Electrochemical device and electronic device

Abstract

To provide an electrochemical device and an electronic device capable of reducing a risk of occurrence of a burr on an edge and falling-off of a material as a die used for punching in accordance with an increase of a use frequency.SOLUTION: An electrochemical device comprises a negative electrode, a positive electrode, and a separator. The negative electrode is provided with a negative electrode active material layer on one surface of a negative electrode current collector, the positive electrode is provided with a positive electrode active material layer on one surface of the positive electrode current collector, an insulating layer is provided on a surface of the positive electrode current collector on a side close to a tab part, the separator is provided between the negative electrode and the positive electrode, and the positive electrode active material layer and the negative electrode active material layer face each other with the separator interposed therebetween. An outer edge of the negative electrode active material layer is located outside the outer edge of the positive electrode active material layer facing the negative electrode active material layer. An inner edge of the insulating layer contacts or partially overlaps the outer edge of the positive electrode active material layer. The outer edge of the insulating layer and the outer edge of the negative electrode active material layer are aligned or located outside the outer edge of the negative electrode active material layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to electrochemical and electronic devices. [Background technology]

[0002] Electrochemical devices such as lithium-ion batteries have properties such as high specific energy, no memory effect, and environmental friendliness, and are widely used in electronic products such as communication devices, laptops, and digital cameras, as well as in electric vehicles. With the rapid development of technology and diversification of market demands, the requirements for the performance of electrochemical devices, such as safety performance, are increasing.

[0003] Many factors affect the safety performance of lithium-ion batteries. For example, when punching pole pieces during the manufacturing process of wound lithium-ion batteries, the risk of burrs and material shedding on the edges of the punching dies increases with the frequency of use. If burrs or material shedding occurs on the pole pieces during the punching process, they may break through the separator, causing a short circuit and posing a safety risk. For another example, lithium deposition in the battery may increase the probability of the battery catching fire or exploding, posing a safety risk. Summary of the Invention

[0004] In some embodiments, the present invention provides an electrochemical device including a negative electrode, a positive electrode, and a separator, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and an insulating layer is provided on a surface of the positive electrode current collector closer to a tab portion, the separator is provided between the negative electrode and the positive electrode, the positive electrode active material layer and the negative electrode active material layer face each other via the separator, an outer edge of the negative electrode active material layer is located outside an outer edge of the positive electrode active material layer facing the negative electrode active material layer, an inner edge of the insulating layer is in contact with or partially overlaps an outer edge of the positive electrode active material layer, and the outer edge of the insulating layer and the outer edge of the negative electrode active material layer are aligned or are located outside the outer edge of the negative electrode active material layer.

[0005] In some embodiments, the tab portion protrudes from the positive electrode current collector.

[0006] In some embodiments, the insulating layer is provided on a surface of the positive electrode current collector facing away from the tab portion.

[0007] In some embodiments, when the width of the portion where the outer edge of the insulating layer exceeds the outer edge of the negative electrode active material layer is defined as A, A satisfies A≦3 mm.

[0008] In some embodiments, when the width of the insulating layer is A', A' satisfies 0.2 mm≦A'≦10 mm.

[0009] In some embodiments, when the width of the portion where the outer edge of the negative electrode active material layer exceeds the outer edge of the positive electrode active material layer is defined as B, B satisfies 0.2 mm≦B≦5 mm.

[0010] In some embodiments, the thickness of the insulating layer is T i and the thickness of the positive electrode active material layer is T p When T i and T p , 0 μm ≦ Tp -T i Meets ≦10μm.

[0011] In some embodiments, the thickness of the insulating layer is T i When T i , 10μm≦T i ≦T p Meet the following.

[0012] In some embodiments, the insulating layer comprises an inorganic material and an adhesive, wherein the inorganic material comprises at least one of barium sulfate, calcium silicate, aluminum oxide, boehmite, magnesium hydroxide, aluminum hydroxide, silica, magnesium oxide, and calcium orthosilicate, and the adhesive comprises at least one of polyvinylidene fluoride, polyurethane, polyacrylate, styrene butadiene rubber, polyetherimide, sodium carboxymethylcellulose, and acrylic ester.

[0013] In some embodiments, the weight fraction of the inorganic material is 60% to 93% and the weight fraction of the adhesive is 7% to 40% relative to the total weight of the insulating layer.

[0014] In some embodiments, the insulating layer has a resistance of 1 KΩ or greater.

