Current collector, preparation method of current collector and positive pole piece

Abstract

The invention provides a current collector, a preparation method of the current collector and a positive pole piece. The current collector comprises a framework and a conductive filler. The framework comprises a net-shaped structure with a plurality of meshes and is used for reducing the contact area of the current collector and other substances in the coating material and reducing heat released by reaction of the current collector and other substances, so that the needling safety of the battery is improved, and thermal runaway of the battery is prevented. And the conductive filler is filled in the meshes and is polymerized with the skeleton. The conductive filler is used for coating the coating material in the positive pole piece, so that the current collector is smoothly coated with the coating material in the positive pole piece, and the current collector and the coating material are combined to form the complete positive pole piece.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a current collector, a method for preparing the current collector, and a positive electrode sheet. Background Art

[0002] A battery is a device that can convert chemical energy into electrical energy. During the process of converting chemical energy into electrical energy, thermal runaway will occur when the temperature inside the battery rises rapidly, causing the battery to burn or explode. In order to reduce the probability of thermal runaway during battery use and improve battery safety, batteries that are to be marketed are usually subjected to a needle puncture test, and the safety of the battery is judged based on the results of the needle puncture test.

[0003] In related technologies, battery puncture safety is generally improved by reducing the number of battery pole pieces or optimizing module heat dissipation and pressure relief channels. However, testers found that the above two methods still cannot prevent thermal runaway of the battery. Summary of the invention

[0004] The present application provides a current collector, a method for preparing the current collector, and a positive electrode plate, which are used to prevent thermal runaway of a battery, thereby improving the puncture safety of the battery.

[0005] In a first aspect, the present application provides a current collector for use in a positive electrode sheet, the current collector may include a skeleton and a conductive filler. The skeleton includes a mesh structure having a plurality of meshes. The mesh structure is made of metal. The conductive filler is filled in the mesh and polymerized with the skeleton. The conductive filler is used to bond the coating material in the positive electrode sheet.

[0006] According to the first aspect, the current collector includes a skeleton and a conductive filler polymerized with the skeleton. The skeleton includes a mesh structure with multiple meshes, which is used to reduce the contact area between the current collector and other substances in the coating material, reduce the heat released by the reaction between the current collector and other substances, and thus prevent the battery from thermal runaway. The conductive filler is filled in the mesh and is used to coat the coating material in the positive electrode sheet, so that the coating material in the positive electrode sheet is smoothly coated on the current collector, so that the current collector and the coating material are combined into a complete positive electrode sheet.

[0007] In a possible design, the outer surface of the skeleton is provided with a coating, and the chemical stability of the coating is higher than that of the skeleton.

[0008] Based on the description of the above embodiments, the chemical stability of the coating arranged on the outer surface of the skeleton is higher than the chemical stability of the skeleton, which prevents the conductive metal in the skeleton from directly contacting other substances in the coating material under the high temperature environment inside the battery and releasing heat, thereby further reducing the probability of thermal runaway of the battery after the puncture test and improving the safety of the battery.

[0009] In a possible design, the skeleton may include a multi-layer mesh structure. The multi-layer mesh structure is stacked along a first direction. The first direction is the thickness direction of the skeleton.

[0010] Based on the description of the above embodiments, the skeleton includes a multi-layer mesh structure stacked along a first direction, which increases the content of the conductive metal in the skeleton, thereby enhancing the conductivity of the current collector.

[0011] In a possible design, the pore size of the mesh is greater than or equal to 2 μm; and the pore size of the mesh is less than or equal to 800 μm.

[0012] Based on the description of the above embodiment, when the mesh aperture is greater than or equal to 2 μm and less than or equal to 800 μm, the battery can have both good conductivity and high safety.

[0013] In one possible design, the surface dyne value of the current collector is greater than or equal to 34 dyn / cm.

