Electrode assembly, secondary battery including the same, and method for manufacturing the same

Abstract

The present invention provides an electrode assembly that can reduce resistance and improve process performance, a secondary battery including the electrode assembly, and a method for manufacturing the electrode assembly. For example, an electrode assembly is disclosed, the electrode assembly comprising: a first electrode plate, a first electrode tab attached to the first electrode plate; a plurality of second electrode plates, a second electrode tab attached to the plurality of second electrode plates; and a diaphragm placed between the first electrode plate and the plurality of second electrode plates, wherein the first electrode plate, the diaphragm, and the plurality of second electrode plates are wound in a state of being stacked on each other, and the second electrode tabs are formed to be symmetrical to each other based on the winding center thereof.

Description

Technical Field

[0001] The present invention relates to an electrode assembly, a secondary battery including the electrode assembly, and a method for manufacturing the electrode assembly. Background Art

[0002] Typically, a secondary battery is manufactured by housing an electrode assembly together with an electrolyte in a housing, the electrode assembly consisting of a positive plate, a negative plate, and a separator inserted between the two electrode plates. Unlike non-rechargeable primary batteries, secondary batteries are rechargeable and dischargeable batteries. With the development of technology for mobile devices such as mobile phones and laptop computers and the increase in the production of mobile devices, the demand for secondary batteries as energy sources has increased rapidly. In recent years, secondary batteries have been actively studied and developed as an alternative energy source to replace fossil fuels, and even for the purpose of electric vehicles or hybrid electric vehicles.

[0003] Currently commercialized secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries and lithium secondary batteries. Among these secondary batteries, lithium secondary batteries have attracted much attention because they hardly show a memory effect compared to nickel-based secondary batteries, so lithium secondary batteries charge and discharge freely, have a very low self-discharge rate, and have a high energy density.

[0004] However, when a lithium secondary battery is overcharged to a certain voltage or higher, the reaction between the positive electrode active material and the electrolyte constituting the lithium secondary battery is excessively carried out, accompanied by structural collapse of the positive electrode active material and oxidation reaction of the electrolyte, and lithium is also extracted from the negative electrode active material. If this state continues, the lithium secondary battery will ignite or explode. Summary of the invention

[0005] Technical issues

[0006] The present invention provides an electrode assembly that reduces resistance and improves process efficiency, a secondary battery including the electrode assembly, and a method of manufacturing the electrode assembly.

[0007] Technical Solution

[0008] According to the present invention, an electrode assembly may include: a first electrode plate, to which a first electrode tab is attached; a plurality of second electrode plates, to which second electrode tabs are respectively attached; and a separator, disposed between the first electrode plate and each of the plurality of second electrode plates, wherein the first electrode plate, the separator and the plurality of second electrode plates are wound while being stacked, wherein the second electrode tab is formed to be symmetrical relative to a winding center.

[0009] Here, the first electrode tab may be located at the winding center.

[0010] In addition, the plurality of second electrode plates may be wound to be respectively located on the first surface and the second surface of the first electrode plate.

[0011] In addition, the separator may be provided in plurality and wound to cover the plurality of second electrode plates respectively.

[0012] In addition, the separator may be folded to cover the plurality of second electrode plates, respectively, so that the plurality of second electrode plates are separated from the first electrode plate.

[0013] In addition, the first electrode tab and the second electrode tab may be located on a straight line on a cross-section perpendicular to a winding axis of the electrode assembly.

[0014] In addition, the plurality of second electrode plates may be respectively wound symmetrically with respect to the first electrode plate.

[0015] In addition, a secondary battery includes the electrode assembly.

[0016] In addition, the method for manufacturing an electrode assembly according to the present invention may include: combining a mandrel to a first electrode plate, a first electrode tab being attached to the first electrode plate at a central portion of the first electrode plate, so that the first electrode tab is prepared to be located on the mandrel; positioning a plurality of second electrode plates on a first surface and a second surface of the first electrode plate, the second electrode tabs being attached to the plurality of second electrode plates, respectively; and enabling the mandrel to rotate in one direction to perform winding.

[0017] Here, the plurality of second electrode plates may be located on the first electrode plate while being covered by a plurality of separators, respectively.

[0018] Beneficial Effects

[0019] An electrode assembly, a secondary battery including the same, and a method of manufacturing the same according to the present invention can reduce resistance of the electrode assembly and improve process efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a perspective view showing a secondary battery according to an embodiment of the present invention.

[0021] Figure 2 is an exploded perspective view showing a secondary battery according to an embodiment of the present invention.

