Pole piece, and electrochemical device and electronic equipment comprising same

Abstract

The application relates to the technical field of electrochemical energy storage, and specifically discloses an electrode sheet, an electrochemical device comprising the same and an electronic device, the electrode sheet comprising a composite current collector, a first active material layer and a second active material layer, the composite current collector comprising a center layer, two sides of the center layer in the thickness direction being respectively provided with a first conductive layer and a second conductive layer; the center layer is made of an insulating material, and the first conductive layer is welded with a tab; the first active material layer is coated on the surface of the first conductive layer, and the second active material layer is coated on the surface of the second conductive layer; the composite current collector is provided with a through hole penetrating through the composite current collector, the through hole is filled with an active material column, and the two ends of the active material column are respectively connected with the first active material layer and the second active material layer; the active material column and the active material layer are made of the same material. The current collector of the electrode sheet only needs to be welded with a tab on one side, the risk of lithium precipitation is low, and the energy density is high.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and more particularly to electrodes and electrochemical devices and electronic equipment including electrodes. Background Technology

[0002] The foil current collector can be welded to only one side in the thickness direction to improve the energy density of the battery and control the cost. However, the heat effect generated during the welding process will significantly degrade the performance of the active material coating layer on the other side of the foil current collector, causing the performance of components such as binder and carboxymethyl cellulose (CMC) to change, which in turn leads to local performance degradation and ultimately induces lithium plating. Utility Model Content

[0003] To address the aforementioned technical issues, this application proposes an electrode where the current collector only requires welding tabs on one side, and it features low lithium plating risk and high energy density.

[0004] This application also proposes an electrochemical device and an electronic device including the aforementioned electrodes.

[0005] The electrode sheet of the first aspect embodiment of this application includes: A composite current collector includes a central layer, on both sides of the central layer in the thickness direction, a first conductive layer and a second conductive layer are respectively provided; the central layer is made of an insulating material, and the first conductive layer is welded with tabs. A first active material layer is coated on the surface of the first conductive layer; A second active material layer is coated on the surface of the second conductive layer; The composite current collector has a through hole that penetrates the composite current collector. The through hole is filled with an active material column. The two ends of the active material column are respectively connected to the first active material layer and the second active material layer. The active material column is made of the same material as the first active material layer and / or the second active material layer.

[0006] In some embodiments of this application, the thermal conductivity of the central layer is from 0.1 W / (m•K) to 0.6 W / (m•K).

[0007] In some embodiments of this application, the first active material layer is provided with a relief groove, and the portion of the electrode tab that is welded to the first conductive layer is located within the relief groove; The area of ​​the relief groove is S, and the projected area of ​​the electrode tab in the relief groove is S1. The relationship between the two is: 1.1S1≤S≤3S1.

[0008] In some embodiments of this application, the distance between the edge of the through hole and the edge of the relief groove is greater than or equal to 3 μm.

[0009] In some embodiments of this application, the composite current collector has at least 50 through holes.

[0010] In some embodiments of this application, the relationship between the pore size R of the through hole and the median particle size Dv50 of the active material used in the first active material layer is: 2*Dv50≤R≤14*Dv50.

[0011] In some embodiments of this application, the thickness of the first conductive layer and / or the second conductive layer is from 1 μm to 3.5 μm.

[0012] In some embodiments of this application, the thickness of the central layer is 1 μm to 8 μm.

[0013] The electrode in the first aspect of this application employs a composite current collector. The thermal conductivity of the central layer of the composite current collector is significantly lower than that of the foil current collector, thereby preventing the heat generated during the welding of the electrode tab to the first conductive layer from affecting the second active material layer coated on the second conductive layer and reducing the risk of lithium plating at the electrode tab welding position. The composite current collector, by providing through holes and connecting the first and second active material layers with the active material pillars filled in the through holes, achieves effective conductivity between the first and second active material layers, eliminating the problem of uneven coating weight on both sides of the composite current collector, allowing the electrochemical reaction to penetrate both sides of the composite current collector and improving the kinetic performance of the electrode. The active material pillars and the first and / or second active material layers are made of the same active material material, which can effectively reduce manufacturing costs.

[0014] The electrochemical device according to the second aspect of this application includes the electrode described above.

[0015] The electronic device according to the third aspect of this application includes the electrochemical device described above.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The embodiments in this application are not limited to the drawings described below, which are only some of the embodiments described herein. Those skilled in the art can obtain drawings of other embodiments based on the content of this application. Figure 1 This is a top view of the electrode sheet according to the first aspect embodiment of this application; Figure 2 This is a cross-sectional view of the electrode sheet according to the first aspect of this application; Figure 3 for Figure 2Enlarged view of point A in the middle.

