Cylindrical secondary battery

Abstract

A cylindrical secondary battery is provided to reduce resistance and improve the safety of the battery cell. [Solution] A cylindrical secondary battery according to one embodiment of the present invention includes an electrode assembly 100 including a negative electrode sheet 110, a positive electrode sheet 120, and a separator 130s, the separator being located at the outermost portion of the electrode assembly, an electrode tab 140 located inside the separator being attached to one of the negative electrode sheet and the positive electrode sheet, and a metal layer 145 located between the electrode tab and the separator including an adhesive material.

Description

Technical Field

[0001] Cross - reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10 - 2018 - 0148564 filed on November 27, 2018, and all of the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a cylindrical secondary battery, and more specifically, to a cylindrical secondary battery with enhanced heat dissipation function.

Background Art

[0003] In recent years, with the rapid increase in the demand for portable electronic products such as notebook computers, video cameras, mobile phones, etc., and the formalization of the development of electric vehicles, energy storage batteries, robots, satellites, etc., many studies have been conducted on secondary batteries used as their drive power sources.

[0004] Such secondary batteries include, for example, nickel - cadmium batteries, nickel - metal hydride batteries, nickel - zinc batteries, lithium secondary batteries, etc. Among these, lithium secondary batteries are widely used in the field of advanced electronic devices because they have almost no memory effect compared to nickel - based secondary batteries, can be charged and discharged freely, have a very low self - discharge rate, a high operating voltage, and a high energy density per unit weight.

[0005] Generally, a lithium secondary battery has a structure in which unit cells composed of a positive electrode, a negative electrode, and a separator interposed therebetween are stacked or wound, and is built into a case of a metal can or a laminate sheet, and is configured by injecting or impregnating an electrolytic solution therein.

[0006] The electrode assembly of the positive electrode / separator / negative electrode structure constituting the secondary battery is roughly classified into a jelly roll type (winding type) and a stack type (lamination type) according to its structure. The jelly roll type has a structure in which a separation membrane is wound between a long sheet-shaped positive electrode and negative electrode coated with an active material, and the stack type has a structure in which a large number of positive electrodes and negative electrodes of a predetermined size are sequentially laminated with the separation membrane interposed therebetween.

[0007] Recently, in order to realize high-output and high-capacity models, the components used tend to be thinned, and as a result, the number of secondary batteries with low resistance and high capacity is increasing. However, while the resistance is lowered and the capacity is increased, higher currents are applied for longer periods of time, and problems with heat generation in secondary batteries due to high-rate discharge or external short circuit are emerging as more important issues.

[0008] Under such circumstances, there is a demand for research on secondary batteries that can effectively control the heat generation of the electrode tabs.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a cylindrical secondary battery for reducing resistance and enhancing the safety of the battery cell.

[0010] However, the problems to be solved by the embodiments of the present invention are not limited to the above-mentioned problems, and can be variously extended within the scope of the technical idea included in the present invention.

Means for Solving the Problems

[0011] A cylindrical secondary battery according to an embodiment of the present invention includes an electrode assembly including a negative electrode sheet, a positive electrode sheet, and a separation membrane, the separation membrane is located on the outermost part of the electrode assembly, and an electrode tab located inside the separation membrane is attached to one of the negative electrode sheet and the positive electrode sheet, and a metal layer located between the electrode tab and the separation membrane contains an adhesive substance.

[0012] The electrode tab includes a tab body attached to one of the negative electrode sheet and the positive electrode sheet, and a protruding portion extending from one end of the electrode assembly, and the protruding portion may be welded to the metal layer.

[0013] The tab body and the metal layer may be bonded by the adhesive substance.

[0014] The electrode tab may be a negative electrode tab.

[0015] The metal layer may be a rod-shaped copper foil.

[0016] The electrode tab and the metal layer may overlap at the end of the separator.

[0017] The metal layer may be connected to the electrode tab and the separator by an adhesive layer formed from the adhesive substance.

[0018] The cylindrical secondary battery may further include an insulating tape for fixing the boundary portion of the separator at the end of the separator.

[0019] The insulating tape and the metal layer may not overlap.

[0020] A device according to another embodiment of the present invention includes the above-described cylindrical secondary battery as a power source.

Advantages of the Invention

[0021] According to the embodiment, by additionally forming a metal layer containing an adhesive component on the negative electrode tab located outside the jelly roll, the jelly roll is fixed, the thickness of the negative electrode tab is increased to reduce resistance and dissipate heat generated during high current application or when a short-circuit situation occurs externally, and a cylindrical secondary battery capable of increasing the stability and life of the battery cell can be realized.