[0022] Figure 3 is a longitudinal sectional view showing a secondary battery according to an embodiment of the present invention.

[0023] Figure 4 is a transverse cross-sectional view showing a secondary battery according to an embodiment of the present invention.

[0024] Figure 5is a perspective view showing an electrode assembly before the electrode assembly is wound in a secondary battery according to an embodiment of the present invention.

[0025] Figure 6 is a cross-sectional view showing an electrode assembly before the electrode assembly is wound in a secondary battery according to an embodiment of the present invention.

[0026] Figure 7 is a cross-sectional view illustrating a process of winding an electrode assembly of a secondary battery by a mandrel according to an embodiment of the present invention.

[0027] [Explanation of Symbols in Main Parts of the Drawings]

[0028] 100: Secondary battery 110: Housing

[0029] 120, 220, 320, 420: electrode assembly 130: cover assembly DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that those having ordinary skill in the art to which the present invention pertains can easily practice the present invention.

[0031] Figure 1 is a perspective view showing a secondary battery according to an embodiment of the present invention. Figure 2 is an exploded perspective view showing a secondary battery according to an embodiment of the present invention. Figure 3 is a longitudinal sectional view showing a secondary battery according to an embodiment of the present invention. Figure 4 is a transverse cross-sectional view showing a secondary battery according to an embodiment of the present invention.

[0032] like Figures 1 to 5 As shown in FIG. 1 , a secondary battery 100 according to the present invention includes a case 110 , an electrode assembly 120 accommodated in the case 110 , and a cap assembly 130 sealing an upper end opening of the case 110 .

[0033] The housing 110 includes a circular bottom 111 and a side 112 extending upward from the bottom 111 by a predetermined length. Here, the secondary battery 100 is shown as a cylindrical secondary battery, but it can be applied to prismatic and pouch-type secondary batteries, and the shape of the secondary battery is not limited to the circular shape in the present invention. In the process of manufacturing the secondary battery, the upper part of the housing 110 is open. As a result, in the process of assembling the secondary battery, the electrode assembly 120 can be inserted into the housing 110 together with the electrolyte. The housing 110 can be made of steel, steel alloy, aluminum, aluminum alloy or its equivalent, but its material is not limited thereto. In addition, the curling portion 113 can be formed at the lower portion of the cap assembly 130 to be recessed into the interior of the cap assembly 130 so that the electrode assembly 120 is not separated to the outside, and the crimping portion 114 bent to the interior of the cap assembly 130 can be formed at the upper portion of the cap assembly 130.

[0034] The electrode assembly 120 is accommodated inside the housing 110 together with the electrolyte. Here, the electrolyte may be an organic liquid containing salt injected so that lithium ions flow between the positive electrode plate and the negative electrode plate constituting the electrode assembly 120, and may include a lithium salt (such as LiPF 6 , LiBF 4 、LiClO 4 ) and a high-purity organic solvent, but the present invention is not limited thereto.

[0035] The electrode assembly 120 includes a negative electrode plate 121, a positive electrode plate 122, and a separator 123, a negative electrode active material is applied on the negative electrode plate 121, a positive electrode active material is applied on the positive electrode plate 122, and a separator 123 is inserted between the negative electrode plate 121 and the positive electrode plate 122 to prevent a short circuit between the negative electrode plate 121 and the positive electrode plate 122 and to enable only lithium ions to flow. The negative electrode plate 121, the positive electrode plate 122, and the separator 123 are wound into a substantially cylindrical shape. In addition, a negative electrode tab 124 protruding downward and extending a predetermined length may be attached to the negative electrode plate 121, and a positive electrode tab 125 protruding upward a predetermined length may be attached to the positive electrode plate 122, and vice versa.

[0036] in addition, Figure 5 and Figure 6 There are shown a perspective view and a cross-sectional view, respectively showing an electrode assembly before the electrode assembly is wound in a secondary battery according to an embodiment of the present invention. Figure 7 A cross-sectional view showing a process of winding an electrode assembly by a mandrel in a secondary battery according to an embodiment of the present invention is shown. Figure 5 , Figure 6 and Figure 7 The configurations of a secondary battery and an electrode assembly according to the present invention are described in detail.

[0037] First, the negative electrode plate 121 of the electrode assembly 120 may be formed by a plate-shaped metal foil made of copper (Cu) or nickel (Ni), and negative electrode coating portions 126a and 126b as an active material made of a transition metal oxide are applied on opposite surfaces of the negative electrode plate 121. Here, the negative electrode coating portions 126a and 126b may include a first negative electrode coating portion 126a formed on a first surface of the negative electrode plate 121 and a second negative electrode coating portion 126b formed on a second surface opposite to the first surface.

