Wound electrochemical device and electronic device

Abstract

A wound electrochemical device and electronic equipment relate to the technical field of energy storage devices. The wound electrochemical device comprises an electrode assembly (100), wherein the electrode assembly (100) comprises a first electrode (10), wherein the first electrode (10) comprises a current collector (11), a protective layer (12), and an active material layer (13) arranged on at least one surface of the current collector (11), wherein the protective layer (12) is located between the current collector (11) and the active material layer (13), and the first electrode (10) is wound to form a straight section (101) and a bent section (102), and the protective layer (12) is arranged on the bent section (102) of the first electrode (10). Through the above arrangement, the brittleness of the current collector (11) at the bent section (102) is improved, the winding performance of the bent section (102) of the first electrode (10) is improved, and the bent section (102) of the first electrode (10) is prevented from cracking or brittle fracture during the winding process, thereby improving the compactness of the electrode and the energy density of the electrochemical device.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of energy storage devices, and in particular to a wound electrochemical device and an electronic device. Background Art

[0002] At present, lithium-ion batteries have become the preferred power source for consumer portable electronic products. With the rapid development of mobile communication devices and multimedia devices, people have put forward higher and higher requirements on the performance of lithium-ion batteries used in these devices, especially the energy density of lithium-ion batteries, requiring lithium-ion batteries to have higher energy density and provide the maximum energy in the smallest possible space.

[0003] During the production process of batteries, the battery electrodes must first be cold pressed. During the cold pressing process, the active layer granular material of the electrode is easily squeezed between the electrode collector and embedded in the collector, causing damage to the collector. In the subsequent winding process, the bending section of the electrode is subjected to greater stress, causing the bending section of the electrode to easily crack or even break. As the electrode compression increases, the brittleness of the electrode increases, and the possibility of cracking and breaking of the bending section of the electrode also increases.

[0004] In the prior art, the electrode is prevented from becoming brittle by reducing the compaction of the electrode, so as to prevent the bent section of the electrode from cracking and breaking during the winding process. However, this approach cannot achieve a high energy density of the battery. Alternatively, the brittleness of the electrode can be improved by mixing main material particles with a smaller roughness into the active material layer. However, reducing the roughness will cause the specific surface area of ​​the main material to become smaller, thereby deteriorating the dynamic performance of the battery.

[0005] In view of this, it is indeed necessary to provide a wound electrochemical device and electronic device that can solve the above problems. Summary of the invention

[0006] The main technical problem solved by the embodiments of the present application is to provide a wound electrochemical device and electronic device that can prevent cracking and brittle fracture of electrodes during the winding process, thereby improving the compaction of the electrodes and the energy density of the electrochemical device.

[0007] In order to solve the above technical problems, a technical solution adopted in the implementation mode of the present application is:

[0008] In one aspect, a wound electrochemical device is provided, the wound electrochemical device comprising an electrode assembly. The electrode assembly comprises a first electrode. The first electrode comprises a current collector, a protective layer, and an active material layer disposed on at least one surface of the current collector, wherein the protective layer is disposed between the current collector and the active material layer. The first electrode is wound to form a straight section and a bent section, and the protective layer is disposed on the bent section of the first electrode.

[0009] In some embodiments, the innermost circle of the first electrode includes a winding starting end, a first bending segment and a second bending segment relative to the first bending segment, the first bending segment is connected to the winding starting end, and the protective layer is arranged on the first bending segment and / or the second bending segment.

[0010] In some embodiments, the first electrode is wound to form a plurality of bending segments, and at least two bending segments are respectively provided with a protective layer along a direction from the innermost circle of the first electrode to the outermost circle of the first electrode.

[0011] In some embodiments, the protective layer is disposed on at least one of the inner side and the outer side of the current collector at the bent section.

[0012] In some embodiments, the length of the protective layer disposed on the inner side of the bending segment is the same as or different from the length of the protective layer disposed on the outer side of the bending segment.

[0013] In some embodiments, the protective layer satisfies at least one of the following characteristics:

[0014] (a) the thickness of the protective layer is 0.5 μm to 20 μm;

[0015] (b) the length of the protective layer is 0.1 cm to 5 cm;

[0016] (c) The width of the protective layer is 0.1 to 1 times the width of the current collector.

[0017] In some embodiments, the protective layer is a conductive coating or a conductive adhesive tape.

[0018] In some embodiments, the conductive coating includes a conductive agent and a binder, the mass of the conductive agent is 50% to 99% of the total mass of the conductive coating, and the mass of the binder is 1% to 50% of the total mass of the conductive coating.

[0019] In some embodiments, the conductive agent includes at least one of a lamellar, mesh, linear or zero-dimensional conductive agent. The binder includes at least one of styrene-butadiene rubber, nitrile rubber, carboxylated styrene-butadiene rubber, phenolic resin glue, polybutylene, polypropylene, polyvinylidene fluoride, polyimide or polyvinyl acetate.

