Secondary batteries

Abstract

The appropriate amount of electrolyte solution 90 must be determined. [Solution] The battery 100 comprises an electrode group 50, a battery case 80 enclosing the electrode group 50, an electrolyte 90 placed in the battery case 80 so that at least a portion of the electrode group 50 is submerged, a float 60 that floats in the electrolyte 90 within the battery case 80 and moves with the movement of the electrolyte 90's surface, and a sensor 70A capable of detecting the position of the float 60 from outside the battery case 80. As a result, the position of the float 60 can be determined by the signal from the sensor 70A. The position of the float 60 indicates the position of the electrolyte 90's surface. Consequently, the amount of electrolyte 90 can be appropriately determined.

Description

Technical Field

[0001] This disclosure relates to a secondary battery, and more particularly to a secondary battery including an electrode body, a case that encloses the electrode body, and an electrolytic solution that is placed in the case such that at least a part of the electrode body is immersed therein.

Background Art

[0002] Conventionally, in a storage battery, there has been a device that displays the liquid level and specific gravity state of an electrolytic solution through a window formed in a side wall of a battery case so that the inside of the battery case can be seen through (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the disclosure of Patent Document 1, the height of the liquid level needs to be visually confirmed. Therefore, there is a possibility that notification to the user may be delayed when the electrolytic solution decreases.

[0005] This disclosure has been made to solve the above-described problems, and an object thereof is to provide a secondary battery capable of appropriately specifying the amount of an electrolytic solution.

Means for Solving the Problems

[0006] The secondary battery according to this disclosure includes an electrode body, a case that encloses the electrode body, an electrolytic solution that is placed in the case such that at least a part of the electrode body is immersed therein, a float that floats in the electrolytic solution within the case and moves as the liquid level of the electrolytic solution moves, and a sensor that can detect the position of the float from outside the case.

[0007] With this configuration, the position of the float can be determined by the signal from the sensor. The position of the float indicates the level of the electrolyte. As a result, it is possible to provide a secondary battery in which the amount of electrolyte can be appropriately determined.

[0008] The case may be a rectangular shape with a cross-section perpendicular to the vertical direction. The electrode body may be formed by stacking a positive electrode plate and a negative electrode plate in a long strip shape with a separator in between, winding them so that the cross-section perpendicular to the winding axis is oval, and the winding axis is parallel to the vertical direction, and the electrode body may be enclosed in the case so that the longitudinal direction of the oval is parallel to the long side of the rectangle of the case in the cross-section perpendicular to the vertical direction. The float may be configured to move vertically through the gap between the corner of the rectangle of the case and the rounded part of the oval of the electrode body in the cross-section perpendicular to the vertical direction.

[0009] With this configuration, the amount of electrolyte can be accurately determined by utilizing the dead space within the case.

[0010] The sensor may be configured to output a signal corresponding to the distance between the sensor and the float. With such a configuration, it is possible to appropriately identify increases or decreases in the amount of electrolyte.

[0011] The sensor may be positioned within a range capable of detecting the float's position when the electrolyte level is at its lower limit. With such a configuration, it is possible to appropriately determine that the electrolyte level is at its lower limit.

[0012] Multiple sensors may be provided, and each sensor may be positioned within a range capable of detecting different float positions. With such a configuration, multiple amounts of electrolyte can be appropriately identified. [Effects of the Invention]

[0013] This disclosure makes it possible to provide a secondary battery in which the amount of electrolyte can be appropriately determined. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example of the battery configuration of this embodiment of disclosure. [Figure 2] This is a schematic diagram showing an example of the configuration of the electrode group in this embodiment. [Figure 3] This is a schematic diagram showing an example of the configuration of the positive and negative electrodes in this embodiment. [Figure 4] This figure shows the configuration for determining the liquid level of the electrolyte in this embodiment. [Figure 5] This figure shows an example of detection by the sensor in this embodiment. [Figure 6] This figure shows a modified example of the electrode group of the battery in this embodiment. [Modes for carrying out the invention]

[0015] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0016] In this disclosure, "non-aqueous electrolyte secondary battery" refers to a battery in which the electrolyte solution does not contain water. Hereafter, a non-aqueous electrolyte secondary battery may be abbreviated as "battery".

