JP2013097903A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which excels in safety against external shorting and also has excellent vibration resistance.SOLUTION: A nonaqueous electrolyte secondary battery 10 of the present invention comprises a wound electrode body 14 composed of a cathode plate 11 and an anode plate 12 wound round while being electrically isolated by a separator 13 and a nonaqueous electrolyte, both of which are housed in a cylindrical battery outer can 17. A cathode current collector tab 22 connected to the cathode plate 11 is bent in shape of the letter S and is electrically connected to a cathode terminal 20 which is fixed to the opening of the battery outer can 17 while being isolated from the battery outer can 17. The cathode current collector tab 22 is made of aluminum or aluminum alloy, and has a notch (not shown) formed between two inflection points X and Y bent in shape of the letter S, the percentage in cubic volume of the notch is made to be 25.0 to 37.5% per length of 1.00 mm.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery that is excellent in safety against external short circuits and also has good vibration resistance.

  High energy density as a driving power source for portable electronic devices such as today's mobile phones, portable personal computers, portable music players, as well as power sources for hybrid electric vehicles (HEV, PHEV) and electric vehicles (EV) Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries having a high capacity are widely used.

  If the nonaqueous electrolyte secondary battery is, for example, a cylindrical one, a cylindrical wound electrode body in which a positive electrode plate and a negative electrode plate are wound via a separator is produced, and this cylindrical wound electrode The body is inserted into the cylindrical battery casing and a non-aqueous electrolyte is injected, and the positive terminal or the negative terminal is sealed in the opening of the cylindrical battery casing so as to be insulated by the insulator. It is made by attaching to the state.

  Also, if it is rectangular, a flat electrode body in which a positive electrode plate and a negative electrode plate are laminated or flatly wound via a separator is produced, and this flat electrode body is placed in a rectangular battery outer body. After inserting and sealing the sealing body provided with at least one of the positive electrode terminal and the negative electrode terminal into the opening of the rectangular battery exterior body, the fitting part is laser welded, and then various electrolyte solutions from the electrolyte injection hole And the electrolyte solution injection hole is sealed.

  These cylindrical non-aqueous electrolyte secondary batteries and prismatic non-aqueous electrolyte secondary batteries have a width as a positive current collector tab or a negative current collector tab in order to suppress thermal runaway during, for example, an internal short circuit or an external short circuit. There are known examples in which a narrower portion is formed than other portions (see Patent Documents 1 to 3 below). An example of a non-aqueous electrolyte secondary battery in which a narrow portion is formed on such a positive electrode current collecting tab or a negative electrode current collecting tab will be described with reference to FIGS. 4A is a partial longitudinal sectional view of a cylindrical nonaqueous electrolyte secondary battery disclosed in Patent Document 1 below, FIG. 4B is a development view of a positive electrode plate or a negative electrode plate, and FIG. 4C is a winding. 4D is a perspective view of an electrode body, and FIG. 4D is a perspective view of a positive electrode current collecting tab. FIG. 5 is an enlarged view of a portion V in FIG. 4A.

  The cylindrical non-aqueous electrolyte secondary battery 50 includes a wound electrode body 53 in which a positive electrode plate 51 and a negative electrode plate 52 are overlapped and wound via a separator (not shown). And a configuration housed in a cylindrical battery outer can 54. A positive electrode current collecting tab 55 or a negative electrode current collecting tab 56 is connected to the positive electrode plate 51 and the negative electrode plate 52, respectively. The opening of the cylindrical battery outer can 54 is sealed by a positive electrode terminal 58 while being insulated by an insulating member 57. The positive electrode current collecting tab 55 is usually made of aluminum or an aluminum alloy, is bent in an S shape, and is connected to the positive electrode terminal 58. The negative electrode current collecting tab 56 is usually made of copper or a copper alloy, and is connected to the bottom of the cylindrical battery outer can 54.

  The positive electrode current collecting tab 55 has a notch 55 a (see FIG. 5) on the outer side of the wound electrode body 53, that is, on the wound electrode body 53 side than the portion connected to the positive electrode terminal 58 of the wound electrode body 53. 4D) is formed. The notch 55a is provided so that the current density in the notch 55a is higher than the current density of the positive electrode current collecting tab 55 other than the notch 55a.

