Secondary battery

Abstract

Embodiments of the present invention relate to a secondary battery, and an object of the present invention is to provide a secondary battery capable of improving flatness of an electrode assembly and reducing internal resistance when the electrode assembly is wound. To this end, disclosed is a secondary battery including: a wound electrode assembly including a positive electrode plate, a negative electrode plate, and a separator, wherein the positive electrode plate has positive electrode uncoated portions provided at a central portion of the wound electrode assembly and end portions of the wound electrode assembly, and the negative electrode plate has negative electrode uncoated portions provided at a central portion of the wound electrode assembly and end portions of the wound electrode assembly; a first positive electrode tab and a second positive electrode tab connected to the positive electrode uncoated portions, respectively; a first negative electrode tab and a second negative electrode tab connected to the negative electrode uncoated portions, respectively; a positive electrode current collector tab connected together with the first positive electrode tab and the second positive electrode tab; a negative electrode current collector tab connected together with the first negative electrode tab and the second negative electrode tab; and a pouch-type case for accommodating the electrode assembly.

Description

Technical Field

[0001] An embodiment of the present invention relates to a secondary battery. Background Art

[0002] Unlike primary batteries, which cannot be recharged, secondary batteries can be charged and discharged. Low-capacity secondary batteries are mainly used in small portable electronic devices such as smartphones, laptops, digital cameras, and camcorders, while large-capacity secondary batteries are widely used for motor driving and power storage in hybrid and electric vehicles.

[0003] This type of secondary battery includes an electrode assembly, terminals extending from the electrode assembly, and a housing for containing the electrode assembly and electrolyte. The electrode assembly, including the positive plate, negative plate, and separator, can be stacked on top of each other or rolled together (in a jelly roll). Furthermore, depending on the appearance of the housing, the housing can be classified into cylindrical, prismatic, and pouch types.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not constitute prior art. Summary of the Invention

[0005] Technical issues

[0006] An embodiment of the present invention provides a secondary battery capable of improving the flatness of an electrode assembly and reducing internal resistance when the electrode assembly is wound.

[0007] Technical Solution

[0008] A secondary battery according to an embodiment of the present invention includes: a wound electrode assembly including a positive electrode plate, a negative electrode plate, and a separator, wherein the positive electrode plate has a positive electrode uncoated portion provided at a center portion and an end portion of its winding, and the negative electrode plate has a negative electrode uncoated portion provided at a center portion and an end portion of its winding; a first positive electrode foil and a second positive electrode foil, respectively connected to the positive electrode uncoated portion; a first negative electrode foil and a second negative electrode foil, respectively connected to the negative electrode uncoated portion; a positive electrode collector sheet connected to the first positive electrode foil and the second positive electrode foil; a negative electrode collector sheet connected to the first negative electrode foil and the second negative electrode foil; and a pouch-type case for accommodating the electrode assembly.

[0009] In addition, the first and second positive electrode foils may have a thickness smaller than that of the positive electrode plate where the positive active material is applied, and the first and second negative electrode foils may have a thickness smaller than that of the negative electrode plate where the negative active material is applied.

[0010] In addition, the first and second positive electrode foils may have a thickness of 25 to 35 μm, and a region of the positive electrode plate to which the positive active material is applied may have a thickness of 90 to 110 μm.

[0011] In addition, the positive electrode current collector sheet may have a thickness of 80 to 100 [μm].

[0012] In addition, the first and second negative electrode foils may have a thickness of 25 to 35 μm, and a region of the negative electrode plate to which the negative electrode active material is applied may have a thickness of 100 to 130 μm.

[0013] In addition, the negative electrode current collector sheet may have a thickness of 80 to 100 [μm].

[0014] Effects of the Invention

[0015] In the secondary battery according to the embodiment of the present invention, the positive electrode foil and the negative electrode foil have a very small thickness compared to the positive electrode plate and the negative electrode plate as a whole, and therefore, when connected to the uncoated portion of the positive electrode and the uncoated portion of the negative electrode, the positive electrode foil and the negative electrode foil may not protrude further outward than the area of ​​the positive electrode plate to which the positive electrode active material is applied and the area of ​​the negative electrode plate to which the negative electrode active material is applied, thereby improving the flatness of the electrode assembly when it is wound, and increasing the energy density and reducing the internal resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a perspective view of a secondary battery according to an embodiment of the present invention.