[0015] The present invention further provides an electronic device including the electrochemical device of the present invention. The technical solution of the present invention has at least the following beneficial effects: The insulating layer provided in the electrochemical device of the present invention can reduce burrs and material shedding caused by punching, and provide support for the edge region of the negative electrode active material layer, thereby more tightly bonding the edge region of the negative electrode active material layer and the separator, reducing the resistance of the negative electrode edge region, improving the dynamics of the negative electrode edge, and improving lithium deposition at the negative electrode edge, thereby reducing the probability of fire or explosion of the electrochemical device, and improving the safety performance of the electrochemical device. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1(a) is a partial cross-sectional view of an electrode body in one embodiment of the present invention, FIG. 1(b) is an exploded view of FIG. 1(a), and FIG. 1(c) is a schematic view of a portion of the electrode body in this embodiment as viewed from the positive electrode side. [Figure 2] FIG. 2(a) is a partial cross-sectional view of an electrode body in another embodiment of the present invention, FIG. 2(b) is an exploded view of FIG. 2(a), and FIG. 2(c) is a schematic view of a portion of the electrode body of this embodiment as viewed from the positive electrode side. [Figure 3] FIG. 3(a) is a partial cross-sectional view of an electrode body in another embodiment of the present invention, FIG. 3(b) is an exploded view of FIG. 3(a), and FIG. 3(c) is a schematic view of a portion of the electrode body of this embodiment as viewed from the positive electrode side. [Figure 4] FIG. 4(a) is a partial cross-sectional view of an electrode body in another embodiment of the present invention, FIG. 4(b) is an exploded view of FIG. 4(a), and FIG. 4(c) is a schematic view of a portion of the electrode body of this embodiment as viewed from the positive electrode side. [Figure 5] FIG. 5(a) is a partial cross-sectional view of an electrode body in another embodiment of the present invention, FIG. 5(b) is an exploded view of FIG. 5(a), and FIG. 5(c) is a schematic view of a portion of the electrode body of this embodiment as viewed from the positive electrode side. DETAILED DESCRIPTION OF THE INVENTION

[0017] It should be understood that the disclosed embodiments are merely examples of the invention, and that the invention can be embodied in various forms, and therefore specific details in this disclosure should not be construed as limiting, but are used merely as a basis for the claims and as an illustrative basis to teach those skilled in the art how to implement the invention in its various forms.

[0018] In describing the present invention, orientations or positional relationships indicated by terms such as "length," "width," "thickness," "inside," and "outside" are orientations or positional relationships shown based on the drawings, and are for the convenience of explaining and simplifying the description of the present invention only, and should be understood as not indicating or suggesting that the devices or elements referred to must have a particular orientation, be configured, or operate in a particular orientation. (Electrochemical Equipment)

[0019] The electrochemical device of the present invention is, for example, a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. The secondary battery is, for example, a lithium secondary battery, and the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0020] In some embodiments, an electrochemical device includes a negative electrode, a positive electrode, and a separator.

[0021] 1(a) to 5(c), the negative electrode 20 includes a negative electrode current collector 21, and a negative electrode active material layer 22 is provided on at least one surface of the negative electrode current collector 21; the positive electrode 10 includes a positive electrode current collector 11, and a positive electrode active material layer 12 is provided on at least one surface of the positive electrode current collector 11; a separator 30 is provided between the negative electrode 20 and the positive electrode 10; the positive electrode active material layer 12 and the negative electrode active material layer 22 face each other via the separator 30; and an outer edge 22a of the negative electrode active material layer is located outside an outer edge 12a of the positive electrode active material layer facing the negative electrode active material layer.

[0022] 1(a) to 5(c) show the width direction (indicated by W in the drawings) and the thickness direction (indicated by T in the drawings), where the width direction corresponds to the length direction. For example, in the case of a strip-shaped positive electrode of a wound battery, the direction of extension of the long side of the long rectangular positive electrode current collector is regarded as the length direction, and the width direction is the direction perpendicular to the length direction. As shown in FIGS. 1(a) to 5(c), at both ends in the width direction, the edge of the positive electrode active material layer 12 closest to the edge of the positive electrode current collector is the outer edge 12a of the positive electrode active material layer, and the edge of the negative electrode active material layer 22 closest to the edge of the negative electrode current collector is the outer edge 22a of the negative electrode active material layer.

[0023] To prevent short-circuiting of the battery, ensure that lithium ions released from the positive electrode active material layer 12 are completely absorbed by the negative electrode active material layer 22, and avoid the safety risk of lithium deposition in the portion of the positive electrode active material layer 12 extending beyond the negative electrode active material layer 22, the width of the negative electrode active material layer 22 is designed to be wider than the positive electrode active material layer 12, thereby creating an overhang area on the negative electrode piece. In the present invention, the outer edge 22a of the negative electrode active material layer is designed to be located outward from the outer edge 12a of the positive electrode active material layer facing the negative electrode active material layer. In some embodiments, when the width B of the portion of the outer edge 22a of the negative electrode active material layer extending beyond the outer edge 12a of the positive electrode active material layer is defined as B, B satisfies the range 0.2 mm≦B≦5 mm. In some embodiments, when the width B of the portion of the outer edge 22a of the negative electrode active material layer extending beyond the outer edge 12a of the positive electrode active material layer is defined as B, B satisfies the range 0.5 mm≦B≦5 mm. In some embodiments, when the width of the portion where the outer edge 22a of the negative electrode active material layer exceeds the outer edge 12a of the positive electrode active material layer is defined as B, B satisfies 0.8 mm≦B≦2 mm.