JP 05-121064 A JP 2001-202946 A Special table 2004-119383 gazette

  According to the non-aqueous electrolyte secondary battery 50 disclosed in Patent Document 1 described above, when an internal short circuit occurs due to an external short circuit or a nail penetration, the current in the notch 55a of the positive electrode current collecting tab 55 is determined. Since the density increases and the notch 55a generates heat and melts, the thermal runaway caused by the concentration of a large current can be prevented.

  On the other hand, the positive electrode current collecting tab of the non-aqueous electrolyte secondary battery is bent in an S shape, but may have a notch portion and a certain width and thickness. Even in such a case, for example, when an internal short circuit due to an external short circuit or a nail stab occurs, a large current may flow through the positive electrode current collecting tab, and a part thereof may be melted. Of the bent portions of the positive electrode current collector tab bent in a letter shape, many are observed on the side of the wound electrode body, that is, in the X portion shown in FIG.

  The reason for this is not necessarily clear, but the X portion includes an ultrasonic weld between the positive electrode plate 51 and the positive electrode current collecting tab 55, and a positive electrode terminal 58 and a positive electrode provided at the opening of the cylindrical battery outer can 54. It may be the midpoint of the ultrasonic weld with the current collecting tab 55. The closer the fusing part is to the wound electrode body 53, the greater the possibility of causing an internal short circuit in the wound electrode body 53 with fusing. Therefore, when the positive electrode current collecting tab 55 is melted, it is necessary for the melted portion to be generated at a position separated from the wound electrode body 53.

  Further, when an external force that shakes the nonaqueous electrolyte secondary battery 50 violently is applied many times, such as in a vibration test, only the X portion of the bent portion of the positive electrode current collecting tab that is bent in an S shape is used. In many cases, the positive electrode current collecting tab 55 is observed to break even at the bending point Y near the positive electrode terminal 58. Therefore, when the positive electrode current collecting tab 55 is bent in an S shape and connected to the positive electrode terminal 58, a position where the melted portion of the positive electrode current collecting tab 55 due to a large current flows is separated from the wound electrode body 53. In addition, the X point and the Y point described above need to be strong enough to withstand breakage due to vibration. The negative electrode current collecting tab is mainly made of copper or a copper alloy, and these copper or copper alloys have higher mechanical strength than the positive electrode current collecting tab made of aluminum or aluminum alloy. Hard to break.

  The present invention has been made to solve the above-described problems of the prior art, the fusing point of the positive electrode current collector tab bent in an S-shape is formed at a position separated from the wound electrode body, and An object of the present invention is to provide a non-aqueous electrolyte secondary battery in which an S-shaped bending point portion of a positive electrode current collecting tab has a strength that can withstand breakage due to vibration.

In order to achieve the above object, a non-aqueous electrolyte secondary battery of the present invention comprises a wound electrode body wound with a positive electrode plate and a negative electrode plate electrically insulated by a separator, a non-aqueous electrolyte solution, Is housed in a cylindrical battery outer can, and a positive electrode current collecting tab connected to the positive electrode plate is bent into an S-shape, and the battery outer can and the opening are formed in the cylindrical battery outer can. Is a non-aqueous electrolyte secondary battery electrically connected to a positive terminal fixed in an insulated state,
The positive electrode current collecting tab is made of aluminum or an aluminum alloy, a notch is formed between two bending points bent in the S shape, and the volume ratio of the notch is 1 in length. It is characterized by being 25.0 to 37.5% per 0.00 mm.

  A non-aqueous electrolyte secondary battery usually uses a positive electrode plate in which a positive electrode mixture layer containing a positive electrode active material is formed on both surfaces of an aluminum foil or an aluminum alloy foil. An electric tab made of aluminum or an aluminum alloy is used. The positive electrode current collector tab in the non-aqueous electrolyte secondary battery of the present invention has a notch formed between two bending points bent in an S shape, and the volume ratio of the notch is 1 in length. Since it is 25.0 to 37.5% per .00 mm, even if the width of the positive electrode current collecting tab is wide, a notch corresponding to that is formed, and a large current is generated during an external short circuit or an internal short circuit. Even if it flows, it is not melted except at the notch, and the notch can be melted accurately. Moreover, since the notch part used as this melt | fusion part is formed between two bending points bent in the S shape spaced apart from the winding electrode body, the notch part of a positive electrode current collection tab melted | fused. However, the possibility of a further internal short circuit is suppressed.