[0020] In some embodiments, the conductive adhesive tape includes an adhesive and conductive particles, the mass of the adhesive is 1% to 90% of the total mass of the conductive adhesive tape, and the mass of the conductive particles is 10% to 99% of the total mass of the conductive adhesive tape.

[0021] In some embodiments, the adhesive comprises at least one of acrylic acid and polyester materials. The conductive particles are metal particles, and the particle size D50 of the metal particles is 0.001 μm to 500 μm.

[0022] In some embodiments, the mechanical properties of the conductive adhesive tape meet at least one of the following characteristics:

[0023] (d) The tensile strength of the conductive tape is ≥50MPa;

[0024] (e) The elongation of the conductive adhesive tape is ≥ 3%.

[0025] On the other hand, an electronic device is also provided, the electronic device comprising:

[0026] The above wound electrochemical device.

[0027] Compared with the prior art, the electrode assembly of the wound electrochemical device of the embodiment of the present application also includes a protective layer, which is arranged at the bending section of the first electrode and is located between the collector and the active material layer. The protective layer protects the collector at the bending section, prevents the active material layer from being embedded in the collector at the bending section during the cold pressing process and causing damage to the collector, improves the brittleness of the collector at the bending section, thereby improving the winding performance of the bending section of the first electrode, and preventing the bending section of the first electrode from cracking and brittle fracture during the winding process, thereby improving the compression of the electrode and the energy density of the wound electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] One or more embodiments are exemplarily described by pictures in the corresponding drawings, which are not limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and the figures in the drawings do not constitute proportional limitations unless otherwise stated.

[0029] Figure 1 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided in one embodiment of the present application;

[0030] Figure 2 is a schematic diagram of a partially unfolded flat state of a first electrode of an electrode assembly according to one embodiment of the present application;

[0031] Figure 3 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided in one embodiment of the present application;

[0032] Figure 4 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided in one embodiment of the present application;

[0033] Figure 5 It is a schematic diagram of a partially unfolded flat state of a first electrode of an electrode assembly according to one embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" / "installed on" another element, it can be directly on another element, or there can be one or more centered elements therebetween. When an element is described as "connected" to another element, it can be directly connected to another element, or there can be one or more centered elements therebetween. The orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "vertical", "horizontal", etc. used in this specification is based on the orientation or positional relationship shown in the accompanying drawings, only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0035] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0036] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0037] The embodiment of the present application provides a wound electrochemical device, which converts chemical energy into electrical energy during discharge to supply power to a load, and converts electrical energy into chemical energy during charge to store energy. The wound electrochemical device includes an electrode assembly 100 .

[0038] See also Figure 1 , Figure 1 The electrode assembly 100 is shown according to one embodiment of the present application, wherein the electrode assembly 100 includes a first electrode 10, wherein the first electrode 10 includes a current collector 11, a protective layer 12, and an active material layer 13 disposed on at least one surface of the current collector 11, wherein the protective layer 12 is located between the current collector 11 and the active material layer 13, wherein during the winding process of the electrode assembly 100, a portion of the first electrode 10 is bent relative to another portion of the first electrode 10, so that the first electrode 10 is wound to form a straight section 101 and a bent section 102, wherein the bent section 102 is located at both ends of the straight section 101, and the protective layer 12 is disposed at the bent section 102 of the first electrode 10.

[0039] Among them, the electrode assembly 100 is roughly in a flat spiral structure after being wound multiple times, and the first electrode 10 can be configured as the innermost electrode of the electrode assembly 100. In addition, the first electrode 10 can be configured as the cathode electrode of the electrode assembly 100, and can also be configured as the anode electrode.

[0040] During the cold pressing process of the electrode, the active material particles in the active material layer are easily squeezed with the collector and embedded in the collector, causing damage to the collector. In the subsequent winding process, the bending section of the electrode is subjected to greater stress, which makes it very easy for the bending section of the electrode to crack and break. As the electrode compaction increases, the brittleness of the electrode increases, and the possibility of cracking and breaking of the bending section of the electrode also increases.

[0041] Please combine Figure 1 and Figure 2 , Figure 2 The figure shows that the bent section 102 of the first electrode 10 provided with a protective layer 12 is in an unfolded flat state. In order to prevent the electrode from cracking or brittle fracture during the winding process, the wound electrochemical device of the embodiment of the present application is provided with a protective layer 12 at the bent section 102 of the first electrode 10, and the protective layer 12 is located between the collector 11 and the active material layer 13. The protective layer 12 is used to protect the collector 11 at the bent section 102, which prevents the active material layer 13 from being embedded in the collector 11 at the bent section during the cold pressing process, thereby improving the brittleness of the collector 11 at the bent section 102, thereby improving the winding performance of the bent section 102 of the first electrode 10, preventing the bent section 102 of the first electrode 10 from cracking or brittle fracture during the winding process, and further improving the compaction of the electrode and the energy density of the wound electrochemical device.

