Composite current collectors and their preparation methods, electrodes, batteries and battery applications

Abstract

This application discloses a composite current collector, its preparation method, electrode, battery, and battery application. The embodiments of this application involve a composite organic porous membrane consisting of two or more stacked layers. Each composite organic porous membrane includes an organic porous base membrane, a metal film bonded to at least one surface of the organic porous base membrane, and a conductor filling the pores of the organic porous base membrane, the conductor being electrically connected to the surface of the metal film; the metal film is stacked between adjacent composite organic porous membranes. The electrodes and batteries of this application both incorporate this composite current collector. Through the combination of organic porous membrane layers and a metal substrate, the composite current collector can effectively reduce or mitigate the risk of battery thermal failure caused by factors such as puncture conditions.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a composite current collector and its preparation method, electrodes, batteries, and battery applications. Background Technology

[0002] Lithium-ion batteries have rapidly gained popularity in automotive power supplies, 3C electronic products, and energy storage devices due to their advantages such as high energy density and low self-discharge. With the widespread application of lithium batteries, their safety has become increasingly important, and safety requirements are becoming more stringent.

[0003] However, lithium batteries are prone to thermal runaway under electrical, thermal, and mechanical faults such as internal and external short circuits, overcharging, thermal abuse, and mechanical abuse, which can easily lead to safety accidents. Currently, in order to mitigate thermal runaway of lithium batteries and reduce the safety hazards caused by it, the focus is mainly on improving the quality of lithium battery packaging and the separation and electrolyte, with relatively little attention paid to improving the current collector to alleviate thermal runaway and improve the safety of lithium batteries. Summary of the Invention

[0004] In view of the above problems, this application provides a composite current collector and its preparation method, electrode, battery and its application, which can effectively alleviate the risk of thermal runaway caused by battery conditions including puncture conditions and improve the safety of lithium batteries.

[0005] In a first aspect, embodiments of this application provide a composite current collector. The composite current collector of this application includes two or more layers of composite organic porous membranes. Each composite organic porous membrane includes an organic porous base membrane, a metal membrane is bonded to at least one surface of the organic porous base membrane, and a conductor is filled in the pores of the organic porous base membrane. The conductor is electrically connected to the surface of the metal membrane.

[0006] Along the thickness direction of the composite organic porous membrane, each of the composite organic porous membranes is stacked, and the metal film contained in each composite organic porous membrane is stacked between two adjacent composite organic porous membranes.

[0007] The composite current collector in this application can effectively reduce or mitigate the risk of battery thermal failure caused by factors such as puncture conditions through the stacking of two or more composite organic porous membranes and the composite synergistic effect, thereby improving the safety performance of the battery.

[0008] In some embodiments, each of the organic porous substrate membranes comprises at least one of the following (1) to (5):

[0009] (1) The thickness of the organic porous base film is 0.5 to 8 μm, and can be selected as 2 μm to 6 μm;

[0010] (2) The porosity of the organic porous base membrane is 40% to 95%, and can be selected as 60% to 85%;

[0011] (3) The pore size of the organic porous base membrane is 200-5000 nm, and can be selected as 500 nm-3500 nm;

[0012] (4) The organic porous base membrane includes a straight-pore organic membrane;

[0013] (5) The tensile strength of the organic porous base membrane is higher than 150 MPa.

[0014] By further controlling the thickness, porosity, and pore size of the organic porous membrane, as well as its mechanical properties, the elastic deformation capability and resistance to physical puncture of the organic porous membrane composite, i.e., the composite current collector of this application embodiment, can be further improved, thereby further reducing or mitigating the risk of battery thermal failure. Simultaneously, the stability of the composite current collector during processing or application of this application embodiment is improved.

[0015] In some embodiments, the organic porous base membrane is made of at least one of polyethylene, polyimide, polypropylene, and polytetrafluoroethylene. These materials provide membranes with good elastic deformation capabilities and other mechanical properties, which can further reduce or mitigate battery thermal runaway caused by factors such as physical puncture or high temperatures, while also further improving the mechanical properties of the composite current collector in the embodiments of this application.

[0016] In some embodiments, the metal film is bonded to both opposite surfaces of the organic porous base membrane. This improves the conductivity and mechanical properties of the composite organic porous membrane, thereby further enhancing the conductivity and mechanical properties of the composite current collector in the embodiments of this application.

[0017] In some embodiments, the thickness of the metal film is 100nm to 1000nm, optionally 200nm to 600nm. The thickness of the metal film is significantly reduced, effectively mitigating the risk of thermal runaway in the battery while also reducing the weight of the composite current collector, thereby significantly improving the battery's energy density.

[0018] In some embodiments, the metal film has through-holes that correspond to the pores contained in the bonding surface of the metal film and the organic porous base film.

[0019] In some embodiments, the metal film includes a metal coating.

[0020] The metal film has low density, high conductivity, and strong adhesion to organic porous base films.

[0021] In some embodiments, the material of the conductor includes at least one of metal, conductive adhesive; and / or

[0022] The conductivity of the conductor is 10. 3 S / m~6×10 7 S / m.

[0023] In some embodiments, the metal film includes a metal coating, and at least a portion of the conductor includes the metal coating deposited on the pore walls of the pores contained in the organic porous substrate film.

[0024] This conductor has good electrical conductivity and can be effectively electrically connected to metal films. In addition, when combined with an organic porous base film, it has good mechanical properties such as elasticity.

[0025] In some embodiments, a conductive adhesive layer is further provided between two adjacent layers of the composite organic porous membrane for bonding the two adjacent layers of the composite organic porous membrane.

[0026] In some embodiments, the metal film includes a metal plating layer, and the surface of the conductive adhesive layer extends through the metal plating layer into the pores of the organic porous base film, constituting the conductor or a part of the conductor.

[0027] In some embodiments, the thickness of the conductive adhesive layer is 0.1 μm to 4 μm.

[0028] In some embodiments, the conductivity of the conductive adhesive layer is 10. 3 S / m~10 4 S / m.

[0029] The provision of this conductive adhesive layer, and the selective control of its conductivity and thickness, can effectively enhance the structural strength and conductivity of the composite current collector in this application embodiment.

[0030] In some embodiments, the total thickness of the composite current collector is 5 μm to 18 μm, and can be selected as 8 μm to 14 μm.

[0031] In some embodiments, the conductivity of the composite current collector is 10. 6 S / m~5×10 7 S / m, selectable as 5×10 6 S / m~3×10 7 S / m.

[0032] The composite current collector of this thickness can effectively reduce or mitigate the risk of battery thermal runaway caused by factors such as physical puncture or high temperature, and its structure is stable, ensuring its processing and operational stability. At the same time, it imparts good electrical conductivity to the composite current collector in the embodiments of this application.

[0033] Secondly, embodiments of this application also provide a method for preparing a composite current collector. The method for preparing the composite current collector according to embodiments of this application includes the following steps:

[0034] At least two organic porous membranes are provided, and a metal membrane is formed on at least one surface of each organic porous membrane to obtain at least two composite membranes;

[0035] Along the thickness direction of the composite membrane, each of the composite membranes is stacked, and the metal film contained in the composite membrane is stacked between two adjacent composite membranes to obtain a composite current collector;

[0036] The method further includes, in at least one step of forming the metal film and performing the stacking process on each of the composite films, filling the pores of each of the organic porous base films with a conductor; and making the conductor electrically connected to the metal film bonded to the surface of the organic porous base film.

[0037] The composite current collector prepared by the method described in this application contains two or more layers of stacked composite organic porous membranes. Through the synergistic effect of these two or more composite organic porous membranes, they can thermally melt to form a sealed film layer under abnormal environments such as elastic deformation during puncture and high temperatures. This mitigates or prevents the continued chemical reaction inside the battery, effectively reducing or mitigating battery thermal failure and improving battery safety performance. Furthermore, the prepared composite current collector exhibits excellent electrical conductivity and a stable structure.

[0038] In some embodiments, the metal film is formed on at least one surface of each of the organic porous membranes using a coating method. The metal film formed by coating is thin, has strong adhesion to the organic porous membrane, and retains through-pores on the surface of the metal film corresponding to the pores contained in the organic porous membrane.

[0039] In some embodiments, the method for stacking the composite films includes the following steps:

[0040] A conductive adhesive wet coating is formed on the surface of the metal membrane contained in the composite membrane that is opposite to the organic porous membrane;

[0041] According to the thickness direction of the composite film, each of the composite films is stacked to form a composite current collector blank;

[0042] The composite current collector blank is pressed and the conductive adhesive portion of the conductive adhesive wet coating is squeezed into the pores contained in the organic porous membrane, and then dried.