[0018] Icon labels: Composite current collector 100, central layer 110, first conductive layer 120, tab 121, second conductive layer 130, through hole 140, active material column 141; First active material layer 200, clearance groove 210; Second active material layer 300. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] In the description of this application, it should be understood that the orientation descriptions, such as up and down, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not 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 this application.

[0021] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] Furthermore, for ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0025] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0026] Reference Figures 1 to 3 The first aspect of this application discloses an electrode sheet, which includes a composite current collector 100, a first active material layer 200 and a second active material layer 300. The composite current collector 100 includes a central layer 110, a first conductive layer 120 and a second conductive layer 130. The first conductive layer 120 and the second conductive layer 130 are respectively disposed on both sides of the central layer 110 in the thickness direction. The first active material layer 200 is coated on the surface of the first conductive layer 120 and the second active material layer 300 is coated on the surface of the second conductive layer 130.

[0027] The first conductive layer 120 is welded with tabs 121; the composite current collector 100 has a through hole 140 penetrating the composite current collector 100, and the through hole 140 is filled with active material pillars 141. The two ends of the active material pillars 141 are connected to the first active material layer 200 and the second active material layer 300, respectively; the active material pillars 141 and the active material layers are made of the same material. The thermal conductivity of the central layer 110 is much lower than that of the metal current collector, thereby avoiding the heat generated when the tabs 121 are welded to the first conductive layer 120 from affecting the second active material layer 300 coated on the second conductive layer 130, and reducing the risk of lithium plating at the welding position of the tabs 121. Specifically, the thermal conductivity of the core layer 110 is typically 0.1 W / (m•K) to 0.6 W / (m•K); in comparison, the thermal conductivity of aluminum current collectors is approximately 205 W / (m•K) to 235 W / (m•K), and that of copper current collectors is approximately 385 W / (m•K) to 401 W / (m•K). Therefore, the core layer 110 has good thermal insulation properties.

[0028] The composite current collector 100, by providing a through hole 140 and filling the through hole 140 with an active material column 141 to connect the first active material layer 200 and the second active material layer 300, achieves effective conductivity between the first active material layer 200 and the second active material layer 300. This eliminates the problem of uneven coating weight on both sides of the composite current collector 100, allowing the electrochemical reaction to proceed through both sides of the composite current collector 100, thus improving the kinetic performance of the electrode. The active material column 141 and the first active material layer 200 and / or the second active material layer 300 are made of the same active material material, which effectively reduces manufacturing costs. The first active material layer 200 and the second active material layer 300 are made of the same active material material.

[0029] In some embodiments, the thickness of the central layer 110 is approximately 1 μm to 8 μm to ensure that the central layer 110 provides sufficient thermal insulation when the first conductive layer 120 is welded to the tab 121. The central layer 110 is made of an insulating material and has good thermal insulation properties. It is typically a polymer, and its components include at least one of polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl chloride (PVC), polyacrylonitrile (PAN), butadiene, styrene, polypropylene (PP), polyethylene, phenolic resin, polyurethane, polyimide (PI), polyamide, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polysulfone, polyaryletherketone, polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, trifluorochloroethylene-ethylene copolymer, polyethylene terephthalate nitrile, and / or derivatives thereof.

[0030] In some embodiments, the thickness of the first conductive layer 120 and / or the second conductive layer 130 is from 1 μm to 3.5 μm, to meet the welding strength requirements of the tab 121 without being too thick and affecting the cell thickness. Preferably, the thicknesses of the first conductive layer 120 and the second conductive layer 130 are equal. The composition of the first conductive layer 120 and / or the second conductive layer 130 is selected from one or more of copper, aluminum, silver, nickel, molybdenum, titanium, niobium, iron, zinc, stainless steel, graphene, carbon nanotubes, Ketjen black, acetylene black, graphite powder, and carbon fiber.

[0031] In some specific embodiments, the first conductive layer 120 and / or the second conductive layer 130 are composed of copper or aluminum. For example, the first conductive layer 120 and / or the second conductive layer 130 in the cathode electrode are typically composed of aluminum, while the first conductive layer 120 and / or the second conductive layer 130 in the anode electrode are typically composed of copper. In the same electrode, the first conductive layer 120 and the second conductive layer 130 have the same material composition; for example, the first conductive layer 120 and the second conductive layer 130 in the cathode electrode are both composed of aluminum, while the first conductive layer 120 and the second conductive layer 130 in the anode electrode are both composed of copper.

[0032] In some embodiments, when the electrode is a cathode electrode, the first active material layer 200 and the second active material layer 300 of the cathode electrode are selected from LiCoO2, LiNiO2, and LiNi. x Mn y O2, Li 1+z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. The positive electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as positive electrode active materials.

