Current collector, method for manufacturing the same, electrode sheet, and battery

Abstract

The application relates to the field of batteries, in particular to a current collector, a preparation method thereof, a pole piece and a battery. The current collector comprises a first supporting layer, the first supporting layer is an insulating layer; two second supporting layers, the two second supporting layers are respectively arranged on the two sides of the first supporting layer, the melting point of the second supporting layer is lower than that of the first supporting layer, and the second supporting layer is an insulating layer; and two conductive layers, the two conductive layers are arranged on the sides of the two second supporting layers which are opposite to the first supporting layer. The current collector can avoid the occurrence of thermal runaway in the process of having high processing performance and straight-through rate, and the safety is improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and particularly to a current collector, its preparation method, an electrode, and a battery. Background Technology

[0002] As batteries develop towards higher energy density and higher safety, the safety of the system gradually decreases. To improve energy density and safety performance, composite current collectors are increasingly being used in power batteries. The structure of a composite current collector consists of an insulating layer in the middle and conductive layers on both sides. The presence of the insulating layer in the middle ensures that the composite current collector has a certain degree of ductility and support.

[0003] Currently, when the melting point of the intermediate insulation layer is high, the temperature at which it reaches the failure state is relatively high, the battery accumulates a lot of heat, and the safety is relatively low. However, when the melting point of the intermediate insulation layer is relatively low, the electrode processing performance is poor and the pass rate is low. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a current collector, its preparation method, electrode and battery, which can achieve high processing performance and pass rate while better avoiding thermal runaway and increasing safety.

[0005] To address the above problems, a first aspect of the present invention provides a current collector, the current collector comprising:

[0006] First support layer, wherein the first support layer is an insulating layer;

[0007] Two second support layers are respectively disposed on both sides of the first support layer. The melting point of the second support layer is lower than that of the first support layer. The second support layer is an insulating layer.

[0008] Two conductive layers are disposed on the side of the two second support layers opposite to the first support layer.

[0009] Furthermore, the melting point of the second support layer is more than 90°C lower than the melting point of the first support layer.

[0010] Preferably, the melting point of the first support layer is greater than 200°C, and the melting point of the second support layer is 100-160°C.

[0011] Furthermore, the elongation at break of the second support layer is lower than that of the first support layer.

[0012] Preferably, the elongation at break of the second support layer is more than 20% lower than the elongation at break of the first support layer.

[0013] Furthermore, the thickness of the second support layer is lower than the thickness of the first support layer.

[0014] Preferably, the thickness of the second support layer is 1 to 6 μm, and the thickness of the first support layer is 2 to 20 μm.

[0015] Furthermore, both the material of the first support layer and the material of the second support layer are selected from polyethylene terephthalate, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyimide and polyamide, and the material of the second support layer has a melting point lower than that of the first support layer.

[0016] Furthermore, the structure of the second support layer is a solid structure or a porous structure.

[0017] A second aspect of the present invention provides a method for preparing a current collector, the method comprising:

[0018] Step S1: Provide the first support layer;

[0019] Step S2: Apply two layers of second support layer to each of the two sides of the first support layer;

[0020] Step S3: Two conductive layers are respectively deposited on the side surface of the second support layer that is opposite to the first support layer.

[0021] Furthermore, in step S2, the second support layer is bonded to both sides of the first support layer by any one of the following methods: bonding, transfer, stretching, and hot melting.

[0022] Further, step S2 includes:

[0023] The material of the second support layer is dispersed in a solvent to form a slurry;

[0024] The slurry is coated onto the surface of the first support layer and the solvent is evaporated to form the second support layer.

[0025] A third aspect of the present invention provides an electrode sheet, the electrode sheet comprising:

[0026] The current collector is any of the current collectors described above;

[0027] The active material is disposed on both sides of the current collector.

[0028] A fourth aspect of the present invention provides a battery, the battery comprising:

[0029] The electrode is the electrode described above.

[0030] Due to the above technical solution, the present invention has the following beneficial effects:

[0031] According to the embodiments of the present invention, the current collector collects current through the conductive layer. During the failure of the conductive layer (e.g., short circuit), the low-melting-point second support layer can cut off the electronic path at a relatively low temperature, avoiding thermal runaway and increasing safety. The high-melting-point first support layer sandwiched between the two second support layers can make the current collector, as well as the electrode and battery using this current collector, have high processing performance and pass rate. It can achieve high processing performance and pass rate while effectively avoiding thermal runaway, thus increasing safety. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of a current collector according to an embodiment of the present invention;

[0034] Figure 2 This is a flowchart of a current collector preparation method according to an embodiment of the present invention.