[0043] This method enables the formation of a conductive bonding layer between the interfaces of two adjacent composite organic porous membranes, and also enables the formation of a conductor within the organic porous membrane, thereby enhancing the stability of the prepared composite current collector structure and improving its conductivity.

[0044] In this embodiment, the pressing process includes performing a first pressing process followed by a second pressing process; wherein the pressure of the first pressing process is less than the pressure of the second pressing process.

[0045] In this embodiment, the first pressing process includes a roller pressing process, and the surface of the roller in the roller pressing process has a convex-concave structure.

[0046] In this embodiment, the pressure of the second pressing process is 0.5 MPa to 5 MPa, and can be selected as 1 MPa to 4 MPa.

[0047] In this embodiment, the second pressing process involves pressing the material more than twice.

[0048] The pressing process and conditions can improve the uniformity of the conductive adhesive layer and ensure that the conductor can fully fill the pores of the organic porous membrane, thereby enhancing the structural stability and conductivity of the prepared composite current collector.

[0049] Thirdly, embodiments of this application also provide an electrode. The electrode of this application embodiment includes an active layer bonded to a current collector, wherein the current collector includes the composite current collector described in the above-described application embodiments or a composite current collector prepared by the composite current collector preparation method described in the above-described application embodiments.

[0050] The electrodes in this application significantly reduce battery thermal failure under puncture conditions and / or abnormal high-temperature environments, while exhibiting excellent conductivity. They may also further possess high energy density and structural robustness.

[0051] In some embodiments, the electrode is at least one of a positive electrode and a negative electrode.

[0052] Fourthly, embodiments of this application also provide a battery. The battery of this application embodiment includes electrodes, which are the electrodes described in the embodiments of the above application.

[0053] The battery embodiments of this application can significantly reduce or mitigate the occurrence of thermal runaway or reduce the hazards caused by thermal runaway under abnormal conditions such as puncture or high temperature, thereby effectively improving the safety performance of the battery embodiments of this application. Moreover, due to the robust and stable electrode structure of the above application, the cycle performance of the battery embodiments of this application is significantly improved.

[0054] In some embodiments, the battery includes any one of a battery cell, a battery module, or a battery pack.

[0055] Fifthly, embodiments of this application also provide an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, wherein the power supply unit or energy storage unit contains a battery, and the battery includes the battery described in the embodiments of the above application. The power supply unit or energy storage unit of the electrical device of this application has high safety and long service life, and the standby or battery life of the electrical device of this application is long.

[0056] Sixthly, embodiments of this application also provide an energy storage device, characterized in that it includes an energy storage unit containing a battery, the battery including the battery described in the above-described embodiments. The energy storage device has high safety, long service life, and further high energy density.

[0057] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0058] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0059] Figure 1 This is a schematic diagram of the structure of the composite current collector in some embodiments of this application;

[0060] Figure 2 This is a schematic diagram of the structure of the composite current collector in some other embodiments of this application;

[0061] Figure 3 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0062] Figure 4 for Figure 3 The diagram shows an exploded view of a single battery cell.

[0063] Figure 5 This is a schematic diagram of one embodiment of the battery module of this application;

[0064] Figure 6 This is a schematic diagram of one embodiment of the battery pack according to this application.

[0065] Figure 7 for Figure 6 The diagram shows the exploded structure of the battery pack.

[0066] Figure 8 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source, as described in the present application.

[0067] The reference numerals in the detailed embodiments are as follows:

[0068] 1- Composite organic porous membrane, 11- Organic porous base membrane, 12- Metal membrane, 13- Conductor

[0069] 2-Conductive adhesive layer;

[0070] 30-Battery cell, 31-Casing, 32-Electrode assembly, 33-Cover plate;

[0071] 40 - Battery Module;

[0072] 50 - Battery pack, 51 - Housing, 52 - Lower housing. Detailed Implementation

[0073] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0074] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0075] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0076] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0077] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0078] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0079] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0080] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0081] Currently, the application of power batteries is becoming increasingly widespread in the market. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of the application areas of power batteries, the market demand is also constantly increasing. Lithium-ion batteries, due to their high energy density and low self-discharge, are rapidly becoming popular in automotive power supplies, 3C electronic products, and energy storage devices. With the widespread application of lithium batteries, their safety is receiving increasing attention, and safety requirements are becoming more stringent.

[0082] Based on the current structure of lithium batteries, they are prone to thermal runaway under electrical, thermal, and mechanical faults such as internal and external short circuits, overcharging, thermal abuse, and mechanical abuse, which can easily lead to safety accidents. Existing measures to improve battery safety mainly focus on improving lithium battery packaging processes, electrolytes, and separators. These improvements include enhancing the packaging process, adding flame retardants to the electrolyte, and modifying the separator to reduce thermal runaway and its resulting hazards. However, improving lithium battery packaging processes involves upgrading production systems and equipment, and improvements to flame retardants and separators can affect battery energy density.

[0083] To effectively reduce thermal runaway and its hazards in lithium batteries and improve their safety performance, research has revealed that creatively adding an organic porous film layer to the surface of the current collector can effectively reduce or delay the risk of thermal runaway, including under puncture conditions, thereby improving battery safety performance. Based on this, the embodiments of this application propose the following technical solutions.

[0084] Composite current collector

[0085] Firstly, embodiments of this application provide a composite current collector. In some embodiments, the composite current collector structure of this application is as follows: Figure 1 and Figure 2 As shown, a composite organic porous membrane 1 comprising two or more layers is provided. Each composite organic porous membrane 1 includes an organic porous base membrane 11, a metal membrane 12 is bonded to at least one surface of the organic porous base membrane 11, a conductor 13 is filled in the pores of the organic porous base membrane 11, and the conductor 13 is electrically connected to the surface of the metal membrane 12.

[0086] Along the thickness direction of the composite organic porous membrane 1, each composite organic porous membrane 1 is stacked, and the metal membrane 12 contained in each composite organic porous membrane 1 is stacked between two adjacent composite organic porous membranes 1.

[0087] In the composite current collector of this application embodiment, the composite organic porous membrane 1 constitutes a repeating unit. In the composite organic porous membrane 1, the conductor 13 filling the pores of the organic porous base membrane 11 and the metal film 12 bonded to the surface of the organic porous base membrane 11 constitute the conductive system of the composite organic porous membrane 1. When two or more layers of composite organic porous membrane 1 are stacked, since the metal film 12 contained in the composite organic porous membrane 1 is stacked between adjacent composite organic porous membranes 1, adjacent composite organic porous membranes 1 are electrically connected. Thus, the conductor 13 and the metal film 12 in each layer of composite organic porous membrane 1 together construct the conductive system of the composite current collector of this application embodiment.

[0088] In this composite organic porous membrane 1, the metal membrane 12 should be conductive, such as a current collector metal material. The organic porous base membrane 11 refers to an organic membrane containing pores. The conductor 13 refers to a component with conductive properties, which fills the pores of the organic porous base membrane 11 to form a conductive path in the organic porous base membrane 11, used to collect or transfer the charge in the electrode active layer and transfer it to the metal membrane 12.

[0089] In the embodiments of this application, the composite current collector constitutes a basic composite organic porous membrane 1 unit through the organic porous base membrane 11, the metal membrane 12 and the conductor 13 contained therein.

[0090] In the normal operating environment of the battery, the conductive system constructed by the metal film 12 and the conductor 13 can collect the charge of the electrode active layer and transfer it to the metal film 12. When the composite current collector of this embodiment is subjected to conditions including puncture, the organic porous base film 11 contained in the organic porous membrane 1 has elastic deformation capability and can effectively deform to significantly reduce or alleviate short circuits inside the battery caused by physical puncture; it can also be thermally melted to form a closed film layer in abnormal temperature environments such as high temperature environments, thereby reducing or alleviating the continued chemical reactions inside the battery. Therefore, the composite current collector of this embodiment can effectively reduce or alleviate battery thermal failure and improve battery safety performance through the synergistic effect of the organic porous membrane 1 more than twice.

[0091] In the composite current collector of this application embodiment, the number of repeating unit membrane layers of the composite organic porous membrane 1 is at least two layers. When there are two layers, the structure of the composite current collector of this application embodiment is as follows: Figure 1 or Figure 2 As shown; when it is a three-layer or higher structure, the structure of the composite current collector in this embodiment of the application is as follows: Figure 1 and Figure 2 Based on the structure shown, at least one repeating unit membrane layer of composite organic porous membrane 1 is added. Regardless of how many repeating unit membrane layers of composite organic porous membrane 1 are contained in the composite current collector of this application embodiment, the metal membrane 12 contained in the composite organic porous membrane 1 is stacked between two adjacent composite organic porous membranes 1, and the metal membrane 12 and the conductor 13 contained in the repeating unit membrane layer of each composite organic porous membrane 1 are electrically connected to each other, and they together construct the conductive system of the composite current collector of this application embodiment.

