Public content

[0004] In view of the technical problems existing in the background technology, the present application provides a composite current collector, which aims to reduce the energy absorption effect of the original polymer film layer, so that the composite current collector can directly form a pole ear through welding or the composite current collector body structure without the need for additional grafting of the pole ear.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a composite current collector, comprising: a polymer-based film layer; and a conductive layer, wherein the conductive layer is provided on at least a portion of the surface of the polymer-based film layer, wherein the elastic modulus of the composite current collector is not less than 0.5 GPa.

[0006] The inventors have discovered that by increasing the rigidity of the composite current collector, the energy absorption effect of the polymer-based film layer can be reduced. In particular, when the elastic modulus of the composite current collector is controlled to be no less than 0.5 GPa, not only can the composite current collector be directly welded, such as ultrasonic welding, to achieve a stable electrical connection between the composite current collector and the tab, but the tab can also be directly formed using the bulk structure of the composite current collector, thus eliminating the need for additional grafting of the tab. Therefore, compared to the prior art, in this application, by controlling the elastic modulus of the composite current collector to be no less than 0.5 GPa, on the one hand, the composite current collector can be made sufficiently rigid to form the tab by welding or its bulk structure, thereby not only simplifying the preparation process and reducing production costs, but also, on the other hand, enabling better current conduction between the composite current collector and the tab, ensuring the charge and discharge function of the battery.

[0007] In some embodiments of the present application, the elastic modulus of the composite current collector is no greater than 10 GPa. When the elastic modulus of the polymer-based film layer meets this range, the composite current collector can also have both good mechanical strength and suitable flexibility, thereby further facilitating reliable mechanical and electrical performance of the connection between the composite current collector and the tab.

[0008] In some embodiments of the present application, the tensile strength of the polymer-based film layer is not less than 100 MPa. When the tensile strength of the polymer-based film layer is within the given range, it is also beneficial for the composite current collector to have appropriate flexibility.

[0009] In some embodiments of the present application, a reinforcing material is distributed within the polymer-based film layer, wherein the reinforcing material has an elastic modulus greater than the elastic modulus of the polymer forming the polymer-based film layer. Distributing the reinforcing material within the polymer-based film layer facilitates flexible and controllable improvement of the elastic modulus and rigidity of the composite current collector.

[0010] In some embodiments of the present application, at least a portion of the reinforcing material is embedded in the polymer-based film layer.

[0011] In some embodiments of the present application, the volume proportion of the reinforcing material distributed in the polymer-based film layer is 10% to 80% based on the volume of the polymer-based film layer. When the volume proportion of the reinforcing material distributed in the polymer-based film layer is within the given range, it is more conducive to making the composite current collector have both good rigidity and suitable flexibility.

[0012] In some embodiments of the present application, the reinforcing material is partially exposed on the surface of the polymer-based film layer, and the exposed height is no greater than the distance between the side of the conductive layer away from the polymer-based film layer and the surface of the polymer-based film layer.

[0013] In some embodiments of the present application, the reinforcing material is chemically stable in an electrolyte environment.

[0014] In some embodiments of the present application, the reinforcing material includes at least one of an organic material, an inorganic non-metallic material, and an inorganic metal material.

[0015] In some embodiments of the present application, the reinforcing material includes at least one of linear fibers, dumbbell-shaped rods, mesh sheets, and non-mesh sheets. Optionally, the mesh sheet is a mesh woven layer.

[0016] In some embodiments of the present application, the lengths of the linear fibers and the dumbbell-shaped rods are independently no less than 5 mm. When the lengths of the linear fibers and the dumbbell-shaped rods are controlled within the given ranges, not only can the rigidity of the composite current collector be further improved, but the composite current collector can also have better tensile strength.

[0017] In some embodiments of the present application, the diameters of the linear fibers and the dumbbell-shaped rods are independently no greater than 20 μm. When the diameters of the linear fibers and the dumbbell-shaped rods are controlled within the given ranges, a good reinforcement effect can be achieved for the composite current collector without significantly changing the overall structure of the composite current collector.

[0018] In some embodiments of the present application, the linear fibers include organic fibers and / or inorganic fibers.

[0019] In some embodiments of the present application, the thickness of the mesh sheet and the non-mesh sheet is independently no greater than 20 μm. When the thickness of the mesh sheet and the non-mesh sheet is controlled within the given range, it can achieve a good reinforcement effect on the composite current collector without significantly changing the overall structure of the composite current collector.

[0020] In some embodiments of the present application, the length and width of the mesh sheet and the non-mesh sheet are independently not less than 5 mm. When the length and width of the mesh sheet and the non-mesh sheet are within the given ranges, a good continuous reinforcement effect can be achieved on the composite current collector, which can significantly improve the rigidity of the composite current collector.

[0021] In some embodiments of the present application, the mesh woven layer is woven from woven fibers, and the woven fibers include organic fibers and / or inorganic fibers.

[0022] In some embodiments of the present application, the mesh woven layer has a woven fiber diameter of no greater than 20 μm, a mesh aperture of no greater than 5 mm, and a porosity of no greater than 90%. When the structure of the mesh woven layer is controlled within the given range, it can achieve a good reinforcement effect on the composite current collector without significantly changing the overall structure of the composite current collector.

[0023] In some embodiments of the present application, the weaving density of the mesh woven layer is not less than 500 strands / 100 mm. When the weaving density of the mesh woven layer is controlled within a given range, the mesh woven layer can further have a better reinforcing effect on the polymer base film layer.

[0024] In some embodiments of the present application, the mesh woven layer is a plain woven layer, a twill woven layer, a satin woven layer, a full twisted woven layer or a half twisted woven layer.

[0025] In some embodiments of the present application, the mesh woven layer includes at least one of plain weave, twill weave, satin weave, full twist weave or half twist weave.

[0026] In some embodiments of the present application, the organic fiber includes polyamide fiber, and the inorganic fiber includes glass fiber and / or metal fiber.

[0027] In some embodiments of the present application, the linear fibers and / or the dumbbell-shaped rods are uniformly dispersed in the polymer-based film layer.

[0028] In some embodiments of the present application, the reinforcing material includes at least one layer of mesh sheet and / or at least one layer of non-mesh sheet, the non-mesh sheet is embedded in the polymer-based film layer, and at least a portion of the mesh sheet is embedded in the polymer-based film layer.

[0029] In some embodiments of the present application, the reinforcing material includes at least one mesh woven layer, and the matrix material of the polymer-based film layer is continuously distributed in the meshes and on at least a portion of the surface of the mesh woven layer.

[0030] In some embodiments of the present application, the mesh woven layer is embedded in the polymer substrate, and the diameter of the woven fibers in the mesh woven layer is no greater than 1 / 2 the thickness of the polymer base film layer. When the structure of the mesh woven layer is within the given range, the elastic modulus and rigidity of the composite current collector can be significantly improved without significantly changing the overall structure of the composite current collector.

[0031] In some embodiments of the present application, the mesh woven layer is partially exposed on the surface of the polymer substrate, and the exposed height is no greater than the thickness of the polymer base film layer. When the exposed height of the mesh woven layer falls within the given range, the surface of the conductive layer facing away from the base film layer has good flatness, while also not significantly affecting the electrical properties between the active material layer and the conductive layer formed later.

[0032] In some embodiments of the present application, the woven fibers of the mesh woven layer include at least one of polyamide fibers, glass fibers, and metal fibers, and the metal fibers include at least one of aluminum, copper, steel, and nickel.

[0033] In some embodiments of the present application, the material of the conductive layer is the same as that of the reinforcing material.

[0034] In some embodiments of the present application, the thickness of the polymer-based film layer is 2 μm to 20 μm.

[0035] In some embodiments of the present application, the thickness of the conductive layer is 0.05 μm to 5 μm.

[0036] In some embodiments of the present application, the conductive layer is a metal plating layer.

[0037] In some embodiments of the present application, the conductive layer includes at least one of aluminum, copper, and nickel.

[0038] In some embodiments of the present application, the composite current collector further includes an elastic buffer layer, which is disposed between the polymer-based film layer and the conductive layer.

[0039] In some embodiments of the present application, the elastic buffer layer is a rubber layer; and / or the thickness of the elastic buffer layer is no greater than 5 μm. Providing an elastic buffer layer not only improves the ductility and tensile strength of the polymer-based film layer, but also provides some protection for the polymer-based film layer, reducing the risk of fracture, improving the battery's deformation resistance, and enhancing battery safety.