[0017] Figure 2a FIG. 4 is a plan view of a positive electrode plate of a secondary battery according to an embodiment of the present invention.

[0018] Figure 2b To follow Figure 2a A cross-sectional view taken along line XX.

[0019] Figures 3a to 3e It is a view sequentially explaining a process of connecting a positive electrode collector tab to a positive electrode foil of a secondary battery according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] Hereinafter, exemplary embodiments of the present invention will be described in detail.

[0021] The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following exemplary embodiments may be modified in various other forms and the present invention should not be construed as being limited to the embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will convey the aspects and features of the present invention to those skilled in the art.

[0022] In addition, in the accompanying drawings, the size or thickness of various components are exaggerated for the sake of brevity and clarity. The same reference numerals refer to the same elements throughout. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In addition, it will be understood that when element A is referred to as being "connected to" element B, element A may be directly connected to element B, or an intervening element C may be present therebetween so that element A and element B are indirectly connected to each other.

[0023] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used herein, unless the context clearly indicates otherwise, the singular is intended to include the plural. It will be further understood that when used in this specification, the terms "comprise" and / or "comprising" specify the presence of the recited features, numbers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components and / or groups thereof.

[0024] It will be understood that although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers, and / or portions, these members, elements, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer, and / or portion from another. Thus, for example, a first member, first element, first region, first layer, and / or first portion discussed below may be referred to as a second member, second element, second region, second layer, and / or second portion without departing from the teachings of the present invention.

[0025] For ease of description, spatially relative terms such as "below," "beneath," "below," "above," and "on" may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the elements or features in the figures are turned over, elements described as "below" or "beneath" other elements or features would be oriented "above" or "on" the other elements or features. Thus, the exemplary term "below" can encompass both above and below orientations.

[0026] Figure 1 is a perspective view of a secondary battery 100 according to an embodiment of the present invention.

[0027] in addition, Figure 2a is a plan view of a positive electrode plate 111 of a secondary battery 100 according to an embodiment of the present invention, and Figure 2b To follow Figure 2aA cross-sectional view taken along line XX.

[0028] refer to Figure 1 The secondary battery 100 includes an electrode assembly 110 , positive electrode foils 121 and 122 , negative electrode foils 131 and 132 , a positive electrode current collector 140 , a negative electrode current collector 150 , and a pouch-type case 160 .

[0029] The electrode assembly 110 includes a positive electrode plate 111 , a negative electrode plate 112 , and a separator 113 .

[0030] The positive electrode plate 111 includes a positive electrode current collector made of, for example, aluminum foil and a positive electrode active material 111A made of, for example, a transition metal oxide and applied to the positive electrode current collector. Figure 2a and Figure 2b As shown in FIG, positive electrode plate 111 includes positive electrode uncoated portions 111B at its left and right ends, where positive electrode active material 111A is not applied. Here, the positive electrode current collector itself may have a thickness of approximately 10 to 12 μm, and the area where positive electrode active material 111A is applied may have a thickness of approximately 100 μm, for example, approximately 90 to 110 μm.

[0031] The negative electrode plate 112 includes a negative electrode current collector made of, for example, copper or nickel foil, and a negative electrode active material made of, for example, graphite or carbon and applied to the negative electrode current collector. Here, the negative electrode plate 112 also includes negative electrode uncoated portions at its left and right ends, representing areas where the negative electrode active material is not applied. Here, the negative electrode current collector itself may have a thickness of approximately 8 to 10 μm, and the area where the negative electrode active material is applied may have a thickness of approximately 100 to 130 μm.

[0032] The separator 113 is made of, for example, polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. Furthermore, the separator 113 interposed between the positive electrode plate 111 and the negative electrode plate 112 prevents a short circuit between the positive electrode plate 111 and the negative electrode plate 112 while allowing, for example, the movement of lithium ions.

[0033] The electrode assembly 110 is wound into a so-called jelly roll configuration based on one end thereof. Hereinafter, one end is referred to as the "center portion of the winding," and the other end is referred to as the "end portion of the winding."

[0034] like Figure 2a As shown in FIG, positive electrode foils 121 and 122 are electrically connected to two positive electrode uncoated portions 111B of the positive electrode plate 111, respectively, to be then exposed outside the top end thereof.

[0035] In addition, the positive electrode foils 121 and 122 may be made of the same material as the positive electrode current collector. For example, if the positive electrode current collector is made of aluminum, the positive electrode foils 121 and 122 may also be made of aluminum.

