JP5128769B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery suitable as a power source for portable devices, information devices, home appliances, particularly small and portable electronic devices.

  Various types of batteries are used as power sources for small electronic devices, and small and large-capacity sealed batteries are used as power sources for mobile phones, notebook computers, etc. Nonaqueous electrolyte secondary batteries are used. In a lithium ion battery, a battery element made of aluminum or an alloy thereof is laminated by winding a positive electrode and a negative electrode through a separator, and a molded battery element is inserted and a lid is provided and stored.

  FIG. 6 is a diagram for explaining a wound body 4 that is a battery element of a conventional non-aqueous electrolyte secondary battery. 6A is a plan view, FIG. 6B is a front view, and FIG. 6C is a side view. The wound body 4 shown in FIG. 6 has a positive electrode lead 2 attached to a positive electrode in which a positive electrode active material such as lithium manganate is formed on a positive electrode current collector made of aluminum foil or the like, and a negative electrode current collector made of copper foil or the like. A negative electrode lead 1 is attached to a negative electrode on which a negative electrode active material such as graphite is formed, and is wound in a flat shape via a separator.

  In nonaqueous electrolyte secondary batteries, reliability is required against dropping and impact. In Patent Document 1, it is proposed to arrange an insulating plate having a T-shaped cross section between a wound body and a battery can in order to improve impact resistance.

  However, when the number of drop tests to confirm the safety of the battery is repeated, the end of the battery element is a wound body due to a drop impact, so that the wound body is shifted in a bamboo shoot shape from the outer peripheral side. The positive electrode lead or the negative electrode lead attached to the positive electrode or the negative electrode is detached, and the battery may not be usable.

  In order to maintain the wound state of the wound body, Patent Document 2 proposes a structure in which the part is fixed with a tape so as to be orthogonal to a part parallel to the winding axis of the wound body and a part perpendicular to the winding axis. ing. In non-aqueous electrolyte secondary batteries, the active material layer is repeatedly expanded and contracted by repeated charge and discharge, and the battery can may be deformed without being able to suppress the expansion of the wound body serving as a battery element. The upper tape is located at the center of the side surface of the battery element that is most likely to swell, and the battery can swells and deforms after the charge / discharge cycle, which makes it difficult to mount the battery on a battery-operated device.

JP 2004-6363 A JP 2001-185224 A

  In a nonaqueous electrolyte secondary battery in which a wound body serving as a battery element according to the prior art is housed, the wound body is displaced in an impact resistance test such as dropping. When the winding body is fixed with tape so as to be orthogonal to prevent the winding body from being displaced, the battery can swell due to expansion of the battery element. In this situation, an object of the present invention is to provide a nonaqueous electrolyte secondary battery that is durable against impacts such as dropping and that is highly reliable against expansion of battery elements due to repeated charge and discharge. It is in.

In order to solve the above problems, the non-aqueous electrolyte secondary battery of the present invention has a wound body in which a positive electrode and a negative electrode are wound in a flat shape with a separator interposed between the wound end surface of the wound body. and tape the portion of the vertical side surface on each of the winding end face over a certain top or bottom surface, at the side, the length of the tape from the upper end or lower end of the side, the height of the side It is characterized by being in the range from 1/4 to 1/3 .

The nonaqueous electrolyte secondary battery of the present invention has a wound body obtained by winding a positive electrode having a positive electrode lead and a negative electrode having a negative electrode lead in a flat shape through a separator, and the positive electrode lead, during the negative electrode lead, among the three places outside of the outer and the anode lead of the positive electrode lead, a portion of the vertical side surface on the winding end surface across the top surface is a winding end faces of the windings of the at least one location The length of the tape from the upper end or the lower end of the side surface is in the range from 1/4 to 1/3 of the height of the side surface. To do.

  According to the non-aqueous electrolyte secondary battery of the present invention, the winding body is fixed with a tape to improve durability against impacts such as dropping, and the center of the side surface of the winding body that is most likely to swell due to a charge / discharge cycle. Since there is no tape in the portion, the battery can be prevented from swelling and a highly reliable nonaqueous electrolyte secondary battery can be provided.

  The nonaqueous electrolyte secondary battery according to the embodiment of the present invention will be described below. However, the present invention is not limited to this embodiment, and may be appropriately changed without changing the object of the present invention. It is possible to implement.