[0035] 100, First support layer; 200, Second support layer; 300, Conductive layer. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0038] To make the objectives, technical solutions, and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. The acquisition, storage, use, and processing of data in the technical solutions of the embodiments of the present invention all comply with the relevant provisions of national laws and regulations.

[0039] The current collector of an embodiment of the present invention will be described below.

[0040] like Figure 1 As shown, the current collector in this embodiment of the invention includes: a first support layer 100, two second support layers 200 and two conductive layers 300.

[0041] First, the first support layer 100 is described. The first support layer 100 is an insulating layer. The material of the first support layer 100 can be polyethylene terephthalate, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyimide, or polyamide.

[0042] Next, the two second support layers 200 will be described. The two second support layers 200 are respectively disposed on both sides of the first support layer 100. The melting point of the second support layer 200 is lower than that of the first support layer 100, and the second support layer 200 is an insulating layer.

[0043] The melting point of the second support layer 200 is lower than that of the first support layer 100. In other words, the high melting point of the first support layer 100 enables it to have high processing performance and high throughput. The low melting point of the second support layer 200 enables the heated part to shrink and collapse rapidly when local heating occurs during the failure of the conductive layer (e.g., short circuit). The low melting point of the second support layer 200 can more easily and quickly cut off the failed circuit when releasing heat, avoiding further thermal runaway and increasing safety.

[0044] The material of the second support layer 200 can also be polyethylene terephthalate, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyimide, or polyamide. However, after selecting one of the above materials as the material of the first support layer 100, it is necessary to select a material whose melting point is lower than that of the first support layer 100, based on the melting point characteristics of each material.

[0045] Furthermore, the second support layer 200 has a solid or porous structure. Therefore, different low-melting-point second support layers 200 can be selected according to requirements to meet diverse needs.

[0046] Finally, the two conductive layers 300 are described. The two conductive layers 300 are disposed on the side of the two second support layers 200 opposite to the first support layer 100.

[0047] The current generated by the battery active material is collected through the conductive layer 300 to form a large current output to the outside.

[0048] The current collector, as described above, collects current through the conductive layer 300. During the failure of the conductive layer 300 (e.g., a short circuit), the low-melting-point second support layer 200, at a relatively low temperature, can cut off the electron path, preventing thermal runaway and increasing safety. The high-melting-point first support layer 100 sandwiched between the two second support layers 200 allows for high processing performance and throughput of the current collector, as well as the electrodes and batteries using this current collector. Therefore, it is possible to achieve high processing performance and throughput while simultaneously effectively preventing thermal runaway, thus increasing safety.

[0049] According to some embodiments of the present invention, the melting point of the second support layer 200 is more than 90°C lower than the melting point of the first support layer 100. For example, the melting point of the second support layer 200 is 100°C or 120°C lower than the melting point of the first support layer 100.

[0050] The melting point of the second support layer 200 is more than 90°C lower than that of the first support layer 100, which can better increase the processing performance and throughput of the current collector, as well as the electrode and battery using this current collector, and better avoid the occurrence of thermal runaway.

[0051] Preferably, the melting point of the first support layer 100 is greater than 200°C, and the melting point of the second support layer 200 is 100-160°C. For example, the melting point of the first support layer 100 is 250°C, and the melting point of the second support layer 200 is 130°C.

[0052] Through multiple experiments and theoretical analyses, the first support layer 100 and the second support layer 200 at this melting point meet the requirements for mass production of current collectors. The current collectors, as well as the electrodes and batteries using these current collectors, can achieve better processing performance, throughput and safety.

[0053] According to some embodiments of the present invention, the elongation at break of the second support layer 200 is lower than that of the first support layer 100. The elongation at break is the percentage of the total elongation of the material after tensile fracture relative to the original gauge length, which can effectively assess the mechanical strength of the material.

[0054] During the failure of the conductive layer 300, the second support layer 200, with its low elongation at break, not only melts more easily but also fractures more easily mechanically, further reducing the electronic conduction transition time and increasing the efficiency of switching on and off. Furthermore, it is more prone to failure during short circuits caused by mechanical forces (external compression or puncture), quickly severing the connection between the first support layer 100 and the conductive layer 300. This results in enhanced safety for the electrodes and batteries using this current collector. Simultaneously, the first insulating layer 100, with its high elongation at break, ensures high processing performance and throughput for the current collector, as well as the electrodes and batteries using it.

