JP4449658B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery, and more particularly, to a secondary battery having a laminated electrode group in which a plurality of positive and negative electrode plates are laminated via a separator, and a battery container that houses the laminated electrode group.

  Conventionally, secondary batteries have been used as power sources for various devices and vehicles. Among such secondary batteries, a lithium secondary battery uses an organic solvent as an electrolytic solution, and has a remarkably low electrical conductivity as compared with an aqueous electrolytic solution. For this reason, in the lithium secondary battery, by increasing the electrode area and making the electrode thinner, the reaction resistance is reduced and the charge / discharge performance is improved.

  Usually, the thickness of an electrode for a lithium secondary battery is about several tens of micrometers (μm) to about 300 μm, and an extremely thin aluminum foil or copper foil of about several μm to several tens of μm is used for the electrode current collector. Yes. Therefore, the fixation of the stacked electrode group in the lithium secondary battery is performed by bringing the electrode into contact with the battery container like a lead storage battery having an electrode thickness and a current collector thickness of several millimeters, or vibrating depending on the current collector strength of each electrode. It is difficult to prevent the movement of the entire electrode group due to.

  In order to solve this problem, a technique is known in which a leaf spring is arranged on the outermost surface of the laminated electrode group and fixed by pressure (for example, see Patent Document 1).

Japanese Patent No. 3413907

  However, in the technique of Patent Document 1, pressure is applied only in the stacking direction of the stacked electrode group, and if the stacking direction is the X-axis direction as a three-dimensional expression, the holding force against vibration in the Y-axis direction or the Z-axis direction. Is extremely low, and it is difficult to say that the laminated electrode group is stably held in the battery container. For this reason, the deterioration in battery performance simply stops due to short-circuit due to misalignment of the positive electrode and negative electrode due to vibration in the Y-axis direction or Z-axis direction, or damage / short-circuit due to the end of the stacked electrode group colliding with the battery container. In addition, there is a problem that should be taken into consideration for safety, such as reaching a battery abnormal state such as thermal runaway.

  In view of the above-described problem, the present invention provides a secondary battery capable of stably fixing a laminated electrode group in a battery container without causing a laminating shift or a short circuit of electrode plates constituting the laminated electrode group. And

In order to solve the above problems, the present invention provides a secondary battery having a laminated electrode group in which a plurality of positive and negative electrode plates are laminated via a separator, and a stainless steel battery container that houses the laminated electrode group. the positive electrode plate, at least one of the negative electrode plate and the separator are fixed in a rectangular plate-shaped electrode assembly support for supporting the laminated electrode group, the electrode group support, projecting in a rectangular shape to the battery container side The battery has a protrusion, and the protrusion is positioned in the battery container by fitting into a groove formed in the battery container, and the battery in a direction intersecting the polar surface direction of the multilayer electrode group It is in contact with a container or a battery constituent member fixed to the battery container.

In the secondary battery of the present invention, a laminated electrode group in which a plurality of positive and negative electrode plates are laminated via a separator is housed in a stainless steel battery container. At least one of the positive electrode plate, the negative electrode plate, and the separator is fixed to a rectangular plate-shaped electrode group support that supports the laminated electrode group, and the electrode group support has a protrusion protruding in a rectangular shape on the battery container side. Since the protrusions are fitted into the grooves formed in the battery container, and are fixed to the battery container and positioned in the battery container, the stacked electrode group does not move greatly inside the battery container. The collision of the electrode group with the battery container due to vibration can be avoided.

Further, in the secondary battery of the present invention, the electrode group support, the battery structure member fixed to the battery container or the battery container in a direction crossing the pole face of the multilayer electrode group not abut Runode, three-dimensional When the stacking direction, that is, the polar surface direction is the X-axis direction, the direction intersecting the polar surface direction is the Y-axis direction or the Z-axis direction, and is fixed to the battery container or the battery container in the direction intersecting the polar surface direction. The contact between the battery constituent member and the electrode group support prevents the electrode group from moving inside the battery even with respect to vibrations in the Y-axis direction or the Z-axis direction. Due to the breakage or short circuit caused by the collision of the end of the laminated electrode group with the battery container, it is possible to avoid reaching a battery abnormal state such as a decrease in battery performance or thermal runaway.

