Pole piece, electrochemical device, and electronic device

Abstract

This application relates to the field of electrochemical energy storage technology, and particularly to electrodes, electrochemical devices, and electronic devices, mainly comprising: a tab; a current collector; an active material layer; and a protective layer disposed on the surface of the current collector and adjacent to the active material layer; the protective layer is also adjacent to the tab, or, along the thickness direction of the electrode, the orthographic projection of the tab lies within the orthographic projection range of the protective layer; the protective layer includes an alloy layer and an insulating layer, the alloy layer being disposed on the surface of the current collector, and the insulating layer being disposed on the side of the alloy layer facing away from the current collector; wherein, the average thickness of the protective layer is T. A µm, the thickness of the active material layer is T1µm, T A T1 and T1 satisfy: T1–5≤T A ≤T1+5. The electrode provided in this application includes a thin and strongly adhesive protective layer, which provides reliable insulation protection while reducing the ineffective space inside the electrochemical device and improving the volumetric energy density of the electrochemical device.

Description

Technical Field

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

[0002] Currently, to improve cell flatness and energy density, a common method is to thin the anode electrode area opposite the cathode tab and then apply an insulating coating. This involves creating a thinned area with an insulating coating on the electrode. This not only physically isolates the internal electrodes, preventing short circuits, but also replaces adhesive tape, reducing cell thickness and increasing volumetric energy density. However, thinning the existing insulating coating reduces its mechanical properties, making it prone to breakage or peeling, leading to other potential safety hazards and hindering a true increase in volumetric energy density. Summary of the Invention

[0003] Based on the shortcomings of the prior art, this application provides an electrode, an electrochemical device, and an electronic device, which aim to maintain the mechanical properties of the insulating coating in the electrode thinning area while reducing the thickness of the insulating coating.

[0004] To achieve the above objectives, this application provides an electrode sheet comprising: a tab; a current collector; an active material layer disposed on at least one surface of the current collector; and a protective layer disposed on the surface of the current collector and adjacent to the active material layer. The protective layer is also adjacent to the tab, or, along the thickness direction of the electrode sheet, the orthographic projection of the tab lies within the orthographic projection range of the protective layer. The protective layer comprises an alloy layer and an insulating layer, the alloy layer being disposed on the surface of the current collector, and the insulating layer being disposed on the side of the alloy layer facing away from the current collector. The average thickness of the protective layer is T. A µm, the thickness of the active material layer is T1µm, T A T1 and T1 satisfy: T1–5≤T A ≤T1+5.

[0005] In some embodiments, the thickness of the alloy layer is T2µm, and the average thickness of the insulating layer is T3µm. A T2 and T3 satisfy: T A =T2+T3, 1µm≤T2≤5µm, 5µm≤T3≤20µm.

[0006] In some implementations, T2 and T3 also satisfy: 1:3≤T2:T3≤1:8.

[0007] In some embodiments, the insulating layer includes at least one bevel that is close to the plane containing the current collector in a direction away from the active material layer.

[0008] In some embodiments, the angle between the extended surface of the inclined plane and the plane containing the current collector is 5° to 75°.

[0009] In some embodiments, the thickness tolerance of the insulating layer is ≤2µm.

[0010] In some embodiments, the thermal conductivity of the insulating layer is from 0.8 W / (m·K) to 2.5 W / (m·K); and / or, The elastic modulus of the insulating layer is 200 GPa to 280 GPa; and / or, The porosity of the insulating layer is 2% to 10%.

[0011] In some embodiments, the average diameter of the columnar crystals in the insulating layer is 50 nm to 200 nm; and / or, The width of the intercolumn cracks in the insulating layer is 10 nm to 50 nm.

[0012] In some embodiments, the alloy layer includes M CrAlY and / or M CrAlSiY, M It is selected from one of Co, Ni, NiCo, and CoNi.

[0013] In some embodiments, the surface roughness of the alloy layer is from 0.8 μm to 1.2 μm.

[0014] This application also provides an electrochemical device, the electrochemical device including the electrode.

[0015] This application also provides an electronic device, which includes any of the electrochemical devices described herein.

[0016] The beneficial effects of this application are as follows: This application incorporates a protective layer in specific areas of the electrode to insulate the tabs and prevent short circuits within the electrochemical device. The protective layer comprises an alloy layer and an insulating layer sequentially disposed on the current collector surface. By designing the thickness and structural position of the protective layer within the cell, and through assembly, winding, and hot-pressing processes, the electrode and separator near the tabs in the electrochemical device can be tightly bonded, avoiding the use of traditional insulating adhesives and directly reducing the volume of ineffective space within the electrochemical device, thus increasing the volumetric energy density. The alloy layer of the protective layer enhances the adhesion between the entire protective layer structure and the current collector, effectively preventing the protective layer from cracking and peeling due to cyclic expansion stress in the electrochemical device. Attached Figure Description

[0017] The embodiments described in this application are not limited to the accompanying drawings, 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.

[0018] Along the thickness direction of the electrode, Figure 1 This is a schematic diagram of the electrochemical device prepared in Example 1 of this application; Figure 2 This is a partial structural schematic diagram of the electrode sheet prepared in Example 1 of this application; Figure 3 This is a schematic diagram of another partial structure of the electrode sheet prepared in Example 1 of this application; Figure 4 This is a schematic diagram of the electrochemical device for the electrode prepared in Example 2 of this application; Figure 5 This is a partial structural schematic diagram of the electrode sheet prepared in Example 2 of this application; Figure 6 This is a schematic diagram of another partial structure of the electrode sheet prepared in Example 2 of this application; Figure 7 This is a partial structural schematic diagram of the electrode sheet prepared in Example 3 of this application; Figure 8 This is a schematic diagram of another partial structure of the electrode sheet prepared in Example 3 of this application; Figures 1 to 8 The labeling explanations are shown in Table 1.

[0019] Table 1. Figures 1 to 8 Label Explanation . Detailed Implementation

[0020] The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. The general term "polymer" includes the terms "homopolymer," "copolymer," "trimer," and "interpolymer."

[0021] The term "binder" refers to a substance used for interfacial interactions to firmly bond two or more materials together. This document may use any organic binder that can bond polymers to porous substrate materials or to each other.

[0022] The term "pore" refers to the tiny voids within a porous medium.

[0023] The term "porosity" refers to the ratio of pore volume to total volume in a porous medium, expressed as a percentage (%).

[0024] The term "elastic modulus" refers to the physical quantity that represents the ratio of stress to strain within the elastic deformation range of a material.

[0025] 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.

