JP2018097937A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery arranged to have a simple structure, and be able to suppress the depletion of an electrolyte solution at an upper location, resulting from its lowering attributed to a force of gravity and to lighten the decrease in charge amount owing to uneven degradation.SOLUTION: A secondary battery comprises: a battery element (5) arranged by bundling a positive electrode and a negative electrode in a layered form; an electrolyte solution (6) permeating the battery element and making contribution to charge and discharge; a battery case (4) containing the battery element and arranged so that a part of the electrolyte solution not permeating the battery element is stored in a bottom part thereof; and a reflexed part (9) formed on an inner face of at least one side wall (4a) of the battery case, and having an inclined surface arranged so that it fluctuates to ward off the electrolyte solution having crept up along the inner face of the side wall inwardly from the side wall in the battery case when an external force is applied thereto.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a secondary battery, and more particularly to a technique for reducing a decrease in the amount of stored electricity due to partial deterioration.

In recent years, electric vehicles that run by operating an electric motor using electric power stored in a secondary battery have become widespread. In such an electric vehicle, how to obtain a high charged amount is a problem. One of the factors that lead to a decrease in the amount of stored electricity is deterioration of the secondary battery.
In a secondary battery, an electrode made of a positive electrode material and a negative electrode material is stacked in a battery case with a porous separator in between, and an electrolyte solution is filled between the positive electrode material and the negative electrode material, and thus in the separator porous material. Configured. Accordingly, in the secondary battery, ions move between the positive electrode and the negative electrode through the electrolytic solution, and thus electrons move to the positive electrode or the negative electrode, whereby electric storage and discharge can be performed.
By the way, the electrolytic solution normally permeates between the positive electrode material and the negative electrode material by capillary action, and thus into the porous body of the separator, but the upper electrolyte solution is depleted by gravity and easily collects at the bottom of the battery case. There is a problem in that the amount of power stored in the secondary battery is reduced because the lower electrode is repeatedly charged and discharged locally and partially deteriorates. In this case, in order to always supply electrolyte solution to the whole electrode, it is possible to increase the quantity of electrolyte solution enclosed in a battery case.
In addition, a technique has been developed in which the lower part of the battery case is pressed more strongly than the upper part, thereby preventing the battery case from expanding due to deterioration and reducing the amount of electrolyte that accumulates at the bottom of the battery case.

Japanese Patent Laying-Open No. 2015-118822

However, increasing the amount of the electrolyte as described above is not preferable because it increases the weight of the secondary battery.
In addition, the technique disclosed in Patent Document 1 is not effective until the battery case expands, and there is a problem that it is not possible to suppress the depletion of the upper electrolyte solution caused by dropping due to gravity.

  The present invention has been made in view of the above problems, and the object of the present invention is to reduce the upper electrolyte caused by gravity and to cause depletion of the upper electrolyte solution with a simple configuration, and to store electricity due to partial deterioration. It is an object of the present invention to provide a secondary battery capable of reducing the decrease in the amount.

In order to achieve the above object, a secondary battery of the present invention contains a battery element in which a positive electrode and a negative electrode are bundled in layers, an electrolyte that permeates the battery element and contributes to charge and discharge, and a battery element. A battery case that stores a part of the electrolyte that does not penetrate into the battery element at the bottom, and is formed on the inner surface of at least one side wall of the battery case, swings in the battery case under an external force, and rises along the inner surface of the side wall And a return portion whose surface is inclined so as to receive the electrolyte solution to be inwardly directed from the side wall.
Thereby, by providing the return portion on the inner surface of the side wall, the electrolyte accumulated at the bottom of the battery case oscillates due to the behavior of the vehicle by acceleration, braking or other external force, and rises along the inner surface of the side wall. Since it flows away in the direction away from the inner surface of the side wall at the return portion and is applied to the upper end of the battery element, it is possible to supply the electrolyte to the upper side of the battery element where the electrolyte tends to be exhausted.