On the other hand, taking a configuration in which the separators and the electrode group support fixed by thermal welding, both the method of fixing it is easy and economical it is not necessary to use a member for fixing. Furthermore, if the shape of the separator is a bag shape, either the positive electrode plate or the negative electrode plate, or both are in the shaped bag-shaped separator, so the positive electrode plate or the negative electrode plate can be positioned by fixing the separator. Therefore, productivity can be improved and positional displacement between the positive electrode plate and the negative electrode plate can be prevented by fixing the bag-shaped separator.

According to the present invention, the positive electrode plate, at least one of the negative electrode plate and the separator are fixed in a rectangular plate-shaped electrode assembly support for supporting stacked electrode group, the electrode group support, in a stainless steel cell container side Since the projection has a rectangular shape and the projection is fitted in a groove formed in the battery container, and is fixed to the battery container and positioned in the battery container, the stacked electrode group is formed in the battery container. It is possible to avoid the electrode group from colliding with the battery container due to vibration without moving greatly inside, and the electrode container support in the direction intersecting the extreme surface direction of the laminated electrode group or the battery Since it is in contact with the battery component fixed to the container, when the stacking direction, that is, the pole face direction is defined as the X axis direction in three dimensions, the direction intersecting the pole face direction is the Y axis direction or the Z axis direction. , This polar direction Avoid contact of the electrode group within the battery with respect to vibration in the Y-axis direction or Z-axis direction by contacting the battery container in the intersecting direction or the battery component member fixed to the battery container and the electrode group support. Therefore, it is possible to avoid reaching a battery abnormal state such as deterioration of battery performance or thermal runaway due to short circuit due to misalignment of positive electrode and negative electrode, or damage / short circuit due to collision of the end of the laminated electrode group with the battery container. The effect that can be obtained.

  Embodiments in which the present invention is applied to a prismatic lithium ion secondary battery will be described below with reference to the drawings.

<Positive electrode plate>
Lithium manganese complex oxide powder as a positive electrode active material, scaly graphite as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are mixed at a weight ratio of 85: 10: 5. A slurry in which N-methylpyrrolidone (NMP) was added and kneaded was applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 20 μm. Then, it dried, pressed, and cut | judged to the rectangular shape, and obtained the positive electrode of thickness 170 micrometers. A positive electrode current collector ear (see reference numeral 3 in FIG. 1) protrudes from the positive electrode current collector.

<Negative electrode plate>
10 parts by mass of polyvinylidene fluoride as a binder is added to 90 parts by mass of the amorphous carbon powder as the negative electrode active material, and the slurry obtained by adding and kneading the dispersion solvent NMP to the thickness is added. It apply | coated on both surfaces of 10 micrometers electrolytic copper foil. Thereafter, drying, pressing, and cutting into a rectangular shape, a negative electrode having a thickness of 130 μm was obtained. A negative electrode current collector ear (see reference numeral 4 in FIG. 1) protrudes from the negative electrode current collector.

<Production of battery>
As shown in FIG. 1, the lithium ion secondary battery 20 of the present embodiment includes a square and stainless steel battery can 8 serving as a battery container. In the central portion of the battery can 8, an electrode group 12 is accommodated in which a plurality of positive plates 5 and negative plates 6, with current collector ears projecting upward, are stacked via a separator 7.

  The separator 7 can be manufactured even in the form of a sheet. However, in the lithium ion secondary battery 20 of the present embodiment, the positive electrode plate or the negative electrode plate can be positioned by fixing the separator 7 so that productivity is improved. In addition, in consideration of advantages such as fixing the separator 7 to prevent displacement of the positive electrode plate and the negative electrode plate, the separator 7 is shaped into a bag shape and the positive electrode plate 5 is included in the bag. Adopted.