[0026] In this application, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features. In this application, numerical ranges are involved; unless otherwise specified, the numerical ranges 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.

[0027] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0028] Currently, to improve battery flatness and energy density, a common method is to thin the anode electrode area opposite the cathode tab and then apply an insulating coating. This involves creating a thinned area with an insulating coating on the electrode. This not only physically isolates the internal electrodes, preventing short circuits, but also replaces adhesive tape, reducing cell thickness and increasing volumetric energy density. However, thinning the existing insulating coating reduces its mechanical properties, making it prone to breakage or peeling, leading to other potential safety hazards and hindering a true increase in volumetric energy density.

[0029] Therefore, it is urgent to maintain the mechanical properties of the insulating coating in the electrode thinning area while reducing the thickness of the insulating coating.

[0030] Based on the shortcomings of the prior art, this application provides an electrode, an electrochemical device, and an electronic device, which aim to maintain the mechanical properties of the insulating coating in the electrode thinning area while reducing the thickness of the insulating coating.

[0031] Based on the above objectives, this solution provides an electrode, which includes: Extreme ear; current collector; An active material layer is disposed on at least one surface of the current collector; A protective layer is disposed on the surface of the current collector and adjacent to the active material layer; the protective layer is also adjacent to the tab, or, along the thickness direction of the electrode, the orthographic projection of the tab is located within the orthographic projection range of the protective layer; the protective layer includes an alloy layer and an insulating layer, the alloy layer is disposed on the surface of the current collector, and the insulating layer is disposed on the side of the alloy layer away from the current collector. The average thickness of the protective layer is T. A µm, the thickness of the active material layer is T1µm. T A T1 and T1 satisfy: T1–5≤T A ≤T1+5.

[0032] In some embodiments, refer to Figures 1 to 3 The tab 201 of the cathode electrode 2 is projected onto the protective layer 103 of the anode electrode 1. The anode electrode 1 includes a protective layer 103 and an active material layer 101 disposed on the surface of its current collector 102. The protective layer 103 is adjacent to the active material layer 101. The protective layer 103 includes an alloy layer 1031 disposed on the surface of the current collector 102 and an insulating layer 1032 disposed on the surface of the alloy layer 1031. The cathode electrode 2 includes a tab 201 and an active material layer 202 disposed on the surface of its current collector 203. The tab 201 is adjacent to the active material layer 202.

[0033] In other embodiments, reference is made to Figures 4 to 8 In the electrode 5, the two ends of the protective layer 503 are adjacent to the tab 504 and the active material layer 501, respectively, and the tab 504 is disposed at the edge or middle of the electrode; wherein, the electrode 5 includes a protective layer 503 and an active material layer 501 disposed on the surface of its current collector 502, the protective layer 503 is adjacent to the active material layer 501, wherein the protective layer 503 includes an alloy layer 5031 disposed on the surface of the current collector 502 and an insulating layer 5032 disposed on the surface of the alloy layer 5031.

[0034] This design incorporates a protective layer in specific areas of the electrode to insulate the tabs and prevent short circuits within the electrochemical device. The protective layer comprises an alloy layer and an insulating layer sequentially disposed on the current collector surface. By designing the thickness and structural position of the protective layer within the cell, and through assembly, winding, and hot-pressing processes, a tight bond can be achieved between the electrode and the separator near the tabs in the electrochemical device. This avoids the use of traditional insulating adhesives and directly reduces the volume of unusable space within the electrochemical device, thereby increasing its volumetric energy density. The alloy layer of the protective layer enhances the adhesion between the entire protective layer structure and the current collector, effectively preventing breakage and peeling of the protective layer caused by cyclic expansion stress within the electrochemical device.

[0035] Furthermore, adjust T1 and T A The relationship ensures that the protective layer is no more than 5µm above the surface of the active material layer, and the active material layer is no more than 5µm above the surface of the protective layer. This reduces the thickness difference between the protective layer and the active material layer, avoids the step-like collapse of the electrode, and, together with the alloy layer improving the conductivity of the electrode, effectively prevents the electrode from experiencing excessively high local current density, which could lead to overheating and lithium plating, further improving the cycle life of the electrochemical device.

[0036] In some embodiments, the thickness of the alloy layer is T2µm, and the average thickness of the insulating layer is T3µm. A T2 and T3 satisfy: T A =T2+T3, 1µm≤T2≤5µm, 5µm≤T3≤20µm.

[0037] This scheme limits the lower limit of the average thickness T2 of the alloy layer to 1µm, which helps maintain the bonding force between the alloy layer and the current collector and the insulating layer. At the same time, it limits the upper limit of its average thickness T2 to 5µm. This not only increases the thickness of the insulating layer by controlling the thickness of the protective layer, but also effectively improves the insulation of the protective layer, thereby improving the physical isolation effect between the electrodes in the electrochemical device and reducing the risk of internal short circuits. It also reduces the thickness of the protective layer, reduces the ineffective volume of the electrodes, and effectively improves the volumetric energy density of the electrochemical device.

[0038] For example, the average thickness T2 of the alloy layer is 1.0µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm, 2.0µm, 2.2µm, 2.4µm, 2.6µm, 2.8µm, 3.0µm, 3.2µm, 3.4µm, 3.6µm, 3.8µm, 4.0µm, 4.2µm, 4.4µm, 4.6µm, 4.8µm, 5.0µm, or falls within the range of any two of the above values.

[0039] Adjusting the lower limit of the average thickness T3 of the insulating layer to 5µm is beneficial to improving the insulation of the insulating layer, thereby maintaining the physical isolation effect between the electrodes in the electrochemical device. Adjusting the upper limit of the average thickness T3 of the insulating layer to 20µm reduces the thickness of the protective layer, which helps to maintain the thickness uniformity of the electrodes, reduces the voids in the electrochemical device, and thus improves the volumetric energy density of the electrochemical device.

[0040] For example, the average thickness T3 of the insulating layer is 5µm, 6µm, 7µm, 8µm, 9µm, 10µm, 11µm, 12µm, 13µm, 14µm, 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, or falls within the range of any two of the above values.

[0041] In some implementations, T2 and T3 also satisfy: 1:3≤T2:T3≤1:8.