[0040] The second aspect of the present application provides a method for preparing a composite current collector, which comprises: (1) preparing a polymer-based film layer using a polymer matrix material and a reinforcing material; and (2) forming a conductive layer on at least a portion of the surface of the polymer-based film layer.

[0041] Compared with the prior art, this method for preparing a composite current collector has at least the following beneficial effects: reinforcing materials can be added to the polymer-based film layer to improve the rigidity of the composite current collector. Not only is the operation simple, but the elastic modulus of the composite current collector can be flexibly adjusted by changing the type or amount of reinforcing materials, so that it meets the requirement of not less than 0.5 GPa, thereby making the prepared composite current collector have sufficient rigidity and can form pole ears by welding or its main structure, thereby not only simplifying the overall preparation process and reducing production costs, but also enabling better current conduction between the composite current collector and the pole ears, thereby ensuring the charge and discharge function of the battery.

[0042] In some embodiments of the present application, step (1) is performed in the following manner: the polymer matrix material and the reinforcing material are melt-blended and molded to obtain the polymer-based film layer.

[0043] In some embodiments of the present application, step (1) is performed in the following manner: the reinforcing material is embedded in the polymer matrix film by hot roller co-extrusion to obtain the polymer matrix film layer.

[0044] In some embodiments of the present application, step (1) is performed in the following manner: the polymer matrix material is subjected to a film casting process, and the reinforcing material is embedded during the film casting process to obtain the polymer base film layer.

[0045] In some embodiments of the present application, in step (2), the conductive layer is formed by at least one of magnetron sputtering, vacuum evaporation, vacuum ion plating, water electroplating and direct composite method.

[0046] In some embodiments of the present application, in step (2), an elastic buffer layer is pre-formed on the surface of the polymer-based film layer, and then the conductive layer is formed on the surface of the elastic buffer layer.

[0047] In some embodiments of the present application, step (2) further includes: performing a passivation treatment on the conductive layer. The passivation process can not only improve the corrosion resistance of the conductive layer and enhance the chemical stability of the composite current collector in an electrolyte environment, but also increase the roughness of the conductive layer and enhance the adhesion of the active material layer to the composite current collector.

[0048] In some embodiments of the present application, step (2) further includes: welding the electrode tabs on the surface of the conductive layer using an ultrasonic welding method; or, cutting the obtained composite current collector to form the electrode tabs; or, reserving the electrode tab area structure before forming the conductive layer, and forming the electrode tabs using the conductive layer and / or the reinforcing material.

[0049] The third aspect of the present application provides a pole piece, which includes: the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application.

[0050] The fourth aspect of the present application provides a battery, which includes: the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application, and / or the electrode of the third aspect of the present application.

[0051] The fifth aspect of the present application provides an electrical device, which includes: the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application, and / or the electrode of the third aspect of the present application, and / or the battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0053] FIG1 is a schematic structural diagram of a composite current collector according to one embodiment of the present application.

[0054] FIG2 is a schematic structural diagram of a composite current collector according to another embodiment of the present application.

[0055] FIG3 is a schematic structural diagram of an electric device according to an embodiment of the present application.

[0056] Description of the drawings:

[0057] 10-polymer base film layer; 11-reinforcement material; 20-conductive layer; 30-elastic buffer layer; h1-thickness of polymer base film layer; h1-thickness of conductive layer. DETAILED DESCRIPTION

[0058] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0059] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0060] The "ranges" disclosed herein are defined in terms of lower and / or upper limits. A given range is defined by selecting a lower limit and / or an upper limit, and the selected lower limit and / or upper limit define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the values ​​and may be combined arbitrarily, i.e., any lower limit may be combined with any upper limit to form an unspecified range, and any lower limit may be combined with any other lower limit to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower or upper limit and be combined with any other point or single value, or with other lower or upper limits, to form an unspecified range. For example, if a range of not more than 90% is listed for a particular parameter, it is understood that ranges of 10% to 80% and 20% to 60%, etc., that meet not more than 90% are also contemplated. In addition, if the minimum range values ​​1 and 5 are listed, and if the maximum range values ​​10 and 30 are listed, the following ranges are all contemplated: 1-10, 1-30, 5-10, and 5-30. In this application, unless otherwise specified, a numerical range such as "30-100" is an abbreviation for any combination of real numbers between 30 and 100, where 30 and 100 are real numbers. For example, the numerical range "1-30" means that all real numbers between "1-30" are listed herein, and "1-30" is only an abbreviation for these numerical combinations.

[0061] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0062] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0063] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, which means that the method may include steps S1 and S2 performed sequentially, or may include steps S2 and S1 performed sequentially. For example, the method may further include step S3, which means that step S3 may be added to the method in any order, for example, the method may include steps S1, S2, and S3, or may include steps S1, S3, and S2, or may include steps S3, S1, and S2, etc.

[0064] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or comprised, or may mean that only the listed components are included or comprised. Furthermore, as used in this application, the terms "plurality" and "multiple" refer to two or more components.

[0065] Unless otherwise specified, the term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0066] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned description of the drawings and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0067] At present, battery current collectors are mainly made of metal materials, and battery pole pieces are formed by attaching active materials on the surface of the current collector. However, from the perspective of market development, current collectors tend to be lighter and thinner to achieve the goals of lightness and efficiency, improving battery energy density, reducing weight, and reducing material costs. However, in order to maintain a certain mechanical strength, metal current collectors cannot be infinitely thinned, and too thin metal current collectors will also increase the difficulty of the preparation process. As a new alternative, a composite current collector structure with a polymer material matrix and a metal conductive layer can not only meet the demand for lighter current collectors, but also help reduce the type and cost of current collectors. Compared with traditional current collectors, composite current collectors can also be improved in safety, energy density and service life. However, during the connection process of existing composite current collectors and tabs, due to the energy absorption effect of the polymer material matrix, it is difficult to achieve electrical connection between the composite current collector and the tab through ultrasonic welding or other methods. The subsequent grafting of pure metal current collectors not only has a complex manufacturing process and low reliability, but also makes it difficult to ensure that each layer of composite current collector and the tab have good current conduction, affecting the battery's charge and discharge function.

[0068] In view of this, the first aspect of the present application provides a composite current collector, which can be understood with reference to FIG1 , wherein the composite current collector includes: a polymer base film layer 10; and a conductive layer 20, wherein the conductive layer 20 is provided on at least a portion of the surface of the polymer base film layer 10, wherein the elastic modulus of the composite current collector is not less than 0.5 GPa, for example, it can be not less than 1 GPa, not less than 1.5 GPa, not less than 2 GPa, not less than 2.5 GPa, not less than 3 GPa, not less than 4 GPa, not less than 5 GPa, not less than 6 GPa, not less than 7 GPa, not less than 8 GPa, not less than 9 GPa, or can be 1 to 10 GPa, 2 to 8 GPa, etc., or can be a range consisting of any of the above values. As a specific example, with reference to FIG1 , the conductive layer 20 can be formed on both surfaces of the polymer base film layer 10 that are opposite to each other, to obtain a composite current collector similar to a sandwich structure.

[0069] The inventors have found that by increasing the rigidity of the composite current collector, the energy absorption effect of the polymer base film layer can be reduced. However, if the rigidity of the composite current collector is insufficient, it is still difficult to effectively reduce the energy absorption effect of the polymer base film layer. By controlling the elastic modulus of the composite current collector to be not less than 0.5GPa, the composite current collector can be made sufficiently rigid, which not only enables the composite current collector to be directly welded, such as ultrasonic welding, to achieve a stable electrical connection between the composite current collector and the tab, but also allows the tab to be directly formed using the bulk structure of the composite current collector, thereby eliminating the need for additional grafting of the tab. Therefore, compared with the prior art, in this application, by controlling the elastic modulus of the composite current collector to be not less than 0.5GPa, on the one hand, the composite current collector can be made sufficiently rigid, and the tab can be formed by direct welding or its bulk structure, thereby not only simplifying the preparation process and reducing production costs, but also enabling better current conduction between the composite current collector and the tab to ensure the charge and discharge function of the battery.