[0024] However, the inventors discovered that when the width of the negative electrode active material layer 22 is larger than that of the positive electrode active material layer 12, the resistance near the negative electrode active material layer 22 corresponding to the outer edge 12a of the positive electrode active material layer is high, reducing the kinetics of the negative electrode edge region and making lithium deposition more likely, posing a safety risk. Reducing the resistance due to polarization during the negative electrode charging process by lowering the charge rate can avoid lithium deposition at the negative electrode edge, but lowering the charge rate increases the charging time, significantly reducing the customer experience and product competitiveness. Improving the kinetics of the negative electrode active material, increasing the proportion of negative electrode active material, and using adhesives with better kinetics, such as CMC-Li (carboxymethylcellulose lithium) instead of CMC-Na (carboxymethylcellulose sodium), or using a styrene-acrylic adhesive instead of a styrene-butadiene rubber adhesive to improve the kinetics of the negative electrode edge region, have shown some effectiveness, but these methods have already reached a bottleneck stage, making it difficult to continue improving at the current rate.

[0025] In the present invention, by providing an insulating layer 13 on the positive electrode current collector 11 and by adjusting the position and dimensional relationship between the insulating layer 13, the positive electrode active material layer 12, and the negative electrode active material layer 22, the resistance of the negative electrode edge region can be reduced, the dynamics of the negative electrode edge can be improved, and lithium deposition at the negative electrode edge can be improved, thereby reducing the probability of fire or explosion of the electrochemical device.

[0026] The insulating layer 13 may be provided only on the surface of the positive electrode current collector 11 that is closer to the tab portion 40, or may be provided on both the surface of the positive electrode current collector 11 that is closer to the tab portion 40 and the surface of the positive electrode current collector 11 that is farther from the tab portion 40.

[0027] In the present invention, tab portion 40 refers to the empty foil area at the edge of the current collector that is set aside during the coating of the pole piece, and in some embodiments, tab portion 40 protrudes from the current collector. After roll pressing and slitting, the empty foil area at the edge of the current collector can be trimmed to form a tab before winding.

[0028] In some embodiments, as shown in a portion of the electrode assembly in Figures 1(a) to 1(c), an insulating layer 13 is provided on the surface of the positive electrode collector 11 near the tab portion 40, with the inner edge 13b of the insulating layer contacting the outer edge 12a of the positive electrode active material layer and the outer edge 13a of the insulating layer positioned outward from the outer edge 22a of the negative electrode active material layer. In some embodiments, as shown in a portion of the electrode assembly in Figures 2(a) to 2(c), an insulating layer 13 is provided on the surface of the positive electrode collector 11 near the tab portion 40, with the inner edge 13b of the insulating layer contacting the outer edge 12a of the positive electrode active material layer and the outer edge 13a of the insulating layer being aligned with the outer edge 22a of the negative electrode active material layer.

[0029] In this case, because the insulating layer 13 is provided on the surface of the positive electrode current collector 11 near the tab portion 40, burrs and material shedding that occur during punching of the electrode piece with the insulating layer 13 can be reduced, improving the safety performance of the electrochemical device. At the same time, the insulating layer 13 is provided on the positive electrode 10 at one end near the tab portion 13, and the inner edge 13b of the insulating layer contacts the outer edge 12a of the positive electrode active material layer, and the outer edge 13a of the insulating layer is located outside the outer edge 22a of the negative electrode active material layer, or the outer edge 13a of the insulating layer and the outer edge 22a of the negative electrode active material layer are aligned. Therefore, when the battery is pressurized for formation, the insulating layer 13 of the positive electrode at this end can support the edge region of the negative electrode active material layer, thereby more tightly bonding the edge region of the negative electrode active material layer and the separator, thereby reducing the resistance of the negative electrode edge region and improving the dynamics of the negative electrode edge. If the outer edge 13a of the insulating layer is located inside the outer edge 22a of the negative electrode active material layer, the portion of the edge of the negative electrode active material layer 22 that extends beyond the insulating layer will be unsupported, and when the battery is pressurized for formation, the bond between this extending portion and the separator will not be tight, resulting in a large electron transport distance, high resistance, and easy lithium precipitation.

