A pole piece and a battery

Abstract

This invention provides an electrode and a battery that improve battery safety performance. The battery provided by this invention improves battery safety performance by providing an insulating layer near the edge of the current collector close to the tab, with the insulating layer partially extending to the surface of the tab. This reduces the generation of burrs at the electrode edge during electrode cutting. Furthermore, by controlling the color difference between the insulating layer and the empty foil area, the uniformity and good coating quality of the insulating layer can be ensured, thereby improving the sealing performance, electrolyte stability, and battery performance of the lithium-ion battery. This contributes to improving the battery's reliability, safety, and overall performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to an electrode and a battery. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density, long cycle life, and environmental friendliness, and are widely used in portable electronic products, new energy vehicles, and other fields. After the electrode sheets of lithium-ion batteries are coated with slurry, dried, and rolled, they need to be cut according to the battery's design structure and specifications.

[0003] Currently, electrode sheets are typically cut using die-cutting and laser cutting. Both methods easily create burrs on the electrode edges during cutting. These burrs can puncture the separator inside the battery, causing an internal short circuit and posing a safety risk. In other words, the safety performance of batteries using existing technology is relatively low. Summary of the Invention

[0004] In view of this, embodiments of the present invention aim to provide an electrode and a battery that improve the safety performance of the battery.

[0005] A first aspect of the present invention provides an electrode sheet, the electrode sheet comprising a current collector and a tab, the tab being disposed on one side of the current collector; The current collector has an insulating layer on at least one side surface near the edge of the electrode tab, and at least a portion of the insulating layer extends to the surface of the electrode tab; The tab includes an empty foil area, and the color difference ΔE1 between the insulating layer and the empty foil area is 8~43.

[0006] A second aspect of the present invention provides a battery comprising the electrode provided in the first aspect of the present invention.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: The current collector of this invention has an insulating layer at its edge near the tab side, and at least a portion of the insulating layer extends to the tab surface. This reduces the generation of burrs at the electrode edge during electrode cutting, thereby improving battery safety. Furthermore, by controlling the color difference ΔE1 between the insulating layer and the empty foil area, the uniformity and good coating quality of the insulating layer can be ensured, thereby improving the sealing performance, electrolyte stability, and battery performance of the lithium-ion battery. This contributes to improving the battery's reliability, safety, and overall performance.

[0008] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0009] Figure 1 The image shown is one of the front views of the electrode sheet provided by the present invention.

[0010] Figure 2 The image shown is a second front view of the electrode sheet provided by this invention.

[0011] Figure 3 The image shown is a third front view of the electrode sheet provided by this invention.

[0012] Figure 4 The image shown is a cross-sectional view of the electrode sheet provided by the present invention.

[0013] Figure 5 The image shown is one of the schematic diagrams of electrode cutting provided by the present invention.

[0014] Figure 6 The image shown is a second schematic diagram of electrode cutting provided by the present invention.

[0015] Explanation of reference numerals in the attached figures: Current collector 10, tab 20, active material layer 11, insulating layer 12, miscible layer 13, empty foil area 21. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 and 4 The present invention provides an electrode sheet, including a current collector 10 and an electrode tab 20, wherein the electrode tab 20 is disposed on the first side of the current collector 10; The current collector 10 has an insulating layer 12 on at least one side surface near the edge of the electrode 20, and at least a portion of the insulating layer 12 extends to the surface of the electrode 20. The tab 20 includes an empty foil area 21, and the color difference ΔE1 between the insulating layer 12 and the empty foil area 21 is 8~43.

[0018] It should be noted that the chromaticity value E includes the lightness value L, the red-green value a, and the yellow-blue value b. Color difference ΔE = (ΔL / b) 2 +Δa 2 +Δb 2 ) 1 / 2 Regarding the color difference between the insulating layer 12 and the empty foil area 21, ΔL, Δa, and Δb are the differences in L, a, and b between the empty foil area 21 and the insulating layer 12, respectively, i.e., ΔL1, Δa1, and Δb1, where ΔE1 = (ΔL1, Δa1, Δb1). 2 +Δa1 2 +Δb1 2 ) 1 / 2 .

[0019] The color difference between the insulation layer and the uncoated foil area provides a reliable indicator for assessing the coating quality and uniformity of the insulation layer. If this color difference ΔE1 exceeds the range of 8 to 43, it may indicate a defect in the insulation coating, such as the presence of voids or uneven coating. This indicator helps manufacturers identify and correct these problems in a timely manner, ensuring a good seal between the insulation layer and the tabs, avoiding cutting burrs caused by coating defects, thus preventing battery leakage and improving battery safety.

