Electrode piece, electrochemical device and electronic device including the same

Abstract

To provide an electrode piece that, even when an electrochemical device receives an external impact or an electrochemical device is broken through, prevents the short-circuit between the electrode pieces and improves the safety performance of the electrochemical device and an electronic apparatus.SOLUTION: An electrode piece of the present invention includes a collector 101, a first active material layer 102, a second active material layer 103, and an insulating layer 104. The first active material layer is provided between the collector and the second active material layer and covers a first portion of a first surface of the collector. The insulating layer covers a second portion different from the first portion of the first surface of the collector. In a longitudinal direction of the electrode piece, the first active material layer includes a first end 102a and a second end 102b, the insulating layer includes a third end 104b and a fourth end 104a, and the first end and the third end are stacked alternately to form an overlap portion. The collector of the electrode piece is covered by a layer with high electric resistivity, thereby improving the safety performance of an electrochemical device and an electronic apparatus.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, in particular to electrode strips, electrochemical devices and the like. This relates to electronic devices, including optical devices. [Background technology]

[0002] Electrochemical devices (e.g., lithium-ion batteries) have become increasingly popular due to advances in science and technology and environmental protection. As demands for lithium-ion batteries have increased, they have already begun to permeate our daily lives. As a result, users have occasionally been concerned about the effects of external forces piercing lithium-ion batteries. Safety issues have arisen, and their safety performance is drawing increasing attention. Due to the occurrence of this problem, users, after-sales service providers, and lithium-ion battery manufacturers In either case, further improvements in the safety performance of lithium-ion batteries are required.

[0003] Currently, methods for improving the safety performance of lithium-ion batteries include, for example, The binder content was increased, and the ceramic coating on the separator surface was made thicker. However, these methods do not achieve the energy density of lithium-ion batteries. Therefore, under the condition of high energy density, lithium-ion batteries There is an urgent need to provide technological means to significantly improve the safety performance of vehicles. Summary of the Invention

[0004] The present invention provides an electrode strip, an electrochemical device, and an electronic device including the electrochemical device. and solve, at least to some extent, at least one problem that existed in a related field. Intend.

[0005] According to one aspect of the present invention, in some embodiments of the present invention, a current collector, a first active material layer, and An electrode strip is provided that includes a first active material layer, a second active material layer, and an insulating layer. The active material layer includes a first active material, and the second active material layer includes a second active material. an insulating layer disposed between the current collector and the second active material layer and covering a first portion of the first surface of the current collector; covers a second portion of the first surface of the current collector, which is different from the first portion, in the longitudinal direction of the electrode piece. the first active material layer includes a first end and a second end, the insulating layer includes a third end and a fourth end, The third end and the second end are stacked on top of each other to form an overlapping portion.

[0006] According to one aspect of the present invention, some embodiments of the present invention include a positive electrode piece, a separator, and and a negative electrode piece, wherein the positive electrode piece and / or the negative electrode piece are the electrode pieces described above. A gas-chemical device is provided.

[0007] According to another aspect of the present invention, in some embodiments of the present invention, the electrochemical device An electronic device including a device is provided.

[0008] The electrochemical device of the present invention employs an electrode piece having a double active material layer structure, and is covered with an active material layer. An insulating layer is provided on the empty portion of the current collector where the first active material layer is not present, and the insulating layer is then superimposed on the first active material layer. By covering the current collector completely with a In the event that the electrochemical device is broken, it is necessary to prevent short circuits between the electrodes and and improve the safety performance of electronic devices.

[0009] Other aspects and advantages of embodiments of the present invention are described in part in the following description. , as shown or explained through the practice of embodiments of the present invention. [Brief explanation of the drawings]

[0010] In the following, in order to explain the embodiments of the present invention, the embodiments of the present invention or the prior art will be described. The drawings described below are related to some of the embodiments of the present invention. It is self-evident that the invention is not too complicated. The structures illustrated in these figures may be used to obtain other embodiment figures. [Figure 1] FIG. 1 is a structural schematic diagram of an electrode piece in which an insulating layer covers a first active material layer in an embodiment of the present invention. [Figure 2] FIG. 2 is a structural schematic diagram of an electrode piece in an example of the present invention in which an insulating layer covers a first active material layer (the edges of the second active material layer and the current collector coincide in the longitudinal direction). [Figure 3] FIG. 3 is a structural schematic diagram of an electrode piece in an example of the present invention, in which an insulating layer covers a first active material layer (the second active material layer partially covers the overlapping portion). [Figure 4] FIG. 4 is a structural schematic diagram of an electrode piece in which the first active material layer covers the insulating layer in an example of the present invention. [Figure 5] FIG. 5 is a structural schematic diagram of an electrode piece in an example of the present invention in which the first active material layer covers the insulating layer (the edges of the second active material layer and the current collector in the longitudinal direction coincide with each other). [Figure 6] FIG. 6 is a structural schematic diagram of an electrode piece in an example of the present invention in which the first active material layer covers the insulating layer (the second active material layer partially covers the overlapping portion). [Figure 7] FIG. 7 is a structural schematic diagram of an electrode piece according to an embodiment of the present invention (active material layer structure on the second surface of the current collector). [Figure 8] FIG. 8 is a structural schematic diagram of the positive electrode piece of Example 1. [Figure 9] FIG. 9 is a structural schematic diagram of the positive electrode piece of Example 7. [Figure 10] FIG. 10 is a structural schematic diagram of the positive electrode piece of Example 8. [Figure 11]FIG. 11 is a structural schematic diagram of the positive electrode piece of Example 9. [Figure 12] FIG. 12 is a structural schematic diagram of the positive electrode piece of Example 11. [Figure 13] FIG. 13 is a structural schematic diagram of the positive electrode piece of Example 12. [Figure 14] FIG. 14 is a structural schematic diagram of the positive electrode piece of Example 13. DETAILED DESCRIPTION OF THE INVENTION

[0011] The embodiments of the present invention are described in detail below. In the present specification, the same or similar assembly Similar reference numerals are used for assemblies with the same or similar functions. The embodiments described in the invention and associated drawings are exemplary and diagrammatic and are not intended to provide a general understanding of the invention. The examples of the present invention are intended to be used for the purpose of understanding the present invention. It shouldn't be.