[0038] In addition, the negative electrode plate 121 may be wound together with the positive electrode plate 122 and the separator 123 by a mandrel, and the winding may start from the center portion of the negative electrode plate 121. In addition, the negative electrode plate 121 may be formed so that the active material is not provided to the center portion of the winding. That is, since the center portion of the negative electrode plate 121 does not have an active material, it does not react with the active material of the positive electrode plate 122, and therefore, the center portion may form a non-reactive region inside the electrode assembly 120 after winding. Therefore, the center portion may be suppressed from being deformed inside the electrode assembly 120.

[0039] In addition, a negative electrode tab 124 is attached to a first surface of the negative electrode plate 121. A portion of the negative electrode tab 124 may be attached to the negative electrode plate 121 by welding, and protrude downward by a predetermined length in the longitudinal direction of the electrode assembly 120. In more detail, the active material is not applied to the front and rear ends of the negative electrode plate 121, respectively, so that a non-coating portion through which the negative electrode plate 121 is exposed may be formed, and the negative electrode tab may be bonded to the non-coating portion to be electrically connected to the negative electrode plate 121. The negative electrode tab 124 may be made of a copper material or a nickel material, but the present invention is not limited thereto.

[0040] The positive electrode plate 122 is composed of a plate-shaped metal foil made of aluminum (Al), and a positive electrode coating portion 127 as an active material made of a transition metal oxide is applied on both surfaces of the positive electrode plate 122. Here, the positive electrode plate 122 may include a first positive electrode plate 122a located on a first surface relative to the negative electrode plate 121 and a second positive electrode plate 122b located on a second surface. That is, the positive electrode plate 122 may be composed of a first positive electrode plate 122a and a second positive electrode plate 122b separated from each other, and may be wound together with the negative electrode plate 121, while the positive electrode plate 122 is located on the top surface and the bottom surface, respectively, relative to the negative electrode plate 121.

[0041] The positive electrode coating portion 127 may be formed on each of the first and second positive electrode plates 122 a and 122 b and may include a first positive electrode coating portion 127 a formed on a first surface and a second positive electrode coating portion 127 b formed on a second surface opposite to the first surface.

[0042] In addition, the positive electrode tab 125 may be formed on the positive electrode plates 122a and 122b. In more detail, the positive electrode tab 125 may include a first positive electrode tab 125a coupled to a first surface of the first positive electrode plate 122a and a second positive electrode tab 125b coupled to a first surface of the second positive electrode plate 122b. Portions of the first positive electrode tab 125a and the second positive electrode tab 125b may be partially welded to be attached to the positive electrode plates 122a and 122b, respectively, and protrude upward by a predetermined length in the longitudinal direction of the electrode assembly 120. The first positive electrode tab 125a and the second positive electrode tab 125b may be formed to be symmetrical with respect to the center of the winding center portion c in the transverse section of the wound electrode assembly 120. In more detail, the first positive electrode tab 125a and the second positive electrode tab 125b are linearly formed to be parallel to each other along the radius r of the transverse section as the length between the winding center c and the outermost portion o in the transverse section, and are located in the reverse direction relative to the winding center c, so that they can be easily coupled to the bottom surface of the shell 110.

[0043] In addition, the negative electrode tab 124 and the positive electrode tab 125 may be located on the same surface of the wound negative electrode plate 121 and the positive electrode plate 122, and may be located on the second surface of the negative electrode plate 121 and the positive electrode plate 122. Here, in the wound electrode assembly 120, the same surface may be a surface facing the outermost o in the same manner, or may be a surface facing the winding center c in the same manner. In addition, when the positive electrode tab 125 is formed on the surface facing the outermost o in the electrode assembly 120, it means that its opposite surface is wound, and vice versa. That is, the present invention is not limited to the surface on which the negative electrode tab 124 and the positive electrode tab 125 are attached in the form of foil on the opposite surfaces of the positive electrode plate 122 and the negative electrode plate 121.

[0044] In addition, the negative electrode tab 124 and the positive electrode tab 125 may be positioned so as to be arranged on the same line in the longitudinal direction in the wound electrode assembly 120. In addition, the negative electrode tab 124 and the positive electrode tab 125 may be positioned so as not to overlap each other in the longitudinal direction in the wound electrode assembly 120. That is, the upper portion of the negative electrode tab 124 and the lower portion of the positive electrode tab 125 may be positioned so as not to overlap each other on the same line in the longitudinal direction of the electrode assembly 120. This is to prevent the winding roundness of the electrode assembly 120 from being reduced when the negative electrode tab 124 and the positive electrode tab 125 having a thickness thicker than that of the positive electrode plate 122 and the negative electrode plate 121 overlap each other in the longitudinal direction of the electrode assembly 120. The positive electrode tab 125 may be made of an aluminum material, but the present invention is not limited thereto.