[0014] Based on the description of the above embodiments, a surface dyne value of the current collector greater than or equal to 34 dyn / cm can make the surface of the current collector smooth, the conductive filler intact and not falling off, and the coating material in the positive electrode sheet can be smoothly coated on the current collector, thereby combining the current collector and the coating material into a complete positive electrode sheet.

[0015] In a second aspect, the present application provides a method for preparing a current collector, the method comprising:

[0016] A skeleton is obtained, wherein the skeleton comprises a mesh structure having a plurality of meshes, and the mesh structure is made of metal.

[0017] Get conductive filler.

[0018] The conductive filler is filled in the mesh and polymerized with the skeleton to obtain a current collector.

[0019] In a possible design, in obtaining the conductive filler, the conductive filler includes a conductive polymer, a conductive additive and a flame retardant. The conductive polymer accounts for 70%-85% of the conductive filler, the conductive additive accounts for 5%-15% of the conductive filler, and the flame retardant accounts for 10%-35% of the conductive filler.

[0020] Based on the description of the above embodiments, increasing the proportion of conductive polymer in the conductive filler can make the current collector have better conductivity, which is suitable for preparing small-capacity batteries with high requirements for conductivity. Increasing the proportion of flame retardant in the conductive filler can make the current collector have better safety, which is suitable for preparing large-capacity batteries with high requirements for safety performance.

[0021] In one possible design, the method further includes: performing surface treatment on the current collector so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm.

[0022] In one possible design, surface treatment of the current collector so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm includes: surface treatment of the current collector by a rolling process. Alternatively, surface treatment of the current collector by a surface processing process. Alternatively, surface treatment of the current collector by a surface processing process is first performed, and then surface treatment of the current collector by a rolling process is performed.

[0023] Based on the description of the above embodiments, the current collector can be surface treated by any one of surface processing technology, rolling technology, or surface processing technology followed by rolling technology, so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm, the surface of the current collector is flat, the conductive filler is intact and not falling off, and the coating material in the positive electrode sheet is smoothly coated on the current collector, so that the current collector and the coating material are combined into a complete positive electrode sheet.

[0024] In a third aspect, the present application provides a positive electrode sheet, comprising a coating material and a current collector according to any one of the above embodiments. The coating material is coated on both sides of the current collector.

[0025] The beneficial effects of the preparation method provided in the above second aspect, the possible implementation modes of the above second aspect, and the positive electrode plate provided in the above third aspect can be referred to the beneficial effects brought about by the above first aspect and the possible implementation modes of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the structure of the current collector in the embodiment of the present application.

[0028] Figure 2 A schematic diagram of the structure of the skeleton in the embodiment of the present application.

[0029] Figure 3 A schematic diagram of the structure of the skeleton in the embodiment of the present application.

[0030] Figure 4 Schematic diagram of the connection structure between the metal foil and the skeleton in the embodiment of the present application.

[0031] Figure 5 This is a schematic diagram of a structure in which metal gold is bolded in an embodiment of the present application.

[0032] Figure 6 This is an exploded view of another structure of the current collector in an embodiment of the present application.

[0033] Description of reference numerals:

[0034] 100-current collector;

[0035] 1-frame; 11-metal wire; 111-plating; 12-mesh; 2-conductive filler; 3-metal foil;

[0036] X first direction. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0039] The terms "comprising" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover but not exclude other contents. The word "a" or "an" does not exclude the presence of a plurality.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0042] The directional words appearing in the following description are all directions shown in the drawings, and do not limit the specific structure of the present application. For example, in the description of the present application, the directions or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present application.

[0043] In addition, the expressions of indicated directions such as the X direction, the Y direction, and the Z direction used to illustrate the operation and construction of the components of the present embodiment are not absolute but relative, and although these indications are appropriate when the components are in the positions shown in the figures, when these positions are changed, these directions should be interpreted differently to correspond to the changes.

[0044] In addition, the terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0045] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).