  Moreover, in the non-aqueous electrolyte secondary battery of the present invention, the width of the positive electrode current collecting tab can be made sufficiently wide, so that the breaking strength of the positive electrode current collecting tab can be increased. The possibility that the current collecting tab is broken is suppressed.

In addition, as a positive electrode plate of the non-aqueous electrolyte secondary battery of this invention, what was formed with the positive mix layer containing a positive electrode active material on both surfaces of well-known aluminum foil or aluminum alloy foil can be used as it is. As the positive electrode active material, for example, a lithium transition metal represented by Li _x MO ₂ (wherein M is at least one of Co, Ni, and Mn) capable of reversibly occluding and releasing lithium ions. Complex oxides, that is, LiCoO ₂ , LiNiO ₂ , LiNi _y Co _1-y O ₂ (y = 0.01 to 0.99), LiMnO ₂ , LiMn ₂ O ₄ , LiCo _x Mn _y Ni _z O ₂ (x + y + z) = 1), or LiFePO ₄ can be used singly or in combination.

Moreover, as a negative electrode plate of the non-aqueous electrolyte secondary battery of the present invention, a negative electrode mixture layer containing a negative electrode active material formed on both surfaces of a known copper foil or copper alloy foil can be used as it is. As this negative electrode active material, for example, graphite capable of reversibly occluding and releasing lithium ions, carbon raw materials such as non-graphitizable carbon and graphitizable carbon, titanium oxides such as LiTiO ₂ and TiO ₂ , silicon and tin Or a semi-metal element such as Sn—Co alloy.

  Examples of the nonaqueous solvent that can be used in the nonaqueous electrolyte secondary battery of the present invention include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and fluorinated cyclic esters. Carbonic acid esters, cyclic carboxylic acid esters such as γ-butyllactone (γ-BL), γ-valerolactone (γ-VL), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl Chain carbonates such as carbonate (MPC) and dibutyl carbonate (DBC), chain carbonates such as fluorinated chain carbonates, methyl pivalate, ethyl pivalate, methyl isobutyrate, methyl propionate, etc. N, N'-dimethylformamide, - amide compounds such as methyl oxazolidinone, sulfur compounds such as sulfolane, etc. ambient temperature molten salt such as tetrafluoroboric acid 1-ethyl-3-methylimidazolium can be exemplified. It is desirable to use a mixture of two or more of these. Among these, those containing a cyclic carbonate and a chain carbonate having a particularly high dielectric constant and a high ionic conductivity of the non-aqueous electrolyte are preferable. Furthermore, in the non-aqueous electrolyte secondary battery of the present invention, the non-aqueous electrolyte may not only be liquid but may be gelled.

  In the non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention, vinylene carbonate (VC), vinyl ethyl carbonate (VEC), succinic anhydride ( SUCAH), maleic anhydride (MAAH), glycolic anhydride, ethylene sulfite (ES), divinyl sulfone (VS), vinyl acetate (VA), vinyl pivalate (VP), catechol carbonate, biphenyl (BP), adiponitrile, pimelonitrile A nitrile compound such as may be added. Two or more of these compounds can be appropriately mixed and used.

Moreover, as an electrolyte salt dissolved in the nonaqueous solvent used in the nonaqueous electrolyte secondary battery of the present invention, a lithium salt generally used as an electrolyte salt in the nonaqueous electrolyte secondary battery can be used. Such lithium salts include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₂ Cl ₁₂ , and mixtures thereof Illustrated. Among these, LiPF ₆ (lithium hexafluorophosphate) is particularly preferable. The amount of electrolyte salt dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / L.

  In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode current collector tab preferably has a width of 3.00 mm or more and a thickness of 0.15 mm or more.

  Even if the positive electrode current collecting tab is made of aluminum or aluminum alloy having a low breaking strength, the positive electrode current collecting tab can be used even if the battery is vibrated vigorously if the width is 3.00 mm or more and the thickness is 0.15 mm or more. The possibility of breaking is substantially eliminated.