[0017] Figure 1 is a schematic diagram showing an example of the configuration of a battery 100 according to an embodiment of this disclosure. Referring to Figure 1, the battery 100 includes a battery case 80. The battery case 80 is rectangular (flat rectangular parallelepiped). However, the battery case in this embodiment may have other shapes. The battery case 80 may be made of a metal material such as Al alloy, stainless steel (SUS), iron (Fe), or a resin material. The battery case 80 may be made of a composite material of a metal material and a resin material (for example, a bag made of aluminum laminate film).

[0018] The battery case 80 is sealed. A terminal 81 is provided on the battery case 80. The battery case 80 may include a current interruption mechanism (CID), a gas discharge valve, a liquid injection hole, etc., not shown in the figure. The battery case 80 houses an electrode group 50 (also referred to as an "electrode body", a "power generation element", or a "power storage element") and an electrolyte 90. The electrode group 50 is electrically connected to the terminal 81.

[0019] FIG. 2 is a schematic diagram showing an example of the configuration of the electrode group 50 of this embodiment. The electrode group 50 is of a wound type. Referring to FIG. 2, that is, the electrode group 50 is formed by laminating a positive electrode 10, a separator 30, a negative electrode 20, and a separator 30 in this order, and then winding these in a spiral shape. The electrode group 50 may be formed in a flat shape.

[0020] FIG. 3 is a schematic diagram showing an example of the configuration of the positive electrode 10 and the negative electrode 20 of this embodiment. FIG. 3(A) is a schematic diagram showing an example of the configuration of the positive electrode 10 of this embodiment. Referring to FIG. 3(A), the positive electrode 10 is a strip-shaped sheet. The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode mixture layer 12. The positive electrode mixture layer 12 is supported on the surface of the positive electrode current collector 11. The positive electrode mixture layer 12 contains a positive electrode active material. The positive electrode 10 may have a portion where the positive electrode current collector 11 is exposed from the positive electrode mixture layer 12 as a connection position with the terminal 81.

[0021] The positive electrode current collector 11 is an electrode base material having conductivity. The positive electrode current collector 11 may be, for example, a pure Al foil, an Al alloy foil, or the like. The positive electrode mixture layer 12 is formed on the surface (both the front and back surfaces or one surface) of the positive electrode current collector 11. The positive electrode mixture layer 12 may include, for example, a positive electrode active material, a conductive material, and a binder.

[0022] Figure 3(B) is a schematic diagram showing an example of the configuration of the negative electrode 20 in this embodiment. Referring to Figure 3(B), the negative electrode 20 is a strip-shaped sheet. The negative electrode 20 comprises a negative electrode current collector 21 and a negative electrode composite material layer 22 formed on the surface of the negative electrode current collector 21. The negative electrode composite material layer 22 is supported, for example, on the surface of the negative electrode current collector 21. The negative electrode 20 may have a portion of the negative electrode current collector 21 that is exposed from the negative electrode composite material layer 22 as a connection position with the terminal 81.

[0023] The negative electrode current collector 21 may be, for example, a Cu foil. The Cu foil may be pure Cu foil or a Cu alloy foil. The negative electrode composite layer 22 is formed on the surface (both front and back surfaces or one surface) of the negative electrode current collector 21. The negative electrode composite layer 22 contains a negative electrode active material. The negative electrode composite layer 22 may further contain other additives (binder, thickener, etc.).

[0024] The separator 30 is a strip-shaped sheet. The separator 30 is interposed between the positive electrode 10 and the negative electrode 20. The separator 30 is an electrically insulating porous membrane. The separator 30 may be made of, for example, polyethylene (PE), polypropylene (PP), etc. The separator 30 may have a multilayer structure.

[0025] The electrolyte 90 is impregnated into the electrode group 50. A portion of the electrolyte 90 is stored at the bottom of the battery case 80. The dashed line in Figure 1 indicates the liquid level of the electrolyte 90. As shown in Figure 1, the battery 100 is used with the terminal 81 facing vertically upward (positive Z-axis direction). Therefore, the liquid level of the electrolyte 90 is on a plane perpendicular to the vertical direction (a plane perpendicular to the Z-axis direction, i.e., a plane parallel to the XY plane).