[0070] Furthermore, after in-depth research, the inventors have discovered that, in addition to meeting the aforementioned conditions, the composite current collector of the present application can further improve its performance by controlling its tensile strength, the selection of reinforcing materials, the amount added, and the volume ratio. That is, in addition to meeting the aforementioned conditions, one or more of the following conditions can also be optionally met.

[0071] In some embodiments of the present application, the elastic modulus of the composite current collector may be no greater than 10 GPa, for example, it may be 1 to 9.5 GPa, 1.5 to 8.5 GPa, 3 to 7 GPa, etc. When the elastic modulus of the polymer current collector meets this given range, the composite current collector can be made sufficiently rigid, the energy absorption effect of the polymer base film layer can be effectively reduced, and the tabs can be formed by direct welding or by utilizing the composite current collector body structure. This can further reduce production costs, and the composite current collector can have both good mechanical strength and suitable flexibility, and can meet certain deformation requirements during the preparation process or when forming the tabs, thereby being more conducive to ensuring that the connection between the composite current collector and the tabs has reliable mechanical and electrical properties.

[0072] In some embodiments of the present application, the tensile strength of the polymer-based film layer 10 may be not less than 100 MPa, for example, it may be 120 MPa to 500 MPa, 200 MPa to 700 MPa, not less than 150 MPa, not less than 180 MPa, not less than 200 MPa, not less than 250 MPa, not less than 300 MPa, not less than 350 MPa, etc., or it may be a range consisting of any of the above values. When the tensile strength of the polymer-based film layer is within the given range, it is also beneficial to make the composite current collector have appropriate flexibility, and can meet certain deformation requirements during the preparation process or when forming the tab, thereby being more conducive to improving the reliability and yield of the preparation process, and making the connection between the composite current collector and the tab have reliable mechanical and electrical properties.

[0073] In some embodiments of the present application, in order to improve the rigidity of the composite current collector, the polymer material forming the polymer base film layer can be improved, the polymer film layer can be reinforced with a reinforcing material, or the thickness of the polymer base film layer and / or the conductive layer can be appropriately increased. Alternatively, one or more of the several methods given can be selected. As some specific examples, a reinforcing material 11 can be distributed in the polymer base film layer 10. The elastic modulus of the reinforcing material 11 is greater than the elastic modulus of the polymer forming the polymer base film layer 10. The reinforcing material 11 is used to enhance the elastic modulus of the polymer base film layer 10, thereby reinforcing the composite current collector and improving its rigidity. It should be noted that the elastic modulus of the reinforcing material and the polymer material depends only on the characteristics of the material itself. When reinforcing materials are distributed in the polymer-based film layer to reinforce the composite current collector, on the one hand, the elastic modulus of the composite current collector can be flexibly adjusted by changing the type or amount of reinforcing materials, so that the composite current collector has sufficient rigidity and can form pole ears through welding or its main structure; on the other hand, by improving the rigidity of the polymer-based film layer used as a supporting layer, it is also beneficial to the smooth progress of the subsequent preparation process of the current collector and the pole piece preparation process; in addition, compared with improving the polymer material itself or increasing the thickness of the conductive layer, the use of reinforcing materials can also improve the elastic modulus of the polymer-based film layer to a relatively better degree.

[0074] In some embodiments of the present application, when the reinforcing material 11 is distributed in the polymer base film layer 10 to reinforce the composite current collector, at least a portion of the reinforcing material 11 is embedded in the polymer base film layer 10, that is, the reinforcing material 11 can be completely embedded in the polymer base film layer 10, or partially embedded in the polymer base film layer 10 and partially exposed on the surface of the polymer base film layer 10. At this time, the exposed height of the reinforcing material 11 exposed on the surface of the polymer base film layer 10 is not greater than the distance between the side of the conductive layer 20 away from the polymer base film layer 10 and the surface of the polymer base film layer 10. This can not only make the surface of the conductive layer away from the base film layer have better flatness, but also will not significantly affect the electrical properties between the active material layer and the conductive layer formed later. When the reinforcing material is entirely embedded in the polymer base film layer, it is more conducive to maintaining the uniformity and flatness of the conductive layer and the electrical properties between the current collector and the active material layer; and when the reinforcing material is partially exposed on the surface of the polymer base film layer, it is not only easy to form a microscopic concave-convex morphology on the surface of the base film layer, so that the connection interface between the polymer base film layer and the conductive layer forms a better mutual embedding structure, thereby improving the bonding strength between the conductive layer and the polymer base film layer, but also conducive to achieving the purpose of further improving the connection strength between the polymer base film layer and the conductive layer by self-connecting the reinforcing material and the conductive layer. For example, as a specific example, a material of the same material as the conductive layer can be used as the reinforcing material, so that the part of the reinforcing material exposed on the surface of the polymer base film layer forms a self-connection with the conductive layer, thereby improving the connection strength between the conductive layer and the polymer base film layer. Optionally, the reinforcing material 11 is chemically stable relative to the conductive layer 20, thereby further improving the reliability of the composite current collector when the reinforcing material is exposed on the surface of the polymer base film layer, and avoiding chemical reactions between the reinforcing material and the conductive layer that affect the performance of the current collector. Alternatively, the reinforcing material 11 is chemically stable in an electrolyte environment and does not chemically react with the electrolyte or conductive layer materials, thereby further improving the reliability of the composite current collector and electrode when the reinforcing material is exposed on the surface of the polymer base film layer.

[0075] In some embodiments of the present application, based on the volume of the polymer-based film layer 10, the volume proportion of the reinforcing material 11 distributed in the polymer-based film layer 10 can be 10% to 80%, for example, 15% to 70%, 20% to 60%, 18%, 25%, 30%, 35%, 40%, 50%, 65%, 75%, etc., or can be a range composed of any of the above values. The inventors found that if the rigidity of the composite current collector is insufficient, it is still difficult to effectively reduce the energy absorption effect of the polymer-based film layer. By controlling the volume proportion of the reinforcing material in the polymer-based film layer to be no less than 10%, the strength of the polymer-based film layer can be significantly improved, thereby making the composite current collector have sufficient rigidity. When the volume proportion of the reinforcing material in the polymer-based film layer is too high, on the one hand, it may lead to an increase in raw material costs, and on the other hand, it may also lead to poor toughness of the composite current collector, affecting the smooth progress of the later preparation process of the current collector and the battery preparation process. When the volume proportion of the reinforcing material distributed in the polymer-based film layer is within the given range, it is more conducive to making the composite current collector have both good rigidity and appropriate flexibility, which is beneficial to the smooth progress of the electrode and battery preparation process, and is also beneficial to making the connection between the composite current collector and the electrode ear have reliable mechanical and electrical properties.

[0076] In some embodiments of the present application, the material of the reinforcing material 11 is not particularly limited, and those skilled in the art can flexibly select it according to actual needs. For example, the reinforcing material 11 may include at least one of an organic material, an inorganic non-metallic material, and an inorganic metal material. Among them, the specific types of organic materials, inorganic non-metallic materials, and inorganic metal materials are not particularly limited. Those skilled in the art can flexibly select it according to actual needs. For example, the organic material may be a carbon fiber material and / or polyamide fiber, etc., the inorganic non-metallic material may be an inorganic non-metal (such as metal oxide or non-metal oxide) filler particle and / or glass fiber, etc., and the inorganic metal material may be one or more of aluminum, copper, steel, nickel, etc.

[0077] In some embodiments of the present application, there is no particular limitation on the form of the reinforcement material 11. Those skilled in the art can flexibly select according to actual needs. For example, the reinforcement material 11 can be in the form of linear fibers, dumbbell-shaped rods, mesh sheets, non-mesh sheets, or a range consisting of any of the above forms. As some specific examples, the linear fibers can be organic fibers and / or inorganic fibers. Optionally, the organic fibers can be carbon fiber materials and / or polyamide fibers, and the inorganic fibers can be one or more of glass fibers, ceramic fibers, and metal fibers. As some specific examples, the dumbbell-shaped rods can be made of metal. As some specific examples, the mesh sheets can be obtained by forming multiple through holes on a non-mesh sheet, or by weaving, i.e., a mesh woven layer. As some specific examples, the non-mesh sheet can be a metal sheet. Optionally, the reinforcing material 11 can be a mesh sheet, wherein selecting the mesh sheet as the reinforcing material is beneficial to improving the overall supporting strength of the polymer matrix membrane and significantly improving the rigidity of the composite current collector, and is also beneficial to achieving self-connection of the polymer matrix located on both sides of the sheet through the mesh holes of the mesh sheet, thereby improving the overall stability of the base membrane layer structure.

