JP2010055790A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having high safety with respect to a short-circuit which is caused by external force. <P>SOLUTION: An insulating tape 7 covers an electrode active material non-applied portion 1b which is located inside an electrode having a tab near the outer periphery, and an electrode active material non-applied portion 2c which is located outside the electrode having a tab near the inner periphery, throughout both surfaces. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery in which an electrode active material uncoated portion is covered with an insulator.

  In recent years, lithium ion secondary batteries have become widespread as power sources for small electronic devices such as mobile phones, notebook personal computers, and digital cameras.

  Currently, with the advancement of technology, small devices have become more powerful, and lithium ion secondary batteries are required to have higher capacities. Moreover, since the use of many people all over the world is increasing due to the widespread use of lithium ion secondary batteries, there is a demand for a more reliable battery for safety.

  When a lithium ion secondary battery is manufactured by winding around a positive electrode and a negative electrode via a separator, the belt-like electrode is continuously cut by a required length. Since the electrode is cut at a portion where the electrode active material is not applied, portions of the foil that do not have the electrode active material exist at portions that become inside and outside of the element when wound.

  FIG. 3 is a schematic view showing the structure of a conventional lithium ion secondary battery element. The lithium ion secondary battery element has positive and negative electrodes, and one electrode has an electrode active material uncoated portion 2c located outside the electrode having a tab in the vicinity of the inner periphery, An inner tab 3 for conductive connection is connected to an electrode active material uncoated portion 2b located inside an electrode having a tab in the vicinity of the peripheral portion. Further, the other electrode has an electrode active material uncoated portion 1b located inside the electrode having a tab in the vicinity of the outer peripheral portion, and an electrode active material not located in the outer side of the electrode having the tab in the vicinity of the outer peripheral portion. An outer tab 5 for conductive connection is connected to the application part 1c. One electrode and the other electrode are insulated by being interposed by the separator 4.

  FIG. 4 is a schematic view showing a cutting position of an electrode having a conventional conductive connection tab on the outside. The strip-shaped electrode is previously welded to the electrode active material uncoated portion 1c positioned outside the electrode having a tab in the vicinity of the outer peripheral portion, and is cut by a required length. Since the position to be cut is the electrode active material uncoated portion, both ends of the electrode are both electrode active material uncoated portions.

  FIG. 5 is a schematic view showing a cutting position of an electrode having a conductive connection tab on the outside and an insulating tape applied to the electrode active material application end. The configuration is the same as in FIG. 4 except that the insulating tape 7 is attached to the electrode active material application end. The insulating tape 7 has both the electrode active material uncoated portion 1b located inside the electrode having a tab near the outer peripheral portion and the electrode active material uncoated portion 1c located outside the electrode having a tab near the outer peripheral portion. Only the part is covered.

  This is done to increase the reliability of the battery, and in order to prevent a short circuit between the positive electrode and the negative electrode, it is effective to affix a tape-like insulating film to the electrode active material coating end. 1.

JP 2007-31265 A

  In FIG. 3, when an external force or the like causes a short circuit between the electrode active material application portion 1 a having a tab near the outer periphery and the electrode active material application portion 2 a having a tab near the inner periphery, When a short circuit occurs between the electrode active material non-applied portion 1b located inside the electrode having a tab in the vicinity and the electrode active material uncoated portion 2b located inside the electrode having a tab near the inner periphery. The latter current tends to flow. For this reason, when the battery is subjected to an impact that is recessed by 10 mm or more, the separator 4 cannot be insulated, and in the latter case, the electrode active material uncoated portion 1b located on the inner side of the electrode having a tab in the vicinity of the outer peripheral portion and the inner peripheral portion There is a possibility that the electrode active material uncoated portion 2b located inside the electrode having a tab in the vicinity of the portion is short-circuited and the battery itself becomes 100 ° C. or higher.

  Further, when the battery element is wound, an electrode having a tab in the vicinity of the outer peripheral portion is cut at an end of the electrode active material uncoated portion 1b located inside the electrode having the tab in the vicinity of the outer peripheral portion. Since there is an electrode having a counter-potential through only one sheet, it is important and complicated to manage burrs at the time of cutting with respect to a short circuit.

  For example, in order to prevent a short circuit when the thickness of the separator is 20 μm, for the sake of safety, the size of the cutting burr must be 10 μm or less, which is half the thickness of the separator. It takes a lot of time to engage when cutting cutters are replaced.

  In the present invention, protecting the electrode active material uncoated portion located inside the electrode having a tab near the outer peripheral portion and the electrode active material uncoated portion located outside the electrode having a tab near the inner peripheral portion; and It is important to solve the problem with cutting burr.

