JP5717193B2 - battery - Google Patents

Description

  The present invention relates to a laminated battery including an electrode element in which an electrode sheet and a separator are laminated to each other and an exterior film that houses the electrode element.

  In recent years, batteries used for power storage, electrically assisted bicycles, automobiles, and the like have been required to be lightweight and have a large capacity. Therefore, flat batteries in which battery elements such as electrode elements and electrolytes are encapsulated by an exterior film have been adopted for these applications. The electrode element includes a positive electrode sheet coated with a positive electrode mixture, a negative electrode sheet coated with a negative electrode mixture, and a separator. As the electrode element, there are a laminated type and a wound type. A stacked electrode element is formed by alternately and repeatedly stacking positive electrode sheets and negative electrode sheets. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and isolates the negative electrode sheet from the positive electrode sheet. A wound electrode element is formed by winding a positive electrode sheet and a negative electrode sheet separated by a separator. Since the electrode elements can be densely arranged inside the exterior film, the laminated electrode element has an advantage that the capacity per unit volume is increased.

  One end of a lead serving as an external terminal of the battery is connected to the electrode element. The other end of the lead is drawn out of the exterior film. The exterior film is thermally welded to the contact portion with the lead to enclose the electrode element in a liquid-tight manner inside the exterior film. The outer film is thermally welded by melting a thermoplastic resin or the like provided in advance on the outer film or the lead. The electrode element is substantially fixed in the exterior film by this resin or the like. However, when subjected to external vibration, a large load is applied to the lead. This load may break or break the lead. If the thickness of the lead is increased in order to prevent the breakage of the lead, the sealing property (liquid tightness) of the exterior film is lowered, and the manufacturing cost and weight are increased.

  Patent Document 1 discloses a non-aqueous electrolyte battery including a film exterior member and an electrode group housed in the film exterior member. The electrode group includes a positive electrode, a negative electrode, and a separator. The separator protrudes from the electrode group, and the protruding portion of the separator is fixed to the inner surface of the exterior member. Thereby, even if an impact is applied from the outside due to vibration, dropping, or the like, displacement of the electrode group in the exterior member can be prevented. As a result, it is said that a decrease in battery voltage and an increase in internal resistance can be suppressed.

  Although different from the object of the invention described in Patent Document 1, Patent Documents 2 to 4 describe batteries in which an electrode element including a separator is sealed in an exterior film or an exterior case.

JP 2007-076552 A Japanese Patent No. 2007-31323 JP-A-11-250873 JP 2000-277062 A

  In the cited document 1, the projecting portion of the separator constituting the electrode element is welded to the exterior member, and the positional deviation of the electrode group in the exterior member can be prevented. However, in the case of an electrode element including a large number of separators, the total thickness of the separators welded to each other may be too large. Thus, when the said exterior film is liquid-tightly sealed while heat-welding the part with large thickness to an exterior film, the liquid-tightness of an exterior film may fall.

  An object of the present invention is to provide a battery including an exterior film with high liquid-tightness that can suppress displacement of an electrode element due to vibration or impact.

  In order to solve the above-described problem, a battery according to one embodiment of the present invention includes an electrode element and an exterior film that houses the electrode element. The electrode element includes a plurality of electrode sheets stacked on each other and a separator disposed between the electrode sheets. The exterior film has thermoplastic resin layers arranged to face each other, and the outer peripheral portions of the resin layers facing each other are heat-welded. At least two of the plurality of separators are formed with protruding portions that protrude from the electrode sheets stacked on each other and are welded to the resin layer of the exterior film. The protrusion part of the 1st separator and the protrusion part of the 2nd separator are arrange | positioned so that it may not mutually overlap among several separators.

  ADVANTAGE OF THE INVENTION According to this invention, the position shift of the electrode element by a vibration and an impact can be suppressed, and a highly liquid-tight exterior film can be provided.

It is a schematic perspective view of the battery in one embodiment. It is a schematic plan view of the battery in one embodiment. It is typical sectional drawing along the 3A-3A line | wire shown in FIG. 2 of the electrode element inside an exterior film. 1 is a schematic plan view of an electrode element in Example 1. FIG. It is a schematic sectional drawing which shows the structure of the outer peripheral part vicinity of the electrode element covered with the exterior film. 6 is a schematic plan view of an electrode element in Example 2. FIG. 6 is a schematic plan view of an electrode element in Example 3. FIG. FIG. 8 is a schematic cross-sectional view of the electrode element in Example 3 taken along line 8A-8A shown in FIG. 6 is a schematic plan view of an electrode element in Example 4. FIG. 10 is a schematic plan view of an electrode element in Example 5. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention can be applied to all types of batteries such as lithium ion secondary batteries. The present invention is particularly effective in a battery including a stacked electrode element in which electrode sheets and separators are stacked.