[0045] In addition, as described below, while the positive plates 122a and 122b are respectively located on the first surface and the second surface of the negative plate 121, the mandrel is combined to fix the negative electrode tab 124 on the negative plate 121, and in this state, the winding is started while rotating in one direction (for example, clockwise). Therefore, since the first positive electrode tab 125a and the second positive electrode tab 125b on the positive plates 122a and 122b are wound from the negative electrode tab 124 inside the mandrel by the same length, the first positive electrode tab 125a and the second positive electrode tab 125b can be positioned to be symmetrical with respect to the winding center c. In addition, in the winding method, since the positive electrode tabs 125a and 125b are easily arranged, the process efficiency thereof can be improved.

[0046] In addition, a first insulating plate 128 coupled to the case 110 and having a first hole 128a formed at the center thereof and a second hole 128b formed outside the first hole 128a may be interposed between the electrode assembly 120 and the bottom 111. The first insulating plate 128 is used to prevent the electrode assembly 120 from electrically contacting the bottom 111 of the case 110. Specifically, the first insulating plate 128 is used to prevent the positive plate 122 of the electrode assembly 120 from electrically contacting the bottom 111. Here, the first hole 128a is used to enable the gas to flow upward quickly when a large amount of gas is generated due to an abnormality of the secondary battery, and the second hole 128b is used to enable the negative electrode tab 124 to pass through the second hole 128b and be welded to the bottom 111. In addition, a center pin (not shown) having a hollow substantially cylindrical tubular shape is also provided so that a large amount of gas generated when the secondary battery is abnormal can be easily discharged through the internal channel of the center pin.

[0047] In addition, a second insulating plate 129 coupled to the housing 110 and having a first hole 129a formed at the center thereof and a plurality of second holes 129b formed outside the first hole 129a may be interposed between the electrode assembly 120 and the cap assembly 130. The second insulating plate 129 is used to prevent the electrode assembly 120 from being in electrical contact with the cap assembly 130. Specifically, the second insulating plate 129 is used to prevent the negative plate 121 of the electrode assembly 120 from being in electrical contact with the cap assembly 130. Here, the first hole 129a is used to enable the gas to flow quickly to the cap assembly 130 when a large amount of gas is generated due to an abnormality of the secondary battery, and the second hole 129b is used to enable the positive electrode tab 125 to pass through the second hole 129b and be welded to the cap assembly 130. In addition, another second hole 129b is used to enable the electrolyte to flow quickly into the electrode assembly 120 in the process of injecting the electrolyte. The electrolyte serves as a flow medium for lithium ions generated by electrochemical reactions in the positive and negative plates in the battery when the battery is charged and discharged.

[0048] The cover assembly 130 includes an upper cover 131 having a plurality of through holes 131d, a safety plate 133 installed at a lower portion of the upper cover 131, a connecting ring 135 installed at a lower portion of the safety plate 133, a lower cover 136 coupled to the connecting ring 135 and having a first through hole 136a and a second through hole 136b, a sub-plate 137 fixed to a lower portion of the lower cover 136 to be electrically connected to the positive electrode tab 125, and an insulating gasket 138 for insulating the upper cover 131, the safety plate 133, the connecting ring 135, and the lower cover 136 from the side 112 of the shell 110.

[0049] Here, the first positive electrode tab 125a and the second positive electrode tab 125b constituting the positive electrode tab 125 may be coupled together to the sub-plate 137. Here, as described above, since the first positive electrode tab 125a and the second positive electrode tab 125b may be linearly formed to be symmetrical with respect to the center of the electrode assembly 120, the first positive electrode tab 125a and the second positive electrode tab 125b may be linearly arranged when coupled to the sub-plate 137.

[0050] The insulating gasket 138 basically has a shape pressed between the curling portion 113 and the crimping portion 114 formed on the side portion 111 of the housing 110. In addition, the through hole 131d formed in the upper cover 131 and the second through hole 136b in the lower cover 136 are used to discharge the internal gas to the outside when abnormal internal pressure is caused in the housing 110. Of course, first, the safety plate 133 is electrically isolated from the sub-plate 137 while being inverted to the upper side, and thereafter, as the safety plate 133 is broken, the internal gas is discharged to the outside.

[0051] Hereinafter, a method for winding an electrode assembly according to an embodiment of the present invention will be explained in more detail.