[0033] In some embodiments, when the electrode is an anode electrode, the first active material layer 200 and the second active material layer 300 of the anode electrode may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres (MCMB), Sn, SnO2, SnO, or Li4Ti5O. 12 At least one of LTO, Si materials, silicon-carbon Si-C composite materials, silicon-nitrogen Si-N composite materials, and silicon-oxygen Si-O composite materials. The negative electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as negative electrode active materials for batteries.

[0034] In some implementations, refer to Figure 1As shown, the first active material layer 200 is provided with a relief groove 210, and the portion of the tab 121 welded to the first conductive layer 120 is located within the relief groove 210. The size of the relief groove 210 is usually larger than the welding area between the tab 121 and the first conductive layer 120 to ensure that the tab 121 can be accurately welded; at the same time, in order to avoid the capacity loss of the electrode due to the excessively large size of the relief groove 210, when the area of ​​the relief groove 210 is S and the projected area of ​​the tab 121 in the relief groove 210 is S1, the relationship between the two is usually set as: 1.1S1≤S≤3S1. The specific dimensions of the relief groove 210 can be set according to the actual situation. For example, if the positioning accuracy of some production lines is high, the size of the relief groove 210 can be reduced accordingly. For example, the area S of the relief groove 210 can be set to 1.1S1 to reserve more area for coating active material to improve the capacity of the electrode. If the processing accuracy of some production lines is low, the size of the relief groove 210 can be reduced accordingly. For example, the area S of the relief groove 210 can be set to 3S1 to ensure that the tab 121 is stably welded in the relief groove 210.

[0035] In some embodiments, to prevent the through hole 140 from entering the relief groove 210, the distance between the edge of the through hole 140 and the edge of the relief groove 210 should be greater than or equal to 3 μm. This means that there should be at least a 3 μm wide active material layer between the edge of the through hole 140 and the edge of the relief groove 210. If the reserved width between the edge of the through hole 140 and the edge of the relief groove 210 is too small, it will greatly increase the processing difficulty, leading to increased manufacturing costs. If the reserved width is too large, it may affect the number of through holes 140 that can be installed on the electrode, thus affecting the dynamic performance of the electrode. In specific production practices, an active material layer of appropriate width can be reserved between the edge of the through hole 140 and the edge of the relief groove 210 according to the actual situation.

[0036] In some implementations, refer to Figure 1 As shown, the composite current collector 100 has at least 50 through holes 140 to ensure that the active material column 141 can effectively conduct the first active material layer 200 and the second active material layer 300, increase the conduction area of ​​the first active material layer 200 and the second active material layer 300, thereby improving the dynamic performance of the electrode and reducing the problem of uneven weight distribution of the composite current collector 100 due to the uneven weight distribution of the first active material layer 200 and the second active material layer 300.

[0037] In the electrode processing of this embodiment, the coating material of the second active material layer 300 flows into the through hole 140 to form an active material column 141. In order to ensure that the coating material of the second active material layer 300 flows into the through hole 140 and passes through the through hole 140 to fuse and conduct with the first active material layer 200, the aperture of the through hole 140 needs to be limited. Generally, the relationship between the aperture R of the through hole 140 and the median particle size Dv50 of the active material used in the first active material layer 200 is: 2*Dv50≤R≤14*Dv50. If the aperture of the through hole 140 is too large, it will lead to the capacity loss of the electrode and increase the risk of tape breakage during electrode processing. If the aperture of the through hole 140 is too small, it will lead to poor permeability of the coating material of the second active material layer 300, thereby affecting the conductivity of the first active material layer 200 and the second active material layer 300.

[0038] During the electrode processing, there is a rolling process. Both the first active material layer 200 and the second active material layer 300 are subjected to rolling. However, the active material column 141 formed by the curing of the coating material in the through hole 140 is not directly subjected to rolling. Therefore, the compaction of the active material column 141 is significantly lower than that of the first active material layer 200 and the second active material layer 300. In other words, the porosity of the active material column 141 is higher. The higher porosity of the active material column 141 can provide better liquid retention, thereby improving the dynamic performance of the electrode.

[0039] It's important to understand that the median particle size (Dv50) of the active material used in the first active material layer 200 is typically measured using laser diffraction particle size analysis. The median particle size (Dv50) is a key indicator of the overall size of the particle group; essentially, it represents the particle size at which the cumulative particle size distribution reaches 50%. Simply put, in the entire particle group, 50% of the particles have a diameter smaller than Dv50, and the other 50% have a diameter larger than Dv50. The median particle size (Dv50) is equivalent to the "median particle size" of the particle group, directly reflecting the overall average size of the particles.

[0040] The specific understanding of the median particle size Dv50 needs to be combined with the "particle size distribution curve". Through experiments such as testing the particle size distribution of the particle group with a laser particle size analyzer, a cumulative distribution curve is obtained. The horizontal axis of the cumulative distribution curve represents the "particle size" such as micrometers (μm) or nanometers (nm), and the vertical axis represents the "cumulative percentage of particles smaller than that size among the total particles". When the cumulative percentage on the vertical axis reaches 50%, the corresponding particle size value on the horizontal axis is the median particle size Dv50.