  In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode current collecting tab is formed between the winding start side and the winding end side of the positive electrode plate, and the negative electrode current collecting tab is the winding start side of the negative electrode plate. The negative electrode current collecting tab on the winding start side is bent so as to contact the inner bottom of the battery outer can at a position corresponding to the gap at the winding center of the winding electrode body. The negative electrode current collecting tab on the winding end side is preferably bent along the inner side of the battery outer can and joined to the inner bottom portion of the battery outer can together with the negative electrode current collecting tab on the first winding side.

  In the cylindrical wound electrode body, a gap is formed at the winding center. To increase the capacity of the battery, it is necessary to reduce the volume of the gap. If the negative electrode current collector tab is made of a hard metal such as copper or copper alloy and is provided on the winding start side of the negative electrode plate, the contact area between the negative electrode plate and the negative electrode current collector tab is increased. In order to reduce the internal resistance, it is necessary to form the negative electrode current collecting tab in an arc shape and arrange it at the winding center of the wound electrode body. However, in the non-aqueous electrolyte secondary battery of the present invention, since the negative electrode current collecting tab formed on both the winding start side and the winding end side of the negative electrode plate is used, the negative electrode current collector on the winding start side is used. Even if the width of the current collector is reduced, the internal resistance on the negative electrode side can be reduced equivalently by increasing the width of the negative electrode current collector on the winding end side. No need to mold

1A is a development view of the positive electrode plate used in each experiment, FIG. 1B is a development view of the negative electrode plate, and FIG. 1C is a longitudinal sectional view of the cylindrical non-aqueous electrolyte secondary battery. It is a top view which shows the dimension of each part of the positive electrode current collection tab used for each experiment. 3A to 3E are diagrams showing dimensions of the positive electrode current collecting tab used in each experiment. 4A is a partial longitudinal sectional view of a conventional cylindrical nonaqueous electrolyte secondary battery, FIG. 4B is a development view of a positive electrode plate or a negative electrode plate, and FIG. 4C is a perspective view of a wound electrode body. 4D is a perspective view of a positive electrode current collecting tab. FIG. 4B is an enlarged view of a portion V in FIG. 4A.

  Hereinafter, embodiments of the present invention will be described in detail using examples and comparative examples. However, the following examples illustrate non-aqueous electrolyte secondary batteries for embodying the technical idea of the present invention, and are not intended to specify the present invention in this example. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

Initially, the specific manufacturing method of the nonaqueous electrolyte secondary battery common to each Example and a comparative example is demonstrated.
[Production of positive electrode plate]
The positive electrode plate 11 was produced as follows. First. 94 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of acetylene black as a conductive agent, and 3 parts by mass of polyvinylidene fluoride (PVdF) powder as a binder were mixed with N-methyl- A positive electrode mixture slurry was prepared by mixing in 2 pyrrolidone (NMP). Next, the central core exposed portion 11b is formed at the center of the positive electrode core 11a and the winding end side core exposed portion 11c is formed at the winding end on both surfaces of the positive electrode core 11a made of an aluminum foil having a thickness of 20 μm. In this way, after coating the positive electrode mixture slurry and passing through the dryer to remove the organic solvent, the thickness of the portion where the positive electrode mixture layer 11d is formed using a roll press machine is 100 μm. Rolled.

  Next, a positive electrode current collecting tab 22 having a width of 4 mm and a thickness of 0.15 mm made of aluminum was attached to the central core exposed portion 11b of the positive electrode core 11a by ultrasonic welding, so that the positive electrode plate 11 was obtained (see FIG. 1A). . In addition, the specific structure of the positive electrode current collection tab 22 part in each experiment and the specific structure of a notch are mentioned later.

[Production of negative electrode plate]
The negative electrode plate 12 was produced as follows. First, 98% by mass of artificial graphite powder as a negative electrode active material, 1% by mass of styrene-butadiene rubber (SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener are mixed, and water is added. And kneaded to prepare a negative electrode mixture slurry. Next, on both sides of the negative electrode core 12a made of copper foil having a thickness of 12 μm, the winding start side core exposed portion 12b on both sides of the winding start side of the negative electrode core 12a and the winding end side core on both sides of the winding end side After coating the negative electrode mixture slurry so that the body exposed portion 12c is formed, and then passing it through a drier and drying it, the thickness of the negative electrode mixture layer 12d is set to 100 μm using a roll press machine. Rolled.