[0042] Adjusting the thickness ratio of the alloy layer to the insulating layer ensures sufficient thickness for both the alloy and insulating layers while regulating the protective layer thickness. This improves the adhesion between the protective layer and the current collector and provides adequate insulation, resulting in a highly adhesive and insulating protective layer on the current collector. Reducing the T2:T3 ratio, for example, to 1:3-4, when used with extremely thin electrodes, maintains the thickness of both the alloy and insulating layers. This maintains the alloy layer thickness to improve the adhesion of the protective layer while ensuring sufficient insulation thickness for adequate insulation protection, reducing the risk of internal short circuits. Conversely, when the electrode is thicker, increasing the T2:T3 ratio, for example, to 1:7-8, not only ensures a suitable alloy layer thickness for the protective layer, improving adhesion, but also increases the insulation thickness for higher insulation protection. Furthermore, by adjusting the protective layer thickness, it reduces the planar drop between the protective layer and the active material layer, mitigating the risk of lithium plating caused by electrode step-like collapse.

[0043] For example, T2:T3 can be 1:3, 1:4, 1:5, 1:6, 1:7, or 1:8, or fall within the range of any two of the above values.

[0044] Furthermore, by limiting the average thickness and ratio of the alloy layer and the insulating layer, the thickness of the protective layer can be controlled. While maintaining its insulating effect, thinning the protective layer not only maintains the uniformity of the electrode thickness, but also improves the adhesion between electrodes and between electrodes and the diaphragm in the electrochemical device, reduces ineffective space, and is conducive to improving the volumetric energy density of the electrochemical device.

[0045] In some embodiments, the insulating layer includes at least one bevel that is close to the plane containing the current collector in a direction away from the active material layer.

[0046] In some embodiments, the cross-sectional shape of the insulating layer along the thickness direction of the electrode includes at least one of a rectangle, a trapezoid, a right triangle, and a pentagon.

[0047] Reference Figure 2 and Figure 5 Along the thickness direction of the electrode, the cross-sectional shape of insulating layer 1032 and insulating layer 5032 is rectangular, which helps maintain the overall thickness uniformity of the electrode. (See also...) Figure 3 and Figure 8 The cross-sectional shapes of insulating layers 1032 and 5032 are right-angled triangles; refer to Figure 6 The cross-sectional shape of the insulating layer 5032 is pentagonal; refer to Figure 7 The insulating layer 5032 has a trapezoidal cross-sectional shape. When the insulating layer has a slope, it can promote a smooth transition in the thickness change of the electrode, reduce the risk of lithium plating caused by the step-like collapse of the electrode, and help improve the cycle life of the electrochemical device.

[0048] In some embodiments, the angle between the extended surface of the inclined plane and the plane containing the current collector is 5° to 75°.

[0049] Based on adjusting the slope of the insulating layer, the upper limit of the included angle is controlled at 75° to further slow down the thickness change of the insulating layer, which is conducive to reducing the step-like collapse of the electrode. The lower limit of the included angle is 5°, which helps to reduce the volume of the insulating layer and indirectly increases the volume ratio of the active material of the electrode, thereby increasing the volumetric energy density of the electrochemical device.

[0050] For example, the included angle is 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, or 75°, or falls within the range of any two of the above values.

[0051] In some implementations, the thickness tolerance of the insulating layer is ≤2µm.

[0052] Controlling the thickness tolerance of the insulating layer to ≤2µm and maintaining the surface flatness of the insulating layer helps to reduce the surface height difference of the electrode, prevent the step-like collapse of the electrode, promote the uniform distribution of interfacial pressure of the electrode, reduce the risk of cracks in the collapsed parts of the electrode due to stress, and avoid lithium plating caused by uneven electrode thickness, thereby improving the cycle life of the electrochemical device.

[0053] For example, the thickness tolerance of the insulating layer is 0.01µm, 0.05µm, 0.10µm, 0.20µm, 0.30µm, 0.40µm, 0.50µm, 0.60µm, 0.70µm, 0.80µm, 0.90µm, 1.00µm, 1.10µm, 1.20µm, 1.30µm, 1.40µm, 1.50µm, 1.60µm, 1.70µm, 1.80µm, 1.90µm, 2.00µm, or falls within the range of any two of the above values.

[0054] In some embodiments, the thermal conductivity of the insulating layer is from 0.8 W / (m·K) to 2.5 W / (m·K).

[0055] The lower limit of the thermal conductivity of the insulating layer is controlled at 0.8 W / (m·K), which helps to improve the heat dissipation of the electrode. The upper limit of the thermal conductivity of the insulating layer is controlled at 2.5 W / (m·K). When the orthogonal projection of the electrode is within the orthogonal projection range of the protective layer, the heat transfer between the electrode and the protective layer can be suppressed, effectively reducing the probability of the protective layer melting and breaking down, thereby reducing the risk of internal short circuit in the electrochemical device.

[0056] For example, the thermal conductivity of the insulating layer is 0.8 W / (m·K), 0.9 W / (m·K), 1.0 W / (m·K), 1.1 W / (m·K), 1.2 W / (m·K), 1.3 W / (m·K), 1.4 W / (m·K), 1.5 W / (m·K), 1.6 W / (m·K), 1.7 W / (m·K), 1.8 W / (m·K), 1.9 W / (m·K), 2.0 W / (m·K), 2.1 W / (m·K), 2.2 W / (m·K), 2.3 W / (m·K), 2.4 W / (m·K), 2.5 W / (m·K), or falls within the range of any two of the above values.

[0057] In some embodiments, the elastic modulus of the insulating layer is 200 GPa to 280 GPa.

[0058] With the thickness tolerance of the insulation layer in coordination, the lower limit of the elastic modulus of the insulation layer is adjusted to 200GPa, which prevents the electrode from collapsing in a step-like manner, effectively improves the flatness of the cell, promotes the uniform distribution of the interfacial pressure of the cell, and thus reduces the risk of lithium plating due to uneven interfacial pressure. Furthermore, the upper limit of the elastic modulus of the insulation layer is limited to 280GPa. If the electrode is an anode electrode, it can reduce the risk of the cathode electrode cracking due to reverse elastic stress and effectively improve the cycle life of the electrochemical device.

[0059] For example, the elastic modulus of the insulating layer is 200 GPa, 205 GPa, 210 GPa, 215 GPa, 220 GPa, 225 GPa, 230 GPa, 235 GPa, 240 GPa, 245 GPa, 250 GPa, 255 GPa, 260 GPa, 265 GPa, 270 GPa, 275 GPa, 280 GPa, or falls within the range of any two of the above values.

[0060] In some implementations, the porosity of the insulating layer is 2% to 10%.

[0061] The lower limit of the porosity of the insulating layer is controlled at 2% to release the internal stress of the insulating layer and avoid cracking, while the upper limit of the porosity of the insulating layer is 10% to further reduce the electrolyte erosion channels, hinder ion invasion, and avoid internal short circuits in the electrochemical device.

