Electrode assembly and secondary battery including the same

Abstract

An electrode assembly according to one embodiment of the present application includes a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the separator are wound together to form a jelly-roll structure. In addition, the electrode assembly further includes an auxiliary separator disposed at a center of the jelly-roll structure so as to be between the first electrode and the separator.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0152524, filed with the Korean Intellectual Property Office on November 16, 2020, and Korean Patent Application No. 10-2021-0153233, filed with the Korean Intellectual Property Office on November 9, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to electrode assemblies and secondary batteries including the electrode assemblies, and more particularly, to electrode assemblies with a jelly roll structure and secondary batteries including the electrode assemblies with the jelly roll structure. Background Technology

[0004] Recently, due to the depletion of fossil fuels, energy prices have risen and concerns about environmental pollution have increased significantly. The demand for eco-friendly alternative energy sources is becoming a crucial factor for the future. Therefore, research into various power generation technologies such as nuclear, solar, wind, and tidal power is ongoing, and energy storage devices for more efficient use of the generated energy are also receiving considerable attention.

[0005] In particular, with the development of technology and the increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing, and therefore, a great deal of research is underway on batteries that can meet a wide range of needs.

[0006] There is typically a high demand for lithium-ion batteries and lithium-ion polymer batteries that have advantages such as high energy density, high discharge voltage, and high output stability.

[0007] Furthermore, based on the shape of the battery box, secondary batteries are divided into cylindrical batteries and prismatic batteries in which the electrode components are embedded in a cylindrical or prismatic metal can, and pouch batteries in which the electrode components are embedded in a pouch box made of aluminum laminate.

[0008] Furthermore, secondary batteries are classified according to the structure of the electrode assembly in which a positive electrode, a negative electrode, and a separator membrane inserted between the positive and negative electrodes are stacked.

[0009] Typically, electrode assemblies may include: jelly roll type electrode assembly, wherein elongated positive and negative electrodes are wound together, wherein a separator membrane is inserted between the positive and negative electrodes; and stacked type electrode assembly, wherein a plurality of positive and negative electrodes cut into units of predetermined size are stacked sequentially, wherein a separator membrane is inserted between the positive and negative electrodes.

[0010] Jelly roll electrode assemblies can be formed by winding positive and negative electrodes, with a separator membrane inserted between them. However, with hundreds or thousands of charge / discharge cycles, the jelly roll electrode assembly shrinks and expands, causing bending deformation at the center of the positive terminal, leading to cracking, disconnection, or short circuit, and severely compromising the safety of the secondary battery. Summary of the Invention

[0011] [Technical Issues]

[0012] The problem to be solved by the present invention is to provide an electrode assembly capable of preventing cracks that may occur in the electrode during the contraction and expansion of a secondary battery, and a secondary battery including the electrode assembly.

[0013] However, the problems to be solved in the exemplary embodiments of the present invention are not limited to the aforementioned problems, and various extensions can be made within the scope of the technical spirit included in the present invention.

[0014] [Technical Solution]

[0015] An exemplary embodiment of the present invention provides an electrode assembly, including: a first electrode; a second electrode; and a separator membrane inserted between the first electrode and the second electrode, wherein the first electrode, the second electrode and the separator membrane are wound together to form a jelly roll structure, and an auxiliary separator membrane disposed between the first electrode and the separator membrane is further included at the center of the jelly roll structure.

[0016] Each of the separator membrane and the auxiliary separator membrane may include a base layer and a coating.

[0017] The end of the first electrode can contact the coating of the auxiliary separator membrane.

[0018] The first electrode can be a positive electrode, and the second electrode can be a negative electrode.

[0019] The auxiliary separator membrane can be wound in the jelly roll structure at a length of more than 0.5 times and less than 1.5 times the circumference of the core.

[0020] The second electrode may include an active material layer formed on the current collector, an uncoated area on which no active material layer is formed, and an electrode tab bonded to the uncoated area. The end of the first electrode may be disposed in the center of the jelly roll structure, and the end of the first electrode is spaced apart from the electrode tab.