[0042] Among them, compared with the method of reducing the compaction of the electrode or mixing main material particles with smaller roughness into the active material layer to prevent the bent section of the electrode from cracking and brittle fracture during the winding process, the electrochemical device provided in the embodiment of the present application can prevent the bent section 102 of the electrode from cracking and brittle fracture during the winding process by providing a protective layer 12 between the collector 11 and the active material layer 13 at the bent section 102 of the first electrode 10, thereby ensuring the high energy density and dynamic performance of the electrochemical device.

[0043] Among them, the protective layer 12 is only set on the bending section 102 of the first electrode 10. Compared with setting the protective layer 12 on the entire first electrode 10, it simplifies the overall structure of the electrode assembly 100, and can significantly suppress the adverse consequences of thickness increase and energy density loss caused by setting the protective layer 12. At the same time, it can reduce the production cost caused by setting the protective layer 12 and improve the production efficiency.

[0044] in, Figure 1 and Figure 2 It is shown that the active material layer 13 is arranged on two opposite surfaces of the collector 11. It can be understood that in some other embodiments of the present application, the active material layer 13 only needs to be arranged on at least one surface of the collector 11, and there is no need to arrange the active material layer 13 on both opposite surfaces of the collector 11. In addition, the active material layer 13 can be continuously arranged on one surface of the collector 11, or a blank area can be reserved on the one surface, and the active material layer 13 is not arranged in the blank area, and the active material layer 13 is arranged outside the blank area. That is, the active material layer 13 can be arranged in sections on one surface of the collector 11, wherein the blank area can be preferentially arranged in the bending section 13. Then, during the cold pressing process of the electrode, the bending section 13 can avoid being punctured by the active material layer 13. Accordingly, there is no need to arrange the protective layer 12 in the bending section 13 where the blank area is arranged.

[0045] The specific position of the bending section 102 where the protective layer 12 is provided will be described below.

[0046] The first electrode 10 is wound to form a plurality of bending segments 102. During the winding process of the first electrode 10, the stress generated by the winding decreases in sequence from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10 and acts on each bending segment 102 respectively. That is, the closer the bending segment 102 is to the center of the electrode assembly 100, the greater the stress is. Therefore, in one embodiment of the present application, at least two bending segments 102 are respectively provided with protective layers 12 along the direction from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10. That is, the protective layer 12 is preferentially arranged in the bending segment 102 of the first electrode 10 close to the center of the electrode assembly 100, wherein the protective layer 12 is located between the collector 11 and the active material layer 13 at the bending segment 102. By setting the distribution pattern of the protective layer 12 as described above, multiple protective layers 12 can be respectively arranged on each bending segment 102 of the first electrode 10 along the direction from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10 as needed, so as to protect the bending segment 102 subjected to greater stress. The bending segment 102 of the first electrode 10 that is prone to cracking and brittle fracture during the winding process can be effectively and specifically protected, which is beneficial to the compaction of the electrode and the improvement of the energy density of the electrochemical device.

[0047] The innermost circle of the first electrode 10 refers to the first circle of the innermost edge formed during the winding process of the first electrode 10; the outermost circle of the first electrode 10 refers to the penultimate circle of the outermost edge formed during the winding process of the first electrode 10. The innermost circle of the first electrode 10 includes a winding start end, a first bending section, and a second bending section relative to the first bending section, and the first bending section is connected to the winding start end.

[0048] The number of protective layers 12 can be selected according to actual needs, as long as the distribution pattern of the protective layers 12 is respectively arranged at each bending segment 102 of the first electrode 10 along a preset direction. For example, the number of protective layers 12 is four, and along the direction from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10, the four protective layers 12 are respectively arranged at the four bending segments 102 of the first electrode 10. For details, please refer to Figure 1 .

[0049] Since the stress generated by winding is easily concentrated in the first bending section and the second bending section, which is easy to cause cracks and brittle fractures in the first bending section and the second bending section, in one embodiment of the present application, the protective layer 12 is arranged in the first bending section and / or the second bending section, wherein the protective layer 12 is located between the collector 11 and the active material layer 13 at the bending section 102, as shown in FIG. Figure 3 As shown, Figure 3 The protective layer 12 is shown to be disposed in the first bending section and the second bending section. It is understandable that the protective layer 12 may also be disposed in only one of the first bending section and the second bending section. By limiting the distribution position of the protective layer 12 to the first bending section and / or the second bending section of the innermost circle of the first electrode 10, the winding performance of the bending section 102 of the first electrode 10 is improved, and the bending section 102 of the first electrode 10 is prevented from cracking and brittle fracture during the winding process, while further suppressing the adverse consequences of thickness increase and energy density loss caused by the provision of the protective layer 12, improving the compaction of the electrode and the energy density of the electrochemical device, further reducing the production cost caused by the provision of the protective layer 12, and improving the production efficiency.