[0062] For example, the porosity of the insulating layer is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within any two of the above values.

[0063] In some embodiments, the average diameter of the columnar crystals in the insulating layer is 50 nm to 200 nm.

[0064] The lower limit of the average diameter of the columnar crystals in the insulating layer is controlled at 50 nm, which helps to improve the longitudinal strength and hardness of the insulating layer, hinders the contact between electrodes in the electrochemical device, and avoids internal short circuits. The upper limit of the average diameter of the columnar crystals in the insulating layer is controlled at 200 nm, which maintains the intergranular spacing of the columnar crystals in the insulating layer, releases the internal stress of the insulating layer, reduces the probability of cracking of the insulating layer, thereby improving the service life of the insulating layer and improving the cycle life of the electrochemical device.

[0065] For example, the average diameter of the columnar crystals in the insulating layer is 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, or 200nm, or falls within the range of any two of the above values.

[0066] In some implementations, the width of the intercolumn cracks in the insulating layer is 10 nm to 50 nm.

[0067] While controlling the average diameter of the columnar crystals in the insulating layer, the lower limit of the width of the inter-column cracks in the insulating layer is limited to 10 nm. This increases the inter-column crystal spacing in the insulating layer, which is beneficial for the release of internal stress in the insulating layer. Furthermore, controlling the upper limit of the width of the inter-column cracks in the insulating layer to 50 nm not only reduces the electrolyte erosion channels in the insulating layer and hinders ion invasion, but also improves the structural stability of the insulating layer, further preventing cracking and extending the service life of the insulating layer, thereby reducing the risk of short circuits in the electrochemical device.

[0068] For example, the width of the intercolumn crack in the insulating layer is 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm, or falls within the range of any two of the above values.

[0069] In some embodiments, the insulating layer includes at least one of Al2O3, Y2O3-ZrO2, and Gd2Zr2O7.

[0070] By selecting the above materials, the insulation layer can be endowed with superior insulation properties. With the synergy of the alloy layer and thickness adjustment, a thinner and higher bonding strength protective layer can be constructed on the current collector. Thus, after being assembled into an electrochemical device, it can achieve a high physical isolation effect between the electrodes and reduce the risk of internal short circuits.

[0071] In some embodiments, the alloy layer includes M CrAlY and / or M CrAlSiY, M It is selected from one of Co, Ni, NiCo, and CoNi.

[0072] This solution selects M CrAlY and M CrAlSiY, combined M The regulation not only improves the mechanical strength of the electrode after combining with the current collector, but also utilizes the oxidation resistance of the elements in the alloy layer to form a dense oxide film on the current collector, effectively improving the bonding force between the insulation layer and the alloy layer, thereby inhibiting the peeling of the insulation layer. At the same time, the composition of the alloy layer gives it a thermal expansion coefficient that is compatible with the current collector, enabling it to act as a thermal expansion buffer during high-temperature cycling of the electrochemical device, further reducing the risk of insulation layer breakage and peeling. In addition, the alloy layer has a certain degree of conductivity, which, combined with the current collector, serves as a conductive support for the protective layer area, reducing the risk of local current density exceeding the electrode due to insufficient conductivity in the protective layer area during electrochemical device cycling, leading to melting and internal short circuits caused by the protective layer melting and breakdown.

[0073] In some embodiments, the surface roughness of the alloy layer is 0.8µm to 1.2µm.

[0074] Further controlling the surface roughness of the alloy layer, making it act as a rough skeleton, significantly improves the adhesion between the insulating layer and the alloy layer, preventing the insulating layer from detaching and thus reducing the risk of internal short circuits in the electrochemical device. Adjusting the lower limit of the alloy layer surface roughness to 0.8µm helps improve the adhesion between the alloy layer and the insulating layer, while controlling the upper limit of the alloy layer surface roughness to 1.2µm maintains the surface smoothness of the alloy layer, improves the uniformity of the insulating layer, and prevents localized thinning of the insulating layer, which could lead to fractures and cracks and cause internal short circuits in the electrochemical device. In some embodiments, the surface roughness of the alloy layer facing the insulating layer is between 0.8µm and 1.2µm.

[0075] For example, the surface roughness of the alloy layer is 0.8µm, 0.9µm, 1.0µm, 1.1µm, 1.2µm, or within the range of any two of the above values.

[0076] This solution does not impose any particular restrictions on the size of the protective layer, as long as it can achieve physical isolation of the electrode. For example, the size of the protective layer in an electrochemical device may be greater than or equal to the size of the tab.

[0077] This solution does not have any particular limitations on the current collector, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of copper foil and aluminum foil. In some embodiments, the current collector includes copper foil.

[0078] In some implementations, the average thickness of the current collector is 4µm to 8µm.

[0079] Setting the lower limit of the average thickness of the current collector to 4µm can maintain the mechanical properties and conductivity of the current collector, which is beneficial to improving the service life of the electrode. Setting the upper limit of the average thickness of the current collector to 8µm can reduce the overall thickness of the electrode, which is beneficial to the fabrication of thinner electrochemical devices to meet the needs of various application scenarios.

[0080] For example, the average thickness of the current collector is 4µm, 4.5µm, 5.0µm, 5.5µm, 6.0µm, 6.5µm, 7.0µm, 7.5µm, 8.0µm, or within any two of the above values.

[0081] In some embodiments, the alloy layer is obtained by supersonic flame spraying or cold spraying onto at least one surface of the current collector.

[0082] This solution utilizes supersonic flame spraying or cold spraying technology to deposit high-speed metal particle raw materials of the alloy layer onto the surface of the current collector. The metal particles undergo instantaneous plastic deformation, resulting in a dual bonding effect of cold welding and mechanical anchoring with the current collector, achieving metallurgical-mechanical interlocking. This significantly improves the bonding force between the alloy layer and the current collector, and enhances the surface roughness of the alloy layer, which is beneficial for improving the adhesion of the insulation layer.

[0083] This scheme does not impose any particular restrictions on the preparation method of the alloy layer, as long as it can achieve the purpose of this scheme, such as including but not limited to the preparation methods mentioned above.

[0084] In some embodiments, the insulating layer is obtained by plasma thermal spraying or plasma spraying-vapor deposition on the surface of the alloy layer.

[0085] Subsequently, this scheme utilizes plasma thermal spraying technology and plasma spraying-vapor deposition technology to deposit and fill the microscopic peaks and valleys of the alloy layer with raw material particles of the insulating layer, forming columnar or layered insulating layers to achieve the insulating effect of the protective layer. Furthermore, plasma thermal spraying technology is beneficial for preparing an insulating layer with a columnar crystal structure with certain porosity, which helps to release the internal stress of the insulating layer, reduce its cracking risk, thereby improving the service life of the insulating layer and effectively improving the cycle life of the electrochemical device.