[0046] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure may refer to a physical connection. For example, the physical connection may be a fixed connection, such as a fixed connection through a fixing member, such as a fixed connection through a screw, bolt or other fixing member; the physical connection may also be a detachable connection, such as a mutual snap connection or snap connection; the physical connection may also be an integral connection, such as welding, bonding or integral molding to form a connection for connection. The "connection" or "connection" of a circuit structure may refer to an electrical connection or a signal connection in addition to a physical connection. For example, it may be a direct connection, that is, a physical connection, or it may be an indirect connection through at least one intermediate element, as long as the circuit is connected, or it may be the internal connection of two elements; the signal connection may refer to a signal connection through a media medium, such as a radio wave, in addition to a signal connection through a circuit. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0047] A battery is a device that can convert chemical energy into electrical energy. During the process of converting chemical energy into electrical energy, thermal runaway may occur when the temperature inside the battery rises rapidly, causing the battery to burn or explode.

[0048] Among them, the causes of thermal runaway may include but are not limited to the following:

[0049] (1) Internal short circuit: Defects in the manufacturing process, physical damage, dendrite growth or diaphragm failure may lead to internal short circuit, resulting in a sharp rise in local temperature.

[0050] (2) Electrolyte decomposition: At high temperatures, the electrolyte in the battery decomposes to produce gas and release a large amount of heat, exacerbating thermal runaway.

[0051] In order to prevent thermal runaway during battery use and improve battery safety, batteries to be marketed are usually subjected to a needle puncture test, and the safety of the battery is judged based on the results of the needle puncture test. The needle puncture test simulates the safety response of the battery when it is penetrated by a sharp object, especially the thermal stability and safety protection capability of the battery in the case of an internal short circuit, so as to test whether the battery can effectively prevent thermal runaway under extreme conditions.

[0052] In related technologies, battery puncture safety is generally improved by reducing the number of battery pole pieces or optimizing module heat dissipation and pressure relief channels. However, testers found that the above two methods still cannot prevent thermal runaway of the battery.

[0053] Based on this, the present application provides a current collector, a method for preparing the current collector, and a positive electrode sheet. By designing the current collector as a mesh composite structure, the heat released by the current collector reacting with other substances is reduced, and thermal runaway of the battery during use is prevented, thereby improving the battery's acupuncture safety. Figure 1-6 Provide specific instructions.

[0054] First, as Figure 1 The current collector 100 provided in the present application is applied to a positive electrode sheet, and the current collector 100 may include a skeleton 1 and a conductive filler 2. The skeleton 1 includes a mesh structure having a plurality of meshes 12. The conductive filler 2 is filled in the meshes 12 and polymerized with the skeleton 1. The conductive filler 2 is used to bond the coating material in the positive electrode sheet.

[0055] The network structure of the skeleton 1 may include but is not limited to the following two preparation methods:

[0056] First, the mesh structure of the skeleton 11 can be made by cutting metal foil. Specifically, a plurality of meshes 12 can be cut out of the entire metal foil. The thickness of the metal foil is less than 13 um, so that the thickness of the current collector 100 does not exceed the upper limit of the conventional size.

[0057] like Figure 2 As shown, the mesh structure of the skeleton 1 can be made of a plurality of metal wires 11, and there is an overlap of the metal wires 11 during the weaving process. The thickness of the overlapping part is made less than 13um, so that the thickness of the current collector 100 does not exceed the upper limit of the conventional size. For example, aluminum wires can be used to weave the skeleton. The diameter of the aluminum wires is 6μm, and the maximum value of the skeleton 1 in the thickness direction is 12μm.

[0058] Furthermore, the mesh 12 may be a planar mesh structure or a three-dimensional mesh structure, which is not specifically limited in this application. The three-dimensional mesh structure is an interconnected and interpenetrating structure formed in a three-dimensional space, and this structure itself has good mechanical and electrical properties. Therefore, setting the mesh 12 of the skeleton 1 as a three-dimensional mesh structure can improve the conductivity and toughness of the positive electrode sheet in this application.