[0078] In some embodiments of the present application, the lengths of the linear fibers and dumbbell-shaped rods can be independently not less than 5 mm, for example, 5-20 mm, 8-15 mm, not less than 6 mm, not less than 7 mm, not less than 9 mm, not less than 10 mm, not less than 12 mm, not less than 16 mm, not less than 20 mm, etc., or can be a range composed of any of the above values. Compared with linear fibers and dumbbell-shaped rods of shorter sizes, when the lengths of the linear fibers and dumbbell-shaped rods are controlled within the given range, on the one hand, the interfacial contact area between the linear fibers and dumbbell-shaped rods and the polymer matrix can be increased. On the other hand, it is also beneficial for the linear fibers and dumbbell-shaped rods to be interwoven with each other in the polymer matrix to form a disordered arrangement, thereby not only further improving the rigidity of the composite current collector, but also making the composite current collector have better tensile strength. Furthermore, the diameters of the linear fibers and dumbbell-shaped rods can each independently be no greater than 20 μm, for example, 1 μm to 20 μm, 2 μm to 18 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 19 μm, etc., or can be any range consisting of the above values. Based on the thickness of the conventional current collector and the thickness of the composite current collector, when the diameters of the linear fibers and dumbbell-shaped rods are controlled within the given range, a good reinforcement effect can be achieved on the composite current collector, significantly improving the rigidity of the composite current collector, without significantly changing the overall structure of the composite current collector.

[0079] In some embodiments of the present application, the thickness of the mesh sheet and the non-mesh sheet may be independently no more than 20 μm, for example, they may be independently 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc., or they may be a range consisting of any of the above values. Based on the thickness of the traditional current collector and the thickness of the composite current collector, when the thickness of the mesh sheet and the non-mesh sheet is controlled within the given range, it can have a better reinforcing effect on the composite current collector, significantly improve the rigidity of the composite current collector, and will not cause a significant change in the overall structure of the composite current collector. Furthermore, The length of the mesh sheet and the non-mesh sheet can be independently not less than 5 mm. Optionally, the length of the mesh sheet and the non-mesh sheet can also be independently 15% to 95%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 95% or 95% of the length of the polymer base film layer; the width of the mesh sheet and the non-mesh sheet can also be independently not less than 5 mm. Optionally, the width of the mesh sheet and the non-mesh sheet can also be independently 15% to 95%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 95% or 95% of the width of the polymer base film layer. 30%, 40%, 50%, 60%, 70%, 80%, 85%, 95% or 95%, etc., which can be flexibly selected according to the length and width of the traditional current collector or electrode. When the length and width of the mesh sheet and the non-mesh sheet are within the given range, it can have a better continuous reinforcement effect on the composite current collector and can significantly improve the rigidity of the composite current collector. Optionally, the width and length of the mesh sheet and the non-mesh sheet can be independently close to but not greater than the width and length of the polymer base film layer, which is more conducive to improving the overall rigidity of the composite current collector.

[0080] In some embodiments of the present application, the mesh sheet can be a mesh woven layer, which is woven from woven fibers. The woven fibers may include organic fibers and / or inorganic fibers. Optionally, the woven fibers may include polyamide fibers, and the inorganic fibers may include glass fibers and / or metal fibers. As some specific examples, the metal fibers may include at least one of aluminum, copper, steel, and nickel. For example, they may be aluminum fibers, copper fibers, steel fibers, nickel fibers, alloy fibers formed by any of several metal fibers, or composite fibers formed by twisting any of several metal fibers. It is understandable that the woven fibers of the mesh woven layer may be either single fibers with a larger diameter or multiple fibers with smaller diameters, which are twisted to form woven fibers. When a mesh woven layer is selected as a reinforcing material, it can not only further improve the overall support strength of the polymer matrix membrane and significantly improve the rigidity of the composite current collector, but also facilitate the self-connection of the polymer matrix located on both sides of the woven layer through the woven mesh, thereby improving the overall stability of the base membrane layer structure. Optionally, the mesh braided layer may be a metal fiber braided layer. Selecting the metal fiber braided layer can not only further improve the rigidity of the composite current collector, but also enable the composite current collector to have better tensile strength.

[0081] In some embodiments of the present application, the diameter of the woven fibers of the mesh woven layer may be no greater than 20 μm, for example, it may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, etc., or it may be a range composed of any of the above values. Optionally, the diameter of the woven fibers of the mesh woven layer may be 1 μm to 12 μm, and may be further selected as 1 μm to 10 μm. Based on the thickness of the traditional current collector and the thickness of the composite current collector, by controlling the diameter of the woven fibers within the given range, it is beneficial to make the maximum thickness of the mesh woven layer no greater than the overall thickness of the current collector, thereby improving the rigidity of the composite current collector while not causing significant changes in the overall structure of the composite current collector.

[0082] Furthermore, the mesh pore size of the mesh woven layer can be no greater than 5 mm, for example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm or 4.5 mm, or it can be a range consisting of any of the above values. The inventors found that if the mesh pore size of the mesh woven layer is too large, on the one hand, it will weaken the reinforcing effect on the current collector and reduce the uniformity of the strength of the composite current collector. On the other hand, it will also reduce the structural stability of the woven layer and increase the process difficulty when it is composited with the polymer. When the mesh pore size of the mesh woven layer is controlled within the given range, it is more conducive to taking into account the reinforcing effect on the composite current collector and the feasibility of the preparation process, while at the same time making the polymer and the mesh woven layer have a better connection effect. Optionally, the mesh pore size of the mesh woven layer can be no less than 1 mm, for example, it can be 1 to 4 mm, etc. Controlling the mesh pore size of the woven layer within the above range is also more conducive to making the polymer embed into the mesh or achieve self-connection through the mesh, so that the polymer and the mesh woven layer have a better connection effect.

[0083] In addition, the porosity of the mesh woven layer can be no greater than 90%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., or it can be a range composed of any of the above values. If the porosity of the mesh woven layer is too large, it will also weaken the reinforcing effect on the current collector, reduce the structural stability of the mesh woven layer, and increase the process difficulty when it is composited with the polymer. When the porosity of the mesh woven layer is controlled within the given range, it is more conducive to taking into account the reinforcing effect on the composite current collector and the feasibility of the preparation process, while at the same time making the polymer and the mesh woven layer have a better connection effect. Optionally, the porosity of the mesh woven layer can be no less than 30%, for example, it can be 35% to 70%, etc. Controlling the porosity of the woven layer within the above range is more conducive to making the polymer embed into the mesh of the woven layer or achieve self-connection through the mesh, so that the polymer and the mesh woven layer have a better connection effect.

[0084] In some embodiments of the present application, the weaving density of the mesh woven layer can be no less than 500 roots / 100mm. For example, taking the plain woven layer as an example, referring to GB / T8946-1998, the warp density × weft density of the mesh woven layer can be no less than 500 roots / 100mm, such as the warp density × weft density can be 32×32 roots / 100mm, 36×36 roots / 100mm, 40×40 roots / 100mm, etc., and can be flexibly selected according to actual conditions such as the diameter of the woven fiber, the aperture of the woven layer mesh, and the porosity. Among them, when the weaving density of the mesh woven layer is controlled within the given range, the mesh woven layer can further have a better reinforcement effect on the polymer base membrane layer, significantly improving the elastic modulus and rigidity of the composite current collector.

[0085] In some embodiments of the present application, the weaving structure of the mesh woven layer is not particularly limited, and those skilled in the art can flexibly select it according to actual conditions. For example, the mesh woven layer can include but is not limited to one or more of plain weave, twill weave, satin weave, full twist weave and half twist weave, among which plain weave is more conducive to improving the structural stability of the woven layer and has a relatively good reinforcement effect, while twill weave and satin weave are more conducive to improving the flexibility of the woven layer. In addition, it should be noted that the number of interlaced layers in the mesh woven layer is not particularly limited, and those skilled in the art can flexibly select it according to actual needs such as the weaving structure. For example, when twist weave is adopted, the number of interlaced layers of the mesh woven layer in the polymer base film layer can be no less than two layers, and when non-twisted weave is selected, the number of interlaced layers of the mesh woven layer in the polymer base film layer can be one or more layers. As some specific examples, the mesh woven layer can be woven from at least one layer of warp fibers and at least one layer of weft fibers, and its weaving structure includes but is not limited to plain weave, twill weave and satin weave, and the number of interlaced layers can be 1 layer, 2 layers or 3 layers, etc.