  FIG. 1 is a schematic perspective view of a battery according to an embodiment of the present invention, and FIG. 2 is a schematic plan view of the battery. The battery 10 includes an electrode element 20 and an exterior film 12 that houses the electrode element 20. Leads 18 a and 18 b used as electrode terminals are connected to the electrode element 20. The leads 18a and 18b are sandwiched between upper and lower thermoplastic resins from the electrode element 20 and are drawn out to the outside. In FIG. 2, a part of the leads 18 a and 18 b covered with the exterior film 12 and the electrode element 20 are indicated by dotted lines.

  As an example, the exterior film 12 is composed of a set of films whose outer peripheral portions are welded together. The exterior film 12 is liquid-tightly sealed so that the electrolytic solution sealed inside does not leak. An aluminum laminate film can be used for each film constituting the exterior film 12. As an example of the aluminum laminate film, there is a film having a three-layer structure including a resin layer such as nylon or polyimide, an aluminum layer, and a thermoplastic resin layer such as polypropylene. Polypropylene has a thickness of about 30 to 100 μm. The exterior film 12 is configured by thermally welding the thermoplastic resin layers of a set of films to each other.

  As another example, the exterior film 12 may have a form in which one film having a resin layer formed on one surface is folded in two. The outer film 12 may be of any form as long as the outer peripheral portions of the resin layers facing each other are welded.

  FIG. 3 is a schematic cross-sectional view of the electrode element 20 taken along the line 3A-3A in FIG. The electrode element 20 includes electrode sheets 21 and 22 and a separator 23. The electrode element 20 includes a positive electrode sheet 21 formed by applying a positive electrode mixture to a metal foil as a current collector, and a negative electrode sheet 22 formed by applying a negative electrode mixture to a metal foil as a current collector. One lead 18 b is connected to the positive electrode sheet 21, and the other lead 18 a is connected to the negative electrode sheet 22.

  As the current collector constituting the positive electrode sheet 21, an aluminum foil can be used. A positive electrode mixture is applied to both surfaces of the aluminum foil. The positive electrode mixture preferably contains lithium cobaltate, lithium nickelate, lithium manganate, or an active material that combines these. Moreover, the positive electrode mixture may contain a binder or the like as necessary. As the current collector constituting the negative electrode sheet 22, a copper foil can be used. A negative electrode mixture is applied to both sides of the copper foil. As the negative electrode mixture, a carbon material such as carbon or graphite capable of occluding and releasing lithium ions, a metal such as Fe, Si, Sn, or Ti, or a compound such as an alloy or oxide containing these metals is used. be able to. The negative electrode composite may be a combination of these carbon materials, metals and compounds. The positive electrode mixture and the negative electrode mixture may contain a conductive additive in order to increase conductivity, and may contain other additives. The positive electrode mixture and the negative electrode mixture are not limited to these examples, and any combination of materials may be used as long as it functions as a battery.

  The positive electrode sheets 21 and the negative electrode sheets 22 are alternately arranged with separators 23 interposed therebetween. The separator 23 insulates the positive electrode sheet 21 and the negative electrode sheet 22 from each other. Separator 23 consists of a polymer sheet holding a nonaqueous electrolyte, for example. The separator 23 has a minute gap, and the gap is impregnated with an electrolyte. The separator 23 may be a single layer of polypropylene or polyethylene, or a laminate of a polypropylene layer and a polyethylene layer. The separator 23 is preferably a material having a melting point equal to or lower than the melting point of the thermoplastic resin constituting the exterior film 12. The separator 23 preferably has a thickness of 15 to 30 μm.