[0020] Furthermore, by maintaining the color difference between the insulating layer and the empty foil area within 8 to 43 degrees, a tight bond between the insulating layer and the tabs can be ensured, preventing electrolyte from seeping in from the edges of the electrode. This helps maintain electrolyte stability, avoids electrolyte corrosion and harmful reactions, and improves battery safety and stability.

[0021] Furthermore, uniform coating of the insulating layer can improve the performance and consistency of multi-tab cells. A uniform insulating layer provides good insulation performance, preventing internal short circuits at the electrode edges. This helps improve the battery's cycle life, capacity retention, and power output.

[0022] Furthermore, in this embodiment of the invention, by making the color difference between the empty foil area and the insulating layer range from 8 to 43, the accuracy of the positioning and cutting position can be improved, thereby cutting the electrode sheet from a suitable cutting position and reducing the generation of burrs on the electrode sheet edge.

[0023] In summary, by controlling the color difference between the insulating layer and the empty foil area, the uniformity and good coating quality of the insulating layer can be ensured, thereby improving the sealing performance, electrolyte stability, and battery performance of lithium-ion batteries. This contributes to improving the reliability, safety, and overall performance of the battery.

[0024] In this invention, the electrode can be either a positive electrode or a negative electrode. When the electrode is a positive electrode, the current collector can be aluminum foil, and the tab can be made of aluminum. When the electrode is a negative electrode, the current collector can be copper foil, and the tab can be made of nickel or nickel-plated copper.

[0025] In this invention, the insulating layer may include a first insulating material and a second insulating material.

[0026] In one embodiment, the first insulating material comprises polyamic acid; the second insulating material comprises at least one of polyimide, polyamide-imide, polyether-imide, polyester-imide, polyurea-imide, and siloxane-polyimide. The mass of the first insulating material ranges from 90% to 99.9% of the total mass of the insulating layer.

[0027] The mass of the first insulating material can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% of the total mass of the insulating layer.

[0028] The mass of the second insulating material can range from 10% to 0.01% of the total mass of the insulating layer. Specifically, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.01%.

[0029] In this invention, the methods for obtaining the above-mentioned electrode tabs include, but are not limited to, the following two: Method 1: The tab is formed by die-cutting the current collector; Method 2: The tab is formed by welding a metal sheet onto the current collector.

[0030] In both methods, an insulating layer extending to the surface of the tabs prevents short circuits between the tabs and the encapsulation film (such as aluminum-plastic film) during electrode encapsulation. Furthermore, heating during encapsulation allows the insulating layer to be thermally melted and sealed to the encapsulation film, preventing battery leakage and improving battery safety.

[0031] Furthermore, for the first method described above, by extending the insulating layer to the surface of the tab, the generation of burrs at the edge of the current collector can be reduced when the current collector is die-cut to form the tab (i.e., the generation of burrs at the edge of the electrode sheet is reduced), thereby improving the safety performance of the battery.

[0032] Furthermore, the electrode tabs may be provided only on one side of the current collector, or they may be provided on both sides of the current collector.

[0033] Furthermore, an insulating layer can be provided only on one surface of the current collector, that is, only on the surface that first comes into contact with the cutting tool, in order to reduce the generation of burrs when the electrode is cut, while an active layer is provided at the corresponding position on the other surface of the current collector to improve the energy density of the battery.

[0034] Alternatively, an insulating layer can be provided on the edge areas near the tabs on both surfaces of the current collector to improve the effect of reducing burr generation when the electrode is cut.

[0035] In this invention, the methods for cutting the electrode sheets include, but are not limited to, the following two: Method 1: For example Figure 5 As shown, a large electrode is cut once (cut along the dotted line) to obtain two electrodes; Method 2: For example Figure 6 As shown, a large electrode is cut twice (along the dotted line) to obtain three electrodes.

[0036] Therefore, in practical applications, one side of the current collector may be the side being cut, or both sides of the current collector may be the side being cut. In an optional embodiment, such as... Figure 2 and 4 As shown, an insulating layer 12 is also provided on at least one side of the edge of the current collector 10 away from the tab side. The edge region of the current collector 10 away from the tab side is located on one side of the current collector 10, and is on opposite sides to the edge region of the current collector 10 near the tab side.

[0037] In this embodiment, both sides of the current collector 10 are the cut sides. Therefore, by providing an insulating layer 12 in both the edge region of the current collector 10 away from the tab and the edge region near the tab, when the electrode is cut on both sides, burrs can be avoided on the edge of the current collector away from the tab, thereby further improving the safety performance of the battery.