[0086] In some embodiments of the present application, the reinforcing material 11 may include linear fibers and / or dumbbell-shaped rods. In this case, the linear fibers and / or dumbbell-shaped rods may be uniformly dispersed within the polymer-based film layer 10. In this application, the term "uniform dispersion" refers to ensuring that the mass or volume of the reinforcing material distributed within the polymer-based film layer at different locations is the same at the same surface density. This can be achieved through melt blending or other methods. By uniformly dispersing the linear fibers and / or dumbbell-shaped rods within the polymer-based film layer, the uniformity of the polymer-based film layer can be further improved, resulting in the polymer-based film layer having better overall strength and rigidity.

[0087] In some embodiments of the present application, the reinforcing material 11 may include at least one layer of mesh sheet material and / or at least one layer of non-mesh sheet material. When a non-mesh sheet material is included, the non-mesh sheet material may be embedded in the polymer base film layer 10; when a mesh sheet layer is included, at least a portion of the mesh sheet material may be embedded in the polymer base film layer 10. For example, the mesh sheet material may be entirely embedded in the polymer base film layer, or partially embedded in the polymer base film layer along its thickness direction, with a portion exposed on the surface of the polymer base film layer. The composite of the mesh sheet material or the non-mesh sheet material with the polymer may be achieved by methods such as cast insert molding or hot roll insert molding.

[0088] As some specific examples, the reinforcing material 11 may include only at least one mesh woven layer, for example, it may include only one mesh woven layer, and the matrix material of the polymer base film layer 10 may be continuously distributed within the mesh of the mesh woven layer and on at least a portion of the surface, thereby further improving the connection strength between the mesh woven layer and the polymer and the structural stability of the polymer base film layer. Furthermore, when the mesh woven layer is built into the polymer base film layer, the diameter of the woven fibers in the mesh woven layer may not be greater than 1 / 2 of the thickness of the polymer base film layer, for example, it may be 1 / 6, 1 / 5, 1 / 4, 1 / 3, 3 / 8 of the thickness of the polymer base film layer; when the mesh woven layer is partially exposed on the surface of the polymer substrate, its exposed height may not be greater than the thickness of the polymer base film layer. By controlling the structure of the mesh woven layer within the above-mentioned range, while significantly improving the elastic modulus and rigidity of the composite current collector, the overall structure of the composite current collector will not be significantly changed.

[0089] In some embodiments of the present application, the material of the polymer base film layer 10 is not particularly limited, and those skilled in the art can flexibly select it according to actual needs. For example, it may include but is not limited to PI (polyimide), PP (polypropylene) and PET (polyethylene terephthalate).

[0090] In some embodiments of the present application, the material of the conductive layer 20 and the material of the reinforcing material 11 may be the same or different. Optionally, the material of the conductive layer is the same as the reinforcing material. For example, when the conductive layer is an aluminum conductive layer, the reinforcing material may be an aluminum woven mesh. When the conductive layer is a copper conductive layer, the reinforcing material may be a copper woven mesh. When the material of the conductive layer is the same as the reinforcing material, on the one hand, when the reinforcing material is exposed on the surface of the polymer base film layer, the impedance of the conductive layer will not be increased, and the reinforcing material and the conductive layer material will not chemically react. On the other hand, the reinforcing material and the conductive layer material can also improve the connection strength between the conductive layer and the polymer base film layer through atomic bonding, thereby improving the structural stability of the polymer base film layer.

[0091] In some embodiments of the present application, the thickness h1 of the polymer base film layer 10 and the thickness h2 of the conductive layer 20 are not particularly limited. Those skilled in the art can flexibly select them according to actual needs. As some specific examples, the thickness h1 of the polymer base film layer 10 can be 2 μm to 20 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 14 μm, 16 μm or 18 μm, or any of the above. As some specific examples, the thickness h2 of the conductive layer 20 can be 0.05μm to 5μm, for example, it can be 0.1μm, 0.25μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, etc., or it can be a range composed of any of the above values. Controlling the thickness of the polymer base film layer and the conductive layer within the given range is more conducive to improving the reliability and performance of the composite current collector.

[0092] In some embodiments of the present application, the conductive layer 20 may be a metal plating layer, formed by methods including but not limited to magnetron sputtering, vacuum evaporation, vacuum ion plating, and water electroplating. Furthermore, the conductive layer 20 may include at least one of aluminum, copper, and nickel. For example, when the composite current collector serves as the positive electrode current collector, the conductive layer may be an aluminum metal layer; when the composite current collector serves as the negative electrode current collector, the conductive layer may be a copper metal layer. Alternatively, the conductive layer may be a pure metal layer, with a purity of no less than 99.8% or 99.9%, thereby further improving the conductivity of the composite current collector.

[0093] In some embodiments of the present application, the conductive layer 20 can be formed directly on the surface of the composite current collector or indirectly formed on the surface of the composite current collector through other film layer structures. For example, referring to FIG2 , as some specific examples, the composite current collector may further include: an elastic buffer layer 30, which may be provided between the polymer-based film layer 10 and the conductive layer 20. The provision of the elastic buffer layer between the polymer-based film layer and the conductive layer can not only improve the ductility and tensile strength of the polymer-based film layer, but also provide a certain degree of protection for the polymer-based film layer, reduce the risk of fracture thereof, improve the deformation resistance of the battery, and improve the safety of the battery.

[0094] Optionally, the elastic buffer layer 30 may be a rubber layer. The rubber layer has high ductility and strong impact resistance, which can further improve the ductility and tensile strength of the polymer base film layer and provide better protection for the composite base film layer and the battery.

[0095] Optionally, the thickness of the elastic buffer layer 30 may be no greater than 5 μm, for example, it may be 0.25 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc., or it may be a range composed of any of the above values. Based on the thickness of the traditional current collector, the thickness of the elastic buffer layer is controlled within the given range, which can further help the composite current collector have better rigidity and tensile strength, and can also provide better protection for the composite base film layer and the battery.

[0096] The second party of the present application also provides a method for preparing a composite current collector, which includes: (1) preparing a polymer-based film layer using a polymer matrix material and a reinforcing material; (2) forming a conductive layer on at least a portion of the surface of the polymer-based film layer, wherein the elastic modulus of the composite current collector is not less than 0.5 GPa.

[0097] It should be noted that the method for preparing a composite current collector in the second aspect of the present application is proposed based on the composite current collector in the first aspect of the present application. The characteristics and effects described for the composite current collector in the first aspect of the present application are also applicable to the method for preparing a composite current collector in the second aspect of the present application, and will not be repeated here. Compared with the prior art, the method for preparing a composite current collector has at least the following beneficial effects: reinforcing materials can be added to the polymer base film layer to improve the rigidity of the composite current collector. Not only is the operation simple, but the elastic modulus of the composite current collector can be flexibly adjusted by changing the type or amount of reinforcing materials, so that it meets the requirement of not less than 0.5GPa, thereby making the prepared composite current collector have sufficient rigidity and can be formed into tabs by welding or its main structure, thereby not only simplifying the overall preparation process and reducing production costs, but also enabling better current conduction between the composite current collector and the tabs to ensure the charge and discharge function of the battery.

[0098] In some embodiments of the present application, the types and structural forms of the reinforcing materials are different, and the composite methods thereof with the polymer matrix material are also different, for example:

[0099] As a specific example, when the reinforcing material is a linear fiber and / or a dumbbell-shaped rod, step (1) can be performed in the following manner: the polymer matrix material and the reinforcing material are melt-blended and formed to obtain a polymer base film layer. Taking polyamide fiber and PET masterbatch as an example, the polyamide fiber and PET masterbatch can be blended, plastically melted, cast, and extruded using a T-die to obtain a polymer base film layer. This method is more conducive to improving the uniformity of the linear fiber and / or dumbbell-shaped rod reinforcing material in the composite base film layer.