Brief Description of the Drawings

[0022]

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Mode for Carrying Out the Invention

[0023] Hereinafter, with reference to the attached drawings, various embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be realized in various different forms and is not limited to the embodiments described here.

[0024] To clearly explain the present invention, parts that are unnecessary for the explanation are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0025] Also, the sizes and thicknesses of the respective configurations shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to the places where it is shown. In the drawings, the thicknesses are enlarged to clearly represent a plurality of layers and regions. And in the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggeratedly shown.

[0026] Also, when a part such as a layer, film, region, or plate is "above" another part, this includes not only the case where it is directly above the other part but also the case where there are other parts in between. Conversely, when a part is "directly above" another part, it means that there are no other parts in between. Also, being "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" in the direction opposite to gravity.

[0027] Also, throughout the specification, when a part "includes" a certain component, this means that, unless there is a contrary description, it does not exclude other components and can further include other components.

[0028] Also, throughout the specification, when it is "planar", this means when the target part is viewed from above, and when it is "cross-sectional", this means when the cross-section obtained by vertically cutting the target part is viewed from the side.

[0029] FIG. 1 is an exploded perspective view showing the state of the electrode assembly according to an embodiment of the present invention before being wound. FIG. 2 is a perspective view showing the state of the electrode assembly of FIG. 1 after being wound.

[0030] Referring to FIGS. 1 and 2, a secondary battery according to an embodiment of the present invention includes an electrode assembly 100 including a negative electrode sheet 110, a positive electrode sheet 120, and a separator 130. The electrode assembly 100 may have a jelly roll type structure. At this time, the separator 130 is interposed between the negative electrode sheet 110 and the positive electrode sheet 120, and a jelly roll structure can be formed in the order of the positive electrode sheet 120, the separator 130, and the negative electrode sheet 110 along the direction from the center to the outside, and at least one such structure can exist. At this time, a separator 130s is located at the outermost part of the electrode assembly 100.

[0031] An electrode tab may be attached to each of the positive electrode sheet 120 and the negative electrode sheet 110, and the electrode tab includes a negative electrode tab 140 attached to the negative electrode sheet 110 and a positive electrode tab 160 attached to the positive electrode sheet 120.

[0032] In this embodiment, the negative electrode sheet 110 is located adjacent to the separator 130 inside the outermost separator 130s of the electrode assembly 100, and a negative electrode tab 140 may be attached to the negative electrode sheet 110. According to this embodiment, a metal layer 145 may be formed between the negative electrode tab 140 and the outermost separator 130s. The metal layer 145 contains an adhesive substance. The adhesive substance may contain an acrylic-based substance.

[0033] The metal layer 145 may be formed from a rod-shaped copper foil. The negative electrode tab 140 and the metal layer 145 may be arranged so as to overlap at the end of the outermost separator 130s. At this time, the metal layer 145 can contact the negative electrode tab 140 and the outermost separator 130s. The metal layer 145 may include a separate adhesive layer formed from an adhesive substance and contact the negative electrode tab 140 and the separator 130s through the adhesive layer.

[0034] Although not shown, one or more positive electrode tabs and negative electrode tabs may be additionally attached for a high-output model. In a secondary battery of a high-output and high-capacity model, when a large current flows in a short time due to high-rate discharge, overcharge, external short circuit, etc., a large amount of heat is generated in the electrode tabs, particularly the negative electrode tab 140, due to current concentration. Since charging and discharging repeatedly occur continuously due to the internal electrochemical reaction of the secondary battery, when the secondary battery thus has a higher capacity, the heat generation due to charging and discharging increases dramatically. Such heat generation may damage the separator 130 etc. and lead to an internal short circuit, or may induce a temperature deviation inside the secondary battery and lead to a deterioration in the performance of the secondary battery.

[0035] In particular, in the case of the negative electrode tab 140, which is a part with particularly high resistance among the internal components of the secondary battery, heat generation will occur most significantly there. In the case of a high-output battery cell, a high current is applied to the battery cell. At this time, the heat of the jelly roll can be dissipated to the battery case formed of a metal material through the electrode tab, so it is important to lower the heat and temperature of the electrode tab part.

[0036] The metal layer 145 according to the above-described embodiment can effectively release the heat generated at the negative electrode tab 140 so as to solve the heat generation problem. Moreover, since the metal layer 145 contains an adhesive substance, by fixing the end of the outermost separator 130s, the form of the electrode assembly 100 of the jelly roll type structure can be maintained as a result, and the phenomenon that the electrode assembly 100 is loosened by internal stress can be prevented. Additionally, the metal layer 145 containing copper has the effect of increasing the thickness of the negative electrode tab 140, reducing the resistance, and reducing the concentration of heat on the negative electrode tab 140.