[0026] The electrolyte 90 contains at least a lithium (Li) salt and a solvent. The Li salt is a supporting electrolyte. The Li salt is dissolved in the solvent. The solvent is aprotic. That is, the electrolyte in this embodiment is a non-aqueous electrolyte. The solvent may be, for example, a mixture of cyclic carbonates and linear carbonates. The solvent may also contain, for example, lactones, cyclic ethers, linear ethers, carboxylic acid esters, etc. Even if the amount of electrolyte 90 is less than the amount required to immerse the entire electrode group 50, as long as it is above the minimum specific amount required to indicate that the electrolyte 90 will impregnate the entire area between the positive electrode 10 and the negative electrode 20 of the electrode group 50, the electrolyte 90 will be held throughout the area between the positive electrode 10 and the negative electrode 20. If the amount of electrolyte 90 falls below the specific amount, the electrolyte 90 will no longer be held throughout the entire area between the positive electrode 10 and the negative electrode 20.

[0027] The battery 100 of this embodiment can be used, for example, as a power source for vehicles such as hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), and plug-in hybrid electric vehicles (PHEVs), as well as for other machines.

[0028] In the aforementioned battery 100, it is conceivable to form a window in the side wall of the battery case 80 so that the inside of the battery case 80 can be seen through. It is conceivable to display the liquid level and specific gravity of the electrolyte through this window. However, in this case, the liquid level must be checked visually. Therefore, there is a possibility that notification to the user when the electrolyte 90 decreases may be delayed.

[0029] Therefore, the battery 100 includes, in addition to an electrode group 50, a battery case 80 enclosing the electrode group 50, and an electrolyte 90 placed in the battery case 80 so that at least a portion of the electrode group 50 is submerged, a float 60 that floats in the electrolyte 90 within the battery case 80 and moves as the liquid level of the electrolyte 90 moves, and a sensor 70A that can detect the position of the float 60 from outside the battery case 80.

[0030] This allows the position of the float 60 to be determined by the signal from the sensor 70A. The position of the float 60 indicates the liquid level of the electrolyte 90. As a result, the amount of electrolyte 90 can be accurately determined.

[0031] Figure 4 shows the configuration for determining the liquid level of the electrolyte 90 in this embodiment. Figure 4(A) shows a cross-section of the battery 100 from a plane parallel to the XY plane. Figure 4(B) shows a cross-section of the battery 100 from a plane parallel to the XZ plane. Referring to Figures 4(A) and 4(B), the float 60 floats in the electrolyte 90 within the battery case 80 and moves as the liquid level of the electrolyte 90 moves. In this embodiment, the float 60 is in the shape of a capsule with hemispheres attached to both ends of a cylinder, but is not limited to this, and can be any shape that allows for easy movement between the battery case 80 and the electrode group 50, for example, it may be spherical, polyhedral, or barrel-shaped.

[0032] Sensor 70A is capable of detecting the position of the float 60 inside the battery case 80 and outputting a signal corresponding to the distance between sensor 70A and the float 60; for example, it is a proximity sensor. When an inductive proximity sensor is used as sensor 70A, the float 60 is made to contain a conductor such as iron or copper that can be detected by the sensor. When a capacitive proximity sensor is used as sensor 70A, the float 60 is made to contain a metal or a dielectric such as resin, liquid, or powder that can be detected by the sensor. When a magnetic proximity sensor is used as sensor 70A, the float 60 is made to contain a magnetic material such as a magnet. After ensuring that the float 60 contains the above-mentioned substances, the types and amounts of other substances included are adjusted so that it has a specific gravity that allows it to float in the electrolyte 90.

[0033] Sensor 70A is positioned within a range that can detect the position of the float 60 when the amount of electrolyte 90 is at a lower limit such as the specific amount mentioned above.

[0034] In this embodiment, the battery case 80 is a rectangular shape with a cross-section perpendicular to the vertical direction (Z-axis direction), as shown in Figures 1 and 4. The electrode group 50 is a long, strip-shaped structure formed by stacking a positive electrode 10 and a negative electrode 20 with a separator 30 in between, winding them together so that the cross-section perpendicular to the winding axis is oval. The electrode group 50 is enclosed in the battery case 80 such that the winding axis is parallel to the vertical direction (Z-axis direction), and the longitudinal direction of the oval in the cross-section in the vertical direction (Z-axis direction) is parallel to the long side of the rectangle of the battery case 80.