The nonaqueous electrolyte secondary battery of the present invention will be described by taking a lithium ion secondary battery as an example. The positive electrode is formed on a strip-shaped aluminum foil and a lithium composite oxide, for example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x MnO ₃ , Li _x Ni _y Co _(1-y) O _2. Apply a positive electrode paint prepared by dispersing and kneading a conductive material such as carbon black and a binder such as polyvinylidene fluoride (PVDF) with a solvent such as N-methyl-2-pyrrolidone (NMP). Thereafter, the film is immediately dried and wound up, and after the application of one surface is completed, the positive electrode paint is similarly applied to a predetermined portion on the opposite surface of the positive electrode current collector and dried to produce a positive electrode.

  The negative electrode has a strip-like copper foil surface that can be doped and dedoped with lithium, such as pyrolytic carbons, pitch coke, needle coke, petroleum coke, graphite, glassy carbon, and phenolic resin. Organic polymer compound fired bodies obtained by firing furan resin, carbonaceous materials such as carbon fiber and activated carbon, conductive polymer materials such as polyacetylene and polypyrrole, etc., conductive materials such as carbon black, polyvinylidene fluoride (PVDF) A negative electrode coating solution prepared by dispersing and kneading a binder such as N-methyl-2-pyrrolidone (NMP) with a coating apparatus is applied by a coating apparatus, and after drying on one side, the opposite side is also predetermined on the opposite side. The negative electrode is prepared by applying and drying the part.

  The positive electrode and the negative electrode thus obtained are compressed to a predetermined thickness by a compression device, and then the electrode is cut into a predetermined shape by a cutting device. After that, a positive electrode lead and a negative electrode lead are joined to the positive electrode and the negative electrode by a winding device, respectively, and a battery in which the positive electrode electrode and the tip of the negative electrode electrode are laminated in a predetermined position via a separator is wound. The winding body used as an element is produced.

  Next, the form which fixes a winding body with a tape is demonstrated using drawing. FIG. 1 is a view for explaining one embodiment (Example 1 and Example 2) of a wound body of a nonaqueous electrolyte secondary battery of the present invention. FIG. 1 (a) is a plan view, and FIG. b) is a front view, and FIG. 1C is a side view. In the wound body 4, the negative electrode lead 1 bonded to the negative electrode at the central part at the beginning of winding is drawn upward, and the positive electrode lead 2 bonded to the positive electrode at the terminal part at the end of winding is drawn upward. The adhesive tape 3 fixes both sides from the upper surface of the height of the side surface of the wound body to the length of 1/3 through the space between the negative electrode lead 1 and the positive electrode lead 2 at the upper part of the wound body 4. After that, the wound body 4 is housed in a battery can, and a lid provided with an external connection terminal, a safety valve for releasing the pressure by increasing the battery internal pressure, a PTC element for cutting off the current by increasing the electric resistance by increasing the battery temperature, etc. After the body is attached and the non-aqueous electrolyte is injected, the sealed non-aqueous electrolyte secondary battery is manufactured by sealing or sealing the wound body with an exterior material made of a flexible material.

  When fixing the wound body 4 with a tape, the tape 3 may be disposed between the negative electrode lead 1 and the positive electrode lead 2, and the tape may be disposed outside the negative electrode lead 1 or the positive electrode lead 2. May be plural. Moreover, you may fix with a tape in the lower part other than upper part. Further, the position of the tape on the side surface of the wound body is preferably a length from the upper surface or the lower surface to 1/3 of the height of the side surface, more preferably from 1/4 to 1/3. The width of the tape is determined so that it does not overlap with the positive electrode lead and the negative electrode lead when the wound body is fixed and does not protrude outside the wound body.

  Next, an embodiment of the present invention will be described with reference to FIG.

  Between the negative electrode lead 1 and the positive electrode lead 2 drawn out from the winding body 4 having a width of 28 mm, a height of 45 mm, and a thickness of 3.5 mm, it is made of PPS (polyphenylene sulfide) having a width of 5 mm and a thickness of 0.14 mm. Adhesive tape 3 was stuck on both sides of the side surface from the upper end of wound body 4 to 11 mm (1/4 of the height), and wound body 4 was fixed. Thereafter, the wound body 4 was accommodated in a battery can made of an aluminum alloy having a width of 30 mm, a height of 47.5 mm, and a thickness of 4.2 mm, and a lid was attached to produce a nonaqueous electrolyte secondary battery.

  The non-aqueous electrolyte secondary was applied in the same manner as in Example 1 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end to 15 mm (1/3 of the height) and the wound body 4 was fixed. A battery was produced.