  Next, the negative electrode current collecting tabs 23a and 23b made of a copper-nickel clad material (thickness 0.15 mm) are placed on the winding start side core exposed part 12b and the winding end side core exposed part 12c of the negative electrode core 12a. Were subjected to ultrasonic welding such that the negative electrode plate 12 was obtained (see FIG. 1B). At this time, the welding position of the negative electrode current collecting tab 23a at the beginning of winding was welded about 5 mm from the beginning of winding. The application amount of the negative electrode mixture is such that the charge capacity ratio (negative electrode charge capacity / positive electrode charge capacity) at the portion where the positive electrode plate 11 and the negative electrode plate 12 face each other is 1 at the charge voltage (4.2 V) as the design standard. Adjusted to be .1.

[Production of wound electrode body]
Using a core having a diameter of 2 mm, the positive electrode plate 11 and the negative electrode plate 12 produced as described above are insulated from each other by a microporous separator 13 made of polyethylene resin and having a thickness of 22 μm. A cylindrical wound electrode body used in the non-aqueous electrolyte secondary battery 10 of Examples 1 and 2 and Comparative Examples 1 to 3; 14 was completed. In addition, the length of the winding start side core exposed portion 12b of the innermost peripheral negative electrode core was set to be two rounds of the outer periphery of the gap 18.

[Preparation of non-aqueous electrolyte]
As a non-aqueous solvent, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 30:70 (25 ° C., 1 atm), and LiPF ₆ as an electrolyte salt was 1 mol / L. It was made to melt | dissolve and it was set as the common nonaqueous electrolyte solution.

[Battery assembly]
Insulating plates 15 and 16 having a hole in the center are arranged above and below the wound electrode body 14 produced as described above, and the negative electrode current collecting tab 23a on the winding start side of the negative electrode plate 12 is the tip of the battery. It was bent into an L shape at an appropriate position so as to be parallel to the bottom of the outer can 17. Further, the negative electrode current collecting tab 23b on the winding end side of the negative electrode plate 12 is bent in an L shape so that the front end portion is parallel to the bottom portion of the battery outer can 17 and the front end portion of the current collecting tab 23a on the winding start side Folded to overlap. The wound electrode body 14 provided with the negative electrode current collecting tabs 23a and 23b bent in this manner was inserted into the cylindrical battery outer can 17 as shown in FIG. 1C. Next, the negative electrode current collecting tabs 23a and 23b were fixed to the inside of the bottom of the battery outer can 17 by resistance welding.

  Further, the positive electrode current collecting tab 22 is bent into an S shape, and the tip portion thereof is ultrasonically welded to the positive electrode terminal 20 attached to the insulating sealing plate 19, and the above-described nonaqueous electrolytic solution is put in the battery outer can 14. Then, the non-aqueous electrolyte secondary battery 10 used for each experiment is manufactured by sandwiching the periphery of the sealing plate 19 with the gasket 21 and crimping and fixing the opening end of the battery outer can 17. did. This nonaqueous electrolyte secondary battery 10 had a diameter of 18 mm, a length of 65 mm, and a design capacity of Min 1500 mAh.

  Next, the configuration of the positive electrode current collecting tab 22 of the positive electrode plate 11 used in each experimental example will be described with reference to FIGS. The positive electrode current collecting tab 22 is a protective tape on both sides so as to cover from the ultrasonic welding to the central part 11b of the positive electrode core body to a portion protruding from the wound electrode body 14 from the position where ultrasonic welding is performed for insulation. 24 is placed. Here, the allowance of the positive electrode current collecting tab 22 from the wound electrode body 14 is set to 13.5 mm. And the length of the welding part between the front-end | tip part of the positive electrode current collection tab 22 and the positive electrode terminal 20 was 2.00 mm, and the length of the following bending part (Y part) was 2.50 mm. Further, the length of the bent portion (X portion) on the side of the wound electrode body 14 of the positive electrode current collecting tab 22 was set to 1.00 mm. If it does so, the length of the notch formation area (Z part) except the bending part X part and Y part of the both sides of the positive electrode current collection tab 22 will be 8.00 mm.