[0038] In this invention, such as Figure 1 and Figure 4 As shown, the electrode also includes an active material layer 11 located on at least one side of the current collector 10. The color difference ΔE2 between the insulating layer and the active material layer is greater than the color difference ΔE1 between the insulating layer and the empty foil area. This design reminds operators to promptly identify and mark unconnected electrodes, preventing breakage of unconnected areas during subsequent processes due to differences in material strength.

[0039] In one embodiment, the color difference ΔE2 between the insulating layer and the active material layer is 68~111. ΔE2 is calculated similarly to ΔE1 described above, ΔE2 = (ΔL2) / (ΔE1) 2 +Δa2 2 +Δb22 ) 1 / 2 Here, ΔL2, Δa2, and Δb2 represent the differences in L, a, and b between the active material layer and the insulating layer, respectively. It should be noted that when ΔE2 is less than 68, the color difference between the insulating layer and the active material layer is small, resulting in an even smaller color difference at their interface. This makes it difficult to accurately distinguish the positions of the insulating and active material layers, leading to a greater distance between them and increasing the risk of breakage at the gap, thus affecting battery safety. Conversely, when ΔE2 is greater than 111, the color of the insulating layer becomes very light, potentially making it difficult to accurately distinguish the insulating layer from the empty foil area. This compromises the tight bond between the insulating layer and the electrode tab, allowing electrolyte to seep in from the electrode edges and affecting battery stability. Therefore, it is necessary to control the color difference ΔE2 between the insulating layer and the active material layer within the range of 68 to 111.

[0040] In this invention, the testing method for the aforementioned chromaticity parameters luminance L, red-green value a, and yellow-blue value b is as follows: First, the colorimeter is calibrated in air and on white paper; then, the sample to be tested is aligned with the test aperture of the colorimeter, and the chromaticity values ​​(L, a, b) of the sample can be obtained on the colorimeter display interface. Under normal circumstances, these chromaticity parameters will change with the content of the main substance in the sample, but this does not mean that a high content of the main substance will result in a high chromaticity. The specific changes are related to the chromaticity parameters of the main substance, and the chromaticity parameters of layered samples are related to their thickness. It should be understood that the changes in these chromaticity parameters are related not only to the content of the main substance in the sample but also to its thickness, width, etc., and should not be limited to the content of the substance.

[0041] In one embodiment, the brightness L of the insulating layer ranges from 78 to 100, the red-green value a of the insulating layer ranges from -9 to 3, and the yellow-blue value b of the insulating layer ranges from 5 to 32. The chromaticity of the insulation layer (i.e., brightness value, red-green value, and yellow-blue value) provides a reliable indicator for assessing the coating quality and uniformity of the insulation layer. If the chromaticity exceeds the specified range, it may indicate a defect in the insulation layer coating, such as the presence of voids or uneven coating. This indicator helps manufacturers identify and correct these problems in a timely manner, ensuring a good seal between the insulation layer and the tabs, preventing battery leakage, and improving battery safety and stability. Furthermore, a uniform insulating layer provides excellent insulation, preventing internal short circuits at the electrode edges. This helps improve the battery's cycle life, capacity retention, and power output.

[0042] In one embodiment, the brightness value L of the empty foil area ranges from 70 to 95, the red-green value a of the empty foil area ranges from -2 to 2, and the yellow-blue value b of the empty foil area ranges from -5 to 2. The chromaticity (i.e., brightness value, red-green value, and yellow-blue value) of the empty foil area can provide a reliable indicator for assessing the impact of the foil in the empty foil area on the materials attached to it. Exceeding this range will cause the adhesion performance of the active material in the active layer and the insulating material in the insulating layer to the foil to deteriorate, making the material on the foil easy to fall off after liquid filling, thus causing the cell to be scrapped directly and the safety performance of the battery to decline.

[0043] In one example, the brightness value L of the active material layer is greater than 0 and less than or equal to 10, the red-green value a of the active material layer is in the range of -10 to 10, and the yellow-blue value b of the active material layer is in the range of -10 to 10. The chromaticity of the active material layer (i.e., brightness value, red-green value, and yellow-blue value) can provide a reliable indicator for assessing whether the content of the main material in the active material layer is within the appropriate range. Exceeding this range indicates that the content of the main material in the active material layer is too high or too low, which will increase the risk of lithium plating in the cell or the risk of low cell capacity, thereby affecting the cycle life, capacity retention, and power output of the battery.