  The lithium ion secondary battery 20 includes a battery lid 9 as a part of a stainless steel battery container. After the electrode group 12 is inserted into the battery can 8, the upper opening periphery of the battery can 8 and the battery lid 9 are arranged. It is sealed by welding the periphery. As shown in FIGS. 1 and 2, the battery lid 9 is fixed with a positive electrode terminal 1 made of aluminum and screwed on the upper side, and a negative electrode terminal 2 made of copper and screwed on the upper side. Has been. The positive terminal 1 and the negative terminal 2 are respectively a thin annular lower packing 21 interposed between the battery lid 9, a thin annular upper packing 22 that contacts the battery lid 9, and a flat washer that contacts the upper packing 22. 23, and is tightened with a nut 25 via a toothed washer 24 that contacts the flat washer 23, and the positive and negative terminal portions are sealed and sealed by the interposition of the upper packing 22 and the lower packing 21. The positive electrode current collector ear 3 and the negative electrode current collector ear 4 are joined to the lower portions of the positive electrode terminal 1 and the negative electrode terminal 2 by ultrasonic welding, respectively, and the positive electrode plate 5 is connected to the positive electrode terminal 1 and the negative electrode plate 6. Is electrically connected to the negative terminal 2.

  A rectangular plate-shaped electrode group support 30 that supports the electrode group 12 is disposed in the center of the electrode group 12. As shown in FIG. 3, the electrode group support body 30 has a protrusion 30a protruding in a rectangular shape on the battery lid 9 side. The battery cover 9 is formed with an elongated groove 9a, and the protrusion 30a is fitted in the groove 9a. Accordingly, the electrode group support 30 is positioned and fixed in the battery can 8 by fitting the protrusions 30a into the grooves 9a. If a resin material is used for the electrode group support 30, the groove 9a is sealed by thermally melting the protrusion 30a fitted in the groove 9a. However, when a metal material is used for the electrode group support 30, A separate seal may be performed.

  In the present embodiment, the bag-like separator 7 is fixed to the electrode support 30. The separator 7 and the electrode group support 30 are fixed to the electrode group support 30 by band-fastening the separator in a portion not in contact with the portion where the active material of the positive electrode plate 5 or the negative electrode plate 6 is disposed, or rivet However, in this embodiment, thermal welding is used as a simple and efficient fixing method that does not use these bands and rivets. For this reason, a metal material can be used as the material of the electrode group support 30 for band fastening or rivet fastening, but a resin material is used because heat welding is used for fixing to the separator 7. A resin material made of polypropylene having a thickness of 2 mm was used. In the present embodiment, at least a part of at least three sides of the bag-like separator 7 is heat-welded to the electrode group support 30 (see the heat-welded portion 31 in FIG. 1). In order to securely fix the separator 7 to the electrode group support 30, it is preferable that the length of the heat-welded portion 31 with respect to each side of the bag-like separator 7 is ½ or more of each side.

The battery lid 9 is provided with a gas discharge valve 10 and a liquid injection port welded with stainless steel foil. The gas discharge valve 10 has a function of releasing the internal gas by breaking the stainless steel foil when the battery internal pressure increases. A non-aqueous electrolyte solution (not shown) in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate is injected from the liquid injection port. Therefore, the liquid injection port is sealed. The battery capacity is 15.0 Ah.

Next, examples of the lithium ion secondary battery 20 produced by variously changing the shape of the electrode group support 30 according to the present embodiment will be described. Of the examples described below, examples 3 and 4 are shown for reference. In addition, a battery of a comparative example manufactured for comparison is also shown.

<Example 1>
In Example 1, using the electrode group support 30 shown in FIG. 3, that is, the same battery as in the above embodiment was produced.