[0035] The float 60 moves vertically (in the Z-axis direction) through the gap between the rectangular corner of the battery case 80 and the oval R-shaped portion of the electrode group 50 in a cross section perpendicular to the vertical direction (Z-axis direction).

[0036] When the battery 100 of this embodiment is installed in a vehicle, the signal from the sensor 70A is output to the vehicle's ECU (Electronic Control Unit). Based on the signal from the sensor 70A, the ECU determines the position of the float 60. If the position of the float 60 is below a specific level corresponding to the lower limit of the electrolyte 90, the ECU stores the fact that the amount of electrolyte 90 is below the lower limit as abnormal information, or notifies the user or maintenance personnel by display, voice, or wirelessly.

[0037] Figure 5 shows an example of detection by the sensor 70A in this embodiment. Referring to Figure 5, when the sensor 70A is mounted at a position corresponding to the amount c of the electrolyte 90, the amount of electrolyte 90 can be detected in the range from amount c+y to amount cy, depending on the detection capability of the sensor 70A. When the amount of electrolyte 90 decreases to amount c+y, the sensor 70A outputs a signal showing the lowest detectable intensity as an average value because the liquid surface of the electrolyte 90 vibrates due to the movement of the vehicle. As the amount of electrolyte 90 decreases further, the sensor 70A outputs a signal showing a gradually increasing intensity. When the amount of electrolyte 90 decreases to amount c, the sensor 70A outputs a signal showing the highest intensity as an average value because the liquid surface of the electrolyte 90 vibrates due to the movement of the vehicle. As the amount of electrolyte 90 decreases further, the sensor 70A outputs a signal showing a gradually decreasing intensity. When the amount of electrolyte 90 decreases to amount cy, the sensor 70A outputs a signal showing the lowest detectable intensity as an average value because the liquid surface of the electrolyte 90 vibrates due to the movement of the vehicle.

[0038] This allows the ECU to determine the amount of electrolyte 90 from amount cy to amount c+y based on a signal from a single sensor 70A.

[0039] [Differentiation] (1) In the embodiment described above, as shown in Figure 4(B), the position of the float 60 is detected by one of the sensors 70A. However, the invention is not limited to this, and as shown in Figure 4(C), the position of the float 60 may be detected by multiple sensors 70B to 70E. The multiple sensors 70B to 70E are each provided in a range that can detect different positions of the float 60. This makes it possible to identify the amount of electrolyte 90 not only in a range that includes a specific amount which is the lower limit of the amount of electrolyte 90, but also in a range that includes multiple other amounts.

[0040] (2) In the embodiment described above, as shown in Figure 1, the electrode group 50 is of the wound type in which the winding axis of the electrode group 50 is parallel to the vertical direction (Z-axis direction). However, it is not limited to this, and other types of electrode groups may be used as the electrode group of the battery 100 as long as the float 60 can move in conjunction with the movement of the liquid level of the electrolyte 90. Figure 6 shows a modified example of the electrode group of the battery 100 in this embodiment. As the electrode group, for example, as shown in Figure 6(A), a wound type electrode group 50A in which the winding axis is parallel to the direction perpendicular to the vertical direction (X-axis direction) may be used. As the electrode group, for example, as shown in Figure 6(B), a stacked type electrode group 50B may be used in which the positive electrode 10 and the negative electrode 20 are stacked alternately with a separator 30 sandwiched between them.

[0041] (3) In the embodiments described above, as shown in Figures 1, 4, and 6, the battery case 80 is a rectangular shape with a cross section perpendicular to the vertical direction (Z-axis direction). However, it is not limited to this, and the battery case 80 may have other shapes as long as the float 60 can move in conjunction with the movement of the electrolyte 90. For example, it may be cylindrical, or it may be a blade shape with a length in the X-axis direction several times that of the one shown in Figure 1, etc.