[0021] At the center, the end of the first electrode may be spaced apart from the end of the electrode tab and wound around 1 / 4 or more of its circumference.

[0022] The coating may include ceramic particles, which include at least one selected from the group consisting of alumina, silicon dioxide, TiO2, SiC and MgAl2O4.

[0023] The base layer may include any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and copolymers of polyethylene (PE) and polypropylene (PP).

[0024] The separator membrane can be configured such that the coating faces the first electrode.

[0025] An auxiliary separator membrane can extend from the separator membrane and be integrally formed with it.

[0026] The separator may include a separator region disposed between the first electrode and the second electrode, and an auxiliary separator region disposed between the separator region and the first electrode.

[0027] The separator membrane may include a base layer and a coating formed on any surface of the base layer, and the coating may be formed on opposite surfaces in the separator membrane region and the auxiliary separator membrane region.

[0028] The coating located in the separator membrane region can be configured to face the first electrode.

[0029] The coating located in the auxiliary separator region can be configured to face the first electrode.

[0030] Another exemplary embodiment of the present invention provides a secondary battery including the electrode assembly.

[0031] [Beneficial Effects]

[0032] According to an exemplary embodiment of the present invention, by forming a separator film in a double-layer structure in the portion of the electrode assembly corresponding to the end of the portion where the positive electrode begins to be wound, it is possible to prevent the negative electrode from breaking in the portion that contacts the end of the positive electrode, thereby preventing disconnection or short circuit and improving the safety of the secondary battery.

[0033] The effects of the present invention are not limited to those described above, and those skilled in the art will clearly understand other unmentioned effects based on the following description. Attached Figure Description

[0034] Figure 1 This is a perspective view of an electrode assembly according to an exemplary embodiment of the present invention.

[0035] Figure 2 It is shown in Figure 1 An exploded perspective view of the electrode assembly before it is wound.

[0036] Figure 3 Is Figure 1 A cross-sectional view of the end portion of the electrode assembly before winding.

[0037] Figure 4 This is a magnified view of the center of the electrode assembly when it is wound up.

[0038] Figure 5 It is magnified. Figure 1 A partial view of the center of the electrode assembly on the lower side.

[0039] Figure 6 This is a cross-sectional view showing a portion of a separator membrane applied to an electrode assembly according to another exemplary embodiment of the present invention.

[0040] Figure 7 It is shown that it is applied Figure 6 A cross-sectional view of the end portion of the separator membrane in an electrode assembly according to another exemplary embodiment, before the electrode assembly is wound. Detailed Implementation

[0041] In the following detailed description, only certain exemplary embodiments of the invention are shown and described by way of illustration only. However, the invention can be implemented in various ways and is not limited to the following embodiments.

[0042] Therefore, the accompanying drawings and descriptions should be considered illustrative rather than restrictive in nature. Throughout the specification, similar reference numerals denote similar elements.

[0043] Furthermore, for ease of understanding and description, the dimensions and thicknesses of each configuration shown in the accompanying drawings are arbitrarily illustrated, but the invention is not limited thereto. In the drawings, the thicknesses of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, the thicknesses of some layers and regions are exaggerated for ease of understanding and description.

[0044] Furthermore, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on the other element, or there may be intermediate elements present. Conversely, when an element is referred to as being "directly" on another element, there are no intermediate elements present. Additionally, when an element is referred to as being "on" a reference portion, the element is located above or below the reference portion, and does not necessarily mean that the element is "on" in the direction opposite to gravity.

[0045] Furthermore, unless explicitly stated otherwise, the word “comprise” and variations such as “comprises” or “comprising” will be understood to mean including the stated element but excluding any other element.

[0046] Furthermore, throughout the instruction manual, when referred to as "on a plane," this means when viewing the target portion from above; and when referred to as "on a cross section," this means when viewing the cross section obtained by vertically cutting the target portion from the side.