[0044] In this invention, when the aforementioned electrode is a positive electrode, the active material layer includes a positive electrode active material, which comprises a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials; the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, etc., with a content of 0.1%-10%; the binder includes at least one of polyvinylidene fluoride, sodium hydroxycellulose, lithium hydroxycellulose, styrene-butadiene rubber, polyacrylic acid, a monomer or copolymer of tetrafluoroethylene and hexafluoropropylene, polyvinyl alcohol, etc., with a binder content of 0.1%-10%.

[0045] In this invention, see Figure 3 and Figure 4 At least a portion of the active material layer 11 and at least a portion of the insulating layer 12 are adjacent to form a miscible layer 13, wherein the color difference ΔE3 between the miscible layer 13 and the insulating layer 12 is greater than the color difference ΔE4 between the miscible layer 13 and the active material layer 11. See Figure 3A miscible layer 13 is provided between the active material layer 11 and the insulating layer 12. The presence of the miscible layer 13 ensures a tight connection between the active material layer 11 and the insulating layer 12, creating a transition zone between the active material and the insulating material with different properties. This prevents the electrode from easily breaking at the gap between the active material layer and the insulating layer. Therefore, by setting the miscible layer, the overall strength of the electrode is improved, thereby enhancing the safety and stability of the battery. Furthermore, by controlling the color difference ΔE3 between the miscible layer and the insulating layer to be greater than the color difference ΔE4 between the miscible layer and the active material layer, it is possible to ensure the presence of active material in the main structure of the miscible layer, ensuring the connection between the insulating layer and the active material layer. The insulating layer includes organic matter, and its strength and flexibility are higher than those of the inorganic active material layer. The presence of the miscible layer is equivalent to a transition zone between the two materials, which helps to enhance the stability of the electrode sheet during each process, prevent electrode sheet breakage, increase the yield of each process, and thus further improve the safety performance of the battery.

[0046] In this invention, the color difference ΔE3 between the miscible layer and the insulating layer is 63~108. The calculation method for ΔE3 is similar to that for ΔE1, ΔE3 = (ΔL3) / (ΔE1) 2 +Δa3 2 +Δb3 2 ) 1 / 2 ΔL3, Δa3, and Δb3 represent the differences in L, a, and b between the mixed layer and the insulating layer, respectively. It should be noted that when ΔE3 is less than 63, it indicates a low proportion of active material in the mixed layer, resulting in insufficient bonding between the active and insulating materials. This affects the stability of the bond, making the gaps prone to breakage and impacting battery safety. Conversely, when ΔE3 is greater than 108, a low proportion of insulating material in the mixed layer also leads to insufficient bonding between the active and insulating materials, affecting the stability of the bond and thus impacting battery safety. Therefore, the color difference ΔE3 between the mixed layer and the active material layer needs to be controlled within the range of 63 to 108.

[0047] In this invention, the color difference ΔE4 between the miscible layer and the active material layer is 0~25. The calculation method for ΔE4 is similar to that for ΔE1, ΔE4 = (ΔL4) / (ΔE1) 2 +Δa4 2 +Δb4 2 ) 1 / 2 Where ΔL4, Δa4, and Δb4 are the differences in L, a, and b between the active material layer and the miscible layer, respectively. It should be noted that when ΔE4 is greater than 25, it indicates that the proportion of active material in the miscible layer is too low, and the bonding between the active material and the insulating material is insufficient, affecting the stability between the two and thus impacting the battery's safety performance. Therefore, the color difference ΔE4 between the miscible layer and the active material layer needs to be controlled within the range of 0 to 25.

[0048] In one example, the color difference ΔE4 between the miscible layer and the active material layer is in the range of 8 to 25.

[0049] In one embodiment, the brightness value L of the miscible layer ranges from greater than 0 to less than or equal to 15, the red-green value a of the miscible layer ranges from -4 to 4, and the yellow-blue value b of the miscible layer ranges from -4 to 4. By controlling the above parameters within a suitable range, the proportions of active and insulating materials in the miscible layer can be ensured to be appropriate, thereby improving the bonding stability between the active and insulating materials. This is beneficial for enhancing the stability of the electrode sheet during each process, preventing electrode sheet breakage, increasing the yield of each process, and further improving the safety performance of the battery.