[0055] Preferably, the elongation at break of the second support layer 200 is more than 20% lower than the elongation at break of the first support layer 100. For example, the elongation at break of the second support layer 200 is 30% or 40% lower than the elongation at break of the first support layer 100.

[0056] The elongation at break of the second support layer 200 is more than 20% lower than that of the first support layer 100, which can better increase the safety of the electrode and battery using this current collector, and make the current collector, as well as the electrode and battery using this current collector, have higher processing performance and pass rate.

[0057] According to some embodiments of the present invention, the thickness of the second support layer is lower than the thickness of the first support layer 100.

[0058] The thinner second support layer 200 is easier to melt and break, which can increase the safety of the electrode and battery using this current collector. The thicker first support layer 100 can increase the current collector, as well as the electrode and battery using this current collector, to have higher processing performance and pass rate.

[0059] Preferably, the thickness of the second support layer 200 is 1–6 μm, and the thickness of the first support layer 100 is 2–20 μm. The thickness of the first support layer 100 is preferably 5–10 μm. For example, the thickness of the second support layer 200 is 2 μm, and the thickness of the first support layer 100 is 10 μm.

[0060] Through multiple experiments and theoretical analyses, the thickness of the first support layer 100 and the second support layer 200 enables the current collector, as well as the electrode and battery using this current collector, to meet the requirements for mass production, and has high processing performance, yield, and safety.

[0061] The method for preparing the current collector according to an embodiment of the present invention will be described below.

[0062] like Figure 2 As shown, the current collector preparation method of this invention includes:

[0063] Step S1: Provide the first support layer 100. That is, remove the first support layer 100.

[0064] In step S2, two second support layers 200 are laminated onto both sides of the first support layer 100. This ensures that the first support layer 100 and the second support layer 200 are tightly connected.

[0065] In step S3, two conductive layers 300 are respectively disposed on the side surface of the second support layer 200 opposite to the first support layer 100. This allows the second support layer 200 and the conductive layers 300 to be tightly connected.

[0066] Therefore, it is possible to prepare current collectors that meet the requirements.

[0067] Step S2 can be implemented in the following two ways:

[0068] In one method, the second support layer 200 is bonded to both sides of the first support layer 100 by any one of the following methods: bonding, transfer, stretching, or hot melting.

[0069] In this approach, the second support layer 200 has a wider range of material options and the process is simpler.

[0070] In the second method, the material of the second support layer 200 is dispersed in a solvent to form a slurry; the slurry is coated on the surface of the first support layer 100 and the solvent is evaporated to form the second support layer 200.

[0071] In this method, the cost is relatively low, the manufacturing process is less, and the second support layer 200 adheres to the first support layer 100 with a higher force.

[0072] The electrode sheet of the present invention will now be described.

[0073] The electrode in this embodiment of the invention includes a current collector and an active material. The current collector is any of the current collectors described above. The active material is disposed on both sides of the current collector.

[0074] By using the aforementioned current collector, the electrode can have higher processing performance and throughput, and during the failure process, the failure time is reduced, thus increasing safety.

[0075] The battery of an embodiment of the present invention will be described below.

[0076] The battery of this invention includes an electrode sheet, which uses the above-mentioned current collector.

[0077] Battery applications using electrodes with the aforementioned current collectors enable batteries to have higher processing performance and throughput, and reduce failure time and increase safety during the failure process.

[0078] The present invention will now be illustrated through specific embodiments and comparative examples.

[0079] In Example 1, the first support layer 100 is made of polyethylene terephthalate (PET), with a melting point of 240°C, an elongation at break of 20%, and a thickness of 6 μm. The second support layer 200 is made of polypropylene, with a melting point of 170°C, an elongation at break of 3%, and a thickness of 1 μm. The second support layer 200 has a solid structure. The conductive layer 300 has a thickness of 1 μm and is deposited on the second support layer 200 by vapor deposition to obtain a current collector. Positive polarity material is coated on both sides of the current collector to obtain an electrode. The electrode is then stacked to obtain a battery.

[0080] In Example 2, the thickness of the first support layer 100 is 6 μm, the thickness of the second support layer 200 is 1 μm, the structure of the second support layer 200 is a porous structure, the thickness of the conductive layer 300 is 1 μm, the conductive layer 300 is deposited on the second support layer 200 by vapor deposition to obtain a current collector, positive polarity material is coated on both sides of the current collector to obtain an electrode, and the electrode is stacked to obtain a battery.