[0036] Furthermore, the positive electrode foils 121 and 122 may have a very small thickness compared to the entire positive electrode plate 111. For example, the positive electrode foils 121 and 122 may have a thickness of approximately 1 / 3 of the area of ​​the positive electrode plate 111 coated with the positive electrode active material 111A. More specifically, the positive electrode foils 121 and 122 may have a thickness of approximately 25 to 35 μm.

[0037] Hereinafter, in the positive electrode plate 111, the positive electrode foil 121 connected to the positive electrode uncoated portion 111B on the side of the center portion of the winding is referred to as the "first positive electrode foil 121", and the positive electrode foil 122 connected to the positive electrode uncoated portion 111B on the side of the end portion of the winding is referred to as the "second positive electrode foil 122".

[0038] When the electrode assembly 110 is wound, the first positive electrode foil 121 and the second positive electrode foil 122 are arranged substantially parallel to each other.

[0039] The negative electrode foils 131 and 132 are electrically connected to two uncoated portions of the negative electrode plate 112 , respectively, to then be exposed outside the top end thereof.

[0040] In addition, the negative electrode foils 131 and 132 may be made of the same material as the negative electrode current collector. For example, if the negative electrode current collector is made of copper, the negative electrode foils 131 and 132 may also be made of copper.

[0041] Furthermore, the negative electrode foils 131 and 132 may have a very small thickness compared to the entire negative electrode plate 112. For example, the negative electrode foils 131 and 132 may have a thickness of approximately ¼ of the negative electrode active material-coated region of the negative electrode plate 112. More specifically, the negative electrode foils 131 and 132 may have a thickness of approximately 25 to 35 μm.

[0042] Hereinafter, in the negative electrode plate 112, the negative electrode foil 131 connected to the negative electrode uncoated portion on the side of the center portion of the winding is referred to as the "first negative electrode foil 131", and the negative electrode foil 132 connected to the negative electrode uncoated portion on the side of the end portion of the winding is referred to as the "second negative electrode foil 132".

[0043] When the electrode assembly 110 is wound, the first negative electrode foil 131 and the second negative electrode foil 132 are arranged to be aligned substantially parallel to each other.

[0044] The positive electrode current collector 140 is connected to the first positive electrode foil 121 and the second positive electrode foil 122 .

[0045] In this regard, Figures 3a to 3eViews for sequentially explaining a process of connecting the positive electrode collector tab 140 to the positive electrode foils 121 and 122 of the secondary battery 100 according to an embodiment of the present invention are viewed from the side when the electrode assembly 110 is wound.

[0046] First, if Figure 3a As shown in FIG. 1 , when the electrode assembly 110 is wound, Figure 3b As shown in FIG, the first positive electrode foil 121 is bent toward the second positive electrode foil 122 to overlap each other. Of course, if necessary, the second positive electrode foil 122 can also be bent toward the first positive electrode foil 121 to overlap each other, and the first positive electrode foil 121 and the second positive electrode foil 122 can be bent together to overlap each other.

[0047] Afterwards, if Figure 3c As shown in FIG, the ends of the first positive electrode foil 121 and the second positive electrode foil 122 are cut to appropriate lengths and then aligned.

[0048] Then, if Figure 3d As shown in FIG, the positive electrode current collector 140 is welded together with the first positive electrode foil 121 and the second positive electrode foil 122 .

[0049] Finally, if Figure 3e As shown in the figure, apply the INSULATION TAPE (T) and you are done.

[0050] Meanwhile, the positive electrode collector sheet 140 may have a thickness of about 80 to 100 [μm].

[0051] The negative electrode current collector 150 is also connected to the first negative electrode foil 131 and the second negative electrode foil 132 .

[0052] exist Figures 3a to 3e In the embodiment, the first negative electrode foil 131, the second negative electrode foil 132 and the negative electrode collector 150 are hidden behind the first positive electrode foil 121, and the second positive electrode foil 122 and the positive electrode collector 140 are not visible, but the same process as above can be performed on them.

[0053] That is, when the electrode assembly 110 is wound, the first negative electrode foil 131 and the second negative electrode foil 132 are overlapped with each other, and then the ends of the first negative electrode foil 131 and the second negative electrode foil 132 are cut to a suitable length and aligned, and then the negative electrode collector 150 is welded to the first negative electrode foil 131 and the second negative electrode foil 132, and then completed by attaching an insulating tape (T).