  FIG. 4 is a schematic plan view of the electrode element 20 in the first embodiment. FIG. 5 is a cross-sectional view of the battery corresponding to the plane along line 5A-5A in FIG. In the first embodiment, protrusions 24a to 24h are formed on the separator 23 on the side 25b opposite to the side (hereinafter referred to as a terminal side) 25a to which the leads 18a and 18b of the electrode element 20 are connected. Yes. Each separator 23 is formed with one protrusion 24a to 24h. That is, each protrusion 24a-24h is formed in a different separator 23. These protrusions 24 a to 24 h are heat-welded together with the exterior film 12 at the outer periphery of the exterior film 12. Thereby, the electrode element 20 and the separator 23 are sealed with the exterior film 12. It is preferable to weld the protrusions 24 a to 24 h of the separator 23 and the exterior film 12 simultaneously with the welding of the resin layers constituting the exterior film 12.

  The protrusions 24a to 24h are arranged at positions that do not overlap each other. The protrusions 24a to 24h are portions WS inside the portion WF where the resin layers of the exterior film 12 are welded to each other, and are sandwiched between the resin layers and welded to the resin layers. Hereinafter, the portion WS where the exterior film 12 and the protruding portions 24a to 24h are welded to each other is referred to as a welded portion. Since the separator 23 is welded to the exterior film 12 by the projecting portions 24 a to 24 h, the electrode element 20 does not move greatly inside the exterior film 12 even if vibration and impact are applied. As a result, the displacement of the electrode element 20 is suppressed, and an internal short circuit can be prevented.

  The protrusions 24a to 24h drawn from the separators 23 are arranged so as not to overlap. Therefore, the distance D between the exterior films 12 facing each other across the projecting portion 24d in the welded portion WS is smaller than when the separator 23 is fused to the exterior film 12 in a state where the projecting portions of the separators 23 are overlapped. Thereby, the exterior film 12 and the protrusion part of the separator 23 can be welded reliably, and the liquid-tightness of an exterior film can be improved.

  The sealing portion of the outer peripheral portion of the exterior film 12 includes a welded portion WS with the projecting portions 24a to 24h, a welded portion WF between the resin layers, and a transition portion α located between the welded portions WS and WF, including. Hereinafter, as shown in FIG. 5, the total width of the welded portions WS and WF and the transition portion α is referred to as a sealing width. When the distance D between the exterior films 12 facing each other across the protrusion 24d increases, it is necessary to widen the transition portion α and the weld WS in order to weld the protrusion 24 and the exterior film 12 with certainty. As a result, the outer shape of the battery 10 is increased. On the other hand, unless the welded portion WS and the transition portion α are increased, the liquid tightness of the exterior film may be lowered.

  In the battery 10 of the present embodiment, the protruding portions 24a to 24h drawn from the plurality of separators 23 are arranged at positions where they do not overlap each other. Therefore, even if the width of the welded portion WS of the exterior film 12 and the width of the transition portion α are small, the liquid tightness of the exterior film 12 can be ensured. Therefore, an increase in the outer shape of the battery 10 can be suppressed while maintaining the adhesion between the exterior films 12 and between the exterior film 12 and the separator 23.

  The energy density of the battery 10 includes volume energy density (Wh / L) and weight energy density (Wh / Kg). The energy amount Wh of the battery 10 is determined by the amount of material used for the electrode element 20. The volume L of the battery 10 is determined by the size of the battery including the exterior film 12. In the battery 10 of the present embodiment, an increase in the volume of the battery 10 can be suppressed, so that a decrease in the volume energy density of the battery 10 can be suppressed. Moreover, since the increase in the weight resulting from the increase in the volume of the battery 10 can also be suppressed, the decrease in the weight energy density of the battery 10 can also be suppressed.

  Of the plurality of separators 23, protrusions 24 a to 24 h may be formed on a part or all of the separators 23 excluding both ends of the electrode element 20 in the stacking direction T. The protrusions 24a to 24h are preferably welded to the exterior film 12 at positions where they do not overlap each other. The protrusions 24 a to 24 h are not necessarily formed on all the separators 23. Projections may be formed only on at least two separators. By providing the protruding portions only on some separators, the thickness of the welded portion WS can be reduced even when the number of separators 23 constituting the electrode element 20 is increased. As a result, the widths of the welded portions WS and WF can be reduced, and as a result, the volume of the battery can be reduced and the decrease in energy density can be suppressed.

  Further, all the separators 23 included in the electrode element 20 may be welded to the exterior film 12 by the protruding portions 24a to 24h. When all the separators 23 are fixed to the exterior film 12, it is possible to reduce the load on all the leads 18a and 18b connected to the positive electrode sheet 21 and the negative electrode sheet 22 when an impact is applied from the outside. it can.