<Example 2>
In Example 2, a battery was produced using an electrode group support 32 shown in FIG. 4 instead of the electrode group support 30. The electrode group support 32 is disposed in such a manner as to be in contact with the direction crossing the polar surface direction of the electrode group 12, that is, the battery lid 9, the bottom of the battery can 8, and the left and right short sides of the battery can 8. A battery was produced in the same manner as in Example 1. The material and thickness of the electrode group support 32 are the same as those of the electrode group support 30.

<Example 3>
In Example 3, an electrode group support 33 shown in FIG. 5 was used in place of the electrode group support 30. The electrode group support 33 was arranged on the outer periphery of the electrode group where the active material of the positive electrode plate and the negative electrode plate was not disposed so as to contact the battery lid 9, the bottom of the battery can 8, and the left and right short sides of the battery can 8. The material and thickness of the electrode group support 33 are the same as those of the electrode group support 30. In Examples 1 and 2, the electrode group supports 30 and 32 are in the portion where the active material mixture layer is disposed, but in Example 3, the active material mixture layer does not have the electrode group support 33 and fills this space. In order to do this, the number of positive electrode plates, negative electrode plates, and separators was increased. For this reason, the battery capacity of Example 3 was 15.5 Ah. A battery was fabricated in the same manner as in Example 1 except for the above.

<Example 4>
In Example 4, the electrode group support 34 shown in FIG. 6 was used as the electrode group support 30. The electrode group support 34 has a plate-like member having the same dimensions as the inner dimensions of the left and right short side surfaces of the battery can 8 attached to the electrode group support 33 shown in FIG. 5 and has a direction other than the direction crossing the polar surface direction of the stacked electrode group. A battery was fabricated in the same manner as in Example 4 except that the surface of the battery can 8 was in contact with the long side surface of the battery can 8. The material and thickness of the electrode group support 34 are the same as those of the electrode group support 30.

<Comparative Example 1>
In Comparative Example 1, a battery was produced in the same manner as in Example 1 except that the electrode group support 30 was not used in FIGS. 1 and 2 and the separator 7 was not formed into a bag shape.

<Test and evaluation>
A vibration test was performed on each of the batteries of Examples and Comparative Examples manufactured as described above. The vibration test conditions were an acceleration of 29.4 m / s ^{2 in} each of three dimensions, a frequency of 5 to 50 Hz, and a sweep speed of 0.5 Hz / s. The battery voltages before and after the vibration test were compared to confirm the presence or absence of a voltage drop, and a battery capacity confirmation test was performed. The battery after the vibration test was disassembled, and the presence or absence of breakage of the conductive path or damage of the positive electrode plate 5 and the negative electrode plate 6 was confirmed. The results are shown in Table 1.

  As shown in Table 1, the battery of Comparative Example 1 caused a voltage drop and a battery capacity drop before and after the vibration test. Investigation after the disassembly confirmed the partial cutting of the current collector ear of the positive electrode plate and the current collector ear of the negative electrode plate and the breakage of the active material mixture layer of the positive electrode plate and the negative electrode plate. However, in Examples 1 to 4, the voltage drop and the battery capacity did not decrease before and after the vibration test, the current collector ear of the positive electrode plate and the current collector ear of the negative electrode plate were broken, and the positive electrode plate and the negative electrode plate were damaged. There was not.

  As described above, in the battery of this embodiment (Examples 1 to 4), at least one of the positive electrode plate 5, the negative electrode plate 6, and the separator 7 is fixed to the electrode group support, and the electrode group support is positioned in the battery container. Alternatively, since the electrode group support is in contact with the battery constituent member fixed to the battery container (battery can 8, battery lid 9) in the direction intersecting with the polar surface direction of the laminated electrode group, the electrode group is inside the battery. Avoiding movement, short circuit due to misalignment of positive electrode and negative electrode, or damage / short circuit due to collision of end of stacked electrode group with battery container, leading to battery abnormalities such as deterioration of battery performance or ignition Can be avoided. In addition, by arranging the electrode group support 33 on the outer periphery of the electrode group 12, the reaction of the active material mixture layer is caused because the active material mixture layer of the positive electrode plate 5 and the negative electrode plate 6 is not located at the layered position. Since the laminated electrode group thickness is not increased by a member other than the active material mixture layer part without loss, the capacity can be increased with the same electrode group volume. Furthermore, since the fixing method with the electrode group support body 30 is heat welding, the number of parts is not increased. Furthermore, since the separator 7 was made into a bag shape, productivity was improved, and it was found that fixing the separator 7 can also prevent displacement of the positive electrode plate 5 and the negative electrode plate 6.