[Positive electrode current collecting tabs of Examples 1 and 2 and Comparative Examples 1 to 3]
Furthermore, the specific structure of Z part of the positive electrode current collection tab of Examples 1, 2 and Comparative Examples 1-3 is demonstrated using FIG. In Comparative Example 1, as shown in FIG. 3A, an aluminum member having a width of 4.00 mm and a thickness of 0.15 mm was directly used as a positive electrode current collecting tab without forming a notch. The positive electrode current collecting tab having a width of 4 mm and a thickness of 0.15 mm is of a size that has been experimentally confirmed to be not broken by a vibration test.

Then, in Comparative Example 2, as shown in FIG. 3B, a positive electrode current collector having notches having a width of 1.00 mm and a width of 1.00 mm formed in the Z portion on both side surfaces of the member used in Comparative Example 1 is used. Used as a power tab. The long notch area of the positive electrode current collecting tab of Comparative Example 2 is 0.50 mm ² , and the ratio of the notch volume per 1.00 mm length is 12.5%. Further, in Example 1, as shown in FIG. 3C, a positive electrode current collector was formed by forming notches with a width of 1.00 mm and a width of 0.50 mm on both sides of the member used in Comparative Example 1. Used as a power tab. The long notch area of the positive electrode current collecting tab of Example 1 is 1.00 mm ² , and the ratio of the notch volume per 1.00 mm length is 25.0%.

Further, in Example 2, as shown in FIG. 3D, a positive electrode current collector was formed by forming notches with a width of 0.75 mm over a length of 1.00 mm in the Z portion on both side surfaces of the member used in Comparative Example 1. Used as a power tab. The long notch area of the positive electrode current collecting tab of Example 2 is 1.50 mm ² , and the ratio of the notch volume per 1.00 mm length is 37.5%. Further, in Comparative Example 3, as shown in FIG. 3E, a positive electrode current collector in which notches having a width of 1.00 mm and a length of 1.00 mm are formed in the Z portion on both side surfaces of the member used in Comparative Example 1. Used as a power tab. The long notch area of the positive electrode current collecting tab of Comparative Example 3 is 2.00 mm ² , and the ratio of the notch volume per length of 1.00 mm is 50%.

  Ten non-aqueous electrolyte secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were produced using the positive electrode current collecting tab produced as described above, and the batteries at a constant current of 1 It = 1500 mA. The battery was charged until the voltage reached 4.20 V, and after the battery voltage reached 4.20 V, the battery was charged at a low voltage of 4.20 V until the charging current reached 1/50 It = 30 mA, and the battery was fully charged. The fully charged non-aqueous electrolyte secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were discharged at a constant current of 1 It until the battery voltage reached 2.75 V. The 1 It discharge capacity was determined.

  Next, all the batteries for which the 1 It discharge capacity has been obtained are fully charged by charging them again under the above charging conditions, and then discharged until the battery voltage reaches 2.75 V at a constant current of 40 A. The battery capacity and average voltage were measured, and the battery capacity was further determined as a ratio (%) to the 1 It discharge capacity. The measurement results are shown in Table 1 as average values.

  Next, two non-aqueous electrolyte secondary batteries in Examples 1 and 2 and Comparative Examples 1 to 3 in a fully charged state were short-circuited with a resistance of 5 mΩ assuming an external short circuit. Then, each battery was disassembled, and the presence or absence and fusing position of the positive electrode current collector tab were confirmed. The results are summarized in Table 1.

  The following can be understood from the results shown in Table 1 above. That is, the discharge capacity, the average voltage, and the discharge capacity ratio at the time of 40 A constant current discharge were almost the same as those in Comparative Example 1 and Comparative Example 2 in both Examples 1 and 2, but were inferior in Comparative Example 3. It has become. This is because in the batteries of Comparative Example 1, Examples 1 and 2, even when the notch portion is formed, the notch volume per length of 1.00 mm is small, so that the internal resistance increases due to the notch portion formation. Indicates that it is practically negligible. On the other hand, in the battery of Comparative Example 3, since the notch volume per 1.00 mm length of the notch portion is large, the increase in internal resistance due to this notch portion formation cannot be ignored, and the battery capacity, average This is thought to have led to a decrease in the voltage and discharge capacity ratio.