[0012] In this specification, unless otherwise specified, the terms "central," "longitudinal," "lateral," and "front "," rear," "right," "left," "inner," "outer," "lower," "higher," "horizontal," "vertical," "higher," "lower," "upper," "lower "side," "top," "bottom," and words derived from these (e.g. "horizontally," Words that express relative positions (such as "looking down" and "looking up") are listed under consideration. These relative positions should be interpreted as referring to the directions in the drawings or as depicted in the drawings. The descriptive words are for convenience of description only and do not necessarily indicate how the invention is to be constructed or operated in a particular manner. It is not a requirement to do so.

[0013] It should be noted that amounts, ratios, and other numerical values ​​may be expressed in range format herein. It should be understood that such range format is used for convenience and brevity and A range such as this not only includes the numbers explicitly specified as being limited to the range, but also All values ​​and subranges contained within said ranges are included unless each value and subrange is expressly specified. It should be understood that this is equivalent to

[0014] Furthermore, for convenience of description, terms such as "first," "second," "third," etc. may be used herein. , used to distinguish different assemblies of a figure or series of figures. Unless otherwise specified, "first," "second," "third," etc. shall refer to the corresponding assemblies. There is no intention to do so.

[0015] Electrochemical devices (e.g., lithium-ion batteries) may be damaged if subjected to external force or if the battery When the gas-chemical device is broken, the positive electrode active material layer-negative electrode active material layer, the positive electrode active material layer-negative electrode active material layer, There are four types of short-circuiting modes: positive electrode current collector, positive electrode current collector-negative electrode current collector, and positive electrode current collector-negative electrode active material layer. In these four types of short-circuit modes, the positive electrode current collector-negative electrode active material layer and the negative electrode The short circuit mode between the electrode current collector and the positive electrode active material layer has a large short circuit power when it occurs, so there are four types. This is the most dangerous short circuit mode of its kind.

[0016] An embodiment of the present invention provides an electrode strip with a double active material layer structure. A first active material layer and a second active material layer covering the first active material layer are provided in a portion of the body covered with the active material layer. The active material layer is provided, and a layer of insulating material is provided in the empty portion of the current collector that is not covered with the first active material layer. In the electrode piece, the bonding method between the first active material layer and the insulating layer is adjusted. This allows the surface of the current collector to be easily broken if the electrode piece is broken by external force. Effectively increases the resistance of the surface, making it suitable for the corresponding measurements (nail penetration or heavy impact) of electrochemical devices. It can improve safety performance in

[0017] The electrochemical device includes a positive electrode piece, a negative electrode piece, a separator, an electrolyte, etc. Both pole pieces include a current collector and an active material layer. In addition to the covered area, there is also the area that is not covered by the active material layer (also called the vacant area of ​​the current collector). For example, if the electrode assembly of the electrochemical device is of a wound type, The empty part of the current collector is the outer layer part of the electrode assembly and the inner layer tab weld part of the electrode assembly. Includes minutes.

[0018] The part covered by the active material layer has a double active material layer structure, and the part close to the current collector A first active material layer is provided on the surface of the current collector, and a second active material layer is provided at a position away from the surface of the current collector. The second active material layer may have a higher energy density than the first active material layer. When the first active material layer is struck or broken, it is easily broken into the current collector and other contacting materials. This increases the contact resistance between the collector and the wire, and provides protection to the current collector. During the test, the open area on the collector may come into direct contact with the nail, which may cause a short circuit. For example, the positive electrode current collector may be electrically connected to the negative electrode active material layer by a nail. This allows for a positive electrode current collector-negative electrode active material layer or a positive electrode current collector-nail-negative electrode active material Therefore, an insulating layer is provided in the open area of ​​the current collector. This effectively protects the current collector of the electrode piece, and also protects the positive electrode current collector. It is possible to avoid the occurrence of a short circuit mode between the negative electrode active material layer or the negative electrode current collector and the positive electrode active material layer. Here, the higher the coverage rate of the insulating layer to the vacant portion of the current collector, the The overlapping portion of the electrode piece of the present invention is connected to the insulating layer. The first active material layer and the second active material layer are stacked and covered with each other, so that the current collector is not exposed at the contact position. This avoids the problem, ensures the coverage of the insulating layer on the current collector, and improves the safety performance of the electrode piece. It is possible.

[0019] 1-3 are structural schematic diagrams of electrode pieces according to some embodiments of the present invention, where: In the overlapping portion, the insulating layer covers the first active material layer. As shown in FIG. 1-3, the electrode piece may include a current collector 101, a first active material layer 102, and a second active material layer 103. The first active material layer 102 includes a current collector 101 and a second active material layer 103 and an insulating layer 104. The first portion on one surface of the current collector 101 is provided between the second active material layer 103 and the first active material layer 104. The insulating layer 104 covers a second portion of the first surface of the current collector 101 that is different from the first portion. In the longitudinal direction of the electrode piece, the first active material layer 102 covers the first end 102a and the second end 102b. 102b, insulating layer 104 includes third end 104b and fourth end 104a, and first end 10 2a and the third end 104b are stacked together to form an overlapping portion 105. Since there is no gap between the first active material layer 104 and the first active material layer 102 in the longitudinal direction of the electrode piece, the current collector 10 1 is hard to expose even if it is subjected to an external impact or broken through

[0020] In some embodiments, the first end 102a of the first active material layer 102 is aligned in the longitudinal direction of the electrode strip. and the edge of the electrode piece at the third end 104b of the insulating layer 104 in the longitudinal direction. The distance between the pieces in the longitudinal direction is 20 mm or less. The length of the overlapping portion 105 between the porous layer 102 and the insulating layer 104 in the longitudinal direction of the electrode piece is 20 m. In some embodiments, the first active material layer 102 and the second active material layer 103 are The length of the overlapping portion 105 with the insulating layer 104 in the longitudinal direction of the electrode piece is 5.0 mm to 20 mm. In some embodiments, the electrical connection between the first active material layer 102 and the insulating layer 104 is The length of the overlapping portion 105 in the longitudinal direction of the pole piece is approximately, for example, 0.5 mm, 1. 0mm, 2.5mm, 5.0mm, 10.0mm, 15.0mm, 20.0mm, or The range is made up of any two of these values.

[0021] In some embodiments, as shown in FIGS. 1-3, in the thickness direction of the electrode strip, The end 102a is provided between the third end 104b and the current collector 101. The end 104b covers the first end 102a of the first active material layer 102 at the overlapping portion 105. The tight process tolerances required to achieve this result in reduced manufacturing time and costs. Cut.