  In the present embodiment, the separator 7 is fixed to the electrode support 30. However, the positive electrode plate 5 or the negative electrode plate 6 may be fixed to the electrode support 30. In this case, the positive electrode current collector ear 3 or the negative electrode current collector ear 4 may be fastened (fixed) to the electrode group support 30 using band fastening or rivets.

  Moreover, although the example which fixed the protrusion 30a to the battery cover 9 was shown in this embodiment, it may be made to fix to the bottom side of the battery can 8 or both the battery cover 9 and the bottom face of the battery can 8. Good. Furthermore, in the present embodiment, an example in which the three sides of the bag-like separator 7 are thermally welded to the electrode group support 30 is shown, but four sides may be thermally welded to the electrode group support 30.

  Moreover, in this embodiment, although the lithium ion secondary battery 20 was illustrated, this invention is not limited to this, For example, it applies to alkaline batteries, lead storage batteries, etc., such as a nickel metal hydride battery and a nickel cadmium battery. May be. Furthermore, the material of the electrode group support body 30 is not limited to what was illustrated, For example, plastics, such as polyethylene and polytetrafluoroethylene (PTFE), wood, a metal, etc. can be used. Furthermore, the shape of the electrode group support is not limited to the above-described embodiments or examples, and other shapes having the effect can of course be taken.

  In the present embodiment, the electrode group support 30 is positioned in contact with the battery can 8 and the battery lid 9, but is not limited thereto, but indirectly by contacting the battery lid 9, that is, the battery Positioning may be performed by contacting a battery constituent member fixed to the lid 9.

  The present invention provides a secondary battery capable of stably fixing a laminated electrode group in a battery container without causing a stacking shift or a short circuit of electrode plates constituting the laminated electrode group. Since it contributes to manufacturing and sales, it has industrial applicability.

It is a partially broken front view of the lithium ion secondary battery of an embodiment to which the present invention is applicable. It is a partially broken side view of the lithium secondary battery of the embodiment, (A) is a negative electrode side, (B) is a side view of the positive electrode side. It is a perspective view of the fitting part of the electrode group support body and battery cover of embodiment. 6 is a perspective view of an electrode group support in Example 2. FIG. 6 is a perspective view of an electrode group support in Example 3. FIG. 6 is a perspective view of an electrode group support in Example 4. FIG.

Explanation of symbols

5 Positive electrode plate 6 Negative electrode plate 7 Separator 8 Battery can (part of battery container)
9 Battery cover (part of battery container)
9a Groove 12 Electrode group (laminated electrode group)
20 Lithium secondary battery (secondary battery)
30, 32, 33, 34 Electrode group support
30a protrusion

Claims (3)

In a secondary battery having a laminated electrode group in which a plurality of positive and negative electrode plates are laminated via a separator, and a stainless steel battery container that houses the laminated electrode group, at least one of the positive electrode plate, the negative electrode plate, and the separator Is fixed to a rectangular plate-shaped electrode group support that supports the laminated electrode group, and the electrode group support has a protrusion protruding in a rectangular shape on the battery container side, and the protrusion is the battery. The battery container positioned in the battery container by being fitted in a groove formed in the container, and the battery container in a direction intersecting the extreme surface direction of the stacked electrode group or a battery component fixed to the battery container A secondary battery characterized by being in contact with the battery. The secondary battery according to claim 1, wherein the separator and the electrode group support are fixed by heat welding. The secondary battery according to claim 1 or claim 2, wherein the shape of the separator is a bag form.

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