[0050] In the specific implementation of this invention, a charge-coupled device (CCD) camera is mainly used to identify the empty foil area, insulating layer, and active material layer on the electrode sheet to determine the location for cutting the electrode sheet. To ensure that the CCD camera successfully identifies the location to be cut, the chromaticity of the empty foil area, insulating layer, and active material layer on the electrode sheet, as well as the color difference between them, needs to be defined. For example, if the color difference ΔE1 between the empty foil area and the insulating layer is less than 8, the CCD camera cannot identify the insulating layer and will issue an NG alarm. An alarm will also be issued when the CCD camera cannot identify other areas. When the color difference ΔE1 between the empty foil area and the insulating layer is greater than or equal to 8, the insulating layer can be identified by the CCD camera, and the relative position of the insulating layer and the active material layer, as well as whether they are connected, can be determined.

[0051] In this invention, the brightness value L of the active material layer, the miscible layer, and the insulating layer gradually increases, that is, the brightness of the insulating layer is relatively enhanced. This setting facilitates the identification of CCD cameras in each process, which is beneficial for the positioning and differentiation of the electrode sheet in processes such as die-cutting and winding, and helps to improve production efficiency.

[0052] In practical applications of this invention, if the width of the miscible layer in the tab extension direction is too short, the effect of improving the overall strength of the electrode is not significant; if the width of the miscible layer in the tab extension direction is too long, it will compress the space of the active material layer, resulting in a reduction in the total amount of active material and thus a lower battery energy density. To solve the above problems, in an optional embodiment, the width of the miscible layer in the tab extension direction is 25μm to 500μm; specifically, the width of the miscible layer in the tab extension direction can be 25μm, 50μm, 100μm, 200μm, 300μm, 400μm, or 500μm. The direction of the above-mentioned "width" value is parallel to the tab extension direction.

[0053] To prevent the active material layer from being missed during electrode rolling, in an optional embodiment, the thickness of the insulating layer is less than the thickness of the active material layer. In this embodiment, by limiting the thickness of the insulating layer to be less than the thickness of the active material layer, it is possible to prevent the active material layer from being missed during rolling, thereby avoiding safety accidents caused by uneven electrode surfaces.

[0054] To save costs and ensure reduced burr formation, in an optional embodiment, the thickness of the insulating layer 12 is 3μm to 30μm; specifically, the thickness of the insulating layer can be 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, or 30μm. When the thickness of the insulating layer is greater than 30μm, the insulating layer will be completely damaged during rolling, making it impossible to manufacture a battery and affecting the battery's safety performance.

[0055] Furthermore, the thickness of the insulating layer affects its chromaticity value; the thicker the insulating layer, the smaller its luminance value L. Therefore, to maintain the luminance value L of the insulating layer within a suitable range, the thickness of the insulating layer can be further limited. Preferably, the thickness of the insulating layer is 7μm-20μm.

[0056] In an optional embodiment, the thickness of the active material layer is 20 μm to 180 μm. Specifically, the thickness of the active material layer can be 20 μm, 50 μm, 100 μm, 130 μm, or 180 μm. In this embodiment, this limitation can save costs while ensuring battery energy density. It should be noted that the thickness of the insulating layer / active material layer mentioned above refers to the thickness of the insulating layer / active material layer on one side of the current collector, and will not be elaborated further here.

[0057] In practical applications of this invention, if the width of the insulating layer located on the tab is too short in the tab extension direction, the effect of reducing burr formation is poor; if the width is too long in the tab extension direction, the effect of the tab in reducing the battery's internal resistance is poor, resulting in a lower battery energy density. Similarly, if the width of the insulating layer located on the current collector is too short in the tab extension direction, the effect of reducing burr formation is poor; if the width is too long in the tab extension direction, it will compress the space of the active material layer, resulting in a reduction in the total amount of active material, and thus a lower battery energy density. To solve the above problems, in an optional embodiment, the width of the insulating layer located on the tab in the tab extension direction is 1.5 mm to 2.5 mm, and the width of the insulating layer located on the current collector in the tab extension direction is 0.1 mm to 1 mm.

[0058] In practice, the insulating layer located in the current collector portion has a width in the tab extension direction that can be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, or 1 mm.

[0059] The width of the insulating layer located on the tab in the direction of tab extension can be 0.5mm, 0.8mm, 1.5mm, 1.7mm, 1.9mm, 2mm, or 2.5mm.

[0060] In this invention, see Figure 4 The thickness of the active material layer gradually decreases in the direction close to the insulating layer.

[0061] In practice, after the active material layer is coated, it overflows outwards from both sides, naturally resulting in a gradual decrease in the thickness of the active material layer towards the insulating layer. To simplify the processing, the thickness of the active material layer is limited to a gradual decrease towards the insulating layer. This eliminates the need for further processing of the active material layer after coating, thus simplifying the process and reducing costs.