[0086] In some embodiments, the voltage of the plasma thermal spraying technology is 28kW to 38kW, the substrate temperature is 180°C to 220°C, and the spraying distance is 80mm to 110mm.

[0087] In some embodiments, the voltage of the supersonic flame spraying technology is 38kW, the spraying distance is 110mm, and the substrate temperature is 180°C. The higher voltage can cause the raw material particles of the ceramic layer to form an extremely fine spray. After passing through a longer distance and at a lower substrate temperature, the ceramic layer can be slowly solidified on the alloy layer and precipitate dense and fine columnar crystals. For example, the average diameter of the columnar crystals is 50~60nm, and the width of the intercolumnar cracks is 10~20nm.

[0088] In other embodiments, the voltage of the supersonic flame spraying technology is 28kW, the spraying distance is 80mm, and the substrate temperature is 220°C. The higher voltage can cause the raw material particles of the ceramic layer to form a fine spray. With the closer distance and higher substrate temperature, the ceramic layer can be rapidly solidified on the alloy layer and precipitate dense and coarse columnar crystals. For example, the average diameter of the columnar crystals is 190~200nm, and the width of the intercolumnar cracks is 40~50nm.

[0089] This solution does not impose any particular restrictions on the preparation method of the insulating layer, as long as it can achieve the purpose of this solution. For example, it may include, but is not limited to, at least one of spraying, coating, printing, and sandblasting.

[0090] In some embodiments, the active material layer includes a positive electrode active material layer and / or a negative electrode active material layer.

[0091] In some embodiments, the positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0092] This solution does not impose any particular restrictions on the positive electrode active material. It can be any positive electrode active material known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode active material layers.

[0093] In some embodiments, the positive electrode active material layer includes a dopant, which includes at least one of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, and Ge.

[0094] This solution does not impose any particular restrictions on the dopant, which can be any dopant known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the dopants mentioned above.

[0095] In some embodiments, the positive electrode active material layer includes a positive electrode binder, which includes at least one of polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropylene, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone, acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer.

[0096] This solution does not impose any particular restrictions on the positive electrode binder, which can be any positive electrode binder known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the positive electrode binders mentioned above.

[0097] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres, Sn, SnO2, SnO, or Li4Ti5O. 12 At least one of Si materials, silicon-carbon composite materials, silicon-nitrogen composite materials, and silicon-oxygen composite materials.

[0098] This solution does not impose any particular restrictions on the negative electrode active material. It can be any negative electrode active material known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode active materials mentioned above.

[0099] In some embodiments, the negative electrode active material layer includes a negative electrode binder; The negative electrode binder includes at least one of the following: polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene.

[0100] This solution does not impose any particular restrictions on the negative electrode binder, which can be any negative electrode binder known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode binders mentioned above.

[0101] In some embodiments, the active material layer includes a conductive agent, which includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, and mesoporous carbon.

[0102] This solution does not impose any particular restrictions on the conductive agent; it can be any conductive agent known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the conductive agents mentioned above.

[0103] In some embodiments, the active material layer includes additives.

[0104] In some embodiments, the additive includes a thickener, which includes at least one of cellulose thickeners, acrylate thickeners, and polyurethane thickeners.

[0105] In some embodiments, the thickener includes at least one of sodium carboxymethyl cellulose, sodium hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polyvinyl alcohol, and polyvinylpyrrolidone.

[0106] This solution does not impose any particular restrictions on the thickener, which can be any thickener known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the thickeners mentioned above.

[0107] In some embodiments, the additive includes a dispersant, which includes surfactant dispersants and / or polymeric dispersants.

[0108] In some embodiments, the dispersant includes at least one of polyvinylpyrrolidone, polyoxyethylene ether, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium lignosulfonate, polyacrylic acid, polymethacrylic acid, sodium polystyrene sulfonate, and sodium carboxymethyl cellulose.

[0109] This solution does not impose any particular restrictions on the dispersant, which can be any dispersant known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the dispersants mentioned above.

[0110] This solution does not impose any particular restrictions on additives, which can be any additives known in the prior art, as long as they can achieve the purpose of this solution. For example, they can include, but are not limited to, at least one of the additives mentioned above.

[0111] In some embodiments, the electrode includes a conductive layer disposed between the current collector and the active material layer. The conductive layer includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0112] This solution does not impose any particular restrictions on the conductive layer, which can be any conductive layer known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the conductive layers mentioned above.

[0113] This solution does not impose any particular restrictions on the position of the electrode tabs. They can be placed in any position known in the prior art, as long as the purpose of this solution can be achieved. For example, they can be placed in the middle of the electrode or at the edge of the electrode.

[0114] This scheme does not impose any particular restrictions on the preparation method of the electrode, as long as it can achieve the purpose of this scheme, such as including but not limited to the preparation methods mentioned above.

[0115] This solution also provides an electrochemical device, which includes an electrode assembly, the electrode assembly including a first electrode, a separator, and a second electrode, the separator being disposed between the first electrode and the second electrode, and the first electrode or the second electrode being an electrode as claimed in any one of claims 1 to 9.

[0116] In some implementations, the first electrode is a positive electrode and the second electrode is a negative electrode; Along the thickness direction of the first electrode, the orthographic projection of the tab of the second electrode lies within the orthographic projection range of the protective layer of the first electrode, and / or, the orthographic projection of the tab of the first electrode lies within the orthographic projection range of the protective layer of the second electrode.

[0117] By sequentially stacking tabs, diaphragms, and protective layers in the electrode assembly, the physical barrier between the tabs of one electrode and another is strengthened, effectively preventing internal short circuits caused by electrode contact.

[0118] The electrochemical devices provided in this solution include any device that performs an electrochemical reaction to convert chemical energy into electrical energy, including but not limited to all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.

[0119] In some embodiments, the electrochemical device includes a lithium secondary battery; Lithium secondary batteries include lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0120] In some embodiments, the electrochemical device also includes an electrolyte.

[0121] In some embodiments, the electrolyte includes at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0122] In some embodiments, the liquid electrolyte includes a non-aqueous solvent; Non-aqueous solvents include at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0123] In some embodiments, the carbonate compound may include at least one of diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butyl carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0124] This scheme does not have any particular restrictions on carbonate compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the carbonate compounds mentioned above.

[0125] In some embodiments, the carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate.