[0022] In some embodiments, the second active material layer is located at the fifth end 10 in the longitudinal direction of the electrode piece. 1, the second active material layer 103 includes a fifth end 103a, and the fifth end 103a is close to the overlapping portion 105. 103 extends from the overlapping portion 105 in the longitudinal direction of the electrode piece and covers a part of the insulating layer 104. This allows the first end 102a of the first active material layer 102 to be covered in the longitudinal direction of the electrode piece. The edge in the longitudinal direction of the electrode piece of the third end 104b and the edge in the longitudinal direction of the electrode piece of the fifth end 103a are The strip should be positioned between the longitudinal edges of the strip.

[0023] In some embodiments, the first end of the first active material layer 102 in the longitudinal direction of the electrode strip The edge of the electrode piece 102a in the longitudinal direction and the electrode piece 103a of the fifth end 103a of the second active material layer 103 The distance between the edges of the strips in the longitudinal direction is 3 mm or less. In the embodiment, the second active material layer 103 covers the insulating layer 104 in the longitudinal direction of the electrode piece. The length of the extended portion is 3 mm or less.

[0024] In some embodiments, as shown in FIG. 2, the fifth end 103a of the second active material layer 103 the edge of the electrode piece in the longitudinal direction of the insulating layer 104 and the edge of the electrode piece in the longitudinal direction of the third end 104b of the insulating layer 104 The connections between them match.

[0025] In some embodiments, as shown in FIG. 3, the fifth end 103a of the second active material layer 103 The edge of the electrode piece in the longitudinal direction of the first end 102a of the first active material layer 102 is between the edge in the longitudinal direction of the electrode piece at the third end 104b of the insulating layer 104 and the edge in the longitudinal direction of the electrode piece at the third end 104b of the insulating layer 104. Located.

[0026] In some embodiments, the second active material layer 103 overlaps the first active material layer 102 in the overlapping portion 10 5. In the case of a lithium ion battery, the overlapping portion of the first active material layer 102 Exposure of parts other than 105 will cause the following situation: Lithium ions in the exposed parts After the lithium ions are released, there is no active material in the corresponding electrode piece of the other polarity into which the lithium ions can be inserted. Therefore, the released lithium ions are transferred to the corresponding current collector of the other polarity (e.g., the negative electrode current collector). As the number of cycles of the lithium-ion battery increases, lithium metal particles form on the surface. The formation of lithium metal particles continues to progress, thereby forming lithium on the surface of the anode piece. Dots made of lithium metal particles appear, reducing the capacity of lithium-ion batteries (electrochemical devices). .

[0027] In some embodiments, the length of the second active material layer 103 in the longitudinal direction of the electrode strip is , which is longer than the length of the portion of the first active material layer 102 other than the overlapping portion 105. In this case, the length of the second active material layer 103 is the length of the portion other than the overlapping portion 105 of the first active material layer 102. The minus length is equal to or less than 4 mm.

[0028] 4-6 are structural schematic diagrams of electrode pieces according to some embodiments of the present invention, where: In the overlapping area, the first active material layer covers the insulating layer. In the direction of the arrow, the third end 104b is provided between the first end 102a and the current collector 101. As shown in FIG. 4, the second active material layer 103 is formed from the overlapping portion 105 in the longitudinal direction of the electrode piece. and can cover a part of the insulating layer 104. The longitudinal edge of the electrode piece is aligned with the longitudinal edge of the electrode piece at the third end 104b and the longitudinal edge of the electrode piece at the fifth end 104c. The insulating layer 104 is positioned between the end 103a and the edge of the electrode piece in the longitudinal direction. Since the insulating effect is better than that of the first active material layer 102, it is resistant to nail punctures or heavy impacts. In this case, the electrode piece shown in FIG. 4 is covered with the first active material layer 102 in the overlapping portion 105. The insulating layer 104 can insulate and separate the current collector 101 better, resulting in high safety. At the same time, the fifth end 103a of the second active material layer 103 is connected to the first active material layer 102. Since the end of the first end 102a is covered, it is resistant to external forces with a large destructive force such as nail penetration or impact. In this case, since the first end 102a is not easily dropped off, the current collector 101 is not exposed, The electrode assembly is safer.

[0029] In some embodiments, as shown in FIG. 5, the fifth end 103a of the second active material layer 103 the edge of the electrode piece in the longitudinal direction of the insulating layer 104 and the edge of the electrode piece in the longitudinal direction of the third end 104b of the insulating layer 104 The connections between them match.

[0030] In some embodiments, as shown in FIG. 6, the fifth end 103a of the second active material layer 103 The edge of the electrode piece in the longitudinal direction of the first end 102a of the first active material layer 102 is between the edge in the longitudinal direction of the electrode piece at the third end 104b of the insulating layer 104 and the edge in the longitudinal direction of the electrode piece at the third end 104b of the insulating layer 104 Located in.

[0031] FIG. 7 is a structural schematic diagram of electrode pieces according to other embodiments of the present invention, and the electrode pieces further The current collector 101 further includes a second surface. The third active material layer 106 is provided between the current collector 101 and the fourth active material layer 107, and , covering the second surface of the current collector. In some embodiments, the third active material layer 106 is The fourth active material layer 107 has the same composition as the second active material layer 103. and the content of the active material in the third active material layer 106 is The content of the active material is smaller than that of the active material.

[0032] As shown in FIG. 7, in some embodiments, the third active material The layer 106 includes a sixth end 106a, the sixth end 106a being proximate to the overlapping portion 105 and The edge of the electrode piece of the sixth end 106a in the longitudinal direction is aligned with the edge of the electrode piece of the first end 102a in the longitudinal direction. The electrode piece 104 is located between the edge of the electrode piece 104 at the fourth end 104a and the edge of the electrode piece 104a in the longitudinal direction.

[0033] In some embodiments, the fourth active material layer 107 is located at the seventh end in the longitudinal direction of the electrode piece. 107a, the seventh end 107a being close to the overlapping portion 105, and the seventh end 107a being It extends beyond the sixth end 106a in the longitudinal direction of the pole piece.