[0041] In some embodiments, the diameters of the multiple through holes 140 can be set to be equal or unequal; for example, in some specific embodiments, the diameters of the multiple through holes 140 may increase or decrease sequentially along the length direction of the electrode; or the diameter of the through hole 140 in the middle of the electrode may be larger than the diameters of the through holes 140 at both ends along the length direction of the electrode; or the diameter of the through hole 140 in the middle of the electrode may be smaller than the diameters of the through holes 140 at both ends along the length direction of the electrode; or the diameters of the through holes 140 may increase or decrease sequentially outward from the relief groove 210; or the diameters of the through holes 140 may increase or decrease sequentially outward from one or more points of the tab 121, etc.

[0042] In some embodiments, the cross-sectional shapes of the multiple through holes 140 can be the same or different. The cross-sectional shape of the through holes 140 can be circular, polygonal, elliptical, star-shaped, etc. For example, in some specific embodiments, all through holes 140 may have the same cross-sectional shape, or all through holes 140 may have different cross-sectional shapes. Alternatively, along the length of the electrode, the cross-sectional shape of the through hole 140 in the middle of the electrode may be different from the cross-sectional shape of the through holes 140 at both ends.

[0043] In some embodiments, the plurality of through holes 140 can be as follows Figure 1 The arrangement is as shown; or, multiple through holes 140 with rows and columns, with the through holes 140 in adjacent rows or columns being staggered; or, multiple through holes 140 are arranged to diffuse outward in a circular pattern around one or more through holes 140 in the middle of the tab 121.

[0044] In some embodiments, the spacing between adjacent through holes 140 can be set to be equal or unequal, preferably equal, and preferably the multiple through holes 140 are evenly spaced to ensure that the conductivity effect at each position of the first active material layer 200 and the second active material layer 300 is the same.

[0045] The electrochemical device provided in the second aspect of this application includes any device in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0046] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, an electrolyte, and a separator, with the separator located between the positive and negative electrodes. The positive and / or negative electrodes used in the electrochemical device are those described above in this application. Since the electrochemical device uses the aforementioned electrodes, it possesses at least all the beneficial effects of the aforementioned electrodes, which will not be elaborated upon here.

[0047] The electronic device provided in the third aspect of this application includes the electrochemical device described above.

[0048] The electronic device described in this application is not particularly limited and may be any electronic device known in the prior art.

[0049] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. According to some embodiments of this application, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, fitness robots, etc.

[0050] Throughout this specification, references to "implementation method," "partial implementation method," "one implementation method," "another method," "specific method," or "partial method" mean that at least one implementation method or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation method or embodiment.

[0051] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0052] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrode sheet, characterized in that, include: A composite current collector includes a central layer, on both sides of the central layer in the thickness direction, a first conductive layer and a second conductive layer are respectively provided; the central layer is made of an insulating material, and the first conductive layer is welded with tabs. A first active material layer is coated on the surface of the first conductive layer; A second active material layer is coated on the surface of the second conductive layer; The composite current collector has a through hole that penetrates the composite current collector. The through hole is filled with an active material column. The two ends of the active material column are respectively connected to the first active material layer and the second active material layer. The active material column is made of the same material as the first active material layer and / or the second active material layer.

2. The electrode sheet according to claim 1, characterized in that, The thermal conductivity of the central layer is from 0.1 W / (m•K) to 0.6 W / (m•K).

3. The electrode sheet according to claim 1, characterized in that, The first active material layer is provided with a relief groove, and the portion of the electrode tab that is welded to the first conductive layer is located within the relief groove; The area of ​​the relief groove is S, and the projected area of ​​the electrode tab in the relief groove is S1. The relationship between the two is: 1.1S1≤S≤3S1.

4. The electrode sheet according to claim 3, characterized in that, The distance between the through hole and the relief groove is greater than or equal to 3 μm.

5. The electrode sheet according to claim 1, characterized in that, The composite current collector has at least 50 through holes.

6. The electrode sheet according to claim 1, characterized in that, The relationship between the pore diameter R of the through hole and the median particle size Dv50 of the active material used in the first active material layer is: 2*Dv50≤R≤14*Dv50.

7. The electrode sheet according to claim 1, characterized in that, The thickness of the first conductive layer and / or the second conductive layer is from 1 μm to 3.5 μm.

8. The electrode sheet according to claim 1, characterized in that, The thickness of the central layer is 1 μm to 8 μm.

9. An electrochemical device, characterized in that, Includes the electrode sheet as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, The electrochemical device described in claim 9 was used.

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