(Comparative Example 1)
The non-aqueous electrolyte secondary is the same as in Example 1 except that the adhesive tape 3 is attached to both sides of the wound body 4 from the upper end of the wound body 4 to 30 mm (2/3 of the height) and the wound body 4 is fixed. A battery was produced.

(Comparative Example 2)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 45 mm and the wound body 4 was fixed.

  FIG. 2 is a diagram for explaining a wound body that is a battery element of Example 3 and Example 4 of the nonaqueous electrolyte secondary battery of the present invention, FIG. 2 (a) is a plan view, and FIG. 2 (b). Is a front view, and FIG. 2C is a side view. An adhesive tape 3 made of PPS having a width of 5 mm and a thickness of 0.14 mm is wound between the negative electrode lead 1 and the positive electrode lead 2 of the wound body 4 produced in the same manner as in Example 1 and outside the negative electrode lead 1. The wound body 4 was affixed on both sides of the side surface from the upper end of the body 4 to 11 mm. Thereafter, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1.

  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 15 mm and the wound body 4 was fixed.

(Comparative Example 3)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end to 30 mm and the wound body 4 was fixed.

(Comparative Example 4)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 45 mm and the wound body 4 was fixed.

  FIG. 3 is a view for explaining a wound body that is a battery element of Example 5 and Example 6 of the non-aqueous electrolyte secondary battery of the present invention, FIG. 3 (a) is a plan view, and FIG. 3 (b). Is a front view, and FIG. 3C is a side view. Adhesive tape made of PPS having a width of 5 mm and a thickness of 0.14 mm between the negative electrode lead 1 and the positive electrode lead 2 of the wound body 4 produced in the same manner as in Example 1 and outside the negative electrode lead and outside the positive electrode lead. 3 was affixed to both sides of the side surface from the upper end of the wound body 4 to 11 mm, and the wound body 4 was fixed. Thereafter, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 5 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 15 mm and the wound body 4 was fixed.

(Comparative Example 5)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 5 except that the adhesive tape 3 was attached to both sides of the wound body 4 from the upper end of the wound body 4 to 30 mm and the wound body 4 was fixed.

(Comparative Example 6)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 5 except that the adhesive tape 3 was attached to both sides of the wound body 4 from the upper end of the wound body 4 to 45 mm and the wound body 4 was fixed.

  FIG. 4 is a diagram for explaining a wound body serving as a battery element of Example 7 and Example 8 of the nonaqueous electrolyte secondary battery of the present invention, where FIG. 4 (a) is a plan view and FIG. 4 (b). Is a front view, and FIG. 4C is a side view. An adhesive tape 3 made of PPS having a width of 5 mm and a thickness of 0.14 mm is placed 11 mm from the upper end of the wound body 4 on the outer side of the negative electrode lead and the outer side of the positive electrode lead of the wound body 4 manufactured in the same manner as in Example 1. The wound body 4 was fixed on both sides of the side. Thereafter, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1.

  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 15 mm and the wound body 4 was fixed.

(Comparative Example 7)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that the adhesive tape 3 was attached to both sides of the wound body 4 from the upper end of the wound body 4 to 30 mm and the wound body 4 was fixed.

(Comparative Example 8)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that the adhesive tape 3 was attached to both sides of the wound body 4 from the upper end of the wound body 4 to 45 mm and the wound body 4 was fixed.

  FIG. 5 is a diagram for explaining a wound body that is a battery element of Example 9 and Example 10 of the nonaqueous electrolyte secondary battery of the present invention, FIG. 5 (a) is a plan view, and FIG. 5 (b). Is a front view, and FIG. 5C is a side view. An adhesive tape 3 made of PPS having a width of 5 mm and a thickness of 0.14 mm is provided between the negative electrode lead 1 and the positive electrode lead 2 of the wound body 4 produced in the same manner as in Example 1 and outside the positive electrode lead. The wound body 4 was fixed on both sides of the side surface from the upper end of 4 to 11 mm. Thereafter, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1.

  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 9 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 15 mm and the wound body 4 was fixed.

(Comparative Example 9)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 9 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 30 mm and the wound body 4 was fixed.

(Comparative Example 10)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 9 except that the adhesive tape 3 was attached to both side surfaces of the wound body 4 from the upper end of the wound body 4 to 45 mm and the wound body 4 was fixed.

(Comparative Example 11)
The wound body 4 produced in the same manner as in Example 1 was accommodated in a battery can made of aluminum alloy having a width of 30 mm, a height of 47.5 mm, and a thickness of 4.2 mm without being fixed with an adhesive tape. A secondary battery was produced.