As another aspect, the surface of the return portion is arcuate. Thus, since the return portion and the inner surface of the side wall are smoothly connected, the momentum of the electrolyte rising along the inner surface of the side wall is not hindered. Even when the momentum of the electrolyte rising along the line is small, the electrolyte can be passed through.
As another aspect, a slope portion whose surface is inclined from the inner surface of the bottom wall toward the inner surface of the side wall is formed at the corner where the inner surface of the side wall where the return portion is formed intersects with the inner surface of the bottom wall. It is characterized by. As a result, the slope portion forms an angle between the inner surface of the side wall and the inner surface of the bottom portion, so that the fluctuation of the electrolyte due to the behavior of the vehicle is small, and the momentum of the electrolyte moving toward the inner surface of the bottom is small. Even in such a case, it is possible to flow the electrolyte in the upward direction with less resistance.

  As another aspect, the surface of the slope portion is arcuate. As a result, the inner surface of the side wall, the inner surface of the bottom portion, and the slope portion are smoothly connected, so that the fluctuation of the electrolyte solution due to the behavior of the vehicle is small, and the momentum of the electrolyte solution that moves toward the inner surface of the bottom portion is smaller Even in such a case, it is possible to satisfactorily flow the electrolyte solution in the upward direction with less resistance.

  As another aspect, the surface is formed from the inner surface of the side wall toward the inner surface of the other side wall at the corner where the inner surface of the side wall formed with the return portion and the slope portion intersects with the inner surface of the other side wall adjacent to the side wall. The pour-in part which inclines is formed, It is characterized by the above-mentioned. Thus, even when the electrolyte is tilted upward from the inner surface of the other side wall toward the inner surface of the side wall due to complex vehicle shaking, the electrolyte moves from the inner surface of the other side wall toward the inner surface of the side wall. Can be passed to the inner surface of the side wall with less resistance.

  As another aspect, the surface of the pour-in part is arcuate. As a result, even when the electrolytic solution is less oscillated due to the behavior of the vehicle and the momentum of the electrolytic solution that rises obliquely from the inner surface of the other side wall toward the inner surface of the side wall due to the complicated vehicle sway, The electrolyte that moves from the inner surface of the side wall toward the inner surface of the side wall can be passed to the inner surface of the side wall with less resistance.

As another aspect, the return portion and the slope portion are continuously formed on the inner surface of the side wall. As a result, the return part on the inner surface of the side wall and the surface in contact with the electrolyte solution of the slope part are smoothly connected so as to form a series, so that the fluctuation of the electrolyte solution due to the behavior of the vehicle is small and the momentum of the electrolyte solution is small Even in this case, it is possible to flow the electrolyte well.
Another aspect is characterized in that the adjacent receiving portions sandwiching the inner surface of the side wall are continuous on the inner surface of the side wall. As a result, the surfaces in contact with the electrolyte solution between the adjacent receiving portions are smoothly connected so that the electrolyte solution rising along the inner surface of the side wall is in the vicinity of the connecting portion of the receiving portion adjacent to the receiving portion. The momentum of the rising electrolyte can be concentrated at one point, and the electrolyte can reach the return portion.

  In particular, by configuring the return portion and the slope portion to be continuous on the inner surface of the side wall and combining the adjacent flush portions on the inner surface of the side wall to be continuous on the inner surface of the side wall, Even if the fluctuation of the electrolyte due to the behavior of the vehicle is small and the momentum of the electrolyte is smaller, the electrolyte can reach the return part well while concentrating the momentum of the rising electrolyte on one point. It is possible.

  According to the secondary battery of the present invention, since the return portion is provided on the inner surface of the side wall, the electrolyte accumulated in the bottom of the battery case is swung by the behavior of the vehicle due to acceleration, braking, or other external force, It rises along the inner surface, but at this time, it can be applied to the upper end of the battery element by flowing the electrolyte in a direction away from the inner surface of the side wall at the return portion, and the upper side of the battery element that tends to be depleted of the electrolyte The electrolyte can be supplied satisfactorily.

  Thereby, it is possible to suppress the depletion of the upper electrolyte solution caused by dropping due to gravity and to reduce the amount of stored electricity due to partial deterioration of the secondary battery with a simple configuration.