[0037] In the above, the negative electrode sheet 110 has been described as being adjacent to the outermost separator 130s. However, the positive electrode sheet 120 may be arranged at the position where the negative electrode sheet 110 is formed. In this case, the negative electrode sheet 110 is arranged at the position of the positive electrode sheet 120, and a jelly roll structure can be formed in the order of the negative electrode sheet 110, the separator 130, and the positive electrode sheet 120 along the direction from the center to the outside. In other words, the positive electrode sheet 120 can also be located adjacent to the separator 130 inside the outermost separator 130s. For example, since heat concentrates on the negative electrode tab 140, the application of the metal layer 145 according to the above-described embodiment is preferable. However, since heat can also be generated at the positive electrode tab 160, the positive electrode sheet 120 is located adjacent to the separator 130 inside the outermost separator 130s, and it is also possible to form a metal layer 145 between the positive electrode tab 160 attached thereto and the outermost separator 130s. At this time, the metal layer 145 may be an aluminum foil and can contain an adhesive substance.

[0038] FIG. 3 is a partial plan view showing an enlarged view of part A in FIG. 2. FIG. 4 is a view of the drawing seen in the X direction of FIG. 2.

[0039] Referring to FIGS. 3 and 4, the negative electrode tab 140 according to this embodiment is attached on the negative electrode sheet 110 located immediately inside the outermost separator 130s. The negative electrode tab 140 may be rod-shaped and includes a protruding portion 140p extending from one end of the electrode assembly 100. A metal layer 145 is formed directly above the negative electrode tab 140, and the metal layer 145 may be formed to cover the left and right side surfaces of the negative electrode tab 140. Here, the metal layer 145 may extend not only on the tab body of the negative electrode tab 140 but also on the protruding portion 140p.

[0040] In this embodiment, the metal layer 145 may be adhered to the negative electrode tab 140 and the outermost separator 130s located on the upper and lower surfaces of the metal layer 145 by an adhesive substance contained in the metal layer 145. In this way, the metal layer 145 containing the adhesive substance can fix the end portion of the outermost separator 130s to maintain the form of the jelly roll type electrode assembly 100 and prevent the phenomenon that the electrode assembly 100 is released due to internal stress.

[0041] The electrode assembly 100 according to this embodiment described above can be housed in a battery case (not shown) such as a metal can to form a cylindrical secondary battery.

[0042] FIG. 5 is a partial plan view of an electrode assembly according to another embodiment of the present invention.

[0043] The embodiment of FIG. 5 is substantially the same as the embodiment described in FIGS. 3 and 4, however, the metal layer 145 may not be formed on the protruding portion 140p of the negative electrode tab 140 and may be formed only on the tab body.

[0044] FIG. 6 is a partial plan view of an electrode assembly according to another embodiment of the present invention. FIG. 7 is a cross-sectional view taken along the cutting line Y-Y' of FIG. 6.

[0045] The embodiments of FIGS. 6 and 7 are substantially the same as the embodiments of FIGS. 3 and 4 described above. However, only the different parts will be described below. Except for the different parts, the content described in the embodiments of FIGS. 3 and 4 is applicable to this embodiment.

[0046] Referring to FIGS. 6 and 7, in the tab body of the negative electrode tab 140, the tab body of the negative electrode tab 140 and the metal layer 145 may be adhered by an adhesive substance contained in the metal layer 145. However, in the protruding portion 140p of the negative electrode tab 140, the protruding portion 147 of the metal layer 145 and the protruding portion 140p of the negative electrode tab 140 can be welded and joined to form a welded portion 140s. By such a welding process, the negative electrode tab 140 and the metal layer 145 are joined, which has the effect of improving the capacitance. Due to heat generation, the temperature cut-off may be reached and sufficient capacitance cannot be used, and the voltage cut-off may occur early. However, according to this embodiment, when the negative electrode tab 140 and the metal layer 145 are joined through the welding process and the heat dissipation effect is increased, it is possible to prevent the voltage cut-off from occurring early, and as a result, the capacitance can be improved.

[0047] FIG. 8 is a perspective view showing an electrode assembly according to another embodiment of the present invention.

[0048] Referring to FIG. 8, it further includes an insulating tape 300 attached to the outer peripheral surface of the electrode assembly 100 included in the secondary battery according to the embodiment described in FIGS. 3 and 4. The insulating tape 300 can serve as a finishing tape at the end of the outermost separator 130s. That is, the boundary portion 150 with the separator 130 can be fixed at the end of the outermost separator 130s. The insulating tape 300 can be located at the end of the outermost separator 130s so as not to overlap the metal layer 145.