[0050] Since the stress generated by winding is most likely to be concentrated in the first bending section, causing cracks and brittle fractures in the first bending section, in one embodiment of the present application, the protective layer 12 is disposed in the first bending section 102, wherein the protective layer 12 is located between the collector 11 and the active material layer 13 at the bending section 102, as shown in FIG. Figure 4 As shown. By limiting the distribution position of the protective layer 12 to the initial bending section 102 of the innermost circle of the first electrode 10, the winding performance of the bending section 102 of the first electrode 10 is improved, and the bending section 102 of the first electrode 10 is prevented from cracking and brittle fracture during the winding process, while further suppressing the adverse consequences of thickness increase and energy density loss caused by the provision of the protective layer 12, improving the compaction of the electrode and the energy density of the electrochemical device, further reducing the production cost caused by the provision of the protective layer 12, and improving the production efficiency.

[0051] The specific location of the protective layer 12 in the bending section 102 is that the protective layer 12 is arranged on at least one of the inner side and the outer side of the collector 11 at the bending section 102, that is, the protective layer 12 can be arranged on one side or both sides of the collector 11 at the bending section 102 as needed. When the protective layer 12 is arranged on one side of the collector 11 at the bending section 102, the protective layer 12 can be arranged on the inner side or the outer side of the collector 11 at the bending section 102 as needed, specifically as follows Figure 2 and Figure 5 As shown, Figure 2 It shows that the protective layer 12 is disposed on both sides of the current collector 11 at the bending section 102, Figure 5 It is shown that the protective layer 12 is disposed on one side of the current collector 11 at the bent section 102. The inner side of the current collector 11 at the bent section 102 refers to the side of the current collector 11 in the wound state facing the center of the electrode assembly 100; the outer side of the current collector 11 at the bent section 102 refers to the other side of the current collector 11 in the wound state facing away from the center of the electrode assembly 100.

[0052] Since the current collector 11 is in an unfolded flat state during the cold pressing process of the electrode, the two side surfaces of the current collector 11 are easily squeezed by the particles of the active material layer 13, resulting in damage to the current collector 11, thereby worsening the brittleness of the current collector 11, causing the current collector 11 to easily crack and break during the winding process. Therefore, in one embodiment of the present application, the protective layer 12 is arranged on the inner and outer sides of the current collector 11 at the bending section 102, so that the protective layer 12 can protect both the inner and outer sides of the current collector 11 at the bending section 102. By arranging the protective layer 12 on the inner and outer sides of the collector 11 at the bending section 102, the winding performance of the electrode under high pressure density is guaranteed, and the two sides of the collector 11 at the bending section 102 are effectively prevented from being punctured by the active material layer 13 on the opposite sides of the collector 11 due to the extrusion stress during the cold pressing process, thereby preventing the bending section 102 of the electrode from cracking and brittle fracture during the winding process, thereby ensuring the feasibility of improving the compaction of the electrode and the energy density of the electrochemical device.

[0053] It should be noted that the protective layer 12 can be partially or completely provided on at least one of the inner side and the outer side of the current collector 11 at the bent section 102, or can be provided to extend to the current collector 11 on the straight section 101 at both ends of the bent section 102. In order to better realize the protective effect of the protective layer 12, the protective layer 12 at least partially covers the top of the current collector 11 at the bent section 102.

[0054] The structural dimension parameters of the protection layer 12 are described below.

[0055] The protective layer 12 satisfies at least one of the following characteristics: (a) along the thickness direction of the current collector 11, the thickness of the protective layer 12 is 0.5 μm to 20 μm; (b) along the winding direction of the current collector 11, the length of the protective layer 12 is 0.1 cm to 5 cm; (c) along the width direction of the current collector 11, the width of the protective layer 12 is 0.1 times to 1 times the width of the current collector 11, and the protective layer 12 is 0.1 times to 1 times the width of the current collector 11. Figure 5 The plan view of FIG. 1 is an example to illustrate that the thickness direction of the protective layer 12 is consistent with the thickness direction of the first electrode 10, the length direction of the protective layer 12 is the length direction of the first electrode 10, the length of the protective layer 12 is the arc length of the bending section in the winding structure, and the width direction of the protective layer 12 is the direction perpendicular to the paper surface, which is consistent with the width direction of the first electrode 10. The above description of the structural dimension parameters (thickness, length and width) of the protective layer 12 is for the protective layer 12 on the same side (inside or outside) of the current collector 11.