[0126] This scheme does not have any particular restrictions on carboxylic acid ester compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the above-mentioned carboxylic acid ester compounds.

[0127] In some embodiments, the ether compound may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0128] This scheme does not have any particular restrictions on ether compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the above-mentioned ether compounds.

[0129] In some embodiments, the non-aqueous solvent includes at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0130] This method does not impose any particular restrictions on non-aqueous solvents, as long as they can achieve the purpose of this method. For example, it may include, but is not limited to, at least one of the non-aqueous solvents mentioned above. The use of non-aqueous solvents is unrestricted, as long as they can serve as a medium to facilitate the movement of ions participating in the electrochemical reaction of the battery.

[0131] In some embodiments, the liquid electrolyte includes lithium salts; Lithium salts may include at least one of LiPF6, LiBF4, LiBOB, LiB(C6H5)4, LiB(C2O4)2, LiAsF6, LiCl, LiClO4, LiCH3SO3, LiCF3SO3, LiC4F9SO3, LiC(SO2CF3)3, LiN(SO2CF3)2, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiSiF6, LiSbF6, LiAlO4, LiAlCl4, LiI, and lithium difluoroborate.

[0132] This scheme does not impose any particular restrictions on lithium salts, as long as they can achieve the purpose of this scheme. For example, it may include, but is not limited to, at least one of the lithium salts mentioned above. The use of lithium salts is unrestricted, as long as they can participate in the ion movement of the battery electrochemical reaction.

[0133] This solution does not impose any particular restrictions on the electrolyte; it can be any electrolyte known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, at least one of the electrolytes mentioned above.

[0134] This solution also provides an electronic device, which includes any of the electrochemical devices described herein.

[0135] The electronic device in this solution is not particularly limited and can be any electronic device known in the prior art. The electrochemical device in this solution is not particularly limited in its application and can be used with any electronic device known in the prior art. According to some embodiments of this solution, 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, robotic dogs, industrial robots, and android robots.

[0136] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the reagents used, unless otherwise specified, are commercially available reagents and materials. The source information of the raw materials used in the following examples and comparative examples is for illustrative purposes only and does not constitute any restriction on the procurement of raw materials. Those skilled in the art will know that the relevant raw materials can be obtained through other commercial channels or prepared by conventional methods in the art.

[0137] Example 1 1. After plasma cleaning of a specific area of ​​a 4µm to 8µm copper foil, a 3µm alloy layer is formed by supersonic flame spraying or cold spraying with CoNiCrAlY. Subsequently, a 12µm insulating layer is formed by plasma thermal spraying or plasma spraying-vapor deposition of Al2O3, resulting in an electrode with a protective layer. The specific area is the edge of the copper foil tab, and / or, in an electrochemical device, when the electrode is an anode, the projection of the cathode tab in the first direction falls on the specific area of ​​the anode. The surface roughness of the alloy layer facing the insulating layer is 1µm, the thickness tolerance of the insulating layer is 0.2µm, the thermal conductivity is 1.5W / (m·K), the elastic modulus is 230GPa, and the porosity is 6%.

[0138] 2. Preparation of the negative electrode: The negative electrode active material artificial graphite, conductive agent SuperP, binder styrene-butadiene rubber and thickener sodium carboxymethyl cellulose in a mass ratio of 98:0.5:1:0.5 are thoroughly mixed in deionized water to obtain a negative electrode slurry. The negative electrode slurry is coated on the active material layer area of ​​the electrode sheet, dried, cold-pressed, slit, dried under vacuum at 85°C for 6 hours, and the tabs are welded to obtain the negative electrode. The thickness T1 of the active material layer of the negative electrode sheet is 10µm.

[0139] 3. Preparation of the positive electrode: The positive electrode active material lithium cobalt oxide, the conductive agent SuperP and the binder polyvinylidene fluoride in a mass ratio of 96:2:2 are thoroughly mixed in the solvent N-methylpyrrolidone to obtain a positive electrode slurry. The positive electrode slurry is coated on the current collector aluminum foil and then dried at 85°C. Subsequently, it is cold-pressed, trimmed and slit in sequence, and then dried under vacuum at 85°C for 6 hours. The tabs are then welded to obtain the positive electrode.

[0140] 4. Preparation of the separating membrane: Commercially available porous polyethylene membrane is used.

[0141] 5. Electrolyte: Composed of organic solvent and lithium hexafluorophosphate; the organic solvent is a mixture of methyl ethyl carbonate, dimethyl carbonate and ethylene carbonate in a mass ratio of 1:1:1; the concentration of lithium hexafluorophosphate is 1 mol / L.

[0142] 6. Preparation of Lithium-ion Secondary Batteries: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrodes are then wound to obtain the electrode assembly. The electrode assembly is placed in a packaging shell, injected with electrolyte, and sealed to obtain a lithium-ion secondary battery.

[0143] Example 2 The difference between Example 2 and Example 1 is: The average thickness T3 of the insulating layer is 10µm, and the thickness T of the protective layer is... A It is 13µm, T1-5 < T A <T1+5; The rest are as described in Example 1.

[0144] Example 3 The difference between Example 3 and Example 1 is: The thickness T1 of the active material layer of the negative electrode is 20µm, and T1-5=T A ; The rest are as described in Example 1.

[0145] Example 4 The difference between Example 4 and Example 1 is: The thickness of the alloy layer T2 is 1.67µm, and the thickness of the insulating layer T3 is 5µm; The rest are as described in Example 1.

[0146] Example 5 The difference between Example 5 and Example 1 is: The thickness of the alloy layer T1 is 1µm, the thickness of the insulating layer T2 is 20µm, and the thickness of the active material layer of the negative electrode sheet T1 is 16µm. The rest are as described in Example 1.

[0147] Example 6 The difference between Example 6 and Example 1 is: The thickness of the alloy layer T2 is 1µm, and the thickness of the insulating layer T3 is 8µm; The rest are as described in Example 1.

[0148] Example 7 The difference between Example 7 and Example 1 is: The thickness of the alloy layer T2 is 5µm, the thickness of the insulating layer T3 is 18µm, and the thickness of the active material layer of the negative electrode sheet T1 is 18µm. The rest are as described in Example 1.

[0149] Example 8 The difference between Example 8 and Example 1 is: The thickness tolerance of the insulation layer is 0.05µm; The rest are as described in Example 1.

[0150] Example 9 The difference between Example 9 and Example 1 is: The thickness tolerance of the insulation layer is 2µm; The rest are as described in Example 1.

[0151] Example 10 The difference between Example 10 and Example 1 is: The thermal conductivity of the insulating layer is 0.8 W / (m·K); The rest are as described in Example 1.