It is a schematic block diagram of the vehicle carrying the secondary battery of this invention. 1 is a schematic configuration diagram schematically illustrating a configuration of a secondary battery according to a first embodiment of the present invention. It is the perspective view which showed the inner wall structure of the case of the secondary battery of FIG. 2 by the longitudinal cross-section. It is the perspective view which showed the inner wall structure of the case of the secondary battery based on 2nd Embodiment of this invention with the longitudinal cross-section. It is a perspective view which shows the case which employ | adopted the return part aggregate | assembly which couple | bonded the return part, the slope part, and the receiving part based on 3rd Embodiment of this invention in a cross section. It is sectional drawing of the II cross section of FIG. It is sectional drawing (a) of the II-II section of Drawing 5 and Drawing 6, sectional drawing (b) of a III-III section, and sectional view (c) of an IV-IV section.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle 1 equipped with a secondary battery 2 of the present invention.
The vehicle 1 is an electric vehicle, and is mounted with a motor 3 that moves by receiving power from an assembly of a plurality of secondary batteries 2 mounted on the vehicle 1. The motor 3 is a so-called motor generator, and functions as a motor when the vehicle 1 travels, and functions as a generator during regenerative braking so that the secondary battery 2 can be charged. Here, a plurality of motors 3 are provided for front wheels and rear wheels, but a single motor 3 may be provided. In addition, when the vehicle 1 is an electric vehicle, the secondary battery 2 is charged by power feeding at a power feeding station. When the vehicle 1 is a hybrid vehicle equipped with an internal combustion engine, the motor 3 is driven by the internal combustion engine. Can be stored in the secondary battery 2 by generating electric power by driving the.
[First Embodiment]
Referring to FIG. 2, there is shown a schematic configuration diagram schematically showing the configuration of the secondary battery 2 according to the present invention. Referring to FIG. 3, the inner wall structure of the case 4 of the secondary battery 2 in FIG. The first embodiment is described with reference to FIGS. 2 and 3.

The secondary battery 2 is, for example, a lithium ion secondary battery mounted on the vehicle 1, and is configured by disposing a battery element 5 in a case (battery case) 4 and infiltrating the electrolytic solution 6 into the battery element 5. ing.
The case 4 is formed of, for example, a rectangular parallelepiped, and includes a pair of side walls 4a and 4a and a bottom wall 4b opposed in the long direction, a pair of side walls 4c and 4c opposed in the short direction, and a lid member 4d forming an upper wall. Yes.

  The battery element 5 is configured by sequentially and repeatedly laminating a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode is composed of, for example, a member obtained by applying lithium cobalt oxide, which is a lithium metal oxide, to an aluminum foil, the negative electrode is composed of, for example, a member obtained by applying a carbon material to copper foil, the separator functions as an insulator, and It is composed of a sheet made of polypropylene, which is a porous polyolefin through which lithium ions can pass.

A positive electrode lead 7 is disposed at the end of the positive electrode, and a negative electrode lead 8 is disposed at the end of the negative electrode so as to protrude from the lid member 4d at the top of the case.
For the electrolytic solution 6, for example, lithium hexafluorophosphate is used as an organic electrolyte using a solute containing lithium ions. The electrolytic solution 6 penetrates into the battery element 5 due to a capillary phenomenon, and lithium ions and thus electrons move between the positive electrode and the negative electrode, whereby charging / discharging is performed via the positive electrode lead 7 and the negative electrode lead 8.

For example, when the vehicle 1 in which the secondary battery 2 is mounted is not operated for a long time, the electrolytic solution 6 gradually drops by gravity due to the electrolytic solution 6 penetrating the upper side of the battery element 5 as described above. There is a problem that the electrolyte solution 6 is easily depleted on the upper side of the battery element 5 while being accumulated at the bottom.
Hereinafter, the configuration according to the present invention of the secondary battery 2 will be described in detail.

  The case 4 is formed with a return portion 9 protruding from the inner surface of the side wall 4a at a position higher than the upper end of the battery element 5 on the side wall 4a. Specifically, the return portion 9 has a substantially right-angled triangular cross-sectional shape such that the upper side protrudes inward of the case 4 and the lower side smoothly inclines toward the inner surface of the side wall 4a. More specifically, as shown in FIGS. 2 and 3, the inclined surface of the return portion 9 is configured to form a concave surface that is curved outward in an arc shape. The inclined surface of the return portion 9 may be a flat surface instead of a concave surface.