[0034] It should be understood that, if not contrary to the technical idea of ​​the present invention, limitations may be imposed according to actual needs. The electrode piece is provided with an insulating layer at one end thereof, which overlaps with the active material layer. For example, the positive electrode current collector can be provided with a pair of electrodes at both ends (in the longitudinal direction of the positive electrode piece) on its two surfaces. an insulating layer may be provided in a vacant portion of the current collector connected to the positive electrode active material layer; Alternatively, an insulating layer may be provided on one surface of the positive electrode current collector.

[0035] In some embodiments, the first active material is a material having a particle size distribution on a volume basis that is smaller than the particle size distribution on a volume basis. Therefore, the particle size at which the cumulative volume reaches 50% (Dv50, average particle size) is 0.2 μm to 15 μm and the first active material has a particle size distribution based on volume in which the particle diameter is gradually increased from the small particle diameter side to the large particle diameter side. The particle diameter at which the volume becomes 90% (Dv90) is in the range of 40 μm or less. When the active material has a small Dv90, it has a high coverage and adhesion to the current collector 101. In some embodiments, the average particle size (Dv50) of the second active material is The average particle diameter (Dv50) of the material is 1:1 to 40:1. The smaller the particles of the first active material, The thickness of the first active material layer can be reduced. That is, the active material is dissolved in a dispersant (ethanol or acetone, or other surfactants) and subjected to ultrasonic treatment for 30 minutes. Place in an Alvern particle size measuring device and measure.

[0036] In some embodiments, the thickness of the first active material layer 102 is between 0.1 μm and 20 μm. Furthermore, in some embodiments, the thickness of the first active material layer 102 is 0.5 μm to 15 μm. In some embodiments, the thickness of the first active material layer 102 is 2 μm to 10 μm. In particular, the thickness of the first active material layer is equal to or greater than the particle size Dv90 of the first active material. This is to ensure the coverage of the first active material layer.

[0037] In some embodiments, the thickness of the insulating layer 104 is greater than the thickness of the first active material layer 102 and the thickness of the second active material layer 104. The thickness of the active material layer 103 is equal to or less than the total thickness of the active material layer 103. In order to achieve a certain insulating effect, the thickness of the insulating layer 104 is greater than 0.1 μm. In some embodiments, the thickness of the insulating layer 104 is between 1 μm and 30 μm. In some other embodiments, the thickness of the insulating layer 104 is between 5 μm and 15 μm.

[0038] In some embodiments, the density of the insulating layer 104 in the overlapping portion 105 is greater than that of the insulating layer 1 In some embodiments, the density is 60% to 90% of the density in the non-overlapping portion of 04. In this case, the length of the overlapping portion of the first active material layer is the length of the non-overlapping portion of the first active material layer. The density in the overlapping portion of the first active material layer is shorter than that in the non-overlapping portion of the first active material layer. Close to density.

[0039] According to some embodiments of the present invention, the insulating layer comprises inorganic particles and / or polymers, The layer may contain a suitable dispersant, which may be ethanol or acetone, or other suitable dispersant. Inorganic particles include, but are not limited to, alumina, silica, maize oxide, and the like. magnesium, titanium oxide, hafnium dioxide, tin oxide, cerium oxide, nickel oxide, Zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, bema Calcium hydroxide, magnesium hydroxide, barium sulfate, and and combinations thereof. The polymer is selected from the group consisting of vinylidene fluoride homopolymers. Polymer, vinylidene fluoride copolymer, hexafluoropropylene copolymer, polystyrene Polyphenylacetylene, sodium polyacrylate, potassium polyacrylate, poly Methyl methacrylate, polyethylene, polypropylene, polytetrafluoroethylene and and combinations thereof.

[0040] In some embodiments, the electrode strip is a positive electrode strip, wherein the first active material and the second active material The properties are independent of each other: lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate um, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, Lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate , lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, nickel cobalt lithium aluminate, lithium titanate, and combinations thereof.

[0041] In some embodiments, the electrode strip is a negative electrode strip, wherein the first active material and the second active material The quality is independent of each other, artificial graphite, natural graphite, mesocarbon microbeads, soft carbon Bon, hard carbon, silicon, silicon-oxygen compounds, silicon-carbon compounds, tin, tin alloys , niobium titanate, lithium titanate, and combinations thereof. .

[0042] In some embodiments, the first active material layer 102 and the second active material layer 103 may be made of a binder. and the binder is polyvinylidene fluoride, vinylidene fluoride-hexafluoro Propylene copolymer, polyamide, polyacrylonitrile, polyacrylate, poly Polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinyl Pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene Polyethylene, polyhexafluoropropylene, and styrene butadiene rubber or On the other hand, the binder may be a material that is a binder for the active material layer and a combination thereof. On the other hand, the binder content increases, and the first active material layer 10 The binder content of the first active material layer 102 is The binder content of the second active material layer 103 is 1.5% to 6% of the total weight of the layer 102. is 0.5% to 4% of the total weight of the second active material layer 103.

[0043] In some embodiments, the first active material layer 12 and the second active material layer 13 further comprise a constant A conductive agent may be included in the composition. The conductive agent may be carbon nanotubes, conductive carbon black, or the like. , acetylene black, graphene, ketjen black, and carbon fiber The conductive material of the first active material layer may include, but is not limited to, one of these or a combination thereof. The content of the conductive agent in the first active material layer is 0.5% to 5% of the total weight of the first active material layer, and the content of the conductive agent in the second active material layer is 0.5% to 5% of the total weight of the first active material layer. The content of is 0.5% to 5% of the total weight of the second active material layer.

[0044] Furthermore, even if other treatments are performed on the first active material layer 102 or the second active material layer 103, Alternatively, the current collector 101 may be subjected to a treatment such as roughening treatment or heat treatment. The principle or effect of this is to increase adhesion to the current collector. Although not specifically described herein, they are included within the scope of the present invention.

[0045] In some embodiments, the electrode strip is a positive electrode strip, and the positive electrode current collector is aluminum foil. or nickel foil, and the electrode piece is a negative electrode piece, the negative electrode current collector of which is copper foil or nickel foil. Although the positive electrode current collector and the negative electrode current collector may be a quartz foil, other positive electrode current collectors and negative electrode current collectors commonly used in this field may also be used. It may also be used.

[0046] It should be understood that, unless it is contrary to the technical idea of ​​the present invention, the adjustment of the electrode piece in the present invention The production method is not limited to the present invention, and any suitable preparation method in the art may be employed.