[0062] In another aspect, the present invention provides a battery including the electrode provided in the first aspect of the present invention. Since the battery provided by the present invention includes the electrode provided in the first aspect of the present invention, it can achieve all the beneficial effects of the electrode provided by the present invention; therefore, to avoid repetition, further details will not be provided here.

[0063] In one specific embodiment, the aforementioned electrode is a positive electrode. The active material of the active material layer is denoted as paste slurry A, and the insulating material of the insulating layer is a mixture of a first insulating material and a second insulating material, denoted as insulating resin layer adhesive B. During the coating process, paste slurry A and insulating resin layer adhesive B are coated simultaneously. Insulating resin layer adhesive B flows out from both sides of paste slurry A and, after drying, forms the positive electrode. This positive electrode is then... Figure 5 After being cut in the manner shown, only one side of the electrode sheet has an insulating layer. The side with the insulating layer is then die-cut to form a tab, and after a series of processes, it is made into a battery.

[0064] In this invention, the battery further includes a negative electrode, an electrolyte, and a separator.

[0065] This invention discloses electrode sheets and lithium batteries. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0066] The reagents, instruments, and materials used in this invention can all be obtained through commercial channels.

[0067] The present invention will be further illustrated below with reference to the embodiments: Example 1 (1) Battery structure The battery in this embodiment uses a wound cell, which includes a positive electrode, a separator, and a negative electrode in sequence.

[0068] 1) Positive electrode plate The structure of the positive electrode: See Figure 1 and Figure 4 The positive electrode includes a current collector 10 and a tab 20. The tab 20 is disposed on the first side of the current collector 10. The current collector is an aluminum foil with a thickness of 10 μm. The current collector 10 has insulating layers 12 on both sides near the edge of the tab 20, and a portion of the insulating layer 12 extends to the surface of the tab 20. The thickness of the insulating layer is 8μm. The portion of the insulating layer 12 located in the tab 20 has a width of 2mm in the extension direction of the tab 20, and the portion of the insulating layer 12 located in the current collector 10 has a width of 0.5mm in the extension direction of the tab 20. The electrode 20 also includes an empty foil area 21; The positive electrode also includes an active material layer 11 located on both sides of the current collector 10, the active material layer having a thickness of 31 μm; A portion of the active material layer 11 and a portion of the insulating layer 12 are adjacent to form a miscible layer 13, and the width of the miscible layer 13 in the extension direction of the tab 20 is 100 μm.

[0069] The tabs of the aforementioned positive electrode are formed by die-cutting the current collector. Before die-cutting, the chromaticity values ​​E (including: brightness value L, red-green value a, and yellow-blue value b) of the insulating layer 12, the empty foil area 21, the active material layer 11, and the miscible layer 13 need to be tested, and the color difference ΔE1 between the insulating layer and the empty foil area, the color difference ΔE2 between the insulating layer and the active material layer, the color difference ΔE3 between the miscible layer and the insulating layer, and the color difference ΔE4 between the miscible layer and the active material layer are calculated. Finally, the empty foil area, the insulating layer, and the active material layer are identified by a charge-coupled device (CCD) camera to determine the accurate position of the die-cutting. The CCD judgment result is NG, indicating that the insulating layer, miscible layer, empty foil area, or active material layer cannot be identified, and an alarm is triggered; the CCD judgment result is OK, indicating that the insulating layer, miscible layer, empty foil area, or active material layer can be identified; the CCD recognition status is recognizable, indicating that the boundaries between the empty foil area, insulating layer, miscible layer, and active material layer can be identified; the CCD recognition status is unrecognizable, indicating that the boundaries between the above layers are unclear. The specific test results are shown in Table 1.

[0070] 2) Negative electrode sheet The negative electrode sheet includes a negative current collector and negative active material layers disposed on both sides thereof.

[0071] 3) Separating membrane The separator is a 5μm thick polymer membrane made of PP material.

[0072] (2) Preparation method Step 1: Preparation of positive electrode sheet The first insulating material and the second insulating material are mixed, NMP is added as a solvent, the solid content is 33%, and the mixture is stirred and dispersed evenly in a vacuum mixing tank to obtain a uniform and stable insulating layer slurry. Conductive carbon black and carbon nanotubes were added to PVDF adhesive and stirred until homogeneous. Then, lithium cobalt oxide was added and stirred until homogeneous to prepare the positive electrode active material layer slurry. The mass fraction of lithium cobalt oxide in the positive electrode active material layer was 97.6%, the mass fraction of PVDF was 1.05%, and the mass fraction of conductive carbon black and carbon nanotubes was 1.35% (where the mass ratio of carbon black to carbon nanotubes was 1:1). The insulating layer slurry and the positive electrode active material slurry are simultaneously coated on the surface of the aluminum foil. The insulating layer slurry flows out from both sides of the positive electrode active material slurry. After baking, rolling, slitting and die cutting, a positive electrode sheet with tab structure is obtained.