  That is, the technical problem of the present invention is to provide a lithium ion secondary battery that is highly safe with respect to a short circuit generated by an external force.

  The lithium ion secondary battery of the present invention is a lithium ion secondary battery having a battery element in which a strip-like positive electrode and a negative electrode are wound through a separator. The electrode active material uncoated portion located inside and the electrode active material uncoated portion located outside the electrode having a tab in the vicinity of the inner peripheral portion are all covered with an insulator.

  The lithium ion secondary battery of the present invention has an electrode active material uncoated portion located outside the electrode having a tab near the outer peripheral portion and an electrode active material uncoated located inside the electrode having the tab near the inner peripheral portion. Among the portions, both the surfaces of the end portions of the respective electrodes are covered with the insulator.

  The lithium ion secondary battery of the present invention is characterized in that the insulator is an insulating tape.

  In the lithium ion secondary battery of the present invention, when the strip-shaped electrode is cut, the electrode active material is within the range where the tab for conductive connection does not exist between the electrode active material application end and the electrode cutting position. The electrode active material uncoated portion is cut together with the insulator covering all surfaces from the coating end to the position beyond the electrode cutting position.

  According to the present invention, a lithium ion secondary battery having high safety with respect to a short circuit generated by an external force can be obtained.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing the structure of a lithium ion secondary battery element according to the present invention. The element structure of the lithium ion secondary battery includes an electrode having an inner tab 3 for conductive connection on the inside and an electrode having an outer tab 5 for conductive connection on the outer side, and a separator 4 is present between both electrodes. To do. Both electrodes have an electrode active material application part 1a of an electrode having a tab in the vicinity of the outer peripheral part, an electrode active material application part 2a of an electrode having a tab in the vicinity of the inner peripheral part, and a part where no electrode active material is applied. . Both ends of the electrode active material application end are substantially at the same position via the separator 4.

  Both sides of the electrode active material uncoated portion 1b located inside the electrode having the tab near the outer peripheral portion and the electrode active material uncoated portion 2c located outside the electrode having the tab near the inner peripheral portion are all made of the insulating tape 7. Covered. Furthermore, an electrode active material uncoated portion 1c positioned outside the electrode having a tab near the outer peripheral portion and an electrode active material uncoated portion 2b positioned inside the electrode having a tab near the inner peripheral portion are the end portions of the electrodes. Are covered with insulating tape 7.

  FIG. 2 is a schematic view showing a cutting position of an electrode having a conductive connection tab on the outside according to the present invention. This electrode is cut by the electrode cutting cutter 6 at the portion where the electrode active material is not applied, but in the present invention, it is cut together with the insulating tape 7 applied in advance. That is, as long as there is no outer tab 5 between the electrode active material application end and the electrode cutting position, the insulating tape 7 is pasted from the electrode active material application end to the position beyond the electrode cutting position. At the same time, the electrode active material uncoated portion is cut. By cutting together with the insulating tape 7, the insulating tape remains in a part of the electrode active material uncoated portion 1c located outside the electrode having a tab in the vicinity of the outer periphery after the electrode is cut. The length of the insulating tape 7 remaining in a part of the electrode active material uncoated portion 1c located outside the electrode having a tab in the vicinity of the outer periphery is from the end of the electrode to a position not reaching the outer tab 5 with the electrode. It is preferable in terms of connection reliability of the outer tab 5.

  The insulating tape used in the present invention is preferably a resinous tape such as polypropylene (PP), polyethylene terephthalate (PET), and polyphenylene sulfide (PPS). The thickness is preferably 10 μm or more and 100 μm or less in terms of design. It is also possible to apply an insulating resin instead of the insulating tape. Similarly, the thickness is preferably 1 μm or more and 100 μm or less in terms of design.

  Covering both sides with insulating tape the electrode active material uncoated part located inside the electrode having a tab near the outer periphery and the electrode active material uncoated part located outside the electrode having a tab near the inner periphery It is possible to prevent a short circuit due to an external force and improve the reliability of the lithium ion secondary battery.

  Also, in the management of electrode cutting burrs, the generation of burrs can be suppressed by cutting with the insulating tape, compared to cutting only the electrode active material uncoated portion. Since both sides of the electrode active material uncoated part are covered with insulating tape, even if there is a problem in the wear management of the electrode cutting cutter and the meshing adjustment when replacing the electrode cutting cutter, the generated cutting burr is It is a tape burr of an insulating tape, not a metal foil in an electrode active material uncoated part. Since this tape burr is non-conductive, it does not lead to an electrical short.