[0047] Some embodiments of the present invention include an electrochemical device including a positive electrode piece, a separator, and a negative electrode piece. At least one of the positive and negative electrode pieces is the electrode piece in the above embodiment. The present invention further provides an electrochemical device.

[0048] In some embodiments, the separator is made of polyethylene, polypropylene, polyethylene At least one selected from polyethylene terephthalate, polyimide, and aramid Examples of polyethylene include, but are not limited to, high density polyethylene, low density polyethylene, At least one component selected from polyethylene and ultra-high molecular weight polyethylene Among them, polyethylene and polypropylene are excellent in preventing short circuits. In addition, the cut-off effect can improve the stability of the battery.

[0049] The separator may further include a porous layer on the surface thereof, and the porous layer may be at least The porous layer includes inorganic particles and a binder, and the inorganic particles are , alumina (Al2O3), silica (SiO2), magnesium oxide (MgO), titanium oxide Tin oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium oxide CeO2, Nickel oxide (NiO), Zinc oxide (ZnO), Calcium oxide (Ca O), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (S iC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and and barium sulfate, or a combination of various kinds thereof. , polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, poly Amides, polyacrylonitrile, polyacrylic esters, polyacrylic acid, polyacrylamides sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ester ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoro propylene or a combination of various thereof.

[0050] The porous layer improves the separator's heat resistance, anti-oxidation performance, and electrolyte penetration performance, This can enhance the adhesion between the separator and the positive or negative electrode piece.

[0051] The electrochemical device of the present invention further comprises an electrolyte, which may be a gel electrolyte, a solid electrolyte, or and an electrolyte solution, the electrolyte solution including a lithium salt and a non-aqueous solvent. .

[0052] In some embodiments of the present invention, the lithium salt is LiPF6, LiBF4, LiA sF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and and lithium difluoroborate. Lithium salts are used in LiP because they can provide high electrical conductivity and improve cycle characteristics. F6 is used.

[0053] The non-aqueous solvent may be a carbonate ester compound, a carboxylic acid ester compound, an ether compound, or the like. It may also be other organic solvents, or a combination thereof.

[0054] The carbonate ester compound may be a chain carbonate ester compound, a cyclic carbonate ester compound, a full carbonate ester compound, or a cyclic carbonate ester compound. The compound may be a hydroxycarbonate compound or a combination thereof.

[0055] Examples of the chain carbonate ester compound include diethyl carbonate (DEC), dimethyl carbonate (DMCO), and methyl carbonate (DMCO). Carbonate (DMC), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate MPC, ethyl propyl carbonate (EPC), methyl ethyl carbonate (M EC), and combinations thereof. Examples of cyclic carbonate ester compounds are ethylene carbonate, Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC) , vinyl ethylene carbonate (VEC), propyl propionate (PP), and An example of a fluorocarbonate compound is fluoroethylene carbonate. FEC, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene ethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-Fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene ethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, tri fluoromethyl ethylene carbonate and combinations thereof.

[0056] Examples of the carboxylic acid ester compound include methyl acetate, ethyl acetate, and n-propyl acetate. , tert-butyl acetate, methyl propionate, ethyl propionate, propionate Pill, gamma-butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone lactones, methyl formate, and combinations thereof.

[0057] Examples of the ether compound include dibutyl ether and tetraethylene glycol dimethyl ether. Ether, Diethylene Glycol Dimethyl Ether, 1,2-Dimethoxyethane, 1,2 -Diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetra hydrofuran and combinations thereof.

[0058] Examples of other organic solvents mentioned above are dimethyl sulfoxide, 1,2-dioxolane, sulfur Folane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2 -pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate triethyl phosphate, trioctyl phosphate, and phosphate esters, and combinations thereof It's a combination.

[0059] It should be understood that, unless it is contrary to the technical idea of ​​the present invention, The preparation method of the device is not limited to the present invention, and any suitable preparation method in the art may be used. In some embodiments, the method for preparing the electrochemical device includes: The separator and negative electrode pieces are wound or stacked in this order to prepare an electrode assembly. After that, it is placed in, for example, an aluminum plastic film, and the electrolyte is poured in. The key point is that by applying and packaging the material, a lithium-ion battery can be obtained.

[0060] In the above exemplary embodiments, lithium ion batteries are used as examples. After reading this specification, it should be understood that, if it is not contrary to the technical idea of ​​the present invention, Specific examples of electrochemical devices include all types of primary or secondary batteries. In particular, the electrochemical device is a lithium metal secondary battery, a lithium ion secondary battery, a lithium The present invention relates to a lithium secondary battery, including a lithium ion polymer secondary battery or a lithium ion polymer secondary battery.

[0061] In some embodiments of the present invention, an electronic device comprising an electrochemical device according to an embodiment of the present invention is An apparatus is also provided.

[0062] The electronic device according to the embodiment of the present invention is not particularly limited and may be used in any electronic device known in the prior art. In some embodiments, the electronic device may be an electronic cigarette, an electronic vapor device, Wireless headset, robot vacuum cleaner, unmanned aerial vehicle, laptop computer, pen case Power computers, mobile computers, e-book players, mobile phones, mobile Type facsimile, portable copier, portable printer, stereo headset, video recorder recorders, LCD TVs, portable cleaners, portable CD players, minidiscs, Walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders -, radio, backup power supply, motor, automobile, motorcycle, auxiliary bicycle, bicycle, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage This includes, but is not limited to, storage batteries and lithium-ion capacitors. .

[0063] Specific Examples In order to better explain the present invention, some specific examples and comparative examples will be given below. Then, for each of the examples and comparative examples, the battery capacity was measured, the battery nail penetration test was performed, and the weight Those skilled in the art will recognize that the preparation methods described in this invention are merely illustrative examples. and any other suitable method of preparation is understood to be within the scope of the present invention. It should be.

[0064] 1.Measurement method 1.1 Battery capacity measurement: After formation, the lithium-ion battery (electrochemical device) was placed in an atmosphere of 25±3°C for 3 Let stand for 0 minutes, then charge at a constant current of 0.5C until the voltage reaches 4.4V (rated voltage). Then, charge at a constant voltage until the current reaches 0.05C, stop charging, and measure the lithium The lithium-ion battery was left for 30 minutes. After that, the current was increased to 0.2C for 3 minutes. The lithium-ion battery was discharged to 0.0V and then left to stand for 30 minutes. The capacity was recorded as the actual battery capacity of the lithium-ion battery. Lithium-ion battery volumetric energy density = Actual battery capacity / (Lithium-ion battery length) length x width x thickness).