[0092] Based on the structure of each composite organic porous membrane 1, the organic porous base membrane 11 contained in each composite organic porous membrane 1 constitutes the base membrane of the composite organic porous membrane 1, thereby endowing the composite organic porous membrane 1 with excellent elastic deformation capability, thereby reducing or mitigating the risk of thermal failure of the battery containing the composite current collector of the present application embodiment in environments including puncture conditions and high temperature thermal anomalies, and improving the safety performance of the battery. In order to enhance the above-mentioned role played by the organic porous base membrane 11 in the composite organic porous membrane 1, that is, in the composite current collector of the present application embodiment, and further reduce the risk of thermal failure caused by environments including puncture conditions and high temperature thermal anomalies, and improve the safety performance of the battery, since the organic porous base membrane 11 is a membrane structure, the organic porous base membrane 11 has two surfaces arranged opposite to each other.

[0093] In some embodiments, the organic porous substrate 11 has at least one or more of the following properties:

[0094] As in the embodiment, the thickness of the organic porous base membrane 11 contained in each composite organic porous membrane 1 is set as follows: Figure 1 The d1 mentioned herein is 0.5 μm to 8 μm, and can be selected as 2 μm to 6 μm. In the exemplary example, the thickness of the organic porous base film 11 can include typical but not uniquely limited thicknesses such as 0.5 μm to 1 μm, 1 μm to 2 μm, 2 μm to 3 μm, 3 μm to 4 μm, 4 μm to 5 μm, 5 μm to 6 μm, 6 μm to 7 μm, and 7 μm to 8 μm. The thickness of the organic porous base film 11 refers to... Figure 1 The distance from one surface of the organic porous base membrane 11 to the other surface is shown. By adjusting the thickness of the organic porous base membrane 11, such as controlling it within this thickness range, it has good elastic deformation capability. This not only significantly reduces or alleviates battery thermal runaway caused by factors such as physical puncture or high temperature, but also improves the mechanical properties of the composite organic porous membrane 1, that is, it can improve the mechanical properties of the composite current collector in the embodiments of this application, and reduce or avoid adverse phenomena such as strip breakage during its processing or application.

[0095] In the embodiments, the porosity of the organic porous base membrane 11 can be 40% to 95%, and optionally 60% to 85%. In exemplary examples, the porosity of the organic porous base membrane 11 can include typical but not unique limiting porosity ranges such as 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 60% to 65%, 65% to 70%, 70% to 75%, 75% to 80%, 80% to 85%, 85% to 90%, and 90% to 95%. Here, porosity refers to the percentage of pore volume contained in the organic porous base membrane 11 per unit volume.

[0096] In the embodiments, the pore size of the organic porous base membrane 11 is 200-5000 nm, and can be selected as 500 nm-3500 nm. In the exemplary examples, the pore size of the organic porous base membrane 11 can include typical but not unique limiting pore size ranges such as 200 nm-500 nm, 500 nm-1000 nm, 1000 nm-1500 nm, 1500 nm-2000 nm, 2000 nm-2500 nm, 2500 nm-3000 nm, 3000 nm-3500 nm, 3500 nm-4000 nm, 4000 nm-4500 nm, and 4500 nm-5000 nm.

[0097] By further controlling the porosity and pore size of the organic porous base membrane 11, such as controlling them within the above-mentioned range, the elastic deformation capability of the organic porous base membrane 11 can be further improved, thereby further improving the elastic deformation capability of the composite organic porous membrane 1. This means that the mechanical properties, such as the elastic deformation capability, of the composite current collector in this embodiment can be further improved, thereby further reducing or mitigating battery thermal runaway caused by factors such as physical puncture or high temperature, and improving battery safety performance. Simultaneously, the stability of the composite current collector in the processing or application process of this embodiment can be further improved. Furthermore, the porosity within the above-mentioned range can also adjust the amount and morphology of the conductor 13 filling the pores of the organic porous base membrane 11, thereby improving the overall conductivity of the composite current collector in this embodiment.

[0098] In the embodiments, the organic porous base membrane 11 has the following mechanical properties: tensile strength higher than 150 MPa.

[0099] The organic porous base membrane 11 with these mechanical properties exhibits good elastic deformation capability and resistance to puncture by physical factors, which can further reduce or mitigate battery thermal failure. It also improves the stability of the composite current collector during processing or application according to the embodiments of this application.

[0100] In the embodiments, the organic porous base membrane 11 in the above embodiments can be an organic straight-pore membrane. The straight-pore membrane is defined as a membrane layer containing pores that extend from one surface to the other. This allows the conductor 13, which fills the pores of the organic porous base membrane 11, to effectively fill the pores and can have one end electrically connected to the surface of the metal membrane 12, while the other end extends to the surface of the organic porous base membrane 11 opposite to the metal membrane 12. This improves the conductivity of the composite organic porous membrane 1, thereby reducing the resistance of the composite current collector in the embodiments of this application.

[0101] In the exemplary embodiments, the material of the organic porous base membrane 11 in the above embodiments may include at least one of polyethylene (PE), polyimide (PI), polypropylene (PP), and polytetrafluoroethylene (PTFE). For example, it can be any organic porous membrane selected from PE porous membrane, PI porous membrane, PP porous membrane, and PTFE porous membrane, or it can be a composite porous membrane with two or more membrane layers stacked together. Of course, it can also be a porous membrane formed from a mixture of these materials. These material membrane layers possess good elastic deformation capabilities and other mechanical properties, which can further reduce or mitigate battery thermal runaway caused by physical puncture or high temperatures, while further improving the mechanical properties of the composite current collector in the embodiments of this application and enhancing its stability during processing or application.

[0102] In the embodiments, the metal film 12 contained in each composite organic porous membrane 1 can be bonded to one surface of the organic porous base membrane 11, such as... Figure 1 As shown; of course, the metal film 12 can also be bonded to at least two opposing surfaces of the organic porous base film 11, as shown. Figure 2 As shown in the figure. When the metal film 12 is bonded to at least two opposing surfaces of the organic porous base film 11, in this embodiment, the conductor 13 filling the pores of the organic porous base film 11 is simultaneously electrically connected to the metal film 12 bonded to the two opposing surfaces of the organic porous base film 11. In this way, the conductor 13 acts as an electrical bridge between the two metal films 12 in the composite organic porous film 1, thereby further reducing the resistance of the composite organic porous film 1 and improving its conductivity, that is, further improving the conductivity of the composite current collector in this embodiment.

[0103] In this embodiment, the metal film 12 may include a metal coating. This metal coating can be a vapor-deposited metal coating, or it can be a chemically electroplated metal coating. In an exemplary embodiment, the material of the metal film 12 can be a highly conductive metal material, such as a commonly used positive electrode current collector metal material, like aluminum; or a commonly used negative electrode current collector metal material, like copper.

[0104] In the embodiments, such as Figure 1As shown in the figure, the metal film 12 also has through holes, which are correspondingly arranged to the pores contained in the bonding surface of the metal film 12 and the organic porous base film 11. The arrangement of these through holes allows for the efficient placement of the conductor 13 filling the pores of the organic porous base film 11. Furthermore, it also results in the surface of the repeating unit membrane of the composite organic porous film 1 having abundant pores. The presence of these pores creates a rough surface on the composite organic porous film 1, thereby increasing the bonding strength between the electrode active layer and the surface of the composite organic porous film 1, and improving the structural stability of the electrode.

[0105] In this embodiment, when the metal film 12 is a metal coating, in addition to being effectively deposited and bonded to the surface of the organic porous base film 11, the metal film 12 can also be further deposited and bonded to the pore walls of the pores contained in the organic porous base film 11. In this case, the metal film 12 extends beyond the surface of the organic porous base film 11 into the pores contained in the organic porous base film 11, such as onto the pore walls. The metal film bonded to the pore walls constitutes the conductor 13 contained in each composite organic porous film 1, or constitutes a part of the conductor 13. When the conductor 13 includes the metal film bonded to the pore walls, the conductivity of the conductor 13 and the stability of its electrical connection with the surface of the metal film 12 can be further improved.