[0030] In the step of applying the slurries, when the slurries for the insulating layer 13 and the positive electrode active material layer 12 are applied to the surface of the positive electrode current collector 11, the slurry for the insulating layer is applied along the edge of the slurry for the positive electrode active material layer. Therefore, the slurry for the insulating layer may partially overlap the slurry for the positive electrode active material layer, forming an overlapping portion 14 between the positive electrode active material layer 12 and the insulating layer 13. In some embodiments, as shown in a portion of the electrode assembly in FIGS. 3( a) to 3(c), the insulating layer 13 is provided on the surface of the positive electrode current collector 11 closer to the tab portion 40, and the inner edge 13b of the insulating layer partially overlaps the outer edge 12a of the positive electrode active material layer, and the outer edge 13a of the insulating layer is located outside the outer edge 22a of the negative electrode active material layer. In some embodiments, as shown in a portion of the electrode body in Figures 4(a) to 4(c), an insulating layer 13 is provided on the surface of the positive electrode current collector 11 closer to the tab portion 40, and the inner edge 13b of the insulating layer partially overlaps the outer edge 12a of the positive electrode active material layer, and the outer edge 13a of the insulating layer and the outer edge 22a of the negative electrode active material layer are aligned.

[0031] In some embodiments, as shown in parts of the electrode body in Figures 5(a) to 5(c), an insulating layer 13 is provided on the surface of the positive electrode current collector 11 closer to the tab portion 40 and on the surface away from the tab portion 40, and the inner edge 13b of the insulating layer is in contact with the outer edge 12a of the positive electrode active material layer, and the outer edge 13a of the insulating layer is located outside the outer edge 22a of the negative electrode active material layer.

[0032] When the insulating layer 13 is provided on both the surface of the positive electrode current collector 11 closer to the tab portion 40 and the surface of the positive electrode current collector 11 farther from the tab portion 40, the inner edge 13b of the insulating layer may partially overlap the outer edge 12a of the positive electrode active material layer, and the outer edge 13a of the insulating layer and the outer edge 22a of the negative electrode active material layer may be aligned. Specifically, this is the same as when the insulating layer 12 is provided only on the surface of the positive electrode current collector 11 closer to the tab portion 40, and therefore a detailed description thereof will be omitted here.

[0033] In this case, since the insulating layer 13 is also provided on the surface of the positive electrode current collector 11 away from the tab portion 40, the total width of the positive electrode active material layer 12 and the insulating layer 13 is greater than the width of the negative electrode active material layer 22. Therefore, when the battery is pressurized and formed, the overhang region of the negative electrode piece can be fully supported by the insulating layer, and the edge region of the negative electrode active material layer can be more tightly bonded to the separator.

[0034] In some embodiments, the insulating layer includes an inorganic material. In the present invention, commonly used inorganic materials known in the art can be used. In some embodiments, the inorganic material includes at least one of barium sulfate (BaSO), calcium silicate (CaSiO), aluminum oxide (AlO), boehmite, magnesium hydroxide, aluminum hydroxide, silica, magnesium oxide, and calcium orthosilicate (CaSiO). In some embodiments, the weight fraction of the inorganic material is 60% to 93% of the total weight of the insulating layer. In some embodiments, the weight fraction of the inorganic material is 80% to 93% of the total weight of the insulating layer.

[0035] In some embodiments, the insulating layer also includes an adhesive, the adhesive including at least one of polyvinylidene fluoride, polyurethane, polyacrylate, styrene butadiene rubber, polyetherimide, sodium carboxymethyl cellulose, and acrylic ester, and in some embodiments, the weight fraction of the adhesive is 7% to 40% of the total weight of the insulating layer.

[0036] In some embodiments, the resistance of the insulating layer is 1 KΩ or greater, which can prevent burrs and electron transport in the insulating layer during punching of the positive electrode current collector, thereby isolating the burrs on the positive electrode current collector from the separator. The resistance of the insulating layer can be tested using an internal resistance meter. Wipe the contacts of the internal resistance meter with dust-free paper soaked in alcohol, turn on the test fixture, adjust the contact pressure to 0.5 MPa, place the test pole piece on the lower contact, start the device, and press down the pole piece with the upper contact for 3-5 seconds. Record the resistance of the pole piece as the resistance of the insulating layer.

[0037] In some embodiments, as shown in Figures 1(a) to 5(c), when the width A of the portion where the outer edge 13a of the insulating layer exceeds the outer edge 22a of the negative electrode active material layer is defined as A, A satisfies the relationship A≦3 mm. If the width A of the portion where the outer edge of the insulating layer exceeds the outer edge of the negative electrode active material layer is too large, it is necessary to increase the width of the separator accordingly, resulting in a loss of energy density in the electrochemical device. Furthermore, even if A exceeds 3 mm, there is no further improvement in lithium deposition at the negative electrode edge, or the further improvement in lithium deposition at the negative electrode edge is weak. In some embodiments, when the width A of the portion where the outer edge 13a of the insulating layer exceeds the outer edge 22a of the negative electrode active material layer is defined as A, A satisfies the relationship 1.5 mm≦A≦3 mm.