[0065] 1.2 Battery nail penetration test: After formation, 10 lithium-ion batteries were placed at room temperature (25±3℃) and 0.5C. The battery was charged at a constant current of 4.4V until the voltage reached 4.4V. Charged until the current reached 0.05C and the battery was fully charged to 4.4V. A nail penetration experiment was conducted on a lithium-ion battery, and a 2.5 mm diameter steel nail (made of carbon steel) , taper is 16.5 mm, total length of steel nail is 100 mm) and nail penetration is 30 mm / s The nail penetration speed and nail penetration depth are based on the taper of the steel nail penetrating the lithium-ion battery. The lithium-ion battery was observed to see if it emitted smoke, caught fire, or exploded. The Um-ion battery is certified as having passed the nail penetration test.

[0066] 1.3 Heavy object impact measurement After formation, 10 lithium-ion batteries were placed at room temperature (25±3℃) and 0.5C. The battery was charged at a constant current of 4.4V until the voltage reached 4.4V. Charged until the current reached 0.05C and the battery was fully charged to 4.4V. A heavy-weight impact test was conducted on a lithium-ion battery, and an impactor (bar, total length 15.8 mm) was used. The weight is 9.1 kg, and the battery is located at a vertical height of 61 cm from the lithium-ion battery. The impactor was dropped and hit the lithium-ion battery, causing the lithium-ion battery to emit smoke, catch fire, If there is no explosion, the lithium-ion battery is not suitable for the heavy-duty impact test. It is recognized as being satisfactory.

[0067] Example 1 Aluminum foil is used as a positive electrode current collector, and a first positive electrode active material is attached to one surface of the aluminum foil. Material (where the particle size of lithium iron phosphate is Dv50: 3 μm, Dv90: 10 μm) The first positive electrode active material layer slurry containing the first positive electrode active material layer was uniformly applied in one layer. The composition is 95.8 wt% lithium iron phosphate, 2.8 wt% polyvinylidene fluoride. and 1.4 wt% of conductive carbon black, dried at 85°C, and Then, a positive electrode active material layer was formed on the positive electrode piece, which was connected to the first positive electrode active material layer at one end in the longitudinal direction of the positive electrode piece. a layer of insulating layer slurry is applied to the open area of ​​the current collector and the area on the first positive electrode active material layer; The composition of the insulating layer slurry is 98 wt% alumina and 2 wt% polyvinylidene fluoride. The insulating layer was dried at 85°C to form an insulating layer having a thickness of 10 µm. The overlapping portion formed by covering the positive electrode active material layer is 2 mm long in the longitudinal direction of the positive electrode piece. Then, a layer of the second positive electrode active material layer slurry was applied onto the dried first positive electrode active material layer. The second positive electrode active material layer slurry was composed of 97.8 wt % cobalt. Lithium oxide (where the particle size of lithium cobalt oxide is Dv50:13μm, Dv90:3 8 μm), 0.8 wt% polyvinylidene fluoride, and 1.4 wt% conductive carbon black The positive electrode piece was then dried at 85°C to form a second positive electrode active material layer. In the direction of the second positive electrode active material layer, the edge of the fifth end is located on the non-overlapping portion of the insulating layer (i.e., , the edge extends beyond the edge of the first end of the first positive electrode active material layer), the second positive electrode active material layer extends and overlaps The length exceeding the overlapping portion was 1 mm. The third positive electrode active material layer was prepared from the first active material layer. The composition of the second positive electrode active material layer is the same as the composition of the fourth positive electrode active material layer. Then, the cathode piece is cold-rolled, where the cold-rolling pressure is 60 T, The rolling speed is 40m / min, and after cutting and slitting, it is heated to 85℃ under vacuum conditions. The mixture was dried for 4 hours to prepare a positive electrode piece. The thickness of the insulating layer is 8 μm, and the thickness of the second positive electrode active material layer and the fourth active material layer is 10 μm. The thickness of the porous layer was 50 μm. The positive electrode current collector 201, the first positive electrode active material layer 202, and the second positive electrode active material layer 203 in the positive electrode piece , and the placement form of the insulating layer 204 refer to FIG.

[0068] Copper foil was used as the negative electrode current collector, and a layer of graphite slurry was uniformly applied to the surface of the copper foil. The slurry composition is 97.7 wt% artificial graphite, 1.3 wt% carboxymethyl cellulose The compound is a combination of sodium carbonate and 1.0 wt% styrene butadiene rubber. The mixture was dried at 100° C., and then cold-rolled, cut, and slit to prepare negative electrode pieces.

[0069] The lithium salt LiPF6 and non-aqueous organic solvent (ethylene carbonate, diethyl carbonate) Propylene carbonate: propyl propionate: vinylene carbonate = 20 A solution of lithium ion (Li:30:20:28:2, mass ratio) prepared in a mass ratio of 8:92 was added to the It was used as the electrolyte for the ON battery.

[0070] The positive and negative electrode pieces are wound up and separated by a polyethylene separator. A wound electrode assembly was obtained by this process, which was then placed in a case and filled with an electrolyte. After going through processes such as packaging, standing, formation, and molding, the finished lithium-ion battery The battery was obtained.

[0071] Examples 2-6 In Example 2-6, the overlapping portion of the first positive electrode active material layer and the insulating layer was Except for the different lengths, the preparation method was the same as in Example 1. See Table 1 for details.

[0072] Example 7 In Example 7, the edge of the fifth end of the second positive electrode active material layer in the longitudinal direction of the positive electrode piece is the overlapping portion. (i.e., located between the edge of the first end of the first positive electrode active material layer and the edge of the third end of the insulating layer) The same procedure as in Example 1 was repeated except that the length of the second positive electrode active material layer covering the overlapping portion was 1 mm. FIG. 9 is a structural schematic diagram of the positive electrode piece of Example 7. a positive electrode current collector 301, a first positive electrode active material layer 302, a second positive electrode active material layer 303, and an insulating layer The installation form of the layer 304 is shown in FIG.