[0047] Figure 1 This is a perspective view of an electrode assembly according to an exemplary embodiment of the present invention. Figure 2 It is shown in Figure 1 An exploded perspective view of the electrode assembly before winding, and Figure 3 Is Figure 1 A cross-sectional view of the end portion of the electrode assembly before winding.

[0048] Reference Figures 1 to 3 An electrode assembly according to an exemplary embodiment of the present invention includes a first electrode 100, a second electrode 200, and a separator 300 inserted between the first electrode 100 and the second electrode 200, wherein the first electrode 100, the second electrode 200, and the separator 300 are wound together to form a jelly roll structure. When forming the jelly roll structure, the separator 300 is additionally provided below the second electrode 200 to prevent contact between the first electrode 100 and the second electrode 200. Furthermore, an auxiliary separator 310 is provided between the innermost end 101 of the first electrode 100 and the separator 300.

[0049] The first electrode 100 may include an electrode current collector 120 made of a thin metal plate and an active material layer 130 formed on the electrode current collector 120. The active material layer 130 may be formed by applying an electrode active material to the electrode current collector 120. Furthermore, the first electrode tab 110 may be bonded after a portion of the electrode current collector 120 is exposed without the active material being applied.

[0050] Similarly, the second electrode 200 may include an electrode current collector 220 made of a thin metal plate and an active material layer 230 formed on the electrode current collector 220. The active material layer 230 can be formed by applying an electrode active material to the electrode current collector 220. Furthermore, the second electrode tab 210 can be bonded after a portion of the electrode current collector 220 is exposed without the active material being applied.

[0051] The first electrode tab 110 and the second electrode tab 210 may protrude in opposite directions relative to the electrode assembly of the jelly roll structure.

[0052] Meanwhile, the first electrode 100 can be a positive electrode formed by applying a positive electrode active material to the electrode current collector 120, and the second electrode 200 can be a negative electrode formed by applying a negative electrode active material to the electrode current collector 220.

[0053] The separator 300 can be formed by coating a base layer 302 with a coating 301 containing ceramic particles. The auxiliary separator 310 may also include a base layer 302 and a coating 301 formed on the base layer 302 in the same manner as the separator 300. For example, the base layer 302 may include any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and copolymers of polyethylene (PE) and polypropylene (PP). The coating 301 may include ceramic particles, including at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. The coating 301 comprising such ceramic particles can be formed by applying a slurry of ceramic particles and a binder to the base layer 302. Furthermore, including the aforementioned coating 301 enhances the safety of the electrode assembly. Figure 2 As shown, all coatings 301 can be configured to face the first electrode 100 to prevent cracking and overheating problems that may occur from the innermost end (edge) 101 of the first electrode 100, which is the positive electrode.

[0054] Further reference will be made below. Figure 4 and Figure 5 The structure in the center (C) of the jelly roll structure is described.

[0055] Figure 4 This is an enlarged view of the center of the electrode assembly when it is wound up, and... Figure 5 It is magnified. Figure 1 A partial view of the center of the electrode assembly on the lower side. Specifically, in Figure 5 For ease of description, the illustration of the separator 300 inserted between the first electrode 100 and the second electrode 200 is omitted.

[0056] Reference Figure 4 and Figure 5 In the jelly roll structure according to this exemplary embodiment, an auxiliary separator 310 is included between the innermost end 101 of the first electrode 100 and the separator 300. At this time, the auxiliary separator 310 and the coating 301 included in the separator 300 (see...) Figure 2 Both are positioned to face the first electrode 100. The innermost end 101 of the first electrode 100 can contact the auxiliary separator 310.

[0057] Here, the center C of the jelly roll structure is the center of the circular structure when viewed from above, and refers to the virtual area corresponding to the portion at the beginning of the winding. In the winding process, as... Figure 4As shown, the electrode assembly includes a rod-shaped winding core with a circular cross-section. The jelly roll structure can be wound based on the winding core, which serves as a support, and the corresponding winding core can be removed from the center when winding is complete. Furthermore, the innermost end 101 of the first electrode 100 refers to the end where the first electrode 100 first begins to be wound.