[0081] In Comparative Example 1, the current collector only has a second support layer 200 and a conductive layer 300. The thickness of the second support layer 200 is 10 μm, and the structure of the second support layer 200 is a solid structure. The thickness of the conductive layer 300 is 1 μm. The conductive layer 300 is deposited on the second support layer 200 by vapor deposition to obtain the current collector. A positive polarity material is coated on both sides of the current collector to obtain the electrode. The electrode is stacked to obtain the battery.

[0082] In Comparative Example 2, the current collector has only a first support layer 100 and a conductive layer 300. The thickness of the first support layer 100 is 10 μm, and the thickness of the conductive layer 300 is 1 μm. The conductive layer 300 is deposited on the second support layer 200 by vapor deposition to obtain the current collector. A positive polarity material is coated on both sides of the current collector to obtain the electrode. The electrode is stacked to obtain the battery.

[0083] In Comparative Example 3, the current collector only has a conductive layer 300. The conductive layer 300 is a 12µm aluminum foil, and a 1µm PTC (positive temperature coefficient thermistor) material is coated on the aluminum foil to obtain the current collector. Positive polarity material is coated on both sides of the current collector to obtain the electrode. The electrode is stacked to obtain the battery.

[0084] The appearance of the current collectors of the above embodiments and comparative examples was compared, and the penetration depth of the batteries of the above embodiments and comparative examples was compared. The results are shown in Table 1.

[0085] Table 1

[0086] Current collector appearance Battery needle penetration depth Example 1 No wrinkles and no visible pinholes 5mm Example 2 No wrinkles and no visible pinholes 5mm Comparative Example 1 The wound film has wrinkles and melt holes larger than 2mm. / Comparative Example 2 No wrinkles and no visible pinholes 2mm Comparative Example 3 / <2mm

[0087] Visual comparison can be used to assess the processing performance and throughput of the current collector, while needle penetration depth comparison can be used to assess the fusing capability during the failure process, thereby assessing safety.

[0088] The comparison results above show that the current collector of the present invention has a better appearance, and the battery has a deeper needle penetration depth. This indicates that the current collector of the present invention has better processing performance and a better first-pass yield, and the battery of the present invention has better safety. The current collector of Comparative Example 1 has wrinkles on the winding film surface and melt holes greater than 2mm, indicating insufficient strength, poor processing performance, and low first-pass yield. The battery of Comparative Example 2 has a needle penetration depth of 2mm, indicating poor safety performance. The battery of Comparative Example 3 has the worst safety performance.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A current collector, characterized in that, include: First support layer, wherein the first support layer is an insulating layer; Two second support layers are respectively disposed on both sides of the first support layer. The melting point of the second support layer is lower than that of the first support layer. The second support layer is an insulating layer. Two conductive layers are disposed on the side of the two second support layers opposite to the first support layer. The melting point of the second support layer is more than 90°C lower than the melting point of the first support layer, the melting point of the first support layer is greater than 200°C, and the melting point of the second support layer is 100-160°C. The thickness of the second support layer is lower than that of the first support layer, the thickness of the second support layer is 1-6 μm, and the thickness of the first support layer is 5-10 μm; Both the first support layer and the second support layer are selected from one of the following materials: polyethylene terephthalate, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyimide, and polyamide. The elongation at break of the second support layer is more than 20% lower than that of the first support layer.

2. The current collector according to claim 1, characterized in that, The second support layer has a solid structure or a porous structure.

3. A method for preparing a current collector, applied to the preparation of the current collector according to any one of claims 1 to 2, characterized in that, include: Step S1: Provide the first support layer; Step S2: Apply two layers of second support layer to each of the two sides of the first support layer; Step S3: Two conductive layers are respectively deposited on the side surface of the second support layer that is opposite to the first support layer.

4. The current collector preparation method according to claim 3, characterized in that, In step S2, the second support layer is bonded to both sides of the first support layer by any one of the following methods: bonding, transfer, stretching, or hot melting.

5. The current collector preparation method according to claim 3, characterized in that, Step S2 includes: The material of the second support layer is dispersed in a solvent to form a slurry; The slurry is coated onto the surface of the first support layer and the solvent is evaporated to form the second support layer.

6. An electrode sheet, characterized in that, include: A current collector, wherein the current collector is the current collector according to any one of claims 1 to 2; The active material is disposed on both sides of the current collector.

7. A battery, characterized in that, include: The electrode is the electrode as described in claim 6.

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