[0152] Example 11 The difference between Example 11 and Example 1 is: The thermal conductivity of the insulating layer is 2.5 W / (m·K); The rest are as described in Example 1.

[0153] Example 12 The difference between Example 12 and Example 1 is: The elastic modulus of the insulation layer is 200 GPa; The rest are as described in Example 1.

[0154] Example 13 The difference between Example 13 and Example 1 is: The elastic modulus of the insulation layer is 280 GPa; The rest are as described in Example 1.

[0155] Example 14 The difference between Example 14 and Example 1 is: The porosity of the insulating layer is 2%; The rest are as described in Example 1.

[0156] Example 15 The difference between Example 15 and Example 1 is: The porosity of the insulating layer is 10%; The rest are as described in Example 1.

[0157] Example 16 The difference between Example 16 and Example 1 is: After plasma cleaning of a specific area of ​​the copper foil, CoCrAlSiY is sprayed by supersonic flame or cold spray to form an alloy layer. The rest are as described in Example 1.

[0158] Example 17 The difference between Example 17 and Example 1 is: The surface roughness of the alloy layer facing the insulating layer is 0.8µm; The rest are as described in Example 1.

[0159] Example 18 The difference between Example 18 and Example 1 is: The surface roughness of the alloy layer facing the insulating layer is 1.2µm; The rest are as described in Example 1.

[0160] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: The average thickness T3 of the insulating layer is 1µm, and the thickness T of the protective layer is... A 4µm, T1-5 > T A ; The rest are as described in Example 1.

[0161] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is as follows: The average thickness T3 of the insulating layer is 15µm, and the thickness T of the protective layer is... A The value is 18µm, and T1+5 > T. A ; The rest are as described in Example 1.

[0162] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is as follows: An insulating layer is directly prepared after plasma cleaning of a specific area of ​​the copper foil. The rest are as described in Example 1.

[0163] Test method: 1. Peel strength between insulation layer and alloy layer, and between current collector and alloy layer: The samples were cut into 25mm strips for testing. A layer of double-sided tape was adhered to a steel plate. The sample to be tested was placed flat and lightly pressed onto the double-sided tape. Then, a layer of test tape was adhered on top of the sample. The sample was repeatedly rolled three times under 2000g conditions. One end of the tape was then torn to the middle of the sample. A tensile testing machine was used to peel the sample at a 90-degree angle for 1 minute at a peel speed of 50mm / min. The tensile force and the width of the test tape were recorded. The same sample was tested three times. The peel force was obtained by dividing the tensile force by the width of the test tape, and the average value was calculated as the peel strength. The negative electrode sheet was used as a sample to test the peel strength between the insulation layer and alloy layer, serving as the peel strength of the protective layer. The copper foil with the alloy layer was used as a sample to test the peel strength between the current collector and the alloy layer.

[0164] 2. Volumetric Energy Density: After the pre-electrode is prepared into a battery, it is charged at 0.1C rate in an environment of 25°C until the upper limit voltage is 4.3V. Then, it is discharged at constant current rate of 1C until the final voltage is 3V. The discharge capacity of the first cycle is recorded as the total capacity C of the battery. At the same time, the volume V of the battery is tested. According to the formula: Volumetric Energy Density = C / V, the volumetric energy density of five batteries of the same embodiment or comparative example is tested repeatedly, and the average value is taken as the volumetric energy density of the embodiment or comparative example.

[0165] 3. Cycle Retention Rate: After the pre-electrode is fabricated into a battery, it is charged at 45°C and a 1C rate until the upper limit voltage reaches 4.3V. Then, it is discharged at a constant current rate of 1C until the final voltage reaches 3V. The discharge capacity of the first cycle is recorded as C1. After repeating the charge-discharge cycle 1200 times, the discharge capacity of the 1200th cycle is recorded as C. 1200 Repeat the tests on C1 and C of five batteries from the same embodiment or comparative example. 1200 And calculate C respectively 1200 100% / C1, take the average value as the battery's cycle capacity retention rate.

[0166] Some process parameters of Examples 1 to 18 and Comparative Examples 1 to 3 are shown in Table 2.

[0167] Table 2. Partial process parameters of Examples 1-18 and Comparative Examples 1-3 According to the above test method, the performance of the negative electrode sheets prepared in Examples 1 to 18 and Comparative Examples 1 to 3 were tested respectively; the performance data of Examples 1 to 18 and Comparative Examples 1 to 3 are shown in Table 3.

[0168] Table 3. Performance data of Examples 1-18 and Comparative Examples 1-3 Among them, the battery prepared in Comparative Example 1 showed brittleness in its insulating layer after being disassembled after cycling; the electrode prepared in Comparative Example 3 had a peel strength of 7 N / cm between its insulating layer and current collector.

[0169] By combining Tables 2 and 3, Figures 1 to 8 It can be known that: The electrode prepared in Example 2 exhibited optimal performance, with peel strengths of 16 N / cm between the alloy layer and the current collector, and 20 N / cm between the insulating layer and the alloy layer, indicating excellent adhesion between the protective layer and the current collector. The volumetric energy density was 835 Wh / L, and the cycle retention rate was 95%, verifying that the electrode provided in this application can improve the volumetric energy density and cycle life of the battery.

[0170] Referring to Examples 1-3 and Comparative Examples 1-2, from T1-5 < T A <T1+5 changes to the comparative T1-5>T A and T A >T1+5, the volumetric energy density decreased by at least 50Wh / L, indicating that within a certain thickness range, the protective layer and active material layer can reduce the ineffective space of the battery and improve the volumetric energy density. Furthermore, the peel strength and cycle retention rate decreased by at least 10N / cm and 11%, respectively, verifying that within this range, the alloy layer can work synergistically with the insulating layer to improve the adhesion of the entire protective layer structure and the current collector, avoid protective layer breakage, and effectively improve the cycle performance of the battery.

[0171] Referring to Examples 1 and 2, Examples 4-5, and Comparative Example 1, the volumetric energy density changed from 835Wh / L to 793Wh / L and 775Wh / L when the insulation layer thickness was varied from 10μm to 5μm and 20μm. This shows that an insulation layer of suitable thickness can improve the internal space of the battery and increase the volumetric energy density of the battery. However, the volumetric energy density of Comparative Example 1 with a 1μm insulation layer was only 750Wh / L, and the cycle retention rate decreased by 17%, and brittleness was also observed. This verifies that an insulation layer that is too thin is difficult to improve the internal space of the battery, and its poor protective performance will lead to a decrease in the volumetric energy density and cycle performance of the battery.