[0049] The insulating tape 300 can include a thermosetting resin selected from the group consisting of polyvinyl chloride, a mixture of nitrile rubber and phenol resin, epoxy resin, polyurethane, and combinations thereof.

[0050] In a state where the insulating tape 300 is attached to the outer peripheral surface of the electrode assembly 100, the outermost separation film 130s is fixed again by the metal layer 145, so that the form of the electrode assembly 100 having a jelly roll type structure can be maintained more stably.

[0051] The secondary battery described above can be applied to various devices. Such devices can be applied to transportation means such as electric bicycles, electric vehicles, and hybrids, but are not limited thereto, and are applicable to various devices that can use secondary batteries.

[0052] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the claims also belong to the scope of the present invention. The following items are also disclosed. [Item 1] An electrode assembly including a negative electrode sheet, a positive electrode sheet, and a separator, wherein the separator is located at the outermost part of the electrode assembly, and an electrode tab located inside the separator is attached to one of the negative electrode sheet and the positive electrode sheet, A cylindrical secondary battery in which a metal layer located between the electrode tab and the separator contains an adhesive substance. [Item 2] The electrode tab includes a tab body attached to one of the negative electrode sheet and the positive electrode sheet, and a protruding portion extended from one end of the electrode assembly, and the protruding portion is welded to the metal layer. The cylindrical secondary battery of Item 1. [Item 3] The tab body and the metal layer are bonded by the adhesive substance. The cylindrical secondary battery of Item 2. [Item 4] The electrode tab is a negative electrode tab. The cylindrical secondary battery according to any one of Items 1 to 3. [Item 5] The metal layer is a rod-shaped copper foil. The cylindrical secondary battery of Item 4. [Item 6] A cylindrical secondary battery according to any one of Items 1 to 5, wherein the electrode tab and the metal layer overlap at an end portion of the separation membrane. [Item 7] A cylindrical secondary battery according to Item 6, wherein the metal layer is connected to the electrode tab and the separation membrane by an adhesive layer formed from the adhesive substance. [Item 8] A cylindrical secondary battery according to any one of Items 1 to 7, further including an insulating tape for fixing a boundary portion of the separation membrane at a terminal end of the separation membrane. [Item 9] A cylindrical secondary battery according to Item 8, wherein the insulating tape and the metal layer do not overlap. [Item 10] A device including a cylindrical secondary battery according to any one of Items 1 to 9 as a power source.

Description of Reference Numerals

[0053] 130, 130s: Separation membrane 140: Negative electrode tab 140p: Protrusion 145: Metal layer

Claims

1. A method for manufacturing a cylindrical secondary battery, comprising an electrode assembly including a negative electrode sheet, a positive electrode sheet, and a separator, wherein the separator is located at the outermost part of the electrode assembly, and an electrode tab located inside the separator is attached to one of the negative electrode sheet and the positive electrode sheet, and a metal layer located between the electrode tab and the separator contains an adhesive substance, wherein the electrode tab includes a tab body attached to one of the negative electrode sheet and the positive electrode sheet, and a protrusion extended from one end of the electrode assembly, and the adhesive substance includes an acrylic-based substance, the method including a welding step of welding the protrusion to the metal layer.

2. The metal layer extends over the tab body and the protrusion, the protrusion is welded and joined to the metal layer extending over the protrusion, and the tab body and the metal layer extending over the tab body are joined by the adhesive substance. The method for manufacturing a cylindrical secondary battery according to Claim 1.

3. The method for manufacturing a cylindrical secondary battery according to Claim 1 or 2, wherein the electrode tab is a negative electrode tab.

4. The method for manufacturing a cylindrical secondary battery according to Claim 3, wherein the metal layer is a rod-shaped copper foil.

5. The method for manufacturing a cylindrical secondary battery according to any one of Claims 1 to 4, wherein the electrode tab and the metal layer overlap at an end of the separator.

6. The method for manufacturing a cylindrical secondary battery according to Claim 5, wherein the metal layer is connected to the electrode tab and the separator by an adhesive layer formed from the adhesive substance.

7. The method for manufacturing a cylindrical secondary battery according to any one of Claims 1 to 6, further including an insulating tape for fixing a boundary portion of the separator at a terminal of the separator.

8. The method for manufacturing a cylindrical secondary battery according to Claim 7, wherein the insulating tape and the metal layer do not overlap.

9. A method for manufacturing a device including the cylindrical secondary battery manufactured by the method for manufacturing a cylindrical secondary battery according to any one of Claims 1 to 8 as a power source.

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