  In Example 1 shown in FIG. 4, the protrusions 24 a to 24 h of the separator 23 are located on the side opposite to the terminal side 25 a of the electrode element 20. Not only this but the protrusion parts 24a-24h of the separator 23 may be located in one or several edge | sides other than the terminal edge 25a (refer also FIGS. 6-10). The protrusions 24 a to 24 h of the separator 23 are preferably disposed on sides other than the terminal side 25 a of the electrode element 20.

  The protrusions 24a to 24h are preferably arranged so as not to overlap each other. It can replace with this and the protrusion parts 24a-24h can also be accumulated in the range by which the liquid-tightness of the exterior film 12 is not inhibited. Specifically, the distance D between the resin layers of the exterior film 12 facing each other across the protrusions 24a to 24h is the thickness 2 of the separator 23 welded to the exterior film 12 by the protrusions 24a to 24h. It is preferable that it is less than 2 times. More specifically, the distance D is preferably 60 μm or less. For this reason, it is preferable that the protrusions 24a to 24h are arranged so as not to overlap three or more. When the overlap of the protrusions 24a to 24h is 2 or less, the separator 23 is directly fixed to the resin layer of the exterior film 12 by the protrusions 24a to 24h. Thereby, the fall of energy density can be suppressed and the liquid-tightness of an exterior film can also be improved.

  Next, results of vibration and impact tests performed on the batteries according to some examples and the batteries of comparative examples will be described. In this test, the distance that the electrode element 20 moved in the exterior film 12 was measured. First, the batteries of the examples and comparative examples will be described.

Example 1
FIG. 4 shows a schematic plan view of the electrode element 20 in the first embodiment. An electrode element was prepared by laminating 8 positive electrode sheets and 9 negative electrode sheets with a separator interposed therebetween. The separator 23 was 16 sheets. The size of the exterior film 12 containing the battery 10 was 150 mm in length and 80 mm in width. Protrusions 24a to 24h each having a width of 8 mm were provided in the separators 23 every other layer. It arrange | positions so that each protrusion part 24a-24h may not overlap. The protrusions 24 a to 24 h are provided on the side opposite to the terminal side 25 a of the electrode element 20. These protrusions 24 are welded to the exterior film 12.

(Example 2)
In Example 2, as shown in FIG. 6, the protruding portion 24 of the separator 23 protrudes from one of the two sides of the electrode element 20 orthogonal to the terminal side 25a. One protrusion 24 is formed in each separator 23. The length of the protruding portion 24 in the direction perpendicular to the terminal side 25a of the electrode element was 8 mm. The number of positive electrode sheets, the negative electrode sheet 22 and the separator 23 and the size of the battery are the same as those in the first embodiment.

(Example 3)
In Example 3, as illustrated in FIG. 7, the protruding portion 24 is formed on the other side of the two sides orthogonal to the terminal side 25 a of the electrode element 20. One protrusion 24 is formed in each separator 23. However, as shown in FIG. 8, each of the projecting portions 24 is disposed so as to overlap each other. The length of the protruding portion 24 in the direction orthogonal to the terminal side 25a of the electrode element 20 was 16 mm. The number of separators 23 and the size of the battery are the same as those in the first embodiment.

Example 4
In Example 4, as shown in FIG. 9, the protrusions 24 formed on the separator 23 are arranged on two sides of the electrode element 20 different from the terminal side 25a. One protrusion 24 is formed in each separator 23. Five protrusions 24 having a width of 14 mm are arranged on the side opposite to the terminal side 25a. Eleven protrusions 24 having a width of 12 mm are arranged on another side. The number of separators 23 and the size of the battery are the same as in the first embodiment.

(Example 5)
In Example 5, as shown in FIG. 10, the protrusion part 24 is arrange | positioned at three sides other than the terminal side 25a of the electrode element 20, respectively. One protrusion 24 is formed in each separator 23. Four protruding portions 24 having a width of 17.5 mm are arranged on the side opposite to the terminal side 25a. On the remaining two sides, six protrusions 24 having a width of 22.5 mm are arranged. The number of separators 23 and the size of the battery are the same as those in the first embodiment.

(Comparative Example 1)
In Comparative Example 1, no separator is formed on any separator, and the separator and the exterior film are not welded. Other configurations are the same as those in the first embodiment.