[0073] Example 8 In Example 8, the edge of the fifth end of the second positive electrode active material layer and the insulating layer The edge of the third end coincides with the edge of the second positive electrode active material layer (i.e., the second positive electrode active material layer and the overlapping portion overlap with each other and are connected). The distance between the second positive electrode active material layer and the overlapping portion is 0 mm. The preparation method was the same as in Example 1. Figure 10 is a structural schematic diagram of the positive electrode piece of Example 8. The positive electrode current collector 401, the first positive electrode active material layer 402, and the second positive electrode active material layer 403 in the positive electrode piece , and the placement form of the insulating layer 404 refer to FIG.

[0074] Example 9 The differences between Example 9 and Example 1 are as follows: In Example 9, first, the aluminum foil A layer of insulating layer slurry is uniformly applied to the surface of the positive electrode piece, and then one end of the positive electrode piece in the longitudinal direction is A first positive electrode active material layer is formed on the open portion of the current collector connected to the insulating layer and on the insulating layer. The first positive electrode active material layer was coated with the insulating layer. The length of the positive electrode piece in the longitudinal direction is 2 mm, and the thickness of the first positive electrode active material layer is 10 μm. m, and the thickness of the insulating layer is 8 μm. Other than the above, Example 9 was the same as Example 1. Figure 11 shows the structure of the positive electrode piece of Example 9. 5 is a diagram showing a positive electrode current collector 501, a first positive electrode active material layer 502, a second positive electrode active material layer 503, and a The arrangement of the positive electrode active material layer 503 and the insulating layer 504 is shown in FIG.

[0075] Example 10 In Example 10, the second positive electrode active material layer extends in the longitudinal direction of the positive electrode piece, and the overlapping portion The preparation method was the same as in Example 9, except that the excess length was 3 mm.

[0076] Example 11 In Example 11, the edge of the fifth end of the second positive electrode active material layer in the longitudinal direction of the positive electrode piece was located at the overlapping portion. (i.e., located between the edge of the first end of the first positive electrode active material layer and the edge of the third end of the insulating layer) ), and the length of the second positive electrode active material layer covering the overlapping portion is 1 mm. The preparation method was the same as that of Example 11. A positive electrode current collector 601, a first positive electrode active material layer 602, a second positive electrode active material layer 603 in the positive electrode piece, 12 for the placement of the insulating layer 604.

[0077] Example 12 In Example 12, the edge of the fifth end of the second positive electrode active material layer and the insulating layer The edge of the third end of the second positive electrode active material layer is aligned with the edge of the second positive electrode active material layer. The distance between the second positive electrode active material layer and the overlapping portion is 0 mm. The preparation method was the same as in Example 9. Figure 13 is a structural schematic diagram of the positive electrode piece of Example 12. Positive electrode current collector 701, first positive electrode active material layer 702, and second positive electrode active material layer in the positive electrode piece of Example 12 The placement of the insulating layer 704 and the insulating layer 703 is shown in FIG.

[0078] Example 13 In Example 13, an insulating layer structure similar to that in Example 1 is provided on both surfaces of the positive electrode current collector. Other than that, the preparation method was the same as in Example 1. Figure 14 is a structural schematic diagram of the positive electrode piece of Example 13. The positive electrode current collector 801, the first positive electrode active material layer 802, the second positive electrode The active material layer 803 and the insulating layer 804 are provided as shown in FIG.

[0079] Comparative Example 1 The differences between Comparative Example 1 and Example 1 are as follows: In Comparative Example 1, the positive electrode piece is The insulating layer slurry is applied to a position 3 mm from the first positive electrode active material layer at one end of the electrode. the distance between the third end of the insulating layer and the first end of the first positive electrode active material layer is 3 mm, and The first positive electrode active material layer after drying, and the space between the first positive electrode active material layer and the insulating layer in the current collector A layer of the second positive electrode active material layer slurry is successively applied onto the portion and dried to form the second positive electrode active material layer. Here, in the longitudinal direction of the positive electrode piece, the edge of the fifth end of the second positive electrode active material layer was a gap between the positive electrode active material layer and the insulating layer and between the edge of the fifth end and the insulating layer; The distance between is 2 mm. Other than the above, Comparative Example 1 was the same as Example 1.

[0080] After the lithium ion battery products of the above examples and comparative examples were completed, The volume, thickness, width and length of the product were recorded to determine the volumetric energy density of the pond. The lithium ion battery products of the above examples and comparative examples were subjected to battery capacity measurement, battery nail puncture test, and Tests and heavy object impact measurements were conducted.

[0081] Table 1 shows the experimental parameters and measurement results for each of the examples and comparative examples.

[0082] [Table 1]

[0083] As shown in Table 1 above, in the electrode piece of the present invention, the first active material layer and the insulating layer overlap each other. By providing overlapping parts to fit together, nail penetration pass rate in nail penetration test and heavy object impact measurement It can effectively improve the pass rate of heavy-duty impact test, and thus improve the safety of electrochemical devices. This improves performance and has little effect on energy density.

[0084] As can be seen from the comparison between Comparative Example 1 and Example 1, a gap was formed between the insulating layer and the first active material layer. In some cases, the heavy-duty impact pass rate of lithium-ion batteries will be significantly reduced, and For example, the nail penetration pass rate of the lithium-ion battery in Comparative Example 1 is slightly lower. is located between the insulating layer and the first positive electrode active material layer and is not protected by a layer with high electrical resistivity. Because of the presence of the positive electrode current collector, if it is subjected to an impact from a heavy object, the positive electrode current collector may be damaged by the negative electrode active material. Contact with the layer can easily short-circuit the lithium-ion battery.

[0085] As can be seen from the comparison of Examples 1 to 6, the overlapping portion between the insulating layer and the first active material layer increases. As a result, the heavy-duty impact pass rate for lithium-ion batteries also increases. However, the increase in overlapping areas This results in a decrease in the energy density of lithium-ion batteries.

[0086] As can be seen from the comparison of Examples 1, 7 and 8, the second active material layer, the first active material layer and the insulating layer The installation form of the lithium-ion battery has a certain effect on the pass rate of heavy-duty impact testing. If the polymer layer extends over and / or beyond the overlap, the lithium-ion battery It has a high pass rate for heavy-duty impact. In addition, the second active material layer extends to cover the overlapping portion or the insulating layer. This allows for a slight increase in the energy density of lithium-ion batteries.