[0058] like Figure 3 and Figure 4 As shown, by configuring the innermost end 101 of the first electrode 100 to contact the dual separator membranes 300 and 310, potential cracking and overheating from the end of the first electrode 100 can be prevented. That is, as the design requirements for high energy density increase, an increase in the density of the first electrode 100, i.e., the positive electrode, is inevitable, and therefore, the stress in the stepped portion of the positive electrode increases. Here, the stepped portion of the positive electrode is a portion in which a physical step is formed in the jelly roll electrode assembly due to the rapid increase in thickness to 100 μm to 200 μm at the starting point of the positive electrode as the positive electrode is inserted, and this stepped portion corresponds to the innermost end 101 of the first electrode 100 in the figure. The stress in the stepped portion of the positive electrode is high, and therefore, when the corresponding portion is continuously compressed during contraction and expansion due to charging / discharging, the portion of the separator membrane in contact with the corresponding portion is damaged, and there is a high risk of fire due to cracking and short circuit. However, according to an exemplary embodiment of the present invention, as described above, since the innermost end 101 of the first electrode is in contact with the double separators 300 and 310, damage to the separators in the stepped portion of the positive electrode can be prevented and a stable buffering action can be performed, thereby preventing rupture and short circuit caused by repeated contraction and expansion at the positive electrode end with high stress, thus preventing the risk of fire.

[0059] That is, with repeated charge / discharge cycles of hundreds or thousands of times, the electrode may shrink and expand, causing bending deformation at the innermost end 101 of the first electrode 100, which may result in electrode breakage. However, the electrode assembly includes a double-septum membrane comprising an auxiliary septum membrane 310, and the coating 301 of the septum membrane 300 and the auxiliary septum membrane 310 is configured to face the first electrode 100, thereby preventing breakage and short circuits caused by the shrinkage and expansion of the innermost end 101 of the first electrode 100, as well as fires caused by breakage and short circuits.

[0060] The auxiliary separator 310 can be configured to have the same arrangement as the separator 300, and can be wound in the jelly roll structure to a length of 0.5 to 1.5 times the circumference of the winding core to contact the innermost end 101 of the first electrode 100. That is, when the winding core is as follows... Figure 4When located at center C, the auxiliary separator 310 can be formed to be 0.5 to 1.5 times the circumference of the wound core. Furthermore, the invention is not limited to this, and the length of the auxiliary separator 310 can be adjusted so that the circumference of the wound core is 0.5 to 1.5 times when winding begins from the innermost portion of the auxiliary separator 310.

[0061] Meanwhile, based on the jelly roll structure, the innermost end of the second electrode 200 can be positioned closer to the center C of the jelly roll structure than the innermost end 101 of the first electrode 100.

[0062] Specifically, in the center C of the jelly roll structure, the second electrode 200 can be wound to extend beyond the first electrode 100. That is, the first electrode 100 can be inserted after the second electrode 200 and the separator 300 are wound to a certain extent, so that the second electrode 200, the separator 300, and the first electrode 100 can be wound together. The first electrode 100 and the second electrode 200 can be the positive and negative electrodes, respectively, and in the chemical reaction of a lithium-ion battery, since the negative electrode must receive lithium ions from the positive electrode, it is preferable that the negative electrode is designed to have a wider length and width than the positive electrode. When the length or width of the formed positive electrode is large, there is insufficient space for receiving lithium ions, so charging and discharging cannot be performed smoothly, and the risk of explosion may increase. Therefore, preferably, at the center C where the jelly roll electrode assembly begins to be wound, the second electrode 200, as the negative electrode, is wound before the first electrode 100, as the positive electrode. For example, the first electrode 100 can be inserted after the second electrode 200 has been wound once or twice, before the first electrode 100 is wound. Therefore, as described above, regarding the jelly roll structure, the innermost end of the second electrode 200 can be positioned closer to the center C of the jelly roll structure than the innermost end 101 of the first electrode 100.