  In addition, a slope portion 11 that smoothly inclines from the inner surface of the bottom wall 4b toward the inner surface of the side wall 4a is formed at a corner portion where the inner surface of the side wall 4a on which the return portion 9 is formed and the inner surface of the bottom wall 4b are orthogonal to each other. ing. Here, as shown in FIGS. 2 and 3, the sloped surface of the slope portion 11 is also configured to form a concave surface that is curved outwardly, but the sloped surface of the slope portion 11 is It may be a flat surface instead of a concave surface.

In addition, about the return part 9, even if it forms in the corner | angular part where the inner surface of the side wall 4a and the inner surface of the cover member 4d cross at right angles, the inner surface of the side wall 4a and the inner surface of the cover member 4d may incline smoothly with a concave surface or a plane. Good.
Moreover, although the case where the return part 9 and the slope part 11 are formed is demonstrated here, only the return part 9 is formed and it is not necessary to necessarily form the slope part 11.

The return portion 9 and the slope portion 11 may be integrated with the case 4 or may be separate. In the case of a separate body, the secondary battery 2 is not deformed even at a high temperature, does not dissolve in the electrolytic solution 6, and is a highly insulating material, for example, the same material as the case 4, heat resistance and resistance. It is desirable to be composed of a highly soluble resin material.
In this way, by forming the return portion 9 at a position higher than the upper end of the battery element 5 on the inner surface of the side wall 4a of the case 4, when the vehicle 1 is shaken by a behavior due to acceleration, braking, or other external force, the case 4 is accompanied by this shake. The electrolytic solution 6 accumulated at the bottom of the base plate oscillates and rises along the inner surface of the side wall 4a. The electrolytic solution 6 thus lifted is separated from the inner surface of the side wall 4a by the return portion 9, that is, inside the case 4. It can be made to flow toward the upper end of the other battery element 5 (indicated by an arrow in FIG. 3). In particular, as shown in FIG. 1, by installing the secondary battery 2 so that the longitudinal direction of the secondary battery 2 is along the traveling direction of the vehicle 1, the electrolyte solution 6 can be used during acceleration or braking of the vehicle 1. Can be swung in the longitudinal direction of the secondary battery 2 to rise along the inner surface of the side wall 4a, and can be received by the return portion 9 toward the upper end of the battery element 5. Thereby, the electrolyte solution 6 can be efficiently supplied to the upper portion of the battery element 5 that tends to be depleted, and the uneven deterioration of the battery element 5 can be prevented.

In addition, by making the inclined surface of the return portion 9, that is, the surface in contact with the electrolytic solution 6 into an arc shape, the flow of the flowing electrolytic solution 6 can be made smooth, and the electrolytic solution is directed toward the upper end of the battery element 5. 6 can be received well.
In addition, by forming the slope portion 11 at a portion where the inner surface of the side wall 4a of the case 4 and the inner surface of the bottom wall 4b are orthogonal to each other, the electrolysis that swings along with the swing of the vehicle 1 and moves toward the inner surface of the side wall 4a. The liquid 6 can be flowed in the upward direction with a small resistance (indicated by an arrow in FIG. 3).

Moreover, the inclined surface of the slope portion 11, that is, the surface in contact with the electrolyte solution 6 is formed in an arc shape, so that the electrolyte solution 6 can also be better flowed to the inner surface of the side wall 4a.
[Second Embodiment]
Referring to FIG. 4, a perspective view showing the inner wall structure of the case 4 of the secondary battery 2 is shown as a longitudinal sectional view as in FIG. 3, and the second embodiment will be described based on FIG. 4. In addition, description is abbreviate | omitted about the structure common to the said 1st Embodiment, and a different part from 1st Embodiment is demonstrated here.

  In the second embodiment, at the corner portion where the inner surface of the side wall 4a and the inner surface of the side wall (other side wall) 4c are orthogonal to each other, the receiving portion 13 that is smoothly inclined from the inner surface of the side wall 4a toward the inner surface of the side wall 4c is formed. ing. Specifically, the inclined surface of the pour-in part 13 is configured to form a concave surface that is curved outward in an arc shape. The inclined surface of the pour-in part 13 may be a flat surface instead of a concave surface.