[0073] Step 2: Negative electrode preparation A negative electrode slurry is prepared by mixing 97.3% graphite, 0.5% conductive carbon black, 1.3% binder and 0.9% dispersant by mass, and then adding an appropriate amount of deionized water to disperse it evenly. The negative electrode slurry is coated on copper foil, and after baking, rolling, slitting and die cutting, a negative electrode sheet with tab structure is obtained.

[0074] Step 3: Battery Assembly The positive electrode, negative electrode and separator are wound to obtain the core, and the core is then packaged, baked, injected with electrolyte, formed, resealed, sorted and OCV to obtain the lithium-ion battery.

[0075] The electrolyte is a commercially available conventional electrolyte, and the lithium salt in it is LiFP6.

[0076] Example 2 group Example 2 was carried out in accordance with Example 1, except that the chromaticity value of the insulating layer was changed to obtain different color differences ΔE1 and ΔE2, as detailed in Table 1.

[0077] Example 3 Group Example 3 was carried out in accordance with Example 1, except that the chromaticity value of the miscible layer was changed to obtain different color differences ΔE3 and ΔE4, as detailed in Table 1.

[0078] Example 4 group Example 4 was carried out in accordance with Example 1, except that the thickness of the active material layer was changed, as detailed in Table 1.

[0079] Example 5 group Example 5 was carried out in accordance with Example 1, except that the thickness of the insulating layer was changed, as detailed in Table 1.

[0080] Example 6 group Example 6 was carried out in accordance with Example 1, except that the width of the miscible layer was changed, as detailed in Table 1.

[0081] Example 7 group Example 7 was carried out in accordance with Example 1, except that the width of the insulating layer in the tab / current collector portion was changed, as detailed in Table 1.

[0082] Example 8 Example 8 was carried out in accordance with Example 1, except that no miscible layer was formed between the active material layer and the insulating layer.

[0083] Comparative Example 1 The same procedure was performed as in Example 1, except that the color difference between the insulating layer and the empty foil area was less than 8.

[0084] Comparative Example 2 The same procedure was performed as in Example 1, except that the color difference between the insulating layer and the empty foil area was greater than 43.

[0085] Table 1 (Table 1 Explanation: In Example 3d, "unidentifiable" indicates that the boundary between the miscible layer and the active material layer is unclear; in Comparative Example 1, "unidentifiable" indicates that the boundary between the insulating layer and the empty foil area is unclear; in Example 8, "NG" indicates that the miscible layer cannot be identified and an NG alarm is issued; in Comparative Example 1, "NG" indicates that the insulating layer cannot be identified and an NG alarm is issued; " / " indicates that no miscible layer is formed between the insulating layer and the active material layer.) Battery performance test examples (1) Capacity testing of lithium-ion batteries The lithium-ion batteries obtained in the examples and comparative examples were subjected to capacity tests on the Blue Battery test cabinet. Within the upper and lower limits of the cell's specified usable voltage, the batteries were discharged at 25℃±2℃ at 0.2C to the lower limit voltage and left to stand for 10 minutes; then charged at 0.7C to the upper limit voltage, cut off at 0.025C, and left to stand for 10 minutes; then discharged at 0.2C to the lower limit voltage, and then the initial capacity test was performed. The capacity obtained at this time is the initial capacity (mAh) of the battery, which is recorded in Table 2.

[0086] (2) Cycle performance test of lithium-ion batteries The lithium-ion batteries obtained in the examples and comparative examples were subjected to charge-discharge cycle tests on the Blue Electric Test Cabinet Battery Charge-Discharge Test Cabinet. The test conditions were 25℃±2℃ and 3.7C / 0.7C charge-discharge. The number of cycles (T) when the battery capacity retention rate dropped to 80% was examined, and the test results were recorded in Table 2.