[0063] In addition, such as Figure 5 As shown, when viewed from the lower end of the electrode assembly, the outwardly protruding second electrode tabs 210 can be spaced apart so as not to overlap with the innermost end 101 of the first electrode 100 at center C. That is, the second electrode tabs 210 are the part electrically connected to the outside, and a large amount of heat may be generated in this part. In this case, when the innermost end 101 of the first electrode 100 comes into contact with the second electrode tabs 210, which have a high heat value, the bending deformation stress and probability of breakage due to contraction and expansion during repeated charge / discharge cycles increase. However, as Figure 5 As shown, the innermost end 101 of the second electrode patch 210 and the first electrode 100 are configured not to overlap, thereby reducing the probability of risk occurrence.

[0064] Specifically, for this purpose, the innermost end 101 of the first electrode 100 is preferably spaced from the end of the second electrode tab 210 by 1 / 4 or more of the winding circumference. This means that in Figure 5 In this configuration, the distance from the end of the second electrode tab 210 to the innermost end 101 of the first electrode 100 is one-quarter or more of the winding circumference of the corresponding portion of the first electrode 100. As described above, by sufficiently separating the innermost end 101 of the first electrode 100 from the second electrode tab 210, contact between the second electrode tab 210 and the innermost end 101 of the first electrode 100 can be prevented. This reduces the probability of bending deformation stress and breakage due to contraction and expansion during repeated charge / discharge cycles, thereby significantly reducing the probability of internal short circuits or fires. Furthermore, the above configuration can be obtained by adjusting the relative positions of the second electrode 200, the second electrode tab 210, and the first electrode 100 at the winding start point, i.e., the center C, during winding.

[0065] Next, we will refer to Figure 6 and Figure 7 Another exemplary embodiment of the present invention is described below.

[0066] Figure 6 This is a cross-sectional view showing a portion of a separator membrane applied to an electrode assembly according to another exemplary embodiment of the present invention, and Figure 7 It is shown that it is applied Figure 6 A cross-sectional view of the end portion of the separator membrane in an electrode assembly according to another exemplary embodiment, before the electrode assembly is wound.

[0067] like Figure 6 and Figure 7 As shown, in another exemplary embodiment of the invention, the separator 300' is folded such that the end integrally extending from the separator 300' becomes an auxiliary separator. Apart from this, the other configurations are the same as those in the foregoing exemplary embodiments, and therefore descriptions of overlapping configurations will be omitted.

[0068] Reference Figure 6 and Figure 7 In an electrode assembly according to another exemplary embodiment of the present invention, a portion of the separator 300' is formed as a separator region 300P disposed between the first electrode 100 and the second electrode 200, and the remaining portion is formed as an auxiliary separator region 310P disposed between the separator region 300P and the first electrode 100. The separator region 300P and the auxiliary separator region 310P form an integrally formed separator 300', as shown below. Figure 7As shown, before winding, the auxiliary separator region 310P is folded above the separator region 300P, and the auxiliary separator region 310P is disposed between the separator region 300P and the first electrode 100. Using this configuration, without providing an auxiliary separator, the separator is integrally extended and folded to serve as an auxiliary separator. The portion of the separator that contacts the positive electrode is formed in a double layer using a simpler structure, which prevents the portion of the negative electrode that contacts the positive electrode from breaking to prevent short circuits, thereby improving the safety of the secondary battery.

[0069] In this case, the separator 300' includes a base layer 302 and a coating 301 similar to those in the aforementioned exemplary embodiment, but the coating 301 is positioned opposite to each other in the separator region 300P and the auxiliary separator region 310P. That is, as... Figure 6 As shown, in the auxiliary separating membrane region 310P, a coating 301 is formed on the surface opposite to the surface in the separating membrane region 300P on which the coating 301 is formed. Using the above configuration, as... Figure 7 As shown, even though the auxiliary separator region 310P is folded between the separator region 300P and the first electrode 100, the coatings of the auxiliary separator region 310P and the separator region 300P can be configured to face the positive electrode, i.e., the first electrode 100. Therefore, even in the electrode assembly according to another exemplary embodiment of the present invention, cracking and short circuits caused by the contraction and expansion of the innermost end 101 of the first electrode 100, as well as fires caused by cracking and short circuits, can be effectively prevented.