[0100] As a specific example, when the reinforcing material is a mesh sheet and / or a non-mesh sheet, step (1) can be performed in the following manner: the reinforcing material is embedded in the polymer matrix film by hot roller co-extrusion to obtain a polymer matrix film layer. Taking the metal woven mesh and PET masterbatch as an example, the PET masterbatch can be plastically melted, cast and extruded using a T-die, and then the woven layer is flattened and embedded in the original film layer by hot roller co-extrusion to obtain a polymer matrix film.

[0101] As a specific example, when the reinforcing material is a mesh sheet and / or a non-mesh sheet, step (1) can be performed in the following manner: the polymer matrix material is subjected to a film casting process, and the reinforcing material is embedded in the film casting process to obtain a polymer base film layer. Taking the mesh sheet and PET masterbatch as an example, the PET masterbatch can be plastically melted, cast, and extruded using a T-type die, wherein the mesh sheet is embedded in the original film during casting, and the film is integrally formed during cooling and extrusion to obtain a polymer base film layer.

[0102] In some embodiments of the present application, the method for forming the conductive layer is not particularly limited. Persons skilled in the art may flexibly select a method based on actual needs, including but not limited to magnetron sputtering, vacuum evaporation, vacuum ion plating, hydro-electroplating, and direct composite methods. As a specific example, a base layer may be first deposited using magnetron sputtering or vacuum evaporation, and then a thickened layer may be deposited using vacuum evaporation to ultimately form the conductive layer.

[0103] In some embodiments of the present application, after the conductive layer is formed, the conductive layer can be further passivated. By passivating the conductive layer, on the one hand, the corrosion resistance of the conductive layer can be improved and the chemical stability of the composite current collector in the electrolyte environment can be improved. On the other hand, when the passivation treatment can increase the roughness of the conductive layer, it is also beneficial to enhance the adhesion of the active material layer on the composite current collector and improve the structural stability of the electrode.

[0104] In some embodiments of the present application, in step (2), an elastic buffer layer may be pre-formed on the surface of the polymer base film layer, and then a conductive layer may be formed on the surface of the elastic buffer layer. The beneficial effects of providing the elastic buffer layer, as well as the material and thickness of the elastic buffer layer, have been described in the previous section and will not be repeated here.

[0105] In some embodiments of the present application, a tab can also be formed on the composite current collector. Based on the characteristics of the composite current collector of the first aspect of the present application, the tab can be directly welded on the composite current collector or the main structure of the composite current collector can be directly used to form the tab. For example, in step (2), as a specific example, after forming the conductive layer, the tab can be welded on the surface of the conductive layer using ultrasonic welding. As another specific example, after forming the conductive layer, the obtained composite current collector can be cut to form the tab. As another specific example, the tab area structure can be reserved before forming the conductive layer, and the tab can be formed using the conductive layer and / or reinforcing material.

[0106] The third aspect of the present application provides a pole piece, which includes: the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application.

[0107] Compared with the pole piece using the traditional current collector, the pole piece formed by using the composite current collector of the first aspect of the present application or the composite current collector prepared by the second aspect of the present application has at least the following beneficial effects: not only is it safer, it can reduce the risk of short circuit caused by lithium dendrites piercing the diaphragm and causing safety problems such as thermal runaway, and because the polymer material has a lower density and the thickness of the composite current collector can be smaller than that of the traditional current collector, it is also beneficial to improve the energy density of the pole piece; in addition, because the elastic modulus of the high molecular polymer material is lower than that of the metal, it is more conducive to absorbing the expansion and contraction stress generated by the insertion and removal of ions in the active material layer of the pole piece during the charging and discharging process of the battery, which is beneficial to maintain the long-term integrity of the pole piece interface and improve the cycle life; furthermore, it is also beneficial to simplify the preparation process, reduce raw material costs or volume costs. In addition, it can be understood that the characteristics and effects described for the composite current collector of the first aspect of the present application and the method for preparing the composite current collector of the second aspect of the present application are also applicable to the pole piece of the third aspect of the present application, and will not be repeated here.

[0108] In some embodiments of the present application, the electrode sheet of the third aspect of the present application can be either a positive electrode sheet or a negative electrode sheet. It is understood that, in addition to the composite current collector, the electrode sheet also includes an active material layer formed on the surface of the composite current collector, wherein the active material layer may include an active material, a conductive agent, and an adhesive, etc., wherein the material composition and structural characteristics of the composite current collector in the electrode sheet, and the material composition and structural characteristics of the active material layer, etc. can be flexibly selected according to actual conditions such as the electrode sheet type, and are not specifically limited in this application.

[0109] As an example, the electrode sheet may be a positive electrode sheet, which may include a positive electrode composite current collector and a positive electrode active material layer disposed on the positive electrode composite current collector. The positive electrode composite current collector may include a PET base film layer and a metal woven mesh distributed in the PET base film layer, with an aluminum conductive layer formed on the surface of the PET base film layer. The positive electrode active material layer may include a positive electrode active material, a conductive agent, and an adhesive, among others. The types and mass ratios of the positive electrode active material, conductive agent, and adhesive are not particularly limited, and those skilled in the art may flexibly select them according to actual needs. For example, the positive electrode active material may include one or more commonly used positive electrode active materials in the art, such as nickel-cobalt-manganese ternary positive electrode active material, lithium iron phosphate, and lithium manganese iron phosphate. The conductive agent may include one or more commonly used positive electrode conductive agents in the art, such as graphene, carbon nanotubes, and superconducting carbon black. The adhesive may be a commonly used positive electrode adhesive in the art, such as polyvinylidene fluoride.

[0110] As an example, the electrode sheet may be a negative electrode sheet, which may include a negative electrode composite current collector and a negative electrode active material layer disposed on the negative electrode composite current collector. The negative electrode composite current collector may include a PET base film layer and a metal woven mesh distributed within the PET base film layer, with a copper conductive layer formed on the surface of the PET base film layer. The negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder. The types and mass ratios of the negative electrode active material, conductive agent, and binder are not particularly limited and can be flexibly selected by those skilled in the art based on actual needs. For example, the negative electrode active material may include, but is not limited to, carbon materials, silicon-carbon materials, and other common negative electrode active materials in the art. The conductive agent may include, but is not limited to, graphene, carbon nanotubes, carbon dots, acetylene black, superconducting carbon black, and other common negative electrode conductive agents in the art. The binder may include, but is not limited to, styrene-butadiene rubber, carboxymethyl cellulose, and other common negative electrode binders in the art.

[0111] A fourth aspect of the present application provides a battery comprising: the composite current collector of the first aspect of the present application, and / or a composite current collector prepared using the method for preparing a composite current collector of the second aspect of the present application, and / or a pole piece of the third aspect of the present application. Optionally, the battery may be a secondary battery.

[0112] In a battery, it usually includes a shell assembly, a positive electrode sheet, a negative electrode sheet, a diaphragm, and an electrolyte. The positive electrode sheet, the negative electrode sheet, the diaphragm, and the electrolyte are located in a receiving cavity formed by the shell assembly. According to the type of battery, the shell assembly can be an aluminum-plastic film or a metal shell assembly, etc. The metal shell assembly can include a square shell assembly and a cylindrical shell assembly. When the shell assembly is a metal shell assembly, it usually includes a shell with an opening on at least one side and a cover for sealing the opening. Regardless of the type of battery, as long as at least one of the positive electrode sheet and the negative electrode sheet includes the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application, and / or the electrode sheet of the third aspect of the present application, it can be understood to be included in the technical scope of the battery of the fourth aspect of the present application.

[0113] Among them, the composition of the positive electrode plate and the composition of the negative electrode plate have been explained in the previous section and will not be repeated here; the specific material or type of the diaphragm can adopt the material or type commonly used in this field, and the composition of the electrolyte can also adopt the common composition in this field. Those skilled in the art can flexibly choose according to actual needs.

[0114] In some embodiments of the present application, the battery can be either a laminated battery or a wound battery. The wound battery can be either a square battery or a cylindrical battery. Optionally, the battery can be a cylindrical battery. Depending on the battery type, the positive electrode sheet, the negative electrode sheet, and the separator can be stacked to form a laminate unit, or can be stacked and then wound to form a wound body.