[0056] It should be noted that if the thickness of the protective layer 12 is less than 0.5 μm, it is difficult for the protective layer 12 to protect the collector 11 at the bending section 102. During the cold pressing process, the particles of the active material layer 13 are easily embedded in the collector 11 through the protective layer 12, causing damage to the collector 11, and cannot effectively prevent the bending section 102 from cracking or brittle fracture during the winding process; if the thickness of the protective layer 12 is greater than 20 μm, when the protective layer 12 is coated on the collector 11 at the bending section 102, there may be a risk of scratching, causing damage to the collector 11, and it cannot be guaranteed that the bending section 102 will avoid cracking or brittle fracture during the winding process, and the energy density of the wound electrochemical device will be reduced to a certain extent. If the length of the protective layer 12 is less than 0.1 cm, the protective layer 12 is also difficult to protect the collector 11 at the bend section 102. During the cold pressing process, the particles of the active material layer 13 are easy to bypass the protective layer 12 and embed into the collector 11, causing damage to the collector 11, and cannot effectively prevent the bend section 102 from cracking and brittle fracture during the winding process; if the length of the protective layer 12 is greater than 5 cm, the energy density of the wound electrochemical device will be reduced to a certain extent. If the width of the protective layer 12 is less than 0.1 times the width of the collector 11, the protective layer 12 is also difficult to protect the collector 11 at the bend section 102. During the cold pressing process, the particles of the active material layer 13 are easy to bypass the protective layer 12 and embed into the collector 11, causing damage to the collector 11, and cannot effectively prevent the bend section 102 from cracking and brittle fracture during the winding process; if the width of the protective layer 12 is greater than the width of the collector 11, the energy density of the wound electrochemical device will be reduced to a certain extent.

[0057] Among them, when the inner and outer sides of the current collector 11 at the bending section 102 are both provided with a protective layer 12, the sizes of the two protective layers 12 respectively located on the inner and outer sides of the current collector 11 can be set according to actual needs, that is, the sizes of the two protective layers 12 respectively located on the inner and outer sides of the current collector 11 can be consistent or different, and only need to meet at least one of the above-mentioned (a), (b) and (c) characteristics. Of course, in order to make the protective layer 12 have a better protective effect, the size of the protective layer 12 can meet the above-mentioned (a), (b) and (c) characteristics.

[0058] The material of the protective layer 12 will be described below.

[0059] In order to achieve a better protective effect of the protective layer 12 and ensure that the collector 11 at the bending section 102 is not damaged during the cold pressing process, so that the bending section 102 of the first electrode 10 does not crack or break during the subsequent winding process, the protective layer 12 is made of an adhesive and a conductive material that is easy to slide or squeeze and is not easy to puncture the collector 11 and has good conductivity. In some embodiments of the present application, the protective layer 12 is a conductive coating or conductive tape.

[0060] For the above-mentioned conductive coating, the conductive coating includes a conductive agent and a binder, the mass of the conductive agent is 50% to 99% of the total mass of the conductive coating, and the mass of the binder is 1% to 50% of the total mass of the conductive coating. It should be noted that if the content of the conductive agent is less than 50% of the total mass of the conductive coating, the internal resistance of the electrode assembly 100 will be deteriorated and the electron mobility will be reduced; if the content of the binder is less than 1% of the total mass of the conductive coating, the bonding force of the conductive coating will be reduced, and there is a risk of delamination.

[0061] The conductive agent includes at least one of a lamellar, mesh, linear or zero-dimensional conductive agent. The lamellar conductive agent releases the extrusion stress by sliding during the cold pressing process, thereby protecting the collector 11. The mesh, linear and zero-dimensional conductive agents can buffer the extrusion stress generated by the main material particles on the collector 11 during the cold pressing process, reduce the degree of damage to the collector 11, and thus protect the collector 11. Among them, the lamellar conductive agent can be, for example, graphene, the mesh conductive agent can be, for example, a graphite fiber mesh, the linear conductive agent can be, for example, a carbon nanotube, a graphite fiber, and the zero-dimensional conductive agent can be, for example, a nanoparticle conductive carbon.

[0062] The binder includes at least one of styrene-butadiene rubber, nitrile rubber, carboxylated styrene-butadiene rubber, phenolic resin glue, polybutene, polypropylene, polyvinylidene fluoride, polyimide or polyvinyl acetate. The binder plays a role of buffering stress during the cold pressing process and reduces the damage of the main material particles to the collector 11.

[0063] The following is an exemplary description of the manufacturing process of the conductive coating: a solvent is added to a container, and then a conductive agent is added, and the two are mixed evenly by stirring, and then a binder is added, and the three are mixed evenly by stirring again. The solvent may be an organic solvent, such as NMP, DMC, or an inorganic solvent, such as deionized water.

[0064] For the above-mentioned conductive adhesive tape, the conductive adhesive tape includes adhesive and conductive particles, the mass of the adhesive is 1% to 90% of the total mass of the conductive adhesive tape, and the mass of the conductive particles is 10% to 99% of the total mass of the conductive adhesive tape.

[0065] The adhesive includes at least one of acrylic acid and polyester materials.

[0066] The conductive particles are metal particles, and the particle size D50 of the metal particles is 0.001 μm to 500 μm. The metal particles may be, for example, gold or silver.