  Further, in the results of the 5 mΩ external short circuit test, the positive electrode current collector tab was melted in all the batteries of Examples 1 and 2 and Comparative Examples 1 to 3. However, in Comparative Examples 1 and 2, the fusing part is the X part, and in Comparative Example 2, the fusing occurs in the X part, not in the Z part provided with the notch part. On the other hand, in Examples 1 and 2 and Comparative Example 3, fusing occurs in the Z portion where all the notches are provided.

  This is because, in the battery of Comparative Example 2, the notch volume per 1.00 mm length of the notch part is too small, so that the Z part where the notch part is formed does not melt and other than the Z part. In view of the measurement data of Example 1, it is preferable that the cutout volume per length of 1.00 mm of the cutout portion of the positive electrode current collecting tab is 25.0% or more because it is considered that X portion was melted out by melting. I understand. Further, in the battery of Comparative Example 3, the notch volume per 1.00 mm length of the notch part is too large, so that it melts out at the Z part where the notch part is formed. In view of the measurement data of Example 2, the notch volume per 1.00 mm length of the notch portion of the positive electrode current collecting tab is 37.5% or less because it is considered that the discharge capacity ratio is reduced. It turns out that is preferable.

  As described above, according to the non-aqueous electrolyte secondary battery according to the present invention, the battery capacity, the average voltage and the discharge capacity are not substantially reduced, and the fusing location of the positive electrode current collecting tab at the time of external short circuit is not present. Since all the notch formation positions are provided, a non-aqueous electrolyte secondary battery that does not adversely affect the discharge performance of the battery, is safer even when externally short-circuited, and can ensure safety even during vibration tests is obtained. I understand.

  DESCRIPTION OF SYMBOLS 10 ... Nonaqueous electrolyte secondary battery 11 ... Positive electrode plate 11a ... Positive electrode core body 11b ... Central core body exposed part (of positive electrode core body) 11c ... (Positive electrode core body) Winding end side core exposed part 11d ... Positive electrode combination Agent layer 12 ... Negative electrode plate 12a ... Negative electrode core 12b ... Winding start side core exposed part (of negative electrode core) 12c ... (Negative electrode core) winding end side core exposed part 12d ... Negative electrode mixture layer 13 ... Separator DESCRIPTION OF SYMBOLS 14 ... Winding electrode body 15, 16 ... Insulation board 17 ... Battery exterior can 18 ... Air gap part 19 ... Sealing board 20 ... Positive electrode terminal 21 ... Gasket 22 ... Positive electrode current collection tab 22a ... Notch (positive electrode current collection tab), 23a, 23b ... negative electrode current collecting tab 24 ... protective tape

Claims (3)

A wound electrode body wound in a state where the positive electrode plate and the negative electrode plate are electrically insulated by a separator, and a non-aqueous electrolyte are accommodated in a cylindrical battery outer can and connected to the positive electrode plate. The positive electrode current collecting tab is bent into an S shape and is electrically connected to a positive electrode terminal fixed to the opening of the cylindrical battery outer can in an insulated state from the battery outer can. In non-aqueous electrolyte secondary batteries,
The positive electrode current collecting tab is:
Made of aluminum or aluminum alloy,
A notch is formed between two bending points bent in the S shape,
The volume ratio of the notch is 25.0 to 37.5% per length of 1.00 mm.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode current collecting tab has a width of 3.00 mm or more and a thickness of 0.15 mm or more.   The positive electrode current collecting tab is formed between the winding start side and the winding end side of the positive electrode plate, and the negative electrode current collecting tab is formed on both the winding start side and the winding end side of the negative electrode plate, The negative electrode current collecting tab on the winding start side is bent so as to contact the inner bottom portion of the battery outer can at a position corresponding to the gap at the winding center of the winding electrode body, and the negative electrode current collecting tab on the winding end side 3. The electric tab according to claim 1, wherein the electric tab is bent along the inner side of the battery outer can and joined to the inner bottom of the battery outer can together with the negative electrode current collecting tab on the winding start side. Non-aqueous electrolyte secondary battery.

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