[0115] In some embodiments of the present application, the battery may be a single cell or a battery module assembled from cells. A battery module may include multiple cells, the specific number of which may be adjusted based on the application and capacity of the battery module. Furthermore, the battery module may also include a packaging assembly having a storage space, which may include a bottom plate, side plates, and a cover plate.

[0116] In some embodiments of the present application, the above-mentioned battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0117] In addition, the present application also provides an electrical device, which includes: the composite current collector of the first aspect of the present application, and / or the composite current collector prepared by the method for preparing the composite current collector of the second aspect of the present application, and / or the electrode of the third aspect of the present application, and / or the battery of the fourth aspect of the present application.

[0118] The battery, such as a cell, a battery module or a battery pack, can be used as both a power source and an energy storage unit for the electrical device. The electrical device may include, but is not limited to, a mobile device (e.g., a mobile phone, a laptop computer), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, and an energy storage system. With reference to FIG3 , as a specific example, the electrical device may be a vehicle.

[0119] The electrical device can select the specific type of battery according to its usage requirements, such as battery cells, battery modules or battery packs.

[0120] As an example, the electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery pack or battery module may be used.

[0121] As another example, the electrical device may be a mobile phone, a tablet computer, or a laptop computer. The electrical device is generally required to be lightweight and thin, and may use a battery cell as a power source.

[0122] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0123] Method for preparing composite current collector:

[0124] Plan I

[0125] (I-1) blending aluminum fibers and a PET masterbatch, plasticizing and melting, casting, and extruding through a T-die to obtain a polymer-based film layer, wherein the short fibers have a length of 10 mm ± 2 mm, a diameter of 3 μm ± 1 μm, a melting temperature of 295° C. ± 15° C., an extrusion molding temperature of 263° C. ± 12° C., and an extrusion molding pressure of 10 kgf ± 5 kgf;

[0126] (I-2) A metal conductive layer (such as an aluminum layer) of equal thickness is deposited on the upper and lower surfaces of the polymer base film layer by vacuum evaporation.

[0127] (I-3) Passivating the metal conductive layer.

[0128] (I-4) Cutting and welding the tabs on the surface of the metal conductive layer using ultrasonic welding.

[0129] Option II

[0130] (II-1) plain weaving the fiber filaments to obtain a mesh woven layer, wherein the fiber filaments are aluminum wires and the mesh aperture is 1 to 2 mm;

[0131] (II-2) plastically melting the PET masterbatch, casting the masterbatch, and extruding the masterbatch using a T-die, wherein the mesh braided layer is embedded in the original film during casting, and the masterbatch is integrally formed during cooling and extrusion to obtain a polymer original film layer, wherein the mesh braided layer is embedded in the original polymer film layer, the melting temperature is 295° C.±15° C., the extrusion molding temperature is 263° C.±12° C., and the extrusion molding pressure is 14 kgf±6 kgf;

[0132] (II-3) A metal conductive layer (such as an aluminum layer) of equal thickness is deposited on the upper and lower surfaces of the polymer base film layer by vacuum evaporation.

[0133] (II-4) performing a passivation treatment on the metal conductive layer;

[0134] (II-5) Cutting and welding the tabs on the surface of the metal conductive layer using ultrasonic welding.

[0135] Option III

[0136] (III-1) plain weaving the fiber filaments to obtain a mesh woven layer, wherein the fiber filaments are aluminum wires and the mesh aperture is 0.5 to 1.5 mm;

[0137] (III-2) plastically melting the PET masterbatch, casting the masterbatch, and extruding the masterbatch using a T-die, and then flattening the mesh woven layer into the original film layer using hot roller co-extrusion to obtain a polymer original film layer, wherein the mesh woven layer is embedded in the original polymer film layer, the melting temperature is 298°C ± 12°C, the extrusion molding temperature is 273°C ± 7°C, and the extrusion molding pressure is 14 kgf ± 6 kgf; the hot roller co-extrusion temperature is 270°C ± 10°C, and the pressure is 18.5 kgf ± 6.5 kgf;

[0138] (III-3) A metal conductive layer (such as an aluminum layer) of equal thickness is deposited on the upper and lower surfaces of the polymer base film layer by vacuum evaporation.

[0139] (III-4) passivating the metal conductive layer;

[0140] (III-5) Cutting and cutting the ends of the obtained composite current collector to form tabs.

[0141] Option IV

[0142] (IV-1) plastically melting the PET masterbatch, casting the masterbatch, and extruding the masterbatch using a T-die to obtain a polymer film layer;

[0143] (IV-2) A metal conductive layer (such as an aluminum layer) of equal thickness is deposited on the upper and lower surfaces of the polymer base film layer by vacuum evaporation.

[0144] (IV-3) performing passivation treatment on the metal conductive layer;

[0145] (IV-4) Cutting and cutting the end of the obtained composite current collector to form a tab.

[0146] Examples 1 to 15 and Comparative Examples 1 to 2

[0147] The composite current collector structures obtained in Examples 1 to 15 and Comparative Examples 1 to 2 are shown in Table 1, where:

[0148] The difference between Examples 2 to 3 and Example 1 is that the reinforcing materials are in different forms and the preparation schemes used are different. The difference between Examples 2 and 3 is that the reinforcing materials are embedded in the polymer base film layer in different ways.

[0149] The difference between Comparative Example 2 and Example 1 is that the volume proportion of the reinforcing material in the polymer base film layer is different.

[0150] The structural differences of the composite current collectors prepared in Examples 4 to 12 and Example 3 are shown in Table 1.

[0151] The difference between Example 13 and Example 2 is that the woven fiber used in Example 13 is PA66.

[0152] The difference between Example 14 and Example 3 is that the braided fiber used in Example 14 is stainless steel wire.

[0153] The difference between Example 15 and Example 2 is that the braided fiber used in Example 15 is nickel wire.

[0154] The current collectors prepared in the examples and comparative examples were evaluated, including:

[0155] (1) Cut the composite current collector obtained by passivation treatment in Schemes I to IV to verify whether the tabs can be welded by ultrasonic welding. The specific operation method and controlled ultrasonic welding conditions are as follows: stack the cut tabs in multiple layers, with the number of stacked layers ≥ 20 layers, and the ultrasonic welding parameters are: the amplitude is controlled at 55μm±15μm, the welding pressure is controlled at 60Psi±20Psi, and the welding energy is controlled at 550J±200J. After welding, the weld mark is subjected to a tensile test. The tensile test method includes shear force and peel force test. After the tensile test is completed, the residual weld melt is tested.

[0156] (2) Cut and end-cut the composite current collector obtained by passivation treatment in Schemes I to IV to form a tab structure and verify whether the tab structure is reliable. The specific operation method and verification method and conditions are as follows: the tab cutting must meet specific shape requirements, and the burr size at the cutting site must not exceed industry specifications;

[0157] (3) Cut the composite current collector obtained by passivation treatment in Schemes I to IV and test its elastic modulus. The specific test reference is the national standard: GB / T 1040.1-2018.

[0158] (4) Cut the composite current collector obtained by passivation treatment in Schemes I to IV and test its tensile strength. The specific test reference is the national standard: GB / T 5187-2008.

[0159] Table 1 Differences and evaluation results of Examples 1 to 15 and Comparative Examples 1 to 2

[0160]

[0161]

[0162] Results and Conclusions:

[0163] In combination with Examples 1 to 15 of the present application, it can be seen that the composite current collector structure of the present application can be used to form pole ears by ultrasonic welding or with the help of the composite current collector body structure, which shows that arranging reinforcing materials in the polymer base film layer can significantly improve the energy absorption effect of the base film layer. Moreover, by comparing Examples 1 to 3, it can be seen that compared with short fibers, when the volume proportion of the reinforcing material in the base film layer is the same, the use of a woven mesh structure as a reinforcing material has a more obvious effect on improving the elastic modulus and tensile strength of the composite current collector, and is more conducive to improving the energy absorption effect of the polymer base film layer; while the method of Comparative Example 1 is adopted, that is, no reinforcement is provided. The reinforcing material cannot achieve effective connection between the composite current collector and the tab by ultrasonic welding or the like, or form an effective tab using the composite current collector body structure; and, by comparing Example 1 and Comparative Example 2, it can be seen that under the same circumstances, when the volume proportion of the reinforcing material in the polymer-based film layer is too low, the improvement effect on the elastic modulus and energy absorption of the composite current collector is insufficient, and a cold weld phenomenon will occur when the tab is welded by ultrasonic welding, and the welding tension and residual ratio are insufficient, making it difficult to achieve effective connection between the composite current collector and the tab by ultrasonic welding, and it is also difficult to form an effective tab using the composite current collector body structure.