[0067] To ensure the protective effect of the conductive tape, the mechanical properties of the conductive tape must meet at least one of the following characteristics: (d) tensile strength ≥ 50 MPa; (e) elongation of the conductive tape ≥ 3%. It should be noted that if the tensile strength of the conductive tape is ≤ 50 MPa and the elongation is ≤ 3%, the conductive tape is easily punctured by the particles of the active material layer 13 during the cold pressing process, and it is difficult to play the role of protecting the collector 11. Of course, in order to make the conductive tape have a better protective effect, the mechanical properties of the conductive tape can meet both (d) and (e) characteristics.

[0068] Please refer to Figure 1 In the embodiment of the present application, the electrode assembly 100 further includes a second electrode 20 and a separator 30. The first electrode 10, the separator 30 and the second electrode 20 are sequentially stacked and wound to form the structural body of the electrode assembly 100. The separator 30 is located between the first electrode 10 and the second electrode 20. The second electrode 20 has an opposite polarity to the first electrode 10. The first electrode 10 can be a cathode electrode, and the second electrode 20 is an anode electrode; accordingly, the first electrode 10 can be an anode electrode, and the second electrode 20 is a cathode electrode.

[0069] In some embodiments of the present application, the structure of the second electrode 20 may be the same as the structure of the first electrode 10 in each of the above embodiments, except that the polarity of the second electrode 20 is opposite to that of the first electrode 10. Specifically, when the first electrode 10 is a cathode electrode, the current collector 11 of the first electrode 10 is a cathode current collector, and the active material layer 13 of the first electrode 10 is a cathode active material layer, and accordingly, the current collector of the second electrode 20 is an anode current collector, and the active material layer of the second electrode 20 is an anode active material layer; when the first electrode 10 is an anode electrode, the current collector 11 of the first electrode 10 is an anode current collector, and the active material layer 13 of the first electrode 10 is an anode active material layer, and accordingly, the current collector of the second electrode 20 is a cathode current collector, and the active material layer of the second electrode 20 is a cathode active material layer. The distribution pattern of the protective layer of the second electrode 20 on the second electrode 20 is the same as the distribution pattern of the protective layer 12 of the first electrode 10 on the first electrode 10 , and the material of the protective layer of the second electrode 20 is the same as the material of the protective layer 12 of the first electrode 10 .

[0070] In some embodiments of the present application, the structure of the second electrode 20 may also be different from the structure of the first electrode 10 in the above-mentioned embodiments, and the polarity of the second electrode 20 is opposite to that of the first electrode 10. Specifically, the bending section 102 of the second electrode 20 is not provided with a protective layer 12; or the number of protective layers of the second electrode 20 is different from the number of protective layers of the first electrode 10, and at the same time, the protective layer of the second electrode 20 is preferentially provided at the bending section of the second electrode 20 close to the center of the electrode assembly 100. Among them, since the stress generated by winding is most likely to be concentrated on the initial or both sides of the innermost circle of the innermost circle electrode, resulting in cracks and brittle fractures in the initial or both sides of the innermost circle of the innermost circle electrode, therefore, during the winding process of the electrode assembly 100, the first electrode 10 is configured as the innermost circle electrode of the electrode assembly 100.

[0071] It should be noted that the first electrode 10 and the second electrode 20 are stacked and wound around the side where one of them faces away from the other, then one of them is the innermost electrode and the other is the outermost electrode.

[0072] The electrochemical device provided in the embodiment of the present application may be a lithium-ion battery, which can prevent the electrode from cracking and brittle fracture during the winding process. Lithium-ion batteries mainly rely on the movement of lithium ions between the cathode electrode and the anode electrode to work. During the charge and discharge process, lithium ions are intercalated and deintercalated back and forth between the cathode electrode and the anode electrode: when charging, lithium ions are deintercalated from the cathode electrode, and are intercalated into the anode electrode through the electrolyte, so that the anode electrode is in a lithium-rich state; when discharging, lithium ions are removed from the anode electrode, and are intercalated into the cathode electrode through the electrolyte, so that the cathode electrode is in a lithium-rich state. Among them, the first electrode 10 can be configured as the innermost electrode of the lithium-ion battery, and the second electrode 20 can be configured as the outermost electrode of the lithium-ion battery. In addition, the first electrode 10 can be configured as a cathode electrode or an anode electrode, and correspondingly, the second electrode 20 can be configured as an anode electrode or a cathode electrode.

[0073] There is no particular restriction on the cathode electrode in this application, as long as the purpose of this application can be achieved. Among them, there is no particular restriction on the cathode collector in this application, for example, aluminum foil, aluminum alloy foil and composite collector, etc. The cathode active material layer includes a cathode active material. The cathode active material in this application is not particularly limited, and any anode active material in the art can be used. For example, it can include lithium nickel cobalt manganese oxide (lithium nickel cobalt manganese oxide model can be NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. At least one.