  Therefore, the wear management of the electrode cutting cutter and the engagement adjustment at the time of replacing the electrode cutting cutter are facilitated, and it is possible to continue to ensure a stable cutting state in terms of quality.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  In FIG. 1, the end portions of the electrodes are the portions where the positive electrode and the negative electrode are not coated with the electrode active material. Where there is no conductive connection tab between the end of the electrode and the electrode active material application end, the insulating tape 7 was applied to both sides of the electrode active material uncoated part. On the other hand, where there is a tab for conductive connection, the insulating tape 7 is attached to a part of both surfaces, that is, the end of the electrode and the end of the electrode active material application.

  As the insulating tape, polypropylene (PP) having a thickness of 14 μm was used. The thickness of the separator was 16 μm. The electrode active material uncoated portion located inside the electrode having a tab near the outer peripheral portion and the electrode active material uncoated portion located outside the electrode having the tab near the outer peripheral portion are positive electrode current collectors and have a thickness of 15 μm. The aluminum tab was used for the outer tab. The electrode active material uncoated portion located inside the electrode having a tab near the inner peripheral portion and the electrode active material uncoated portion located outside the electrode having the tab near the inner peripheral portion are negative current collectors. A 8 μm thick copper foil was used, and a nickel tab was used for the inner tab.

  After applying the insulating tape to the electrode, the positive electrode and the negative electrode were cut, and an aluminum tab was welded to the positive electrode and a nickel tab was welded to the negative electrode. The positive electrode and the negative electrode were wound through a separator and then housed in a can case to produce a lithium ion secondary battery.

  Between the electrode active material non-applied part located inside the electrode having a tab near the outer peripheral part and the electrode active material non-applied part located inside the electrode having a tab near the inner peripheral part by an external force, or near the outer peripheral part In order to cause a short circuit between the electrode active material uncoated portion located outside the electrode having the tab and the electrode active material uncoated portion located outside the electrode having the tab in the vicinity of the inner periphery, In addition, it was necessary to apply an external force that penetrates the insulating tape, and it was confirmed that the insulation was strengthened and the safety was high compared to the conventional penetration only by the separator.

  Also in the management of electrode cutting burrs, compared to cutting only the electrode active material uncoated part, the electrode cutting part is covered with insulating tape on both sides, so the occurrence of metal burrs is suppressed, and the electrode cutting cutter It became easy to adjust the meshing at the time of wear management and electrode cutting cutter replacement, and it was possible to keep a stable cutting state in terms of quality.

  From this, it was confirmed that a lithium ion secondary battery having high safety with respect to a short circuit generated by an external force can be obtained.

The schematic diagram which shows the structure of the lithium ion secondary battery element by this invention. The schematic diagram which shows the cutting position of the electrode which has the tab for conductive connection by this invention outside. The schematic diagram which shows the structure of the conventional lithium ion secondary battery element. The schematic diagram which shows the cutting position of the electrode which has the tab for the conventional conductive connection outside. The schematic diagram which shows the cutting position of the electrode which has the tab for electroconductive connection outside, and stuck the insulating tape on the electrode active material application end.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Electrode active material application | coating part 1b of the electrode which has a tab in the outer peripheral part vicinity The electrode active material uncoated part 1c located inside the electrode which has a tab in the outer peripheral part vicinity The electrode located in the outer side of the electrode which has a tab in the outer peripheral part Active material non-applied part 2a Electrode active material applied part 2b of an electrode having a tab in the vicinity of the inner peripheral part Electrode active material uncoated part 2c located inside the electrode having a tab in the vicinity of the inner peripheral part A tab is provided in the vicinity of the inner peripheral part Electrode active material non-applied portion 3 located on the outside of the electrode having the inner tab 4 separator 5 outer tab 6 electrode cutting cutter 7 insulating tape

Claims (4)

  In a lithium ion secondary battery having a battery element in which a strip-like positive electrode and a negative electrode are wound through a separator, an electrode active material uncoated portion located inside an electrode having a tab in the vicinity of the outer peripheral portion And a lithium ion secondary battery in which both surfaces of the electrode active material uncoated portion located outside the electrode having a tab near the inner peripheral portion are covered with an insulator.   The electrode active material uncoated part located outside the electrode having a tab near the outer peripheral part and the electrode active material uncoated part located inside the electrode having a tab near the inner peripheral part The lithium ion secondary battery according to claim 1, wherein both surfaces of the lithium ion secondary battery are covered with the insulator.   The lithium ion secondary battery according to claim 1, wherein the insulator is an insulating tape.   When cutting the strip-shaped electrode, the electrode active material coating end is crossed from the electrode active material coating end within a range where the tab for conductive connection does not exist between the electrode active material coating end and the electrode cutting position. 4. The lithium ion secondary battery according to claim 1, wherein the lithium ion secondary battery is formed by cutting the electrode active material uncoated portion together with the insulator covering all of the two surfaces.

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