[0087] (3) Battery safety performance test The lithium-ion batteries in the examples and comparative examples were subjected to a nail penetration test. A pass was deemed successful if the lithium-ion battery did not catch fire or explode; otherwise, it failed. The specific test method for the needle penetration test is as follows: Using a fully charged lithium-ion battery, a high-temperature resistant steel needle with a diameter of ф(±0.5) mm (the needle tip has a conical angle of 45℃-60℃, and the surface of the needle is smooth, free of rust, oxide layer, and oil) is inserted at a speed of (100mm±5mm / s) perpendicular to the electrode sheet, with the puncture point close to the tab side, allowing the needle to remain inside the cell. The test is stopped after 1 hour or when the highest surface temperature of the cell drops to a peak temperature of 10℃ or below. Each group of lithium-ion batteries undergoes 20 tests. The test results are expressed by the following formula: Number of passes (passes) / Number of tests (passes).

[0088] Table 2 The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrode sheet, characterized in that, It includes a current collector and a tab, wherein the tab is disposed on one side of the current collector; The current collector has an insulating layer on at least one side surface near the edge of the electrode tab, and at least a portion of the insulating layer extends to the surface of the electrode tab; The electrode tab includes an empty foil area, and the color difference ΔE1 between the insulating layer and the empty foil area is 8~43. The electrode further includes an active material layer located on at least one side of the current collector surface. The color difference ΔE2 between the insulating layer and the active material layer is greater than the color difference ΔE1 between the insulating layer and the empty foil area. The color difference ΔE2 between the insulating layer and the active material layer is 68~111. At least a portion of the active material layer and at least a portion of the insulating layer are adjacent to form a miscible layer, wherein the color difference ΔE3 between the miscible layer and the insulating layer is greater than the color difference ΔE4 between the miscible layer and the active material layer, wherein the color difference ΔE3 between the miscible layer and the insulating layer is 63~108, and the color difference ΔE4 between the miscible layer and the active material layer is 0~25; Where, ΔE1=(ΔL1) 2 +Δa1 2 +Δb1 2 ) 1 / 2 ΔE2=(ΔL2) 2 +Δa2 2 +Δb2 2 ) 1 / 2 ΔE3=(ΔL3) 2 +Δa3 2 +Δb3 2 ) 1 / 2 ΔE4=(ΔL4) 2 +Δa4 2 +Δb4 2 ) 1 / 2 ΔL1, Δa1, and Δb1 are the differences in L, a, and b between the empty foil area and the insulating layer, respectively; ΔL2, Δa2, and Δb2 are the differences in L, a, and b between the active material layer and the insulating layer, respectively; ΔL3, Δa3, and Δb3 are the differences in L, a, and b between the miscible layer and the insulating layer, respectively; and ΔL4, Δa4, and Δb4 are the differences in L, a, and b between the active material layer and the miscible layer, respectively. L is the brightness value, a is the red-green value, and b is the yellow-blue value.

2. The electrode sheet according to claim 1, characterized in that, The brightness value L of the insulating layer ranges from 78 to 100, the red-green value a of the insulating layer ranges from -9 to 3, and the yellow-blue value b of the insulating layer ranges from 5 to 32.

3. The electrode sheet according to claim 1, characterized in that, The brightness value L of the empty foil area ranges from 70 to 95, the red-green value a of the empty foil area ranges from -2 to 2, and the yellow-blue value b of the empty foil area ranges from -5 to 2.

4. The electrode sheet according to claim 1, characterized in that, The brightness value L of the active material layer is greater than 0 and less than or equal to 10, the red-green value a of the active material layer is in the range of -10 to 10, and the yellow-blue value b of the active material layer is in the range of -10 to 10.

5. The electrode sheet according to claim 1, characterized in that, The brightness value L of the mixed layer is greater than 0 and less than or equal to 15, the red-green value a of the mixed layer is in the range of -4 to 4, and the yellow-blue value b of the mixed layer is in the range of -4 to 4.

6. The electrode sheet according to claim 1, characterized in that, The brightness value L of the active material layer, the miscible layer, and the insulating layer gradually increases.

7. The electrode sheet according to claim 1, characterized in that, The thickness of the active material layer is 20μm~180μm; And / or, the thickness of the insulating layer is 3μm~30μm; And / or, the thickness of the active material layer gradually decreases in the direction approaching the insulating layer; And / or, the thickness of the insulating layer is less than the thickness of the active material layer; And / or, the width of the miscible layer in the direction of the tab extension is 25 μm to 500 μm; And / or, the portion of the insulating layer located on the tab has a width of 1.5mm to 2.5mm in the tab extension direction, and the portion of the insulating layer located on the current collector has a width of 0.1mm to 1mm in the tab extension direction.

8. A battery, characterized in that, Includes the electrode as described in any one of claims 1 to 7.

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