[0106] When the metal film 12 contains the aforementioned through-holes, that is, the metal coating is deposited along with the surface skeleton of the organic porous base film 11, without sealing the pores on the surface of the organic porous base film 11.

[0107] Regardless of the composite organic porous membrane 1 is Figure 1 The structure shown is still Figure 2 The structure shown includes an organic porous membrane 1 containing an organic porous base membrane 11, with a conductor 13 electrically connected to the surface of a metal membrane 12 filling the pores of the organic porous base membrane 11. Therefore, in some embodiments, the thickness of the metal membrane 12 bonded to one surface of the organic porous base membrane 11 can be set very thin, significantly thinner than the thickness of conventional current collectors, and can be controlled within the nanometer thickness range. For example, in one embodiment, the thickness of the metal membrane 12 bonded to one surface of the organic porous base membrane 11 is set as follows: Figure 1 The d2 mentioned herein can be 100–1000 μm, or more specifically 200–600 μm. In the example, it can be a typical but not unique limiting thickness range such as 100–200 μm, 200–250 μm, 250–300 μm, 300–350 μm, 350–400 μm, 400–450 μm, 450–500 μm, 500–600 μm, 600–700 μm, 700–800 μm, 800–900 μm, 900–1000 μm.

[0108] Using conventional current collectors with aluminum foil thickness of 10 μm and copper foil thickness of 6 μm, the conventional current collectors account for approximately 7% and 9% of the mass of the battery cell, respectively. This is because reducing the thickness of conventional current collectors leads to a decrease in tensile strength, affecting coating thickness and significantly increasing the incidence of strip breakage. However, in the composite current collector of this application embodiment, due to the presence of the organic porous base film 11 in the repeating unit of the composite organic porous membrane 1, the thickness of the contained metal film 12 can be significantly reduced, such as by controlling it within the aforementioned nanometer thickness range. This effectively reduces or mitigates the risk of thermal runaway in the battery while significantly reducing the weight of the composite current collector, thereby significantly improving the battery's energy density. Furthermore, because the organic porous base film 11 possesses good mechanical properties such as toughness, even if the thickness of the metal film 12 is controlled within the nanometer thickness range, it will not cause adverse phenomena such as strip breakage during the processing or application of the composite current collector of this application embodiment.

[0109] In this embodiment, the conductor 13 contained in each composite organic porous membrane 1, that is, the conductor 13 filling the pores of the organic porous base membrane 11, plays a conductive role. Its bonding with the metal membrane 12 electrically connects the surface of the organic porous base membrane 11, thus providing a conductive connection between the metal membranes 12. Simultaneously, when the electrode active layer is bonded to the composite current collector of this embodiment, the conductor 13 becomes electrically connected to the electrode active layer. Therefore, at this time, the conductor 13 also serves to electrically connect the electrode active layer and the metal membrane 12 in the composite current collector of this embodiment, thereby effectively transferring the charge of the electrode active layer to the metal membrane 12.

[0110] In some embodiments, the conductivity of conductor 13 can be 10. 3 S / m~6×10 7 S / m, selectable as 3×10 7 S / m~6×10 7 The higher the conductivity (S / m) of the conductor 13, the better. When the conductor 13 is formed by extending and filling the pores of the organic porous base film 11 from the conductive adhesive layer 2 described below, the conductivity of the conductor 13 can be the same as or close to the conductivity of the conductive adhesive layer 2 described below. When the conductor 13 contains a metal film or metal filler that extends and fills the pores of the organic porous base film 11 from the metal film 12, the conductivity of the conductor 13 can be significantly improved, such as reaching 3 × 10⁻⁶. 7 S / m~6×10 7 S / m. Furthermore, by selecting the material of conductor 13, the conductivity of conductor 13 can also be made greater than 6 × 10⁻⁶. 7 In the example, the conductivity of the conductor 13 can include 3 × 10⁻⁶ S / m. 7S / m, 4×10 7 S / m, 5×10 7 S / m, 6×10 7 Typical but not unique limiting conductivity values ​​such as S / m. Conductors 13 within this range exhibit good conductivity and low internal resistance, effectively providing a good conductive connection between the various metal films 12, or further collecting charges in the electrode active layer and transferring them to the metal film 12, thereby improving the conductivity of the composite current collector in the embodiments of this application and reducing the battery's internal resistance.

[0111] In some embodiments, the depth to which the conductor 13 fills the pores of the organic porous base film 11 can be 4 / 5 to 5 / 5 of the thickness of the organic porous base film 11. Typical but not unique ratios, such as 4–4.2:5, 4.2–4.5:5, 4.5–4.8:5, and 4.8–5:5, can be included in the examples. By controlling the filling depth of the conductor 13, the electrical contact between the composite current collector and the electrode active layer in this application embodiment can be enhanced, and the internal resistance of the electrode can be reduced.

[0112] In some embodiments, when the metal film 12 is a metal coating, and the metal film 12 is deposited and bonded not only on the surface of the organic porous base film 11, but also further deposited and bonded to the pore walls of the pores contained in the organic porous base film 11, at least a portion of the material of the conductor 13 includes the metal film bonded to the pore walls of the pores. Here, "at least a portion of the conductor 13" means that some conductors 13 contain the metal film, and some do not; of course, it also includes all conductors 13 containing the metal film. The main reason is that, in the actual deposition process, the probability of the metal film being deposited into the pores of the organic porous base film 11 is random. When the material of the conductor 13 contains the metal film, the conductivity of the conductor 13 can be improved.

[0113] In some embodiments, the material of the conductor 13 may include at least one of metal and conductive binder. When the material of the conductor 13 contains metal, it may be the metal contained in the metal film 12, specifically formed by the metal film 12 extending into the pores. When the material of the conductor 13 contains the conductive binder, the conductive binder, in addition to having good conductivity, also has good elasticity and other mechanical properties, enabling it to bond with the organic porous base film 11 to form a whole, enhancing the elastic deformation capacity and other mechanical properties of the organic porous base film 11, and further reducing or mitigating battery thermal runaway caused by physical puncture or high temperature. Furthermore, the electrical connection with the surface of the metal film 12 is stable, improving the processing and operational stability of the composite current collector in this application embodiment. Of course, the material of the conductor 13 can also be other materials with conductive properties; any conductive material that can cooperate with the organic porous base film 11 and has good elasticity and a stable electrical connection with the surface of the metal film 12 is within the scope of the embodiments disclosed in this application.

[0114] The composite current collectors described in the above embodiments are composed of at least two layers of repeating unit membranes 1 stacked together. In some embodiments, such as... Figure 1 and Figure 2 As shown, in the above embodiments, each composite organic porous membrane 1 is bonded together by a conductive adhesive layer 2. That is, a conductive adhesive layer 2 is also provided between two adjacent composite organic porous membranes 1 for bonding and bonding. By bonding two adjacent composite organic porous membranes 1 together by the conductive adhesive layer 2, the stability of the composite current collector structure of this application embodiment is effectively enhanced. More importantly, the conductive adhesive layer 2 also has good elasticity, which can work in conjunction with the elasticity of the organic porous base membrane 11 to enhance the elastic deformation capacity and other mechanical properties of each composite organic porous membrane 1, that is, the composite current collector of this application embodiment, so as to further reduce or alleviate the battery thermal runaway caused by physical puncture or high temperature. At the same time, the conductive adhesive layer 2 also has good conductivity, which can ultimately transfer the charge in the active layer of the collector electrode of the conductor 13 to the metal film 12, thereby improving the conductivity of the composite current collector of this application embodiment and reducing the battery internal resistance.

[0115] In this embodiment, the thickness of the conductive adhesive layer 2 is 0.1 μm to 4 μm. Specifically, as shown below... Figure 1 and Figure 2 As shown, the thickness of the conductive adhesive layer 2 between two adjacent composite organic porous membranes 1 is set as follows: Figure 1 The d3 mentioned herein is 0.1μm to 4μm, and can be selected as 0.5μm to 2μm. In the exemplary example, d3 can include typical but not uniquely limited thicknesses such as 0.1μm to 0.5μm, 0.5μm to 1μm, 1μm to 1.5μm, and 1.5μm to 2μm. By controlling the thickness of the conductive adhesive layer 2 within the specified range, the bonding strength between two adjacent composite organic porous membranes 1 can be effectively enhanced. At the same time, it can further enhance the mechanical properties such as the elastic deformation capability of the composite current collector of the present application embodiment, so as to further reduce or alleviate the battery thermal runaway caused by factors such as physical puncture or high temperature; and reduce the resistance of the composite current collector.