[0052] Refer again Figure 7 , the negative electrode plate 121 is combined to pass through the center of the mandrel before winding, and the negative electrode tab 124 can be positioned at the center of the mandrel. In addition, the first positive electrode plate 122a can be positioned on the first surface of the negative electrode plate 121, and the second positive electrode plate 122b can be positioned on the second surface of the negative electrode plate 121. The first surface and the second surface of the positive plates 122a and 122b can be covered by the separator 123. In this case, the separator 123 can also be set to have two sheets, and the separator can be folded to cover the first positive electrode plate 122a and the second positive electrode plate 122b, respectively.

[0053] In this state, if the core shaft starts to rotate in one direction (for example, clockwise), winding begins relative to the negative electrode tab 124, so the first positive electrode tab 125a and the second positive electrode tab 125b can be formed to be symmetrical in the reverse direction relative to the negative electrode tab 124.

[0054] In addition, in this case, since the negative electrode tab 124 is positioned at the center of the electrode assembly 120, and the positive electrode tabs 125a and 125b are respectively formed at positions symmetrical to each other, that is, formed at uniform positions of the electrode assembly 120, the resistance can be reduced, and as a result, the number of tabs can be reduced.

[0055] Furthermore, since winding in the above-described manner enables the positive electrode tabs 125 a and 125 b to be positioned symmetrically to each other, process efficiency is improved.

[0056] The above embodiment is merely one embodiment for realizing an electrode assembly and a secondary battery including the electrode assembly. The present invention is not limited to this embodiment. The technical spirit of the present invention includes all technical scopes that can be variously modified by ordinary technicians in the field to which the present invention belongs without departing from the essence of the present invention as claimed in the attached claims.

Claims

1. An electrode assembly, comprising: a first electrode plate, a first electrode tab attached to the first electrode plate at a central portion of the first electrode plate; a pair of second electrode plates, respectively located on a first surface and a second surface of the first electrode plate, and second electrode tabs are respectively attached to the pair of second electrode plates; as well as a separator disposed between the first electrode plate and each of the pair of second electrode plates, wherein the first electrode plate, the separator, and the pair of second electrode plates are wound while being stacked, The first electrode terminal tab is located at the winding center, the second electrode terminal tab is formed symmetrically with respect to the winding center, and Before the first electrode plate, the separator and the pair of second electrode plates are wound, the first electrode tab and the second electrode tab do not overlap in the thickness direction of the first electrode plate, and the second electrode tabs do not overlap each other in the thickness direction of the first electrode plate.

2. The electrode assembly according to claim 1, wherein: Before the first electrode plate, the separator, and the pair of second electrode plates are wound, each of the pair of second electrode plates does not overlap a center portion of the first electrode plate in a thickness direction of the first electrode plate.

3. The electrode assembly according to claim 1, wherein: The diaphragm is arranged in plurality to be wound so as to respectively cover the pair of second electrode plates, wherein the first electrode plate includes a first non-coating portion, wherein each of the pair of second electrode plates includes a second non-coating portion, and wherein the first non-coating portion and the second non-coating portion do not overlap in a thickness direction of the first electrode plate.

4. The electrode assembly according to claim 3, wherein: The separators are folded to cover the pair of second electrode plates, respectively, so that the pair of second electrode plates are separated from the first electrode plate.

5. The electrode assembly according to claim 1, wherein: The first electrode tab and the second electrode tab are located on a straight line on a cross-section perpendicular to a winding axis of the electrode assembly.

6. The electrode assembly according to claim 1, wherein: The pair of second electrode plates are respectively wound symmetrically with respect to the first electrode plate. 7 . A secondary battery comprising the electrode assembly according to claim 1 .

8. A method for manufacturing an electrode assembly, the method comprising: combining a mandrel to the first electrode plate, a first electrode tab being attached to the first electrode plate at a central portion of the first electrode plate such that the first electrode tab is prepared to be located on the mandrel; positioning a pair of second electrode plates on the first surface and the second surface of the first electrode plate, the second electrode tabs being attached to the pair of second electrode plates, respectively; as well as Enables the mandrel to rotate in one direction to perform winding, wherein, before the first electrode plate, the separator and the pair of second electrode plates are wound, the first electrode terminal tab and the second electrode terminal tab do not overlap in the thickness direction of the first electrode plate, and the second electrode terminal tabs do not overlap each other in the thickness direction of the first electrode plate, and The second electrode terminal tab is symmetrical with respect to the winding center.

9. The method according to claim 8, wherein: The pair of second electrode plates are located on the first electrode plate and are respectively covered by a plurality of separators.

Images