The receiving part 13 may be integrated with the case 4 or may be a separate body. In the case of a separate body, similarly to the return portion 9 and the slope portion 11, the secondary battery 2 is not deformed even when the temperature becomes high, does not dissolve in the electrolytic solution 6, and has a highly insulating material, for example, the case 4. It is desirable to be composed of the same material as above and a resin material having high heat resistance and high dissolution resistance.
In this way, by forming the flush portion 13 at the corner where the inner surface of the side wall 4a and the inner surface of the side wall 4c are orthogonal to each other, the electrolyte 6 accumulated at the bottom of the case 4 is complicated by the shaking of the vehicle 1 and the side wall 4c. Even in the case of rising obliquely from the inner surface toward the inner surface of the side wall 4a, the electrolytic solution 6 moving from the inner surface of the side wall 4c toward the inner surface of the side wall 4a can be passed to the inner surface of the side wall 4a with a small resistance. (Indicated by arrows in FIG. 4). Thus, the electrolyte 6 that rises obliquely from the inner surface of the side wall 4c toward the inner surface of the side wall 4a can be received toward the upper end of the battery element 5 by the return portion 9 formed on the inner surface of the side wall 4a. .

Further, by making the inclined surface of the receiving portion 13, that is, the surface in contact with the electrolytic solution 6 into an arc shape, the flow of the electrolytic solution 6 can be made smooth, and the electrolytic solution 6 can reach the return portion 9 better. Can do.
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.

Referring to FIG. 5, a perspective view of the case 4 adopting the return portion assembly 15 in which the return portion 9, the slope portion 11, and the receiving portion 13 are coupled is shown as a cross-sectional view.
The return portion assembly 15 is configured such that the arc portions of the return portion 9 and the slope portion 11 are connected to each other on the side wall 4a to form a series, and adjacent flush portions 13 are similarly connected to each other on the side wall 4a. The inner surface shape shown in FIG. 5 is formed such that these are combined and overlapped.

Referring to FIG. 6, a cross-sectional view taken along the line II of FIG. 5 is shown. As shown in the drawing, the surfaces of the return portion assembly 15 on the inner surface of the side wall 4a that are in contact with the electrolyte solution 6 of the return portion assembly 15 and the slope portion 11 are smooth so as to form a series at the central portion of the inner surface of the side wall 4a. It is connected and has an arc shape as a whole.
Referring to FIG. 7, there are shown a sectional view (a) taken along the line II-II in FIGS. 5 and 6, a sectional view taken along the line III-III (b), and a sectional view taken along the line IV-IV (c). Yes. As shown in FIGS. 7A to 7C, the return portion 9 on the inner surface of the side wall 4a and the surface of the slope portion 11 in contact with the electrolyte 6 are smoothly connected so as to form a series, and the adjacent receiving portions 13 are connected. The surfaces in contact with each other's electrolyte 6 are smoothly connected so as to form a series, and these are combined and overlapped to form a concave surface having an elliptical cross section and an arc shape toward the outside of the side wall 4a. Is formed.

That is, the return portion assembly 15 is formed on the inner surface of the side wall 4a so that the surface in contact with the electrolyte 6 has a substantially spoon-like shape with an elliptical cross section toward the outer side of the side wall 4a. Yes.
When the return portion assembly 15 is formed in this way, the electrolytic solution 6 rising from the bottom of the case 4 to the return portion 9 through the slope portion 11 flows so as to gather at the upper end portion of the return portion 9. The flow rate of 6 increases. Therefore, for example, even if the vehicle 1 is small in swing, and therefore the degree of swing of the electrolyte 6 in the secondary battery 2 is small, and the amount of the electrolyte 6 rising on the inner surface of the side wall 4a is small It is possible to favorably flow the electrolytic solution 6 toward the upper end of the battery element 5 located inside the case 4 while concentrating the momentum of the electrolytic solution to be concentrated on one point.