[0038] In some embodiments, as shown in FIGS. 1(a) to 5(c), when the width of the insulating layer 13 is designated A', A' satisfies the range of 0.2 mm≦A'≦10 mm. In the present invention, the width of the insulating layer refers to the width of the insulating layer on one side of the positive electrode active material layer, i.e., the width of the portion where the outer edge of the insulating layer extends beyond the outer edge of the positive electrode active material layer. If the width A' of the insulating layer is too large, it is necessary to increase the width of the separator accordingly, resulting in a loss of energy density in the electrochemical device. Furthermore, even if A exceeds 10 mm, there is no further improvement in lithium deposition at the negative electrode edge, or the improvement in lithium deposition at the negative electrode edge is weak. If the width A' of the insulating layer is too small, it is not possible to effectively reduce burrs and material shedding that occur during punching, which affects the improvement in safety performance. In some embodiments, when the width A' of the insulating layer 13 is designated A', A' satisfies the range of 1 mm≦A'≦5 mm. In some embodiments, when the width of the insulating layer 13 is A', A' satisfies 3 mm≦A'≦5 mm.

[0039] In an embodiment of the present invention, the combined width of the positive electrode active material layer 12 and the insulating layer 13 is equal to or less than the width of the separator 30 to reduce the impact on the width of the battery and avoid loss of energy density of the electrochemical device.

[0040] The thickness of the insulating layer affects the supporting effect of the insulating layer on the edge region of the negative electrode active material layer. i and the thickness of the positive electrode active material layer is T p When T i and T p , 0 μm ≦ T p -T i ≦10 μm. If the thickness of the insulating layer is too small relative to the thickness of the positive electrode active material layer, the insulating layer's support effect on the edge region of the negative electrode active material layer will be weak, affecting the effect of improving lithium deposition at the negative electrode edge. If the thickness of the insulating layer is greater than the thickness of the positive electrode active material layer, it will be difficult to achieve a predetermined compacted density during cold pressing, which will further affect the energy density of the electrochemical device. In some embodiments, the thickness of the insulating layer is set to T iand the thickness of the positive electrode active material layer is T p When T i and T p , 0 μm ≦ T p -T i Meets ≦2μm.

[0041] In some embodiments, the thickness of the insulating layer is T i When T i , 10μm≦T i ≦T p Meet the following.

[0042] In the present invention, the thickness T of the insulating layer i is the thickness of the insulating layer provided on one surface of the positive electrode current collector, and the thickness T p is the thickness of the positive electrode active material layer provided on one surface of the positive electrode current collector.

[0043] In some embodiments, the negative electrode current collector is a metal, such as, but not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0044] The negative electrode active material layer includes a negative electrode active material, which can be selected from materials usable in electrochemical devices that can absorb and release active ions or materials that can dope and dedope active ions. In some embodiments, the negative electrode active material includes at least one of a carbon material, a metal alloy, a lithium-containing oxide, and a silicon-containing material. The negative electrode manufacturing method can be a method for manufacturing a negative electrode that can be used in an electrochemical device. In some embodiments, the negative electrode slurry is typically prepared by adding a solvent, a negative electrode active material, and a negative electrode binder, and optionally adding a conductive material and a thickener, and then dissolving or dispersing them in the solvent to prepare the negative electrode slurry. The solvent is removed by evaporation during the drying process. The solvent is a solvent usable in the negative electrode active material layer, such as, but not limited to, water. The thickener is a thickener usable in the negative electrode active material layer, such as, but not limited to, sodium carboxymethyl cellulose (abbreviated as CMC). In the present invention, the mixing ratio of the negative electrode active material, negative electrode binder, and thickener in the negative electrode active material layer is not particularly limited, and can be controlled depending on the desired performance of the electrochemical device.

[0045] In some embodiments, the positive electrode current collector is a metal, such as, but not limited to, copper foil or aluminum foil.