[0164] Furthermore, compared to Examples 1-3, Examples 5, 7, and Examples 9-15, although Examples 4, 6, and 8 can also form tabs through ultrasonic welding or using the composite current collector body structure, they also have the risk of cold welding during actual operation. The possibility of insufficient welding tension and residual ratio is greater than that of other examples, but less than that of Comparative Example 2. The main reason is that the volume proportion of the reinforcing material in the polymer base film layer is relatively small or the thickness of the woven mesh used as the reinforcing material is relatively thin, which has a relatively low effect on improving the rigidity of the composite current collector. Optionally, the volume proportion of the reinforcing material in the polymer base film layer is not less than 15%; when a mesh woven layer is selected as the reinforcing material, the thickness of the mesh woven layer embedded in the base film layer can optionally be not less than 4μm. In addition, by comparing Examples 2-3 and Examples 13-15, it can be seen that under the same structural conditions, the mesh woven layers obtained by using woven fibers of different materials can achieve good reinforcement effects. In addition, by comparing the various examples, it can be seen that appropriately increasing the volume proportion of the reinforcing material in the polymer base film layer or the thickness of the reinforcing material is more conducive to improving the rigidity of the composite current collector.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A composite current collector, wherein: include: A polymer base film layer; as well as A conductive layer, wherein at least a portion of the surface of the polymer base film layer is provided with the conductive layer, Wherein, the elastic modulus of the composite current collector is not less than 0.5 GPa.

2. The composite current collector according to claim 1, wherein: The elastic modulus of the composite current collector is not greater than 10 GPa; and / or the tensile strength of the polymer-based film layer is not less than 100 MPa.

3. The composite current collector according to claim 1 or 2, wherein: A reinforcing material is distributed in the polymer-based film layer, and the elastic modulus of the reinforcing material is greater than the elastic modulus of the polymer forming the polymer-based film layer.

4. The composite current collector according to claim 3, wherein: At least a portion of the reinforcement material is embedded in the polymer-based film layer.

5. The composite current collector according to claim 3 or 4, wherein: Based on the volume of the polymer-based film layer, the volume proportion of the reinforcing material distributed in the polymer-based film layer is 10% to 80%.

6. The composite current collector according to any one of claims 3 to 5, wherein: The reinforcing material is partially exposed on the surface of the polymer-based film layer, and the exposed height is no greater than the distance between the side of the conductive layer away from the polymer-based film layer and the surface of the polymer-based film layer; and / or, The reinforcing material is chemically stable in an electrolyte environment.

7. The composite current collector according to any one of claims 3 to 6, wherein: The reinforcing material comprises at least one of an organic material, an inorganic non-metallic material and an inorganic metallic material; and / or, The reinforcing material includes at least one of linear fibers, dumbbell-shaped rods, mesh sheets, and non-mesh sheets. Optionally, the mesh sheets are mesh woven layers.

8. The composite current collector according to claim 7, wherein: At least one of the following conditions is met: The lengths of the linear fibers and the dumbbell-shaped rods are independently no less than 5 mm; The diameters of the linear fibers and the dumbbell-shaped rods are independently no greater than 20 μm; The linear fibers include organic fibers and / or inorganic fibers; The thickness of the mesh sheet and the non-mesh sheet is independently no greater than 20 μm; The length and width of the mesh sheet and the non-mesh sheet are independently not less than 5 mm.

9. The composite current collector according to claim 7 or 8, wherein: At least one of the following conditions is met: The mesh woven layer is woven from woven fibers, and the woven fibers include organic fibers and / or inorganic fibers; The diameter of the woven fibers of the mesh woven layer is not greater than 20 μm, the mesh hole diameter is not greater than 5 mm, and the porosity is not greater than 90%; The weaving density of the mesh braided layer is not less than 500 strands / 100mm; The mesh woven layer includes at least one of a plain weave, a twill weave, a satin weave, a full twist weave or a half twist weave; The mesh woven layer is woven from at least one layer of warp fibers and at least one layer of weft fibers.

10. The composite current collector according to claim 8 or 9, wherein: The organic fibers include polyamide fibers, and the inorganic fibers include glass fibers and / or metal fibers.

11. The composite current collector according to any one of claims 7 to 10, wherein: The linear fibers and / or the dumbbell-shaped rods are uniformly dispersed in the polymer-based film layer.

12. The composite current collector according to any one of claims 7 to 11, wherein: The reinforcing material includes at least one layer of mesh sheet and / or at least one layer of non-mesh sheet, the non-mesh sheet is embedded in the polymer-based film layer, and at least a portion of the mesh sheet is embedded in the polymer-based film layer.

13. The composite current collector according to any one of claims 7 to 12, wherein: At least one of the following conditions is met: The reinforcing material comprises at least one mesh woven layer, and the matrix material of the polymer-based film layer is continuously distributed in the meshes of the mesh woven layer and on at least a portion of the surface; The mesh woven layer is built into the polymer substrate, the diameter of the woven fibers in the mesh woven layer is not greater than 1 / 2 of the thickness of the polymer base film layer, or the mesh woven layer is partially exposed on the surface of the polymer substrate, and the exposed height is not greater than the thickness of the polymer base film layer; The woven fibers of the mesh woven layer include at least one of polyamide fibers, glass fibers and metal fibers, and the metal fibers include at least one of aluminum, copper, steel and nickel.

14. The composite current collector according to any one of claims 3 to 13, wherein: The material of the conductive layer is the same as that of the reinforcing material.

15. The composite current collector according to any one of claims 1 to 14, wherein: At least one of the following conditions is met: The thickness of the polymer base film layer is 2 μm to 20 μm; The thickness of the conductive layer is 0.05 μm to 5 μm; The conductive layer is a metal plating layer; The conductive layer includes at least one of aluminum, copper and nickel.

16. The composite current collector according to any one of claims 1 to 15, wherein: Also includes: An elastic buffer layer is provided between the polymer base film layer and the conductive layer.

17. The composite current collector according to claim 16, wherein: The elastic buffer layer is a rubber layer; and / or the elastic buffer layer has a thickness of no more than 5 μm.

18. A method for preparing the composite current collector according to any one of claims 1 to 17, wherein: include: (1) preparing a polymer-based film layer using a polymer matrix material and a reinforcing material; (2) forming a conductive layer on at least a portion of the surface of the polymer-based film layer.

19. The method according to claim 18, wherein: Step (1) is performed in one of the following ways: Melt-blending and molding the polymer matrix material and the reinforcing material to obtain the polymer base film layer; Embedding the reinforcing material into the polymer matrix film by hot roller co-extrusion to obtain the polymer matrix film layer; The polymer matrix material is subjected to a film-casting treatment, and the reinforcing material is embedded during the film-casting process to obtain the polymer-based film layer.

20. The method according to claim 18 or 19, wherein: At least one of the following conditions is met: In step (2), the conductive layer is formed by at least one of magnetron sputtering, vacuum evaporation, vacuum ion plating, water electroplating and direct composite method; In step (2), an elastic buffer layer is preliminarily formed on the surface of the polymer base film layer, and then the conductive layer is formed on the surface of the elastic buffer layer; Step (2) also includes: performing a passivation treatment on the conductive layer; Step (2) also includes: welding the pole lugs on the surface of the conductive layer by ultrasonic welding; or, cutting the obtained composite current collector to form the pole lugs; or, reserving the pole lug area structure before forming the conductive layer, and forming the pole lugs using the conductive layer and / or the reinforcing material.

21. A pole piece, wherein: include: The composite current collector according to any one of claims 1 to 17, and / or the composite current collector prepared by the method according to any one of claims 18 to 20.

22. A battery, wherein: include: The composite current collector according to any one of claims 1 to 17, and / or the composite current collector prepared by the method according to any one of claims 18 to 20, and / or the pole piece according to claim 21.

23. An electrical device, wherein: include: The composite current collector according to any one of claims 1 to 17, and / or the composite current collector prepared by the method according to any one of claims 18 to 20, and / or the pole piece according to claim 21, and / or the battery according to claim 22.

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