[0074] There is no particular limitation on the anode electrode in the present application, as long as the purpose of the present application can be achieved. Among them, there is no particular limitation on the anode collector in the present application, for example, copper foil, aluminum foil, aluminum alloy foil and composite collector, etc. The anode active material layer includes an anode active material, and the anode active material in the present application is not particularly limited, for example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, silicon, silicon carbon or lithium titanate.

[0075] The following is an exemplary description of the production process of the cathode electrode: the cathode active materials lithium cobalt oxide (LiCoO2), Super P, and polyvinylidene fluoride are mixed in a weight ratio of 97:1.4:1.6, N-methylpyrrolidone (NMP) is added, and the system is stirred until the system is uniform under the action of a vacuum mixer to obtain a cathode slurry, wherein the solid content of the cathode slurry is 72wt%; then, the cathode slurry is evenly coated on the cathode collector aluminum foil; then, the cathode collector aluminum foil is dried at 110°C, and then cold pressed and cut to obtain a cathode electrode.

[0076] The following is an exemplary description of the production process of the anode electrode: the anode active material can be, for example, a mixture of artificial graphite and silicon. The anode active material, Super P, a binder, and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96.2:1.5:0.5:1.8, and deionized water is added. An anode slurry is obtained under the action of a vacuum mixer, wherein the solid content of the anode slurry is 54wt%; then, the anode slurry is evenly coated on the anode collector copper foil; then, the anode collector copper foil is dried at 85°C, and then, after cold pressing and slitting, an anode electrode is obtained.

[0077] The electrochemical device of the present application further comprises an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte and an electrolyte solution, wherein the electrolyte solution comprises a lithium salt and a non-aqueous solvent.

[0078] In some embodiments of the present application, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB and lithium difluoroborate. For example, the lithium salt can be selected from LiPF6 because it can provide high ionic conductivity and improve cycle characteristics.

[0079] In some embodiments of the present application, the non-aqueous solvent may be one or more of carbonate compounds, carboxylate compounds, ether compounds, and other organic solvents.

[0080] The carbonate compound may be one or more of a chain carbonate compound, a cyclic carbonate compound, and a fluorinated carbonate compound.

[0081] The carboxylate compound may be one or more of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone, mevalonolactone, and caprolactone.

[0082] The ether compound may be one or more of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0083] The other organic solvents may be one or more of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0084] The above-mentioned linear carbonate compound may be one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and ethylmethyl carbonate (MEC).

[0085] The cyclic carbonate compound may be one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinyl ethylene carbonate (VEC).

[0086] The above-mentioned fluorinated carbonate compound can be one or more of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0087] The electrochemical device of the present application further comprises an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte and an electrolyte solution, wherein the electrolyte solution comprises a lithium salt and a non-aqueous solvent.

[0088] The electrochemical device of the present application further includes a packaging bag, which is used to accommodate the electrode assembly 100 .

[0089] The preparation process of the electrochemical device is well known to those skilled in the art and is not particularly limited in this application. For example, a lithium-ion battery can be manufactured by the following process: stacking the cathode electrode and the anode electrode in sequence via a separator, and placing them in a packaging bag after winding, folding, etc. as needed, injecting an electrolyte into the packaging bag and sealing it, wherein the cathode electrode used is the first electrode 10 or the second electrode 20 provided in this application, and the anode electrode used is the second electrode 20 or the first electrode 10 provided in this application. In addition, overcurrent protection elements, guide plates, etc. can also be placed in the housing as needed to prevent the pressure inside the lithium-ion battery from rising and overcharging and discharging.

[0090] Of course, the electrochemical device provided in the embodiments of the present application may also be a lithium battery, a lithium ion polymer battery, etc.

[0091] The wound electrochemical device in the above embodiment and the wound electrochemical device in the comparative example were tested and the experimental results in the following Table 1 were obtained. The protective layer 12 was not provided in the current collector 11 of the wound electrochemical device in the comparative example 1, and the protective layer 12 was coated on the entire current collector 11 of the wound electrochemical device in the comparative example 2.

[0092] Table 1 Comparative Examples 1-2 and Examples 1-19

[0093]

[0094]

[0095]

[0096]

[0097] As can be seen from Table 1, after the protective layer 12 is provided at the bending section 102 of the first electrode 10 of the wound electrochemical device according to Examples 1-20 provided by the present application, the ultimate compaction of the first electrode 10 and the energy density of the wound electrochemical device are improved. In the wound electrochemical device of Example 13, a protective layer 12 with a length of 2 cm is provided on the inner and outer sides of the collector 11 at the first bending section and the second bending section, respectively, and the protective layer 12 is made of graphene accounting for 85% of the total mass of the protective layer 12 and styrene-butadiene rubber accounting for 15% of the total mass of the protective layer 12. The electrode compaction and the energy density of the electrochemical device of the wound electrochemical device of this embodiment are improved to the greatest extent. Therefore, the experimental results in Table 1 prove that the wound electrochemical device provided in the embodiment of the present application can protect the corresponding bent segment 102 by setting a protective layer 12 on the collector 11 at the bent segment 102, thereby improving the winding performance of the bent segment 102 of the first electrode 10 and preventing the bent segment 102 of the first electrode 10 from cracking and brittle fracture during the winding process, thereby improving the compression of the electrode and the energy density of the electrochemical device.