  For the non-aqueous electrolyte secondary batteries produced in Examples 1 to 10 and Comparative Examples 1 to 11, a drop test was repeated in which the lid was dropped from a height of 1.5 m onto the concrete in a charged state. did. The number of drops before the impedance at 1 kHz increased by 5 mΩ compared to before the test was defined as the number of drops.

  Moreover, about the nonaqueous electrolyte secondary battery produced in Examples 1-10 and Comparative Examples 1-11, at 20 degreeC, charge current 720mA and charge final voltage 4.2V, total charge time 150 minutes, and discharge current 720mA Charging / discharging was performed 500 cycles under the condition of an end-of-discharge voltage of 3.0 V, and the maximum can thickness of the battery can in the charged state after 500 cycles was measured. The drop limit number in the drop test is shown in Table 1 and FIG. 7, and the battery can thickness after the cycle is shown in Table 1 and FIG.

  As shown in Table 1 and FIG. 7, it was confirmed that the number of drops was improved as compared with the tape of Comparative Example 11 without the tape, as shown in Table 1 and FIG. Further, after the cycle, as shown in Table 1 and FIG. 8, the can thickness was 11 mm and 15 mm compared with the tape of Comparative Example 11 without the tape, that is, 1/4 to 1/1 of the height of the wound body. Thickness up to 3 is fixed with tape, but the can thickness does not swell after the cycle, but 30mm and 45mm, that is, 2/3 and 3/3 of the height of the wound body, it is swollen with tape. It was confirmed that In the embodiment, the case of only one part on the outer side of the negative electrode lead or the outer side of the positive electrode lead is not described, but it is needless to say that the same effect as the other examples can be obtained.

The figure explaining the winding body used as the battery element of Example 1, 2 of the nonaqueous electrolyte secondary battery of this invention, Fig.1 (a) is a top view, FIG.1 (b) is a front view, FIG.1 (c) ) Is a side view. The figure explaining the winding body used as the battery element of Example 3, 4 of the nonaqueous electrolyte secondary battery of this invention, Fig.2 (a) is a top view, FIG.2 (b) is a front view, FIG.2 (c) ) Is a side view. The figure explaining the wound body used as the battery element of Example 5 and 6 of the nonaqueous electrolyte secondary battery of this invention, Fig.3 (a) is a top view, FIG.3 (b) is a front view, FIG.3 (c) ) Is a side view. The figure explaining the winding body used as the battery element of Example 7 and 8 of the nonaqueous electrolyte secondary battery of this invention, Fig.4 (a) is a top view, FIG.4 (b) is a front view, FIG.4 (c) ) Is a side view. The figure explaining the winding body used as the battery element of Example 9, 10 of the nonaqueous electrolyte secondary battery of this invention, Fig.5 (a) is a top view, FIG.5 (b) is a front view, FIG.5 (c) ) Is a side view. FIG. 6A is a plan view, FIG. 6B is a front view, and FIG. 6C is a side view illustrating a conventional non-aqueous electrolyte secondary battery and a wound body that is a battery element of Comparative Example 11. Figure. The figure which shows the fall limit frequency | count of this invention and the conventional nonaqueous electrolyte secondary battery. The figure which shows the can thickness after the charging / discharging cycle of this invention and the conventional nonaqueous electrolyte secondary battery.

Explanation of symbols

1 Negative electrode lead 2 Positive electrode lead 3 Tape 4 Winding body

Claims (3)

The positive and negative electrodes has a winding body wound in a flat shape via a separator, the wound body is wound end surface is the upper surface or respectively over the lower surface the winding end faces of the vertical side surface of the A part is fixed with a tape, and the length of the tape from the upper end or the lower end of the side surface is in a range from 1/4 to 1/3 of the height of the side surface. A non-aqueous electrolyte secondary battery. A winding body in which a positive electrode provided with a positive electrode lead and a negative electrode provided with a negative electrode lead are wound in a flat shape with a separator interposed between the positive electrode lead and the negative electrode lead; of the three places of the outer, part of the vertical side surfaces and tape respectively across the top surface is a winding end faces of the windings of the at least one location on the winding end face, at the side, the side A nonaqueous electrolyte secondary battery , wherein the length of the tape from the upper end of the side wall is in a range from 1/4 to 1/3 of the height of the side surface. The tape extends across the upper surface of the wound body between the positive electrode lead and the negative electrode lead and at least one of the outer side of the positive electrode lead or the outer side of the negative electrode lead among the three locations. 2. The nonaqueous electrolyte secondary battery according to 2.

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