[0087] As can be seen from the comparison between Example 1 and Example 9, in the overlapping portion, the first positive electrode active material layer By covering the insulating layer, a high pass rate for heavy impact tests can be achieved. As can be seen from the comparison, the fifth end of the second positive electrode active material layer covers the first end of the first positive electrode active material layer. This makes the first end 102a less likely to fall off, resulting in better nail penetration pass rate and weight. It can have a mass impact pass rate.

[0088] By comparing the above examples, it can be seen that the electrode piece of the present invention can effectively improve the safety performance of the electrochemical device. It is clearly seen that the effect on the energy density can be reduced. .

[0089] Throughout the specification, the terms "some embodiments," "some embodiments," "one embodiment," "other embodiments," "others," "others," "others," "some sub-embodiments ... References to "one example," "example," "particular example," or "some examples" of the present invention are to be construed as meaning the same. At least one embodiment or example may include the specific features, structures, materials, etc. described in that embodiment or example. Therefore, the term "material" as used herein means to include any material or feature described in various places throughout the specification, even if the material or feature is not specifically mentioned. For example, "in some embodiments," "in an embodiment," "in one embodiment," "In another example," "in an example," "in a particular example," or "example" does not necessarily The same embodiment or example of the present invention is not necessarily cited. The materials or properties may be combined in any suitable manner in one or more embodiments or examples. It can be adjusted.

[0090] While illustrative embodiments have been disclosed and described, those skilled in the art will recognize that the above embodiments are not limiting of the invention. and cannot be construed as violating the technical idea, principle, and scope of the present invention. It should be understood that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit and scope of the present invention. do.

Claims

1. a current collector including a first surface; a first active material layer including a first active material; a second active material layer including a second active material; an insulating layer; and the first active material layer is provided between the current collector and the second active material layer and covers a first portion of a first surface of the current collector; the insulating layer covers a second portion of the first surface of the current collector that is different from the first portion; In the longitudinal direction of the electrode piece, the first active material layer includes a first end and a second end, and the insulating layer includes a third end and a fourth end, the first end and the third end are stacked on top of each other to form an overlapping portion; the second active material layer includes a fifth end in the longitudinal direction of the electrode piece, When observed along the thickness direction of the electrode piece toward the current collector, the projection of the fifth end falls on the insulating layer.

2. 2. The electrode piece according to claim 1, wherein the distance between the edge of the electrode piece at the first end in the longitudinal direction and the edge of the electrode piece at the third end in the longitudinal direction is 20 mm or less than 20 mm.

3. The electrode piece according to claim 1 , wherein the first end is provided between the third end and the current collector in a thickness direction of the electrode piece.

4. The electrode piece according to claim 1 , wherein the third end is provided between the first end and the current collector in the thickness direction of the electrode piece.

5. The electrode piece according to any one of claims 1 to 4, wherein an edge of the fifth end in the longitudinal direction of the electrode piece and an edge of the third end in the longitudinal direction of the electrode piece coincide with each other, and when observed along the thickness direction of the electrode piece toward the current collector, a projection of the fifth end falls on the edge of the insulating layer.

6. An electrode piece according to any one of claims 1 to 4, wherein the longitudinal edge of the electrode piece at the fifth end is located between the longitudinal edge of the electrode piece at the first end and the longitudinal edge of the electrode piece at the third end.

7. An electrode piece according to any one of claims 1 to 4, wherein the longitudinal edge of the electrode piece at the first end is located between the longitudinal edge of the electrode piece at the third end and the longitudinal edge of the electrode piece at the fifth end.

8. 8. The electrode piece according to claim 7, wherein the distance between the edge of the electrode piece at the first end in the longitudinal direction and the edge of the electrode piece at the fifth end in the longitudinal direction is 3 mm or less than 3 mm.

9. 2. The electrode piece according to claim 1, wherein the electrode piece further includes a third active material layer and a fourth active material layer, the current collector further includes a second surface, and the third active material layer is disposed between the current collector and the fourth active material layer and covers the second surface of the current collector.

10. In the longitudinal direction of the electrode piece, the third active material layer includes a sixth end, 10. The electrode piece according to claim 9, wherein a longitudinal edge of the electrode piece at the sixth end is located between a longitudinal edge of the electrode piece at the first end and a longitudinal edge of the electrode piece at the fourth end.

11. The electrode piece according to claim 10 , wherein the fourth active material layer includes a seventh end in the longitudinal direction of the electrode piece, the seventh end extending beyond the sixth end in the longitudinal direction of the electrode piece.

12. 2. The electrode piece according to claim 1, wherein the density of the insulating layer in the overlapping portion is 60% to 90% of the density of the insulating layer in the portion other than the overlapping portion.

13. 2. The electrode strip of claim 1, wherein the first active material and the second active material are each independently selected from the group consisting of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, lithium manganate, lithium nickel oxide, lithium nickel cobalt manganate, lithium excess manganese-based materials, lithium nickel cobalt aluminate, lithium titanate, and combinations thereof.

14. 2. The electrode strip of claim 1, wherein the first active material and the second active material are each independently selected from the group consisting of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon, silicon-oxygen compounds, silicon-carbon composites, tin, tin alloys, niobium titanate, lithium titanate, and combinations thereof.

15. Both the first active material layer and the second active material layer further comprise a binder and a conductive agent; the binder is selected from the group consisting of polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, polyamides, polyacrylonitriles, polyacrylic esters, polyacrylic acids, polyacrylates, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ethers, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene butadiene rubber, and combinations thereof; and The electrode strip of claim 1 , wherein the conductive agent is selected from the group consisting of carbon nanotubes, conductive carbon black, acetylene black, graphene, ketjen black, carbon fiber, and combinations thereof.

16. the insulating layer contains inorganic particles and / or a polymer; the inorganic particles are selected from the group consisting of alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and combinations thereof; 2. The electrode strip of claim 1, wherein the polymer is selected from the group consisting of a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylacetylene, sodium polyacrylate, potassium polyacrylate, polymethyl methacrylate, polyethylene, polypropylene, polytetrafluoroethylene, and combinations thereof.

17. An electrochemical device comprising a positive electrode piece, a separator, and a negative electrode piece, wherein the positive electrode piece and / or the negative electrode piece is an electrode piece according to any one of claims 1 to 16.

18. An electronic device comprising the electrochemical device of claim 17.

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