(Comparative Example 2)
In Comparative Example 2, a protruding portion that protrudes from one side opposite to the terminal side of the electrode element is formed on all separators that constitute the electrode element. These protrusions are all overlaid. All the separators are welded to the exterior film by the protrusions. Other configurations are the same as those in the first embodiment.

  Vibration and impact tests were performed on the batteries of the above examples and comparative examples according to the following procedure.

[Procedure 1]
Fully charge each battery.

[Procedure 2]
Marks are made with a pen at the positions of the end portions of the electrode elements of the exterior film, more specifically, the portions corresponding to the rising portions of the embossing.

[Procedure 3]
The battery is placed in an atmosphere having a temperature of 20 ± 5 ° C. and an atmospheric pressure of 11.6 kPa or less for 6 hours or more.

[Procedure 4]
Subsequently, a thermal shock is applied to the battery. The battery is maintained at 75 ± 2 ° C. for a minimum of 6 hours and subsequently maintained at 40 ± 2 ° C. for a minimum of 6 hours. The interval between temperature changes is within 30 minutes. This change in temperature is repeated a total of 10 times.

[Procedure 5]
The battery is fixed to the vibration table of the vibration device so that vibration is reliably transmitted to the battery. The vibration is a logarithmic sweep of a sinusoidal waveform, and the vibration frequency is changed from 7 Hz to 200 Hz and returned to 7 Hz. This lasts 15 minutes. This vibration is performed twelve times in three directions perpendicular to the battery.

[Procedure 6]
Let the battery be completely discharged.

[Procedure 7]
The battery is fixed to the impact device by a rigid fixing jig, and a half-sine wave impact with a peak acceleration of 150 gn and a pulse duration of 6 milliseconds is applied to the battery. In three directions perpendicular to each other, the battery is impacted three times in the positive and negative directions.

[Procedure 8]
The positional deviation of the electrode element from the mark attached in the procedure 2 is measured with a scale.

  Table 1 shows the results of the above tests for the batteries of Examples 1 to 5 and the comparative example.

  It was found that the amount of displacement of the electrode element 20 was very small as compared with Comparative Example 1 if there was at least one side where the separator 23b and the exterior film 12 were welded. Therefore, it can be seen that the battery of this example has improved resistance to vibration and impact.

  When the separator of all layers is heat-welded with an exterior film like the battery of the comparative example 2, the sealing width of an exterior film is needed about 8 mm. As a result, as described above, it was found that the energy density of the battery was lowered. On the other hand, in the battery of this example, since only some of the separators 23b are welded to the exterior film 12, an increase in the sealing width can be suppressed. As a result, a decrease in battery energy density can be suppressed.

  Although the preferred embodiments and examples of the present invention have been presented and described in detail above, the present invention is not limited to the above-described embodiments and examples, and various changes and modifications can be made without departing from the gist. Please understand that this is possible.

DESCRIPTION OF SYMBOLS 10 Battery 12 Exterior film 18a Lead 18b Lead 20 Electrode element 21 Positive electrode sheet 22 Negative electrode sheet 23 Separator 24, 24a-24h Projection part of separator

Claims (7)

An electrode element comprising a plurality of electrode sheets laminated together and a separator disposed between the electrode sheets;
A battery comprising: an exterior film that houses the electrode element, the exterior film having thermoplastic resin layers disposed opposite to each other, and the outer peripheral portions of the resin layers facing each other being thermally welded to each other Because
At least two of the plurality of separators are formed with protruding portions that protrude from the electrode sheets stacked on each other and are welded to the resin layer of the exterior film,
The battery, wherein the protruding portion of the first separator and the protruding portion of the second separator of the plurality of separators are arranged so as not to overlap each other. The protrusion is formed on at least three of the separators,
The protrusion formed on a third separator different from the first and second separators is arranged so as to overlap the protrusion formed on the first separator. The battery described. The protrusions are formed on all of the separators,
The battery according to claim 1, wherein the plurality of protrusions are arranged so as not to overlap three or more.   4. The distance between the resin layers facing each other across the protrusion is not more than twice the thickness of the separator welded to the exterior film by the protrusion. 5. The battery according to item.   The battery according to any one of claims 1 to 4, wherein a lead drawn from each of the electrode sheets to the outside of the exterior film is provided.   The battery according to claim 5, wherein the protrusion is formed on a side different from one side of the electrode sheet on which the lead is formed.   The battery according to any one of claims 1 to 6, wherein a melting point of the separator on which the protrusion is formed is lower than a melting point of the resin layer.

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