[0046] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be selected from materials that can be used as positive electrode active materials in electrochemical devices and that can reversibly absorb and release active ions. In some embodiments, the positive electrode active material can be LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, LiNi x Co y Mn z M 1-x-y-zThe positive electrode may include at least one of the following: O2, where M is one or more selected from the group consisting of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and satisfying the following conditions: 0≦y≦1, 0≦x≦1, 0≦z≦1, and x+y+z≦1. The positive electrode may be manufactured using a method for manufacturing a positive electrode suitable for an electrochemical device. In some embodiments, the positive electrode slurry is typically prepared by adding a solvent, a positive electrode active material, and a binder, optionally adding a conductive agent and a thickener, and then dissolving or dispersing the mixture in the solvent to form the positive electrode slurry. The solvent is removed by evaporation during the drying process. The solvent is a solvent suitable for use in the positive electrode active material layer, such as, but not limited to, N-methylpyrrolidone (NMP). The binder is a binder suitable for use in the positive electrode active material layer, such as, but not limited to, polyvinylidene fluoride (PVDF). The conductive agent is a conductive agent that can be used in the positive electrode active material layer, such as, but not limited to, Super P. In the present invention, the mixing ratio of the positive electrode active material, positive electrode binder, and positive electrode conductive agent in the positive electrode active material is not particularly limited and can be controlled depending on the desired performance of the electrochemical device.

[0047] The separator is a separator that can be used in electrochemical devices in the art. In the present invention, the material and shape of the separator are not particularly limited.

[0048] The electrochemical device also includes an electrolyte. The electrolyte is any electrolyte known in the art for use in electrochemical devices. In some embodiments, the electrolyte includes an organic solvent, an electrolyte salt, and an additive. In some embodiments, the electrolyte salt is selected from lithium salts. In some embodiments, the lithium salt is selected from LiPF6.

[0049] In some embodiments, the electrochemical device also includes an outer casing, which may be any casing available in the art for electrochemical devices and stable with respect to the electrolyte used, such as, but not limited to, a metal-based casing.

[0050] In some embodiments, the tab portion includes multiple positive electrode tabs and multiple negative electrode tabs. The multiple tabs can increase the electron channels during charging and discharging of the electrochemical device and reduce polarization and cell heat generation. In some embodiments, the number of positive electrode tabs and negative electrode tabs is equal to the number of cell layers, or the number of positive electrode tabs and negative electrode tabs is half the number of cell layers. The positive electrode tabs and negative electrode tabs are stacked after winding the cell and are welded to nickel-aluminum metal sheets, respectively. (electronic equipment)

[0051] Examples of electronic devices according to the present invention include, but are not limited to, any electronic device, such as a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headphone, a video recorder, an LCD TV, a portable vacuum cleaner, a portable CD player, a minidisc, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash lamp, a camera, a large-scale household storage battery, and a lithium-ion capacitor. The electrochemical device according to the present invention can be applied to energy storage power plants, maritime vehicles, and air vehicles in addition to the above-mentioned electronic devices. Air vehicles include both atmospheric and extraterrestrial air vehicles.

[0052] In some embodiments, the electronic device comprises the above-described electrochemical device of the present invention.

[0053] The present invention will be described in more detail below in conjunction with examples. It should be understood that these examples are for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention. In the following specific examples of the present invention, only examples in which the battery is a lithium ion battery are shown, but the present invention is not limited thereto. Reagents, materials, and equipment used in the following examples and comparative examples can be obtained commercially or by synthesis, unless otherwise specified. Example 1

[0054] Step S1: The positive electrode active material, lithium cobalt oxide, the conductive agent, Super P, and the binder, PVDF, were thoroughly mixed in a weight ratio of 98:1:1 in an appropriate amount of NMP with sufficient stirring to obtain a uniformly mixed positive electrode slurry. The inorganic material, BaSO4, and the adhesive, PVDF, were thoroughly mixed in a weight ratio of 93:7 in an appropriate amount of NMP with sufficient stirring to obtain a uniformly mixed insulating slurry.

[0055] Step S2: The prepared positive electrode slurry was applied to one side of an aluminum foil serving as a positive electrode current collector using an extrusion coater to a thickness of 30 μm, and an insulating slurry was applied along the edge of the positive electrode slurry on the side closer to the tab portion of the positive electrode slurry to a width of 3.5 mm and a thickness of 30 μm. After drying, the insulating slurry was similarly applied to the other side of the aluminum foil serving as a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode piece.

[0056] Step S3: Graphite as the negative electrode active material, styrene butadiene rubber as the binder, and carboxymethyl cellulose lithium as the thickener were thoroughly stirred and mixed in an appropriate amount of deionized water in a weight ratio of 97.5:1.3:1.2 to form a uniform negative electrode slurry. The negative electrode slurry was then applied to one side of copper foil as the negative electrode current collector using an extrusion coater, dried, and then similarly applied to the other side of the copper foil as the negative electrode current collector, dried, and cold-pressed to obtain negative electrode pieces.

[0057] Step S4: A PE porous polymer film was used as a separator, and the separator was placed between the negative electrode piece and the positive electrode piece. The positive electrode active material layer and the negative electrode active material layer were opposed to each other through the separator, and the outer edge of the negative electrode active material layer exceeded the outer edge of the positive electrode active material layer by 2 mm, and the outer edge of the insulating layer exceeded the outer edge of the negative electrode active material layer by 1.5 mm.