[0059] Specifically, the material of the mesh structure may be aluminum. The selection criteria of the mesh structure material may include: aluminum has good electrical conductivity, aluminum has certain processability, and the reaction potential of aluminum and the working potential of the battery in this application do not overlap in a large area.

[0060] However, technicians found in the test that the current collector 100 reacts with other substances in the coating material to release a large amount of heat, thereby exacerbating the thermal runaway. For example, under high temperature conditions, the current collector 100 made of sheet aluminum foil in the positive electrode sheet reacts with the metal oxide in the coating material to release a large amount of heat.

[0061] Based on this, in the current collector 100 of the present application, only the mesh structure is made of aluminum, and since the mesh structure has a plurality of meshes 12, the aluminum mesh structure has a greatly reduced aluminum content compared to the same volume of sheet aluminum foil, which reduces the heat released by the reaction between the current collector 100 and the metal oxide. In addition, the mesh structure of the skeleton 1 includes a plurality of meshes 12, thereby reducing the contact area between the current collector 100 and the above-mentioned metal oxide, further reducing the heat released by the reaction between the current collector 100 and other substances, thereby improving the safety of the battery.

[0062] Furthermore, a coating material needs to be coated on the surface of the current collector 100 to prepare a complete positive electrode sheet, thereby ensuring the performance of the battery.

[0063] In order to reduce the contact area between the current collector 100 and the above metal oxide while being able to smoothly apply the coating material, such as Figure 1 As shown, the current collector 100 in the present application can reduce the aluminum content and also add a conductive filler 2 in the skeleton 1 to ensure that the current collector 100 has a complete coating surface so that the coating material can be smoothly coated on the current collector, thereby preparing a positive electrode sheet with high safety.

[0064] In addition, the conductive filler 2 may include conductive polymers, conductive additives, functional additives, polymer modifiers, and the like.

[0065] The content of the conductive polymer in the conductive filler 2 can be 70% to 100%. Specifically, the conductive polymer can include but is not limited to polypyrrole, polyaniline, polythiophene, polyacetylene, polyphenylene, etc. and one or more of their modified materials. The conductive polymer is solid at room temperature, resistant to electrolyte corrosion, and has a conductivity of 10 -10 S / cm or more.

[0066] It can be seen that the high conductivity of the conductive polymer can make the current collector 100 have good conductivity. Since the content of the conductive metal in the grid structure is reduced, the current collector 100 with good conductivity can also be used to ensure the conductivity of the positive electrode sheet in this application.

[0067] The conductive additive may include, but is not limited to, one or more materials such as conductive carbon black, graphite particles, carbon nanotubes, graphene, metal powder, etc. The conductive additive is resistant to electrolyte corrosion and can increase the conductivity of the conductive filler 2. Specifically, the content of the conductive additive in the conductive filler 2 can be 0 to 30%.

[0068] Among them, the functional additives may include but are not limited to one or more materials such as flame retardants, expanders, heat insulating agents, microcapsules, etc., which can enable the current collector 100 to obtain the above functions corresponding to the performance of the additives. For example, adding a flame retardant to the conductive filler 2 can make the current collector 100 in the present application difficult to burn. Specifically, the content of the functional additive in the conductive filler 2 is 0 to 15%.

[0069] The polymer modifier may include but is not limited to one or more functional materials such as dispersants and softeners, which can appropriately improve the toughness of the current collector 100, making the current collector 100 less likely to break during processing, thereby improving the production yield of the current collector 100. Specifically, the content of the polymer modifier in the conductive filler 2 can be 0-5%.

[0070] In summary, the conductive polymer is used to improve the conductivity of the current collector 100, and the conductive additive is used to improve the conductivity of the conductive filler 2. The flame retardant is used to improve the safety of the current collector 100. The polymer modifier is used to facilitate the processing of the current collector 100.

[0071] Furthermore, the specific method of adding the conductive filler 2 to the skeleton 1 may include: Figure 1 and Figure 2 As shown, the conductive filler 2 is filled in the mesh 12 and is polymerized with the skeleton 1 to form the current collector 100 .