[0042] [summary] (1) As shown in Figures 1 to 4 and Figure 6, the battery 100 comprises electrode groups 50, 50A, and 50B, a battery case 80 that encloses the electrode groups 50, 50A, and 50B, an electrolyte 90 placed in the battery case 80 such that at least a portion of the electrode groups 50, 50A, and 50B are submerged, a float 60 that floats in the electrolyte 90 within the battery case 80 and moves with the movement of the electrolyte 90's surface, and sensors 70A, 70B to 70E that can detect the position of the float 60 from outside the battery case 80.

[0043] This allows the position of the float 60 to be determined by signals from sensors 70A, 70B, and 70E. The position of the float 60 indicates the liquid level of the electrolyte 90. As a result, the amount of electrolyte 90 can be accurately determined.

[0044] (2) As shown in Figures 1, 4 and 6, the battery case 80 may be a rectangular shape with a cross section perpendicular to the vertical direction. As shown in Figures 1 and 4, the electrode group 50 may be a long strip-shaped structure in which a positive electrode 10 and a negative electrode 20 are stacked with a separator 30 in between and wound up, so that the cross section perpendicular to the winding axis is oval, and the winding axis is parallel to the vertical direction, and the long side of the oval in the cross section perpendicular to the vertical direction is parallel to the long side of the rectangle of the battery case 80, so that it is enclosed in the battery case 80. As shown in Figure 4, the float 60 may move vertically through the gap between the rectangular corner of the battery case 80 and the R portion of the oval of the electrode group 50 in the cross section perpendicular to the vertical direction.

[0045] This allows the amount of electrolyte 90 to be accurately determined by utilizing the dead space within the battery case 80.

[0046] (3) As shown in Figure 5, sensors 70A, 70B to 70E may be configured to output a signal corresponding to the distance between the sensors 70A, 70B to 70E and the float 60. This makes it possible to appropriately identify increases or decreases in the amount of electrolyte 90.

[0047] (4) As shown in Figure 4(B), the sensor 70A may be positioned within a range that can detect the position of the float 60 when the amount of electrolyte 90 is at its lower limit. This makes it possible to appropriately identify that the amount of electrolyte 90 is at its lower limit.

[0048] (5) As shown in Figure 4(C), multiple sensors 70B to 70E may be provided, and each of the multiple sensors 70B to 70E may be positioned within a range that can detect different float 60 positions. This makes it possible to appropriately identify multiple amounts of electrolyte 90.

[0049] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0050] 10 Positive electrode, 11 Positive electrode current collector, 12 Positive electrode composite layer, 20 Negative electrode, 21 Negative electrode current collector, 22 Negative electrode composite layer, 30 Separator, 50, 50A, 50B Electrode group, 60 Float, 70A, 70B~70E Sensor, 80 Battery case, 81 Terminal, 90 Electrolyte, 100 Battery.

Claims

1. Electrode body and A case for enclosing the electrode body, An electrolyte solution placed in the case such that at least a portion of the electrode body is immersed, A float that floats in the electrolyte within the case and moves as the liquid level of the electrolyte changes, A secondary battery comprising a sensor capable of detecting the position of the float from outside the case.

2. The aforementioned case has a rectangular cross-section perpendicular to the vertical direction, The electrode body is formed by stacking a positive electrode plate and a negative electrode plate in a long strip shape with a separator in between, winding them together so that the cross-section perpendicular to the winding axis is oval, and the winding axis is parallel to the vertical direction, and the long side of the oval in the cross-section in the vertical direction is parallel to the long side of the rectangle of the case, and is enclosed in the case. The secondary battery according to claim 1, wherein the float moves in the vertical direction within the gap between the rectangular corner of the case and the oval R portion of the electrode body in a cross section perpendicular to the vertical direction.

3. The secondary battery according to claim 1, wherein the sensor is capable of outputting a signal corresponding to the distance between the sensor and the float.

4. The secondary battery according to any one of claims 1 to 3, wherein the sensor is provided within a range capable of detecting the position of the float when the amount of the electrolyte is at its lower limit.

5. Multiple sensors are provided, The secondary battery according to any one of claims 1 to 3, wherein the plurality of sensors are provided within a range in which each can detect the position of a different float.

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