[0054] Here, the negative electrode collector sheet 150 may have a thickness of about 80 to 100 [μm].

[0055] The case 160 includes a lower case 161 having a recessed space for accommodating the electrode assembly 110 and an electrolyte, and an upper case 162 coupled to and sealing the lower case 161 .

[0056] Here, the electrolyte may include, for example, an organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and a lithium salt such as LiPF6 or LibF4.

[0057] According to the above-described secondary battery 100, the positive electrode foils 121 and 122 and the negative electrode foils 131 and 132 have a very small thickness compared to the positive electrode plate 111 and the negative electrode plate 112 as a whole, and therefore, when coupled to the positive electrode uncoated portion 111B and the negative electrode uncoated portion, the positive electrode foils 121 and 122 and the negative electrode foils 131 and 132 may not protrude further outward than the region of the positive electrode plate 111 to which the positive electrode active material 111A is applied and the region of the negative electrode plate 112 to which the negative electrode active material is applied, thereby improving the flatness of the electrode assembly 110 when it is wound.

[0058] In addition, according to the secondary battery 100 , energy density can be increased and internal resistance of the battery can be reduced.

[0059] In this regard, Table 1 shows DCIR (Direct Current Internal Resistance) measurement values ​​when current was applied to the secondary battery for 1 second, and Table 2 shows DCIR measurement values ​​when current was applied to the secondary battery for 30 seconds.

[0060] As used herein, the term "conventional secondary battery" refers to a secondary battery including an electrode assembly in which a positive electrode plate and a negative electrode plate have a positive electrode uncoated portion and a negative electrode uncoated portion each provided at one end, and a positive electrode material sheet and a negative electrode material sheet of approximately 80 [μm] are connected to the positive electrode uncoated portion and the negative electrode uncoated portion, respectively.

[0061] Table 1

[0062]

[0063] Table 2

[0064]

[0065] Referring to Table 1 and Table 2, it can be confirmed that the internal resistance of the secondary battery 100 according to the embodiment of the present invention is reduced by about 36 to 42 [%] compared with the conventional secondary battery.

[0066] While the foregoing embodiments have been described to practice the secondary battery 100 according to the present invention, those skilled in the art will understand that various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the following claims.

Claims

1. A secondary battery comprising: A wound electrode assembly comprising a positive electrode plate, a negative electrode plate, and a separator, wherein the positive electrode plate has a positive uncoated portion provided at one end thereof and a positive uncoated portion provided at the other end thereof, respectively, and the negative electrode plate has a negative uncoated portion provided at one end thereof and a negative uncoated portion provided at the other end thereof, respectively; a first positive electrode foil and a second positive electrode foil respectively connected to the uncoated portion of the positive electrode; a first negative electrode foil and a second negative electrode foil respectively connected to the uncoated portion of the negative electrode; a positive electrode current collector connected to the first positive electrode foil and the second positive electrode foil; a negative electrode current collector connected to the first negative electrode foil and the second negative electrode foil; and a bag-type housing for accommodating the electrode accessory, wherein the first positive electrode foil and the second positive electrode foil have a thickness smaller than a thickness of a positive electrode active material applied to a positive electrode collector of the positive electrode plate, wherein the first negative electrode foil and the second negative electrode foil have a thickness smaller than a thickness of a negative electrode active material applied to a negative electrode collector of the negative electrode plate, wherein the positive electrode current collector sheet has a thickness greater than that of the first positive electrode foil or the second positive electrode foil, wherein the negative electrode current collector sheet has a thickness greater than that of the first negative electrode foil or the second negative electrode foil, wherein the first positive electrode foil and the second positive electrode foil have a thickness of 25 μm to 35 μm, and the first negative electrode foil and the second negative electrode foil have a thickness of 25 μm to 35 μm, and The positive electrode current collector sheet has a thickness of 80 μm to 100 μm, and the negative electrode current collector sheet has a thickness of 80 μm to 100 μm. 2 . The secondary battery according to claim 1 , wherein a region of the positive electrode plate to which the positive electrode active material is applied has a thickness of 90 μm to 110 μm. 3 . The secondary battery according to claim 1 , wherein a region of the negative electrode plate to which the negative electrode active material is applied has a thickness of 100 μm to 130 μm.

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