[0072] In addition, the conductive polymer may also have adhesive properties, so as to enable the coating material in the positive electrode sheet to be smoothly coated on the current collector 100 , thereby combining the current collector 100 and the coating material into a complete positive electrode sheet.

[0073] In summary, the current collector 100 provided in the present application includes a skeleton 1 and a conductive filler 2 polymerized with the skeleton 1. Among them, the skeleton 1 includes a mesh structure with multiple meshes 12, which is used to reduce the contact area between the current collector 100 and other substances in the coating material, reduce the heat released by the reaction between the current collector 100 and other substances, and thus prevent the battery from thermal runaway. The conductive filler 2 is filled in the mesh 12 and is used to coat the coating material in the positive electrode sheet, so that the coating material in the positive electrode sheet is smoothly coated on the current collector 100, so that the current collector 100 and the coating material are combined into a complete positive electrode sheet.

[0074] Furthermore, in order to further improve the safety of the battery, the present application may also make the following improvements:

[0075] In some embodiments, Figure 3 As shown, the outer surface of the skeleton 1 is provided with a coating 111. The chemical stability of the coating 111 is higher than that of the skeleton 1.

[0076] Specifically, when the chemical stability of the coating 111 is higher than that of the frame, the high temperature environment inside the battery will not melt the coating 111, thereby preventing the frame 1 from being exposed, thereby preventing the conductive metal in the frame 1 from reacting with other substances in the coating material and releasing heat.

[0077] Optionally, 1 μm titanium is plated on the surface of the skeleton. Titanium is a silvery white transition metal with the advantages of high melting point, high strength and good stability risk. Therefore, when the coating 111 on the outer surface of the skeleton 1 is titanium, the high temperature environment inside the battery will not melt the titanium, thereby preventing the skeleton 1 from being exposed, thereby preventing the conductive metal in the skeleton 1 from reacting with other substances in the coating material and releasing heat.

[0078] Specifically, when the conductive metal in the skeleton 1 is aluminum, the reaction potential of titanium is similar to that of aluminum, which can prevent aluminum from reacting with metal oxides in the coating material to release a large amount of heat while keeping the conductivity of the current collector 100 intact.

[0079] In summary, the chemical stability of the coating 111 disposed on the outer surface of the skeleton 1 is higher than that of the skeleton 1, thereby preventing the conductive metal in the skeleton 1 from directly contacting other substances in the coating material under the high temperature environment inside the battery and releasing heat, thereby further reducing the probability of thermal runaway of the battery after the puncture test and improving the safety of the battery.

[0080] Furthermore, in order to ensure the safety and conductivity requirements of the battery, the present application also makes the following improvements:

[0081] In some embodiments, the pore size of the mesh 12 is greater than or equal to 2 μm; and, the pore size of the mesh 12 is less than or equal to 800 μm.

[0082] Specifically, the smaller the pore size of the mesh 12, the higher the content of the conductive metal in the skeleton 1, and the better the conductivity of the battery. Conversely, the larger the pore size of the mesh 12, the smaller the contact area between the conductive metal and other substances in the coating material, and the better the safety of the battery.

[0083] According to multiple tests, it can be concluded that when the mesh size is greater than or equal to 2 μm and less than or equal to 800 μm, the battery can have both good conductivity and high safety. Specifically, the mesh size 12 can be 50 μm, 200 μm or 700 μm.

[0084] Furthermore, in order to improve the flatness of the current collector, the present application may perform surface treatment on the current collector so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm.

[0085] The dyne value is used to reflect the surface flatness of the current collector 100. The higher the dyne value, the higher the surface flatness of the current collector 100. When the dyne value of the surface of the current collector 100 is greater than or equal to 34, the current collector 100 has a higher flatness, which increases the surface tension of the current collector 100, and can prevent the conductive filler 2 from falling while allowing the coating material in the positive electrode sheet to be smoothly coated on the current collector 100, so that the current collector 100 and the coating material are combined into a complete positive electrode sheet.