[0116] In some embodiments, the conductivity of the conductive adhesive layer 2 can be 10. 3 S / m~10 4 For conductive adhesive layer 2, the higher the conductivity (S / m), the better. For example, by selecting the appropriate material for conductive adhesive layer 2, its conductivity can also be greater than 10. 4 S / m. The conductive adhesive layer 2 in this range has good conductivity and low internal resistance, which improves the conductivity of the composite current collector in the embodiments of this application and reduces the internal resistance of the battery.

[0117] When the conductor 13 filling the pores of the organic porous base film 11 contains a conductive binder, the conductive binder contained in the conductive adhesive layer 2 can be the same as the conductive binder of the conductor 13, or it can be different.

[0118] In this embodiment, the conductive binder contained in the conductor 13 and the conductive binder contained in the conductive adhesive layer 2 may be the same or different, including a binder base material and a conductive filler dispersed in the binder base material. The binder base material can be a binder commonly used in the battery field, such as at least one of polyimide (PI), polyamide (PA), polypropylene, and polyvinylidene fluoride (PVDF). The conductive agent may include, but is not limited to, at least one of conductive carbon black (SP), Ketjen black, carbon nanotubes (CNT), and graphene. The amount of conductive agent added can make the conductivity of the conductive adhesive layer 2 and the conductor 13 within the aforementioned range. Of course, if the binder base material itself has good conductivity, the content of the conductive agent can be controlled to 0, that is, the conductive agent may not be added.

[0119] In the embodiments, when the conductive adhesive contained in the conductor 13 is the same as the conductive adhesive contained in the conductive adhesive layer 2, the conductor 13 can be formed by extending from the surface of the conductive adhesive layer 2 into the pores of the organic porous base film 11.

[0120] Based on the composite organic porous membrane 1 contained in the composite current collectors of the above embodiments, or the conductive adhesive layer 2 used to bond adjacent composite organic porous membranes 1, by controlling the thickness of each composite organic porous membrane 1 or the thickness of the conductive adhesive layer 2, in some embodiments, the total thickness of the composite current collector in this application embodiment can be 5μm to 18μm, optionally 8μm to 14μm. In exemplary examples, the total thickness of the composite current collector can include typical but not unique thickness ranges such as 5μm to 7μm, 7μm to 8μm, 8μm to 10μm, 10μm to 12μm, 12μm to 14μm, 14μm to 16μm, and 16μm to 18μm. The total thickness of the composite current collector is the distance from one surface of the current collector to another surface, such as... Figure 1 The sum of (d1+d2)×2+d3 shown; as Figure 2 The sum of the thicknesses of the two organic porous base membranes 11 and the conductive adhesive layer 2 shown.

[0121] The composite current collector of this thickness can effectively reduce or mitigate the risk of battery thermal runaway caused by factors such as physical puncture or high temperature, and it also has a stable structure and stable processing and operation. At the same time, it endows the composite current collector of the present application embodiments with good conductivity and low internal resistance. For example, in some embodiments, the conductivity of the composite current collector of the present application embodiments is 10. 6 S / m~5×10 7 S / m, optional, optional 5×10 6 S / m~3×10 7 In the example, the conductivity of the composite current collector can include 5 × 10⁻⁶ S / m. 6 S / m, 6×10 7 S / m, 7×10 7 S / m, 8×10 7 S / m, 9×10 7 S / m, 10×10 7 S / m, 11×10 7 S / m, 12×10 7 S / m, 13×10 7 Typical but not unique limiting conductivity values ​​include S / m.

[0122] Preparation method of composite current collector

[0123] Secondly, embodiments of this application also provide a method for preparing a composite current collector, comprising the following steps:

[0124] S10: Provide at least two organic porous membranes; and form a metal membrane on at least one surface of each organic porous membrane to obtain at least two composite membranes;

[0125] S20: Along the thickness direction of the composite membrane, each of the composite membranes is stacked, and the metal film contained in the composite membrane is stacked between two adjacent composite membranes to obtain a composite current collector;

[0126] The method further includes, in at least one step of forming the metal film and performing the stacking process on each of the composite films, filling the pores of each organic porous base film with a conductor; and making the conductor electrically connected to the metal film bonded to the surface of the organic porous base film.

[0127] Step S10:

[0128] The organic porous membrane in step S10 can be, for example, Figure 1 and Figure 2 The organic porous membrane 11 contained in the composite current collector of the above-described embodiment is shown in the text application.

[0129] The number of organic porous membranes is at least two, which is the same as the number of organic porous membranes 11 contained in the composite current collector of the above-described embodiment.

[0130] The formed metal film can be, for example, Figure 1 and Figure 2 The metal film 12 contained in the composite current collector of the above-described embodiment can be bonded to one surface of each organic porous membrane, or to two opposing surfaces of the organic porous membrane. In a further embodiment, the metal film 12 has through holes, and the through holes are provided corresponding to the pores contained in the bonding surface of the metal film 12 and the organic porous base membrane 11.

[0131] In the step of forming the metal film, a conductor can be filled into the pores contained in each organic porous base film 11 at the same time.

[0132] The structure of the composite membrane prepared in step S10 constitutes the framework of the repeating unit membrane layer composite organic porous membrane 1 or the composite organic porous membrane 1 contained in the composite current collector of the above-described embodiments. This framework refers to a structure that, compared to the organic porous membrane 1 described above, lacks or partially lacks the conductor 13.

[0133] Step S20:

[0134] The stacking process of the composite membranes prepared in step S10 refers to the stacking of the composite membranes prepared in step S10 according to the stacking rules of the repeating unit membrane layer composite organic porous membrane 1 contained in the composite current collector of the above-described embodiment. During the stacking process, a conductor may be filled into the pores contained in each organic porous base membrane 11.

[0135] In addition, the conductor can be formed during the metal film formation process in step S10, or during the lamination process in step S20, or it can be formed by combining steps S10 and S20.

[0136] Therefore, the composite current collector prepared by the method of this application contains two or more layers of stacked composite organic porous membranes, which can undergo elastic deformation under puncture conditions to significantly reduce or alleviate short circuits caused by physical puncture. Simultaneously, in abnormal environments such as high temperatures, the organic porous base membrane contained in the composite organic porous membrane can also be thermally melted to form a closed film layer, alleviating or preventing the continued chemical reaction inside the battery. Therefore, the composite current collector of this application can effectively reduce or alleviate battery thermal failure and improve battery safety performance. Furthermore, the conductor and metal film filling the pores of the organic porous base membrane construct a conductive system in the composite current collector, giving it excellent conductivity and low internal resistance. Secondly, the process conditions of the composite current collector preparation method of this application are controllable, ensuring the stability of the prepared composite current collector's quality and other properties.

[0137] In some embodiments, the method of forming a metal film on at least one surface of each organic porous membrane in step S10 includes a deposition method, that is, forming a metal film on at least one surface of each organic porous membrane using a deposition method. In an exemplary example, a vapor deposition method can be used to form a metal film on at least one surface of each organic porous membrane. The vapor deposition conditions can be controlled according to the thickness of the metal film and the properties of the metal material. For example, by controlling the vapor deposition conditions, the formed metal film can be a nanometer-thick film. Furthermore, the metal film can be formed on the organic framework surface of the organic porous base membrane 11, so that the formed metal film retains the pore structure of the surface of the organic porous base membrane 11. It can also be further possible to deposit the metal film in the pores, such as depositing and bonding it to the inner wall of the pores.

[0138] In this embodiment, the method for stacking the composite films in step S20 includes the following steps:

[0139] S21: A conductive adhesive wet coating is formed on the surface of the metal membrane contained in the composite membrane that is away from the organic porous membrane;

[0140] S22: The composite films are stacked in the thickness direction of the composite films to form a composite current collector blank;

[0141] S23: The composite current collector blank is pressed and the conductive adhesive portion in the conductive adhesive wet coating is squeezed into the pores contained in the organic porous membrane, and then dried.

[0142] The conductive adhesive wet coating formed in step S21 can be formed on the surface of the metal film contained in one of the composite films stacked in adjacent quantities, or it can be formed on the surface of the metal film contained in both composite films stacked in adjacent quantities.

[0143] In addition, the thickness of the formed conductive adhesive wet coating should at least ensure that during the pressing process in step 23, the conductive adhesive wet coating is partially squeezed into the pores of the organic porous membrane, and a conductive adhesive layer is formed between two adjacent composite membranes. The thickness of the conductive adhesive layer should be the same as the thickness of the conductive adhesive layer 2 contained in the composite current collector of the above-described embodiment.