[0058] Step S5: The stacked separator, negative electrode pieces, and positive electrode pieces are wound to form an electronic assembly, which is then packaged, and the electrolyte is injected and allowed to stand to obtain an insufficiently impregnated electronic assembly, which is then subjected to a formation and capacity process to obtain a lithium-ion battery. Examples 2 to 21

[0059] Examples 2 to 21 were produced using the same manufacturing method as Example 1, except that the parameters of the insulating layer, positive electrode active material layer, and negative electrode active material layer were adjusted. Example 22

[0060] In Example 22, the insulating slurry was applied to both sides of the positive electrode slurry (the side closer to the tab portion and the side farther from the tab portion) along the edge of the positive electrode slurry, and the application width of the insulating slurry on each side was 8 mm. In Example 22, the parameters of the other insulating layer, positive electrode active material layer, and negative electrode active material layer were adjusted, and the manufacturing method was the same as that of Example 1. Example 23

[0061] Example 23 was produced using the same manufacturing method as Example 22, except that the parameters for the insulating layer, positive electrode active material layer, and negative electrode active material layer were adjusted. Example 24

[0062] Example 24 was produced using the same manufacturing method as Example 5, except that the parameters for the insulating layer, positive electrode active material layer, and negative electrode active material layer were adjusted. Comparative Examples 1-2

[0063] Comparative Examples 1 and 2 were manufactured by the same method as Example 1, except that the parameters of the insulating layer, positive electrode active material layer, and negative electrode active material layer were adjusted. In Comparative Examples 1 and 2, the outer edge of the negative electrode active material layer was positioned outside the outer edge of the insulating layer.

[0064] The parameters in Examples 1 to 24 and Comparative Examples 1 and 2 are as shown in Table 1. Lithium-ion battery performance testing:

[0065] Hotbox Test: 1) At 20±5°C, discharge the battery at 0.5C to 3.0V, then leave it for 5 minutes. 2) Charge at 0.5C to 4.45V, then charge at constant voltage to 0.05C (4.45V system), 3) Leave it at 20±5℃ for 60 minutes, 4) Raise the temperature to 130°C ± 2°C at a rate of 5°C / min ± 2°C / min and hold for 60 minutes. 5) After the test was completed, the cell's appearance was inspected, and if the battery caught fire, the test was failed.

[0066] 25℃ 3C Lithium Deposition Test: The test was carried out in an environment of 25°C. 1) Leave the battery for 30 minutes. 2) Charge at 0.5C to 4.45V, then charge at constant voltage to 0.05C. 3) Leave it for 5 minutes, 4) Discharge at 0.5C to 3V, 5) Leave it for 60 minutes, 6) Charge at 3C to 4.45V, then charge at constant voltage to 0.05C. 7) Leave it for 5 minutes, 8) Discharge to 3V at 1C, 9) Leave it for 5 minutes, 10) Repeat steps 6) to 9) 10 times. 11) Leave it for 120 minutes, 12) Charge at 3C to 4.45V, then charge at constant voltage to 0.05C. 13) After leaving it for 5 minutes, the state of lithium deposition in the lithium ion battery was observed and classified according to the following criteria.

[0067] The lithium-ion battery was disassembled to obtain a negative electrode sheet. The golden color was the normal region, and the white color was the lithium precipitation region. Photographs were taken with a microscope at a high magnification (20 times or more), and different regions were analyzed. When the ratio n of the white region to the total area satisfied 0 < n < 1%, it was recorded as "no lithium precipitation". When the ratio n of the white region to the total area satisfied 1% < n < 10%, it was recorded as "mild lithium precipitation". When the ratio n of the white region to the total area satisfied 10% < n < 100%, it was recorded as "severe lithium precipitation".

[0068]

Table 1

[0069] As can be seen from the data analysis in Table 1, the outer edge of the negative electrode active material layer is located outside the outer edge of the positive electrode active material layer facing the negative electrode active material layer, an insulating layer is provided on the side close to the tab portion of the positive electrode current collector, and the inner edge of the insulating layer contacts or partially overlaps with the outer edge of the positive electrode active material layer, and the outer edge of the insulating layer and the outer edge of the negative electrode active material layer are aligned, or when it is located outside the outer edge of the negative electrode active material layer, the lithium precipitation state of the negative electrode of the lithium-ion battery can be improved, and the qualified rate of the thermal destruction test can be increased. In Comparative Example 1 and Comparative Example 2, an insulating layer is provided on the side close to the tab portion of the positive electrode current collector. However, after the cell is manufactured, since the outer edge of the negative electrode active material layer is located outside the outer edge of the insulating layer, the insulating layer cannot support the edge region of the negative electrode active material layer, the lithium precipitation of the negative electrode is likely to occur, and the qualified rate of the thermal destruction test is low.