[0086] Specifically, when the surface flatness of the current collector 100 is qualified, it can be manifested as: the number of holes, depressions and protrusions on the current collector 100 per square meter is less than 10.

[0087] Among them, the surface treatment processes may include but are not limited to the following three:

[0088] Process 1: Surface treatment of the current collector 100 is performed by a rolling process.

[0089] Process 2: Surface treatment of the current collector 100 is performed through a surface processing process.

[0090] Process three: firstly, the surface of the current collector 100 is treated by a surface processing process, and then the surface of the current collector 100 is treated by a rolling process.

[0091] Furthermore, the current collector 100 after surface treatment needs to have a certain toughness so that the current collector 100 can be bent and rolled up to meet the tape walking requirements of the current collector 100 coating process.

[0092] In summary, the current collector can be surface treated by any of the following methods: surface processing, rolling process, or surface processing followed by rolling process, so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm, the surface of the current collector is flat, the conductive filler is intact and not falling off, and the coating material in the positive electrode sheet is smoothly coated on the current collector, so that the current collector and the coating material are combined into a complete positive electrode sheet.

[0093] Furthermore, in order to smoothly prepare the current collector 100 and the positive electrode sheet, the present application also makes the following improvements:

[0094] In some embodiments, Figure 4 As shown, a metal foil 3 is disposed on the side of the current collector 100 .

[0095] Specifically, the two ends of the positive electrode sheet composed of the current collector 100 and the coating material need to be welded with the pole ears. However, the skeleton 1 of the current collector 100 is a mesh structure with meshes 2. Based on this, metal foils 3 can be respectively arranged on both sides of the current collector 100 near the pole ears for welding the pole ears. Specifically, the pole ears are used to realize the conduction of the current inside and outside the battery.

[0096] Furthermore, in order to facilitate processing, metal foils 3 of the same specification may be provided on all sides of the current collector 100. In addition, the material of the metal foil 3 may be the same as that of the frame 1.

[0097] In summary, the metal foil 3 is disposed on the side of the current collector 100 for welding the tabs of the positive electrode sheet to achieve conduction of the current inside and outside the battery.

[0098] For the current collector 100 in which the skeleton 1 is prepared by braiding the metal wire 11, in other embodiments, as Figure 5 As shown, the diameter of the metal wire 11 is increased so that the metal wire 11 is used for welding the electrode tabs.

[0099] Specifically, the metal wire 11 at the edge of the current collector 100 is thickened, and the thickened metal wire 11 is used for welding the electrode tab.

[0100] Furthermore, since the skeleton 1 in the current collector 100 is a mesh structure, relatively few metal materials can be used for conducting electricity in the current collector 100. In order to further ensure the conductivity of the current collector 100, the present application can also add the following features to the skeleton 1:

[0101] In some embodiments, Figure 6 As shown, the skeleton 1 may include a multi-layer mesh structure. The multi-layer mesh structure is stacked along a first direction X. The first direction X is the thickness direction of the skeleton 1.

[0102] According to the description of the above embodiment, the skeleton 1 includes a multi-layer mesh structure stacked along the first direction X, which increases the content of the conductive metal in the skeleton 1 and thus enhances the conductivity of the current collector 100 .

[0103] Furthermore, in order to ensure the current connectivity between the multi-layer mesh structures, in some embodiments, the tabs between the multi-layer mesh structures may be pressurized and welded.

[0104] In a second aspect, the present application further provides a method for preparing a current collecting plate, which is used to prepare the current collector 100 according to any one of the above embodiments. The method may include:

[0105] Step 1: Obtain a skeleton, wherein the skeleton comprises a mesh structure having a plurality of meshes, and the mesh structure is made of metal.