[0144] The stacking process in step S22 should be in accordance with including Figure 1 or Figure 2 The order shown is for fitting together.

[0145] The pressing process in step S23 is to enhance the adhesion strength between the two adjacent composite films and improve their bonding stability. At the same time, during the pressing process, the conductive adhesive wet coating applied between the two adjacent composite films is squeezed by the pressure, causing part of the conductive adhesive wet coating to pass through the metal film and enter and fill the pores along the pores of the organic porous film. The remaining conductive adhesive wet coating is retained between the interfaces of the adjacent composite films.

[0146] The pressing process refers to applying pressure to the surface of the composite film. In this embodiment, the pressing process includes a first pressing process followed by a second pressing process; wherein the pressure of the first pressing process is less than the pressure of the second pressing process.

[0147] Thus, this first pressing process serves as an initial pressing step, ensuring the initial adhesion of the stacked composite films and reducing significant displacement of the conductive adhesive wet coating during the pressing process. This enhances the relatively uniform distribution of the conductive adhesive wet coating during pressing. In this embodiment, the first pressing process includes a roller pressing process, and the roller surface of the roller pressing process has a textured structure. By providing a textured structure on the roller surface, during the first pressing process, the conductive adhesive in the conductive adhesive wet coating can be partially squeezed into the concave structure on the roller surface under pressure. This significantly improves the uniformity of the conductive adhesive wet coating distribution between the interfaces of adjacent composite films after the first pressing process, avoiding significant displacement of the conductive adhesive wet coating as the roller advances, which is common with rollers with smooth surfaces. Alternatively, the conductive adhesive in the conductive adhesive wet coating can partially penetrate the metal film and fill the pores of the organic porous membrane. Simultaneously, this roller allows for continuous operation, improving the efficiency of the pressing process. For the purpose of the first pressing process, the pressure of the first pressing process only needs to be sufficient to ensure that the wet coating of the conductive adhesive is distributed relatively evenly.

[0148] The second pressing process ensures that the laminated composite films are tightly bonded together, enhancing the strength and stability of the bonding between the composite films. At the same time, it allows some of the conductive adhesive in the wet coating of the conductive adhesive to be further squeezed into the pores of the organic porous membrane to form a conductor.

[0149] In the embodiments, the pressure of the second pressing process can be 0.5 to 5 MPa, and can be selected as 1 MPa to 4 MPa. In the exemplary examples, the pressure of the second pressing process can include typical but not unique pressure ranges such as 0.5 to 1.5 MPa, 1.5 to 2 MPa, 2 to 2.5 MPa, 2.5 to 3 MPa, 3 to 3.5 MPa, 3.5 to 4 MPa, 4 to 4.5 MPa, and 4.5 to 5 MPa.

[0150] By selectively controlling the pressure of the second pressing process, the bonding strength between the composite membranes can be effectively enhanced, the structure and quality stability of the prepared composite current collector can be improved, and the conductive binder can be effectively filled in the pores of the organic porous membrane to form a conductor.

[0151] In the embodiments, the second pressing process can be performed multiple times, such as more than two times. In the example, there can be 2 to 5 second pressing processes to further enhance the bonding strength between the composite films, thereby further enhancing the structural and quality stability of the prepared composite current collector.

[0152] The drying process in step S23 involves curing and drying the wet coating of conductive adhesive remaining between adjacent composite films after the pressing process, as well as the conductive adhesive that has been extruded and filled into the organic porous membrane. After the drying process, the conductive adhesive that has been extruded and filled into the organic porous membrane cures to form a conductor, specifically forming a conductor as shown in the image. Figure 1 and Figure 2 The composite current collector in the embodiment of the above application contains a conductor 13; the remaining conductive adhesive wet coating between two adjacent composite films is cured to form a conductive adhesive layer, specifically forming a conductive adhesive layer as shown in the figure above. Figure 1 and Figure 2 The conductive adhesive layer 2 contained in the composite current collector of the embodiment of the above text application.

[0153] electrode

[0154] Thirdly, embodiments of this application also provide an electrode. The electrode in this application includes a current collector and an electrode active layer bonded to the current collector.

[0155] The current collector is the composite current collector of the above-described embodiments. The electrode active layer is an active layer containing electrode material; therefore, the active layer can be an active layer containing positive electrode material or an active layer containing negative electrode material. When the active layer is an active layer containing positive electrode material, the electrode of this embodiment is a positive electrode; when the active layer is an active layer containing negative electrode material, the electrode of this embodiment is a negative electrode. It should be understood that the electrode active layer contained in the electrode of this embodiment is electrically connected to the metal film contained in the composite current collector of the above-described embodiments or further to the conductor filling the pores of the organic porous film layer.

[0156] Based on the structure and performance of the composite current collector in the embodiments of the above application, such as the composite current collector containing an organic porous membrane layer with good elastic deformation capability, it can significantly reduce or mitigate battery thermal failure caused by the electrode in the embodiments of the application under puncture conditions and / or abnormal high-temperature environments, thereby improving battery safety performance. Simultaneously, the electrode in the embodiments of the application has excellent conductivity.

[0157] In the embodiments, since the weight of the composite current collector contained in the electrode of the present application embodiment can be significantly reduced (e.g., the thickness of the metal film contained in the composite current collector is effectively reduced), the weight of the electrode of the present application embodiment can be significantly reduced, that is, the energy density can be significantly improved.

[0158] In the embodiments, since the electrode active layer contained in the electrode of this application embodiment is directly bonded to the metal film contained in the composite current collector, and the metal film is bonded to the surface of the organic porous membrane, the metal film may have a rough surface or may further contain through holes corresponding to the pores on the surface of the organic porous membrane layer. Therefore, the surface features of the metal film effectively increase the contact area with the electrode active layer and increase the mechanical bonding force with the electrode active layer, thereby significantly enhancing the bonding strength between the electrode active layer and the composite current collector and improving the cycle performance of the electrode.

[0159] Battery

[0160] Fourthly, embodiments of this application also provide a battery. The battery of this application embodiment includes electrodes, and these electrodes are the electrodes described in the above-described application embodiment, specifically electrodes containing the composite current collector described in the above-described application embodiment.

[0161] In this embodiment, when the positive electrode of the battery is the electrode of the above embodiment, then the composite current collector contained therein is a positive current collector (the metal matrix contained in the composite current collector is a positive current collector matrix), and the electrode active layer is a positive active layer. When the negative electrode of the battery is the electrode of the above embodiment, then the electrode of the above embodiment is a negative electrode, then the composite current collector contained therein is a negative current collector (the metal matrix contained in the composite current collector is a negative current collector matrix), and the electrode active layer is a negative active layer. Furthermore, the positive and negative electrodes of the battery can simultaneously be the electrodes of the above embodiment.

[0162] Since the electrodes of the battery in this application embodiment are the same as those in the previous application embodiment, the battery in this application embodiment can significantly reduce or mitigate the occurrence of thermal runaway or reduce the hazards caused by thermal runaway under abnormal conditions such as puncture or high temperature, thereby effectively improving the safety performance of the battery in this application embodiment. Moreover, since the electrode structure of the previous application is robust and has good stability, the cycle performance of the battery in this application embodiment is significantly improved.

[0163] In the embodiments, when the thickness of the metal substrate in the composite current collector of the battery of the present application embodiment is significantly smaller than that of the conventional current collector, the energy density of the electrode is significantly improved. In this case, the energy density of the battery of the present application embodiment is also significantly improved.

[0164] In the embodiments of this application, the battery may include any one of a battery cell, a battery module, or a battery pack.

[0165] Here, a battery cell refers to a battery casing and electrode assemblies encapsulated within the battery casing. The shape of the battery cell is not particularly limited; it can be cylindrical, square, or any other arbitrary shape. In the example, the battery cell can be as follows: Figure 3 The shown is a square-structured battery cell 30.

[0166] In some embodiments, such as Figure 4 As shown, the outer packaging of the battery cell 30 may include a housing 31 and a cover plate 33. The housing 31 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 31 has an opening communicating with the receiving cavity, and the cover plate 33 is used to cover the opening to close the receiving cavity. In this embodiment, the positive electrode, separator, and negative electrode contained in the battery cell 30 may be formed into an electrode assembly 32 by a winding process and / or a stacking process. The electrode assembly 32 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 32. The number of electrode assemblies 32 contained in the battery cell 30 may be one or more, which can be adjusted according to actual needs.

[0167] The method for preparing the battery cell 30 is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form the battery cell 30. As an example, the positive electrode, the separator, and the negative electrode can be formed into an electrode assembly 32 by a winding process or a stacking process. The electrode assembly 32 is placed in an outer package, dried, and then injected with an electrolyte. After vacuum sealing, settling, formation, shaping, and other processes, the battery cell 30 is obtained.