Thereby, the electrolyte solution 6 can be efficiently supplied to the upper part of the battery element 5 in which the electrolyte solution 6 tends to be exhausted, and uneven deterioration of the battery element 5 can be prevented.
In the third embodiment, the return portion assembly 15 in which the surfaces of the return portion 9 and the slope portion 11 are both arc-shaped concave surfaces has been described as an example. However, in the return portion assembly 15, the return portion 9 and the slope portion. The surface of 11 may be a flat surface, or any one of the return portion 9 and the slope portion 11 may be configured as an arcuate concave surface and the other as a flat surface. Similarly, the surface of the flow receiving portion 13 has been described as an arc-shaped concave surface, but the flow receiving portion 13 is not limited to the concave surface and may be a flat surface.

Although the description of the secondary battery according to the present invention is finished above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, a secondary battery mounted on an electric vehicle or a hybrid vehicle has been described. However, as long as the secondary battery is mounted and the secondary battery is shaken, for example, a secondary battery mounted on a railway vehicle or a ship is used. It is also possible to apply the present invention to a secondary battery.

In the above embodiment, the lithium ion secondary battery has been described as an example. However, the secondary battery may not be a lithium ion secondary battery, and may be, for example, a lead storage battery or an alkaline storage battery as long as it has an electrolytic solution. May be.
Moreover, in the said embodiment, although the case 4 was comprised by the rectangular parallelepiped, it may not be a rectangular parallelepiped and may be cylindrical.

Moreover, although the case where the return part 9 was formed in the inner surface of the side wall 4a was demonstrated in the said embodiment, you may form the return part 9 in the inner surface of the side wall 4c. Similarly, the slope portion 11 may be formed at a corner where the inner surface of the side wall 4c and the inner surface of the bottom wall 4b are orthogonal to each other.
Moreover, in the said embodiment, although the return part 9 was formed in the position higher than the upper end of the battery element 5, it is not restricted to this, You may make it form in the position lower than the upper end of the battery element 5. That is, as long as the electrolytic solution 6 can be supplied to a location where the electrolytic solution 6 of the battery element 5 is easily depleted, the position where the electrolytic solution 6 is flowed is not limited to the upper end of the battery element 5. For example, the return portion 9 may be formed so as to flow the electrolyte solution 6 in the middle of the battery element 5, and the electrolyte solution 6 may be permeated into a portion where the electrolyte solution 6 is easily depleted by capillary action.

1 Vehicle 2 Secondary Battery 3 Motor 4 Case (Battery Case)
4a Side wall 4b Bottom wall 4c Side wall (other side wall)
4d Lid member 5 Battery element 6 Electrolytic solution 7 Positive electrode lead 8 Negative electrode lead 9 Return portion 11 Slope portion 13 Flowing portion 15 Return portion assembly

Claims (8)

A battery element in which a positive electrode and a negative electrode are bundled in layers,
An electrolyte that penetrates into the battery element and contributes to charge and discharge;
A battery case that houses the battery element and stores a part of the electrolyte solution that does not penetrate into the battery element at the bottom;
A surface is formed on the inner surface of at least one side wall of the battery case, and the surface is swung in the battery case upon receiving an external force and flows upward along the inner surface of the side wall to receive the electrolyte from the side wall inward. An inclined return portion;
Secondary battery equipped with.   The secondary battery according to claim 1, wherein the surface of the return portion has an arc shape.   A slope portion having a surface inclined from the inner surface of the bottom wall toward the inner surface of the side wall is formed at a corner where the inner surface of the side wall formed with the return portion intersects with the inner surface of the bottom wall. Item 3. The secondary battery according to Item 1 or 2.   The secondary battery according to claim 3, wherein the surface of the slope portion has an arc shape.   The surface is inclined from the inner surface of the side wall toward the inner surface of the other side wall at the corner where the inner surface of the side wall formed with the return portion and the slope portion intersects with the inner surface of the other side wall adjacent to the side wall. The secondary battery according to any one of claims 1 to 4, wherein a pour-through portion is formed.   The secondary battery according to claim 5, wherein the surface of the pour-in part has an arc shape.   The secondary battery according to claim 3, wherein the return portion and the slope portion are continuously formed on the inner surface of the side wall.   The secondary battery as described in any one of Claims 5-7 in which the receiving parts adjacent on both sides of the inner surface of the said side wall become continuous on the inner surface of the said side wall.

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