[0106] Specifically, the skeleton can be woven with aluminum wires, wherein the diameter of the aluminum wires is 6 μm, and the aperture of the mesh 12 of the woven mesh structure is 200 μm. The maximum value of the skeleton 1 in the thickness direction is 12 μm.

[0107] Furthermore, when a coating is provided on the outer surface of the skeleton, 1 μm titanium may be plated on the surface of the aluminum wire.

[0108] Step 2: Obtain conductive filler.

[0109] Step three, filling the mesh with conductive fillers and polymerizing with the skeleton to obtain a current collector.

[0110] Specifically, the conductive filler and the skeleton may include but are not limited to the following three polymerization methods, which are not specifically limited in this application.

[0111] Method 1: Slurry coating method. The advantage of polymerizing the above conductive filler and the skeleton into a current collector by the slurry coating method is that it is easy to form a sheet and the overall performance of the finished product is good.

[0112] Method 2: Dry process: The advantages of polymerizing the above conductive filler and the skeleton into a current collector through a dry process are fast production speed and simple preparation.

[0113] Method 3: Surface polymerization method. The advantage of polymerizing the above conductive filler with the skeleton to form a current collector by surface polymerization method is that the conductive filler can have stronger adhesion to the skeleton and is easy to achieve mass production.

[0114] In summary, technicians can select one or more of the above three polymerization methods to prepare the current collector according to actual needs.

[0115] Furthermore, according to the above content, it can be known that adjusting the ratio of each component in the conductive filler can make the current collector have higher conductivity or higher safety, so as to adapt to batteries of different specifications.

[0116] Based on this, in some embodiments, the present application can further design the proportion of each component in the conductive filler in step 2, so that the conductive polymer accounts for 70%-85% of the conductive filler, the conductive additive accounts for 5%-15% of the conductive filler, and the flame retardant accounts for 10%-35% of the conductive filler, so that the current collector can meet different performance requirements. The following is a specific description in combination with two embodiments:

[0117] Embodiment 1: In step 2, the conductive filler may include a conductive polymer, a conductive additive and a flame retardant, wherein the conductive polymer accounts for 85% of the conductive filler, the conductive additive accounts for 10% of the conductive filler, and the flame retardant accounts for 10% of the conductive filler.

[0118] Specifically, the proportions of the above conductive fillers are: polypyrrole (conductive polymer) accounts for 85%, conductive carbon black (conductive additive) accounts for 2.5%, carbon nanotubes (conductive additive) accounts for 2.5%, and triphenyl phosphate (flame retardant) accounts for 10%.

[0119] Embodiment 2: In step 2, the conductive filler includes a conductive polymer, a conductive additive and a flame retardant, wherein the conductive polymer accounts for 70% of the conductive filler, the conductive additive accounts for 5% of the conductive filler, and the flame retardant accounts for 25% of the conductive filler.

[0120] Specifically, the proportions of the above conductive fillers are: iodine-doped polyacetylene (conductive polymer) accounts for 70%, conductive carbon black (conductive additive) accounts for 2.5%, carbon nanotubes (conductive additive) accounts for 2.5%, and ethoxypentafluorocyclotriphosphazene (flame retardant) accounts for 25%.

[0121] Among them, polypyrrole has better conductivity than iodine-doped polyacetylene, and the proportion of conductive polymer in Example 1 is larger.

[0122] Ethoxypentafluorocyclotriphosphazene has a better flame retardant effect than triphenyl phosphate, and the proportion of the flame retardant in Example 2 is larger.

[0123] Based on the description of the above embodiments, the conductive polymer is used to improve the conductivity of the current collector, and the flame retardant is used to improve the safety of the current collector.

[0124] Therefore, the current collector prepared by Example 1 can have better conductivity and is suitable for preparing small-capacity batteries with high conductivity requirements, such as 20Ah high-nickel ternary 811 soft-pack batteries. Similarly, the current collector prepared by Example 2 has better safety and is suitable for preparing large-capacity batteries with high safety requirements, such as 560Ah lithium iron phosphate square shell batteries.