[0168] A battery module is assembled from the battery cell 30, which means it can contain multiple battery cells 30. The specific number can be adjusted according to the application and capacity of the battery module.

[0169] In some embodiments, Figure 5 This is a schematic diagram of battery module 40 as an example. Figure 5 As shown, in the battery module 50, multiple battery cells 30 can be arranged sequentially along the length of the battery module 40. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 30 can be secured using fasteners.

[0170] Optionally, the battery module 40 may also include a housing with a receiving space in which multiple battery cells 30 are received.

[0171] A battery pack refers to an assembly of the aforementioned battery cells 30, meaning it can contain multiple battery cells 30. These multiple battery cells 30 can be assembled into the aforementioned battery module 50. The specific number of battery cells 30 or battery modules 40 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0172] As in the example, Figure 6 and Figure 7 This is a schematic diagram of a battery pack 50 as an example. The battery pack 50 may include a battery compartment and multiple battery modules 40 disposed within the battery compartment. The battery compartment includes an upper compartment 51 and a lower compartment 52. The upper compartment 51 covers the lower compartment 52, forming a closed space for accommodating the battery modules 40. The multiple battery modules 40 can be arranged in any manner within the battery compartment.

[0173] Electrical appliances

[0174] Fifthly, this application also provides an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, and may also include other auxiliary or necessary components. The power supply unit or energy storage unit contains the battery described in the above application embodiment. The power supply unit or energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the electrical device of this application embodiment contains the battery described in the above application embodiment, the power supply unit or energy storage unit of the electrical device of this application embodiment has high safety and a long service life, and the standby or battery life of the electrical device of this application embodiment is long.

[0175] Figure 8 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0176] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0177] Energy storage devices

[0178] Sixthly, embodiments of this application also provide an energy storage device, which includes an energy storage unit and may also include other auxiliary or necessary components. The energy storage unit contains the battery described in the above application embodiment. The energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the energy storage device of this application embodiment contains the battery described in the above application embodiment, the energy storage device has high safety, long service life, and further high energy density.

[0179] Example

[0180] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0181] 1. Examples of Composite Current Collectors and Their Preparation Methods

[0182] Example A1

[0183] This application provides a composite positive current collector comprising two layers of composite porous membranes stacked together, with the interface between the two composite porous membranes bonded together by a conductive adhesive layer; wherein each composite porous membrane comprises a PE porous film and a metal aluminum film bonded to two opposite surfaces of the PE porous film, and a conductor formed by a conductive adhesive is also filled in the pores of the PE porous film.

[0184] The composite positive electrode current collector has a total thickness of 14 μm, and the conductive adhesive layer at the interface of the two composite porous membranes has a thickness of 1 μm. In each composite porous membrane, the PE porous film has a thickness of 6 μm, a porosity of 80%, and a pore size of 1500 nm; the aluminum metal film has a thickness of 400 nm.

[0185] The binder of the conductive adhesive layer includes a PI binder and a conductive agent doped in the PI binder, wherein the conductive agent is SP and its content in the conductive adhesive layer is 30%.

[0186] The preparation method of the composite positive current collector in this application includes the following steps:

[0187] S1: Aluminum films are deposited on two opposite surfaces of a PE porous film by vapor deposition to form a composite film; there are two composite films.

[0188] S2: Apply the conductive adhesive used to form the conductive adhesive layer onto the surface of an aluminum film of the two composite films to form a wet coating of conductive adhesive.

[0189] S3: Two composite films coated with conductive adhesive wet film layers are bonded together to obtain a composite current collector blank;

[0190] S4: The composite current collector blank is pressed by micro-concave rubber roller, then pressed by 4 steel rollers / rubber rollers, and then dried (to dry the conductive adhesive) and wound up to obtain the composite positive current collector; wherein, the pressure of micro-concave rubber roller pressing is controlled to be less than the pressure of steel roller / rubber roller pressing, and the pressure of steel roller / rubber roller pressing is 3MPa.

[0191] Example A2

[0192] This application provides a composite positive electrode current collector, which differs from the composite positive electrode current collector in Example A1 in that the PE porous film is replaced with a PP porous film. The PP porous film has a thickness of 6μm, a porosity of 80%, and a pore size of 1500nm.

[0193] The preparation method of the composite positive current collector in this embodiment refers to the preparation method steps and conditions in Embodiment A1, and is adjusted in combination with the composite positive current collector of this embodiment.

[0194] Example A3

[0195] This application provides a composite positive electrode current collector, which differs from the composite positive electrode current collector in Example A1 in that: the total thickness of the composite positive electrode current collector is 12 μm; the thickness of the PE porous film is 4 μm, the porosity is 60%, and the pore size is 1000 nm; the thickness of the aluminum metal film is 200 nm.

[0196] The preparation method of the composite positive current collector in this embodiment refers to the preparation method steps and conditions in Embodiment A1, and is adjusted in combination with the composite positive current collector of this embodiment.

[0197] Example A4

[0198] This application provides a composite positive electrode current collector, which differs from the composite positive electrode current collector in Example A1 in that: the total thickness of the composite positive electrode current collector is 12 μm; the PE porous film is replaced with a PP porous film, the PP porous film has a thickness of 5 μm, a porosity of 90%, and a pore size of 2000 nm.

[0199] The preparation method of the composite positive current collector in this embodiment refers to the preparation method steps and conditions in Embodiment A1, and is adjusted in combination with the composite positive current collector of this embodiment.

[0200] Example A5

[0201] This application provides a composite positive electrode current collector, which differs from the composite positive electrode current collector in Embodiment A4 in that: an aluminum film is deposited only on one surface of each PP porous film, that is, an aluminum film is deposited on one surface of a single-layer PP porous film, and no aluminum film is deposited on the other surface. The other aspects of the composite positive electrode current collector in Embodiment A4 are the same.

[0202] The preparation method of the composite positive current collector in this embodiment refers to the preparation method steps and conditions in Embodiment A1, and is adjusted in combination with the composite positive current collector of this embodiment.

[0203] Example A6

[0204] This application provides a composite negative electrode current collector, which differs from the composite positive electrode current collector in Example A1 in that: the total thickness of the composite negative electrode current collector is 8 μm; the thickness of the PE porous film is 2.5 μm, the porosity is 80%, and the pore size is 1500 nm; and the aluminum film is replaced with a copper film with a thickness of 300 nm.

[0205] The preparation method of the composite positive current collector in this embodiment refers to the preparation method steps and conditions in Embodiment A1, and is adjusted in combination with the composite positive current collector of this embodiment.

[0206] Example A7

[0207] This application provides a composite negative electrode current collector, which differs from the composite positive electrode current collector in embodiment A1 in that a PI porous film is replaced with a PE porous film.

[0208] Comparative Example A1

[0209] A 14μm thick aluminum foil was used as the positive electrode current collector;

[0210] Comparative Example A2

[0211] A 6μm thick copper foil was used as the negative electrode current collector.

[0212] The composite current collectors provided in Examples A1 to A7 and the current collectors provided in Proportions A1 to Comparative Examples A2 were subjected to the relevant performance tests shown in Table 1 below.

[0213] The relevant performance testing methods are as follows:

[0214] Maximum force and elongation at break: The above current collector was cut into strips 2cm wide and 10cm long, and stretched using a tensile testing machine at a stretching speed of 50mm / min. The maximum force and elongation at break were recorded.

[0215] Adhesion force test: The electrode sheet was prepared according to the method in (2. Example of secondary battery cell) below. After cold pressing, it was stretched using a tensile testing machine at a stretching speed of 50 mm / min. The peel adhesive force at 180° was recorded.

[0216] Current collector density test:

[0217] Cut a standard area sample block, weigh it, measure its thickness, and then calculate the current collector density.

[0218] The test results are shown in Table 1 below:

[0219] Table 1

[0220]

[0221]

[0222] As shown in Table 1, comparing Examples A1 to A5 with Comparative Example A1, and Example A6 with Comparative Example A2, it can be seen that, with the same total thickness, the tensile strength of the composite current collector in this application reaches that of a pure aluminum / copper foil current collector, and can even surpass it. Furthermore, the elongation at break of the composite current collector in this application is significantly improved, and its density is significantly reduced, contributing to reducing the risk of battery thermal failure and increasing energy density. Simultaneously, because the metal film contained in the composite current collector is bonded to the surface of the organic porous film layer, the adhesion between the composite current collector and the electrode active layer is significantly improved, resulting in a significantly higher adhesion strength between the electrode containing the composite current collector and the electrode containing a pure aluminum / copper foil current collector.