[0172] Referring to Examples 1 and 6-7, when the alloy layer thickness was changed from 3 μm to 5 μm, the peel strength between the alloy layer and the current collector increased by at least 2 N / cm, but the volumetric energy density decreased by 22 Wh / L. This indicates that a thicker alloy layer can have stronger adhesion, but it will slightly sacrifice the volumetric energy density of the battery. When the alloy layer thickness was changed to 1 μm, the peel strength decreased by at least 5 N / cm, verifying that an excessively thin alloy layer has a poor effect on improving the adhesion of the protective layer, resulting in a decrease in the cycle performance of the battery.

[0173] Referring to Examples 1 and 8-9, the thickness tolerance of the insulating layer was adjusted from 0.05μm and 2μm to 0.2μm, the volumetric energy density increased from 785Wh / L and 795Wh / L to 800Wh / L, and the cycle retention rate increased slightly from 86% and 89% to 92%. This verifies that an insulating layer with appropriate thickness tolerance can reduce the surface height difference of the electrode, help reduce the ineffective space inside the battery, and improve the volumetric energy density and cycle life of the battery.

[0174] Combining Examples 1 and 10-15, the peel strength of the insulation layer-alloy layer in Example 1 increased by at least 6 N / cm, indicating that the insulation layer with suitable thermal conductivity, elastic modulus and porosity can have excellent adhesion to the alloy layer. Furthermore, the volumetric energy density and cycle retention rate of Example 1 increased by at least 15 Wh / L and 7%, respectively, further verifying that the insulation layer can provide excellent insulation protection for the protective layer area of ​​the electrode, effectively improving the cycle life of the battery. In addition, the combination of the protective layer and the active material layer improves the internal space of the battery and improves the volumetric energy density of the battery.

[0175] Referring to Examples 1 and 16, and Comparative Example 3, the performance of the electrodes and batteries prepared in Examples 1 and 16 was similar after adjusting the type of alloy layer. However, the peel strength between the insulating layer and the current collector in Comparative Example 3, where the alloy layer was removed, was only 7 N / cm, indicating that the alloy layer improved the adhesion of the protective layer. Moreover, the volumetric energy density and cycle retention rate decreased by 45 Wh / L and 15%, respectively, further verifying that setting an alloy layer in the protective layer helps to improve the volumetric energy density and cycle life of the battery.

[0176] Referring to Examples 1 and 17-18, the surface roughness of the alloy layer was adjusted from 1 μm to 0.8 μm and 1.2 μm, the peel strength between the alloy layer and the current collector changed from 15 N / cm to 13 N / cm and 17 N / cm, and the peel strength between the insulation layer and the alloy layer changed from 18 N / cm to 10 N / cm and 14 N / cm. This shows that the alloy layer with suitable surface roughness can improve the adhesion between the insulation layer and the alloy layer, and indirectly improve the adhesion between the protective layer and the current collector. Furthermore, the volumetric energy density improved from 782-788 Wh / L to 800 Wh / L, and the cycle retention rate improved from 80-83% to 92%, further verifying the improvement in battery volumetric energy density and cycle life.

[0177] Referring to Examples 1 and 2, Examples 4-7, and Comparative Example 1, T2:T3 has been adjusted to some extent, but as can be seen from Examples 4 and 6, T2:T 3= Compared to out-of-range performance data, the 1:3 to 1:8 ratio is superior, with volumetric energy density and cycle retention increasing by at least 18Wh and 2% respectively, demonstrating that setting a certain ratio of protective layer can have a more significant effect on improving battery volumetric energy density and cycle life.

[0178] Based on comparative examples 1-18 and comparative examples 1-3, this application, through a protective layer including an alloy layer and an insulating layer, and by comprehensively adjusting the thickness and relationship of each layer, as well as adjusting parameters, prepares a protective layer with strong adhesion and insulation in a specific area of ​​the electrode, thereby achieving thinning of the protective layer while maintaining its mechanical properties, thus improving the volumetric energy density and cycle life of the battery.

[0179] The above description is only a part or preferred embodiment of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. An electrode sheet, characterized in that, include: Extreme ear; current collector; An active material layer is disposed on at least one surface of the current collector; A protective layer is disposed on the surface of the current collector and adjacent to the active material layer; The protective layer is also adjacent to the tab, or, along the thickness direction of the electrode, the orthographic projection of the tab is located within the orthographic projection range of the protective layer; the protective layer includes an alloy layer and an insulating layer, the alloy layer is disposed on the surface of the current collector, and the insulating layer is disposed on the side of the alloy layer away from the current collector; wherein the average thickness of the protective layer is T A μm, the thickness of the active material layer is T1 μm, the thickness of the alloy layer is T2 μm, the average thickness of the insulating layer is T3 μm, T A and T1 satisfy: T1 - 5 ≤ T A ≤ T1 + 5; T A T2 and T3 satisfy: T A =T2+T3, 1µm≤T2≤5µm, 5µm≤T3≤20µm, and 1:3≤T2:T3≤1:

8.

2. The electrode sheet according to claim 1, characterized in that, The insulating layer includes at least one inclined surface that is close to the plane where the current collector is located in a direction away from the active material layer.

3. The electrode sheet according to claim 2, characterized in that, The angle between the extended surface of the inclined plane and the plane containing the current collector is 5° to 75°.

4. The electrode sheet according to claim 3, characterized in that, The thickness tolerance of the insulating layer is ≤2µm.

5. The electrode sheet according to claim 1, characterized in that, The thermal conductivity of the insulating layer is from 0.8 W / (m·K) to 2.5 W / (m·K); and / or, The elastic modulus of the insulating layer is 200 GPa to 280 GPa; and / or, The porosity of the insulating layer is 2% to 10%.

6. The electrode sheet according to claim 5, characterized in that, The average diameter of the columnar crystals in the insulating layer is 50 nm to 200 nm; and / or, The width of the intercolumn cracks in the insulating layer is 10 nm to 50 nm.

7. The electrode sheet according to claim 1, characterized in that, The alloy layer includes M CrAlY and / or M CrAlSiY, M It is selected from one of Co, Ni, NiCo, and CoNi.

8. The electrode sheet according to claim 7, characterized in that, The surface roughness of the alloy layer is 0.8µm to 1.2µm.

9. An electrochemical device, characterized in that, The electrochemical device includes an electrode assembly, which includes a first electrode, a separator, and a second electrode. The separator is disposed between the first electrode and the second electrode. The first electrode or the second electrode is an electrode as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, The electronic device includes the electrochemical device according to claim 9.

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