[0098] The following is an exemplary description of the compaction test method: take a pole piece with an area of ​​S (the pole piece includes a current collector and an active material layer coated on the current collector), weigh its film layer (active material layer) mass as M, measure its film layer thickness as T, then, the film layer compaction (limit compaction) PD = M / T / S. Among them, the total mass M of the film layer is calculated: before coating, take an empty aluminum foil (current collector) with an area of ​​S, weigh its mass as m, coat the empty aluminum foil with a film layer to form a pole piece and weigh the pole piece mass as M0, then, M = M0-m; the film layer thickness T is calculated: the total thickness of the pole piece after cold pressing is measured with a micrometer as T0, and the thickness of the empty aluminum foil used is measured with a micrometer as t, then, T = T0-t.

[0099] The following is an exemplary description of the energy density test method of the electrochemical device: the electrochemical device is charged to 4.48V at a current of 0.5C, then charged at a constant voltage of 4.48V to a current of 0.05C, and finally discharged to 3.0V at a current of 0.5C, and the discharge energy is recorded. Then, the energy density ED = discharge energy / electrochemical device volume (length*width*thickness).

[0100] The following is an illustrative description of the tensile strength and elongation test methods: Blank aluminum foil (strip width 15 mm, gauge length 50 mm): Use a high-speed rail tensile testing machine to stretch it at a speed of 5 mm / min along the length direction, and take the strength and elongation at break as the test results; Conductive adhesive tape (strip width 15 mm, gauge length 20 mm): Use a high-speed rail tensile testing machine to stretch it at a speed of 5 mm / min in the direction parallel to the length of the electrode after adhesive bonding, and take the strength and elongation at break as the test results.

[0101] An embodiment of the present application also provides an electronic device, which includes the wound electrochemical device provided by any of the above embodiments, and the wound electrochemical device has a higher energy density.

[0102] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments of the present application, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0103] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the description and drawings of the present application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A wound electrochemical device, comprising an electrode assembly, characterized in that: The electrode assembly includes a first electrode, which includes a collector, a protective layer and an active material layer arranged on at least one surface of the collector, wherein the protective layer is conductive tape, the conductive tape is located between the collector and the active material layer, the first electrode is wound to form a straight section and a bent section, and the conductive tape is arranged on the bent section of the first electrode.

2. The wound electrochemical device according to claim 1, characterized in that: The innermost circle of the first electrode includes a winding starting end, a first bending section and a second bending section relative to the first bending section, the first bending section is connected to the winding starting end, and the protective layer is arranged on the first bending section and / or the second bending section.

3. The wound electrochemical device according to claim 1, characterized in that: The first electrode is wound to form a plurality of bending segments, and the protective layer is respectively disposed on at least two of the bending segments along a direction from the innermost circle of the first electrode to the outermost circle of the first electrode.

4. The wound electrochemical device according to any one of claims 1 to 3, characterized in that: The protective layer is disposed on at least one of the inner side and the outer side of the current collector at the bent section.

5. The wound electrochemical device according to claim 4, characterized in that: The length of the protective layer disposed on the inner side of the bending section is the same as or different from the length of the protective layer disposed on the outer side of the bending section.

6. The wound electrochemical device according to any one of claims 1 to 3, characterized in that: The protective layer satisfies at least one of the following characteristics: (a) the thickness of the protective layer is 0.5 μm to 20 μm; (b) the length of the protective layer is 0.1 cm to 5 cm; (c) The width of the protective layer is 0.1 to 1 times the width of the current collector.

7. The wound electrochemical device according to claim 1, characterized in that: The conductive adhesive paper comprises an adhesive and conductive particles, the mass of the adhesive is 1% to 90% of the total mass of the conductive adhesive paper, and the mass of the conductive particles is 10% to 99% of the total mass of the conductive adhesive paper.

8. The wound electrochemical device according to claim 7, characterized in that: The adhesive includes at least one of acrylic acid and polyester materials; The conductive particles are metal particles, and the particle size D50 of the metal particles is 0.001 μm to 500 μm.

9. The wound electrochemical device according to claim 1, characterized in that: The mechanical properties of the conductive adhesive tape meet at least one of the following characteristics: (d) The tensile strength of the conductive tape is ≥50 MPa; (e) The elongation of the conductive adhesive tape is ≥ 3%.

10. An electronic device, characterized in that: include: A wound electrochemical device as claimed in any one of claims 1 to 9.

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