[0223] 2. Example of a secondary battery cell

[0224] Examples B1 to B7 and Comparative Examples B1 to B2;

[0225] Examples B1 to B7 and Comparative Examples B1 to B2 each provide a secondary battery cell, each secondary battery cell including an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also including an electrolyte.

[0226] In this study, the composite current collectors provided in Examples A1 to A5 and the pure aluminum foil provided in Comparative Example A1 were used to prepare positive electrode sheets for lithium iron phosphate batteries, and the composite current collector provided in Example A6 and the pure copper foil provided in Comparative Example A2 were used to prepare negative electrode sheets for lithium iron phosphate batteries. The prepared electrode sheets are designated as M1 to M6 and N1 to N2, respectively.

[0227] Battery assembly: According to the pairing relationship of positive and negative electrode plates in Table 2 below, the cells are assembled into hard-shell cells of each lithium iron phosphate battery according to the battery assembly requirements and processes.

[0228] Performance tests of secondary battery cells:

[0229] Each battery provided in Examples B1 to B7 and Comparative Examples B1 to B2 was subjected to a needle penetration test; the needle penetration test was performed in accordance with GB / T 31485-2015. The steel needle diameter was 8mm, the penetration speed was 30mm / s, and the battery passed if it did not ignite or explode.

[0230] Energy density testing method: Charge the battery at a constant current rate of 1C to 4.2V at 25℃, then charge it at a constant voltage until the current is ≤0.5C, and then discharge it at a constant current rate of 1C to 2.8V. The discharge capacity at this point is the battery capacity. Cell mass energy density = Battery capacity * 3.6 / Cell mass.

[0231] The results of the acupuncture test are shown in Table 2 below:

[0232] Table 2

[0233]

[0234] As shown in Table 2, all batteries containing the composite current collector of this application passed the puncture test, while Comparative Example B1, which used a conventional pure metal current collector, failed the puncture test. Therefore, it can be concluded that the batteries of this application, due to the inclusion of the composite current collector, exhibit significantly improved thermal failure performance and enhanced safety under puncture conditions and in abnormal environments such as high temperatures.

[0235] Meanwhile, the electrodes based on the composite current collectors in Table 1, which contain the embodiments of this application, have significantly reduced density and significantly improved structural strength. Therefore, the energy density and cycle performance of the batteries in the embodiments of this application are also significantly improved.

[0236] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite current collector, characterized by, The composite organic porous film comprises two or more layers of composite organic porous films, each of the composite organic porous films comprising an organic porous base film, a metal film being combined with at least one surface of the organic porous base film, and an electrically conductive body being filled in the pores of the organic porous base film and being electrically connected with the surface of the metal film; The composite organic porous films are arranged in a stacked manner along the thickness direction of the composite organic porous film, and the metal films contained in each of the composite organic porous films are arranged in a stacked manner between two adjacent composite organic porous films; an electrically conductive adhesive layer is further arranged between two adjacent layers of the composite organic porous films for the adhesive combination of the two adjacent layers of the composite organic porous films, the metal film comprises a metal plating layer, and the surface of the electrically conductive adhesive layer extends into the pores of the organic porous base film through the metal plating layer, thereby constituting the electrically conductive body or part of the electrically conductive body.

2. The composite current collector of claim 1, wherein: Each of the organic porous base films comprises at least one of the following (1) to (5): (1) the thickness of the organic porous base film is 0.1 μm to 8 μm; (2) the porosity of the organic porous base film is 40% to 95%; (3) the pore size of the pores contained in the organic porous base film is 200 nm to 5000 nm; (4) the organic porous base film comprises a single straight-pored organic film; (5) the tensile strength of the organic porous base film is higher than 150 MPa.

3. The composite current collector of claim 2, wherein: The thickness of the organic porous base film is 2 μm to 6 μm; and / or, The porosity of the organic porous base film is 60% to 85%; and / or, The pore size of the pores contained in the organic porous base film is 500 nm to 3500 nm.

4. The composite current collector of claim 1 or 2, wherein: The material of the organic porous base film comprises at least one of polyethylene, polyimide, polypropylene, and polytetrafluoroethylene; and / or Both of the oppositely arranged surfaces of the organic porous base film are combined with the metal film.

5. The composite current collector of claim 1, wherein: The thickness of the metal film is 100 nm to 1000 nm; and / or The metal film has a through hole arranged corresponding to the pores contained in the combined surface of the metal film and the organic porous base film.

6. The composite current collector of claim 5, wherein: The thickness of the metal film is 200 nm to 600 nm.

7. The composite current collector of claim 1, wherein: The material of the electrically conductive body comprises at least one of metal and electrically conductive adhesive; and / or The electrical conductivity of the electrically conductive body is 10 3 S / m ~ 6 x 10 7 S / m.

8. The composite current collector of claim 1, wherein: The metal film comprises a metal plating layer, and at least part of the electrically conductive body comprises the metal plating layer deposited on the pore wall of the pores contained in the organic porous base film.

9. The composite current collector according to claim 1, wherein: The thickness of the electrically conductive adhesive layer is 0.1 μm to 4 μm; and / or The electric conductivity of the conductive adhesive layer is 10 3 S / m ~ 10 4 S / m.

10. The composite current collector of claim 1, wherein: The total thickness of the composite current collector is 5 μm to 18 μm; and / or The composite current collector has an electrical conductivity of 10 6 S / m ~ 5 x 10 7 S / m.

11. The composite current collector of claim 10, wherein: The total thickness of the composite current collector is 8 μm to 14 μm; and / or The composite current collector has an electrical conductivity of 5 x 10 6 S / m ~ 3 x 10 7 S / m.

12. A method of making a composite current collector as claimed in any one of claims 1 to 11, characterised in that, The method comprises the following steps: At least two organic porous films are provided, and a metal film is formed on at least one surface of each of the organic porous films to obtain at least two composite films; The composite films are subjected to a stacking treatment along the thickness direction of the composite films, and the metal films contained in the composite films are arranged in a stacked manner between two adjacent composite films to obtain a composite current collector; The method comprises the following steps: At least two organic porous films are provided, and a metal film is formed on at least one surface of each of the organic porous films to obtain at least two composite films; The composite films are subjected to a stacking treatment along the thickness direction of the composite films, and the metal films contained in the composite films are arranged in a stacked manner between two adjacent composite films to obtain a composite current collector; At least in the step of forming the metal film and the step of laminating the composite films, the method further comprises filling the pores of each organic porous substrate with an electrically conductive material, and the electrically conductive material is electrically connected to the metal film on the surface of the organic porous substrate.

13. The production method according to claim 12, characterized by: The metal film is formed on at least one surface of each organic porous film by plating.

14. The production method according to claim 12 or 13, characterized by, The method of laminating the composite films comprises the following steps: forming a wet layer of electrically conductive adhesive on the surface of the metal film of each composite film that is away from the organic porous film; stacking the composite films in the thickness direction of the composite films to form a composite current collector precursor; performing a pressing process on the composite current collector precursor, and extruding part of the electrically conductive adhesive in the wet layer of electrically conductive adhesive into the pores of the organic porous film, and then performing a drying process.

15. The production method according to claim 14, characterized by: The pressing process comprises a first pressing process and a second pressing process, and the pressure of the first pressing process is lower than the pressure of the second pressing process.

16. The production method according to claim 15, characterized by: The first pressing process comprises a rolling process, and the surface of the roller in the rolling process has a convex-concave structure; and / or The pressure of the second pressing process is 0.5-5 MPa; and / or The second pressing process is performed more than twice.

17. The method of claim 16, wherein: The pressure of the second pressing process is 1-4 MPa.

18. An electrode comprising a current collector and an active layer bonded to the current collector, characterized in that: The current collector is the composite current collector according to any one of claims 1-11 or is prepared by the preparation method according to any one of claims 12-17.

19. The electrode of claim 18, wherein The electrode is at least one of a positive electrode and a negative electrode.

20. A battery, characterized by The electrode is the electrode according to claim 18 or 19.

21. The battery of claim 20, wherein the cathode comprises a lithium metal oxide. The battery is any one of a battery cell, a battery module, and a battery pack.

22. An electrical device, comprising: The power supply unit or the energy storage unit comprises a battery, and the battery comprises the battery according to claim 20 or 21.

23. An energy storage device, comprising: The energy storage unit comprises a battery, and the battery comprises the battery according to claim 20 or 21.

Images