[0125] In one example, 20 current collectors are prepared by Example 1. Ten of the current collectors are respectively applied to 10 20Ah high nickel ternary 811 soft pack batteries, so that the 20Ah high nickel ternary 811 soft pack battery is sample one.

[0126] The other 10 current collectors are respectively applied to 10 560Ah lithium iron phosphate square shell batteries, making the above 560Ah lithium iron phosphate square shell battery sample two.

[0127] Then, 10 current collectors were prepared according to Example 2, and the current collectors were applied to 10 560Ah lithium iron phosphate square shell batteries respectively, so that the 560Ah lithium iron phosphate square shell batteries were sample three.

[0128] The puncture test is performed on 10 samples 1, 10 samples 2, and 10 samples 3. The standard of the puncture test can refer to GB / T31485-2015.

[0129] The test results are as follows:

[0130] All 10 samples one met the above standards; 2 samples two met the above standards; all 10 samples three met the above standards.

[0131] The conclusions that can be drawn from the above test results are:

[0132] Increasing the proportion of conductive polymer in the conductive filler can make the current collector have better conductivity, which is suitable for preparing small-capacity batteries with high requirements for conductivity. Increasing the proportion of flame retardant in the conductive filler can make the current collector have better safety, which is suitable for preparing large-capacity batteries with high requirements for safety performance.

[0133] In a third aspect, the present application provides a positive electrode sheet, comprising a coating material and a current collector according to any one of the above embodiments. The coating material is coated on both sides of the current collector.

[0134] Those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0135] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A current collector, applied to a positive electrode sheet, characterized in that: The current collector comprises: a skeleton and a conductive filler; The skeleton comprises a mesh structure having a plurality of meshes, and the mesh structure is made of metal; The conductive filler is filled in the mesh and polymerized with the skeleton; The conductive filler is used to bond the coating material in the positive electrode sheet.

2. The current collector according to claim 1, characterized in that: The outer surface of the skeleton is provided with a coating; The chemical stability of the coating is higher than that of the skeleton.

3. The current collector according to claim 2, characterized in that: The skeleton comprises a multi-layer mesh structure; The multi-layer mesh structure is stacked along a first direction; Wherein, the first direction is the thickness direction of the skeleton.

4. The current collector according to claim 2, characterized in that: The mesh has a pore size greater than or equal to 2 μm; Furthermore, the mesh has a pore size less than or equal to 800 μm.

5. The current collector according to claim 2, characterized in that: The surface dyne value of the current collector is greater than or equal to 34 dyn / cm.

6. A method for preparing a current collector, characterized in that: The method comprises: Acquire a skeleton, wherein the skeleton comprises a mesh structure having a plurality of meshes, and the mesh structure is made of metal; Obtaining a conductive filler; The conductive filler is filled in the mesh and polymerized with the skeleton to obtain the current collector.

7. The method for preparing a current collector according to claim 7, characterized in that: In the step of obtaining the conductive filler, the conductive filler comprises a conductive polymer, a conductive additive and a flame retardant; The conductive polymer accounts for 70%-85% of the conductive filler, the conductive additive accounts for 5%-15% of the conductive filler, and the flame retardant accounts for 10%-35% of the conductive filler.

8. The method for preparing a current collector according to claim 7, characterized in that: The method further comprises: The current collector is surface treated so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm.

9. The method for preparing a current collector according to claim 8, characterized in that: The surface treatment of the current collector so that the surface dyne value of the current collector is greater than or equal to 34 dyn / cm2 comprises: Performing surface treatment on the current collector by a rolling process; or, Performing surface treatment on the current collector by a surface processing technique; or, The current collector is firstly subjected to surface treatment by a surface processing process, and then subjected to surface treatment by a rolling process.

10. A positive electrode sheet, characterized in that: A coating material and a current collector according to any one of claims 1 to 6; The coating material is coated on both side surfaces of the current collector.

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