[0070] The thickness of the insulating layer affects the improvement effect of the lithium precipitation of the negative electrode and the qualified rate of the thermal destruction test of the lithium-ion battery. As can be seen from the data of Examples 8 to 12, when the thickness of the insulating layer is too small, the improvement effect of the lithium precipitation of the negative electrode and the qualified rate of the thermal destruction test of the lithium-ion battery deteriorates.

[0071] The composition and resistance of the insulating layer affect the improvement of the pass rate of the thermal breakdown test of the lithium-ion battery. As can be seen from the data of Examples 9, 14 to 21, if the mass ratio of the inorganic material in the insulating layer is too small, the resistance of the insulating layer will be low, and the improvement of the pass rate of the thermal breakdown test of the lithium-ion battery will be poor.

[0072] While the above detailed description describes several exemplary embodiments, it is not intended to be limited to the combinations expressly disclosed herein. Thus, unless otherwise indicated, various features disclosed herein can be combined to form several additional combinations not shown for clarity. [Explanation of symbols]

[0073] Positive electrode: 10, positive electrode current collector: 11, positive electrode active material layer: 12, outer edge of positive electrode active material layer: 12a, insulating layer: 13, outer edge of insulating layer: 13a, inner edge of insulating layer: 13b, overlapping portion of positive electrode active material layer and insulating layer: 14, negative electrode: 20, negative electrode current collector: 21, negative electrode active material layer: 22, outer edge of negative electrode active material layer: 22a, separator: 30, tab portion: 40.

Claims

1. An electrochemical device including a negative electrode, a positive electrode, and a separator, the negative electrode includes a negative electrode current collector, and a negative electrode active material layer is provided on at least one surface of the negative electrode current collector; the positive electrode includes a positive electrode current collector, a positive electrode active material layer is provided on at least one surface of the positive electrode current collector, and an insulating layer is provided on a surface of the positive electrode current collector that is closer to the tab portion; the separator is provided between the negative electrode and the positive electrode, and the positive electrode active material layer and the negative electrode active material layer face each other via the separator; an outer edge of the negative electrode active material layer is located outside an outer edge of the positive electrode active material layer facing the negative electrode active material layer; an inner edge of the insulating layer is in contact with or partially overlaps an outer edge of the positive electrode active material layer, and the outer edge of the insulating layer and the outer edge of the negative electrode active material layer are aligned or are located outward of the outer edge of the negative electrode active material layer; an electrochemical device, wherein A satisfies 0 mm≦A≦3 mm, where A is the width of the portion where the outer edge of the insulating layer exceeds the outer edge of the negative electrode active material layer;

2. The electrochemical device according to claim 1 , wherein the insulating layer is provided on a surface of the positive electrode current collector away from the tab portion.

3. 3. The electrochemical device according to claim 1, wherein when the width of the insulating layer is A', A' satisfies 0.2 mm≦A'≦10 mm.

4. 3. The electrochemical device according to claim 1, wherein B is a width of a portion where the outer edge of the negative electrode active material layer exceeds the outer edge of the positive electrode active material layer, and B satisfies 0.2 mm≦B≦5 mm.

5. The thickness of the insulating layer is T ｉ and the thickness of the positive electrode active material layer is T ｐ When this is done, T ｉ and T ｐ 0 μm≦T ｐ -T ｉ 3. The electrochemical device according to claim 1, wherein the thickness satisfies the following condition: ≦10 μm.

6. The thickness of the insulating layer is T ｉ and the thickness of the positive electrode active material layer is T ｐ When this is done, T ｉ and T ｐ is 10 μm≦T ｉ ≦T ｐ The electrochemical device according to claim 1 or 2, which satisfies the above.

7. the insulating layer includes an inorganic material and an adhesive; the inorganic material includes at least one of barium sulfate, calcium silicate, aluminum oxide, boehmite, magnesium hydroxide, aluminum hydroxide, silica, magnesium oxide, and calcium orthosilicate; 3. The electrochemical device of claim 1, wherein the adhesive comprises at least one of polyvinylidene fluoride, polyurethane, polyacrylate, styrene butadiene rubber, polyetherimide, sodium carboxymethyl cellulose, and acrylic ester.

8. 8. The electrochemical device according to claim 7, wherein the weight fraction of the inorganic material is 60% to 93% and the weight fraction of the adhesive is 7% to 40% relative to the total weight of the insulating layer.

9. 3. The electrochemical device according to claim 1, wherein the insulating layer has a resistance of 1 KΩ or more.

10. 3. The electrochemical device according to claim 1, wherein the total width of the positive electrode active material layer and the insulating layer is equal to or less than the width of the separator.

11. An electronic device comprising the electrochemical device according to any one of claims 1 to 10.

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