[0070] In this exemplary embodiment, terms indicating direction, such as front, back, left, right, up, and down, are used, but these terms are only for ease of explanation and may vary depending on the position of the object or the observer's position.

[0071] The electrode assembly described above according to this exemplary embodiment can be housed together with the electrolyte in a battery case to form a secondary battery, and the secondary battery can be applied to various devices. Specifically, the electrode assembly can be applied to vehicles such as electric bicycles, electric vehicles, and hybrid vehicles, but is not limited thereto, and the electrode assembly can be applied to various devices that can use secondary batteries.

[0072] Although exemplary embodiments of the invention have been described in detail, the scope of the invention is not limited to these embodiments. Various changes and modifications made by those skilled in the art using the basic concepts of the invention as defined in the appended claims should be interpreted as falling within the scope of the invention.

[0073] <Explanation of Figure Labels and Symbols>

[0074] 100: First electrode

[0075] 200: Second electrode

[0076] 300: Separator membrane

[0077] 310: Auxiliary separator membrane

[0078] 301: Coating

Claims

1. An electrode assembly, comprising: First electrode; Second electrode; as well as A separator membrane is inserted between the first electrode and the second electrode. The first electrode, the second electrode, and the separator membrane are wound together to form a jelly roll structure. At the center of the jelly roll structure, an auxiliary separator membrane is also included, disposed between the first electrode and the separator membrane. The auxiliary separator membrane is an independent membrane stacked on top of the separator membrane, which overlaps with the end of the first electrode at the center of the jelly roll structure and does not extend beyond the separator membrane. Each of the separating membrane and the auxiliary separating membrane includes a base layer and a coating.

2. The electrode assembly according to claim 1, wherein: The end of the first electrode is in contact with the coating of the auxiliary separator membrane.

3. The electrode assembly according to claim 1, wherein: The first electrode is the positive electrode, and the second electrode is the negative electrode.

4. The electrode assembly according to claim 1, wherein: The auxiliary separator film is wound in the jelly roll structure at a distance of more than 0.5 times and less than 1.5 times the circumference of the core.

5. The electrode assembly according to claim 1, wherein: The second electrode includes an active material layer formed on the current collector, an uncoated area thereon where the active material layer is not formed, and an electrode tab bonded to the uncoated area. The end of the first electrode is disposed at the center of the jelly roll structure, and the end of the first electrode is spaced apart from the electrode tab.

6. The electrode assembly according to claim 5, wherein: In the center, the end of the first electrode is spaced apart from the end of the electrode tab by 1 / 4 or more of its circumference.

7. The electrode assembly according to claim 1, wherein: The coating comprises ceramic particles, which include at least one selected from the group consisting of alumina, silicon dioxide, TiO2, SiC and MgAl2O4.

8. The electrode assembly according to claim 1, wherein: The base layer comprises any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and copolymers of polyethylene (PE) and polypropylene (PP).

9. The electrode assembly according to claim 1, wherein: The separator is configured such that the coating faces the first electrode.

10. The electrode assembly according to claim 1, wherein: The auxiliary separator extends from the separator and is integrally formed with the separator.

11. The electrode assembly of claim 10, wherein: The separator includes a separator region disposed between the first electrode and the second electrode, and an auxiliary separator region disposed between the separator region and the first electrode.

12. The electrode assembly according to claim 11, wherein: The separator membrane comprises a base layer and a coating formed on any surface of the base layer, and The coating is formed on the opposing surfaces of the separating membrane region and the auxiliary separating membrane region.

13. The electrode assembly according to claim 12, wherein: The coating, located in the separating membrane region, is positioned to face the first electrode.

14. The electrode assembly of claim 12, wherein: The coating, located in the auxiliary separator region, is positioned to face the first electrode.

15. A secondary battery comprising the electrode assembly according to claim 1.

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