Secondary batteries

Abstract

To suppress the transfer of heat to adjacent electrodes in the event of abnormal overheating of an electrode body. [Solution] A secondary battery comprising a plurality of electrode bodies and a case housing the plurality of electrode bodies, wherein the case contains an insulating material provided between the plurality of electrode bodies inside the case and a thermal expansion material provided between the lower surface of the electrode bodies and the bottom of the case.

Description

Technical Field

[0001] The present invention relates to a secondary battery.

Background Art

[0002] Patent Document 1 discloses a secondary battery having a structure in which an electrode body and a current collector terminal are joined by welding, and a thermal expansion material is disposed between the electrode body and the current collector terminal, and when abnormal heat generation occurs, the thermal expansion material thermally expands to break the joint between the electrode body and the current collector terminal. ]>

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a secondary battery including a plurality of electrode bodies is known. In a secondary battery including a plurality of electrode bodies, since the plurality of electrode bodies are arranged adjacent to each other inside the case, it is desirable to suppress heat transfer from any one of the electrode bodies to the adjacent electrode body when abnormal heat generation occurs.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery capable of suppressing heat transfer from an electrode body that abnormally generates heat to an adjacent electrode body.

Means for Solving the Problems

[0006] The present invention is a secondary battery including a plurality of electrode bodies and a case that houses the plurality of electrode bodies, and includes a heat insulating material provided between the plurality of electrode bodies inside the case, and a thermal expansion material provided between the lower surface of the electrode body and the bottom of the case.

Effects of the Invention

[0007] In this invention, it is possible to suppress the transfer of heat to adjacent electrode bodies in the event of abnormal heat generation in one electrode body. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing a secondary battery in an embodiment. [Figure 2] This diagram illustrates the case where the electrode body overheats abnormally, causing the thermal expansion material to expand. [Figure 3] This is a schematic diagram showing a secondary battery in a modified example. [Figure 4] This diagram illustrates a case where the electrode body of a modified example overheats abnormally, causing the thermal expansion material to expand. [Modes for carrying out the invention]

[0009] The secondary battery in the embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 is a schematic diagram showing a secondary battery in an embodiment. The secondary battery 1 comprises a plurality of electrode bodies 2, a case 3, an insulating material 4, and a plurality of thermal expansion materials 5. The secondary battery 1 in this embodiment includes two electrode bodies 2 and two thermal expansion materials 5.

[0011] Electrode body 2 comprises a positive electrode sheet, a negative electrode sheet, and a separator. Electrode body 2 has a laminate formed by stacking the positive electrode sheet, the negative electrode sheet, and the separator. For example, electrode body 2 is a wound body. In this case, electrode body 2 comprises a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator. Electrode body 2 is a flat electrode body formed by winding a laminate in which the positive electrode sheet and the negative electrode sheet are stacked with a separator in between. Before winding, the laminate is stacked in the thickness direction in the order of positive electrode sheet, separator, negative electrode sheet, and separator. In electrode body 2, the positive electrode sheet, the negative electrode sheet, and the separator are stacked so that their respective longitudinal directions coincide. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is a long positive electrode substrate. The positive electrode active material layer is provided on the positive electrode current collector. The positive electrode current collector includes an unpainted positive electrode side at one end in the width direction where the positive electrode active material layer is not formed and the positive electrode current collector is exposed. The unpainted positive electrode side constitutes the positive electrode current collector section when the positive electrode sheet is wound around it. A positive electrode tab is connected to the positive electrode current collector section. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is a long negative electrode substrate. The negative electrode active material layer is provided on the negative electrode current collector. The negative electrode current collector includes an unpainted negative electrode side at the other end in the width direction where the negative electrode active material layer is not formed and the negative electrode current collector is exposed. The unpainted negative electrode side constitutes the negative electrode current collector section when the negative electrode sheet is wound around it. A negative electrode tab is connected to the negative electrode current collector section.

[0012] The two electrode bodies 2 are composed of a first electrode body 11 and a second electrode body 12. The first electrode body 11 and the second electrode body 12 are constructed to have the same structure. The first electrode body 11 and the second electrode body 12 are wound bodies formed in a substantially rectangular parallelepiped shape. When there is no particular distinction between the first electrode body 11 and the second electrode body 12, they are simply referred to as electrode body 2.

[0013] Case 3 is a battery case that houses multiple electrode bodies 2. Inside Case 3, a first electrode body 11 and a second electrode body 12 are arranged and housed side by side in the X direction. Case 3 is a rectangular case formed in a roughly rectangular parallelepiped shape. The secondary battery 1 is a rectangular battery having multiple electrode bodies 2. Case 3 is a metal case. For example, Case 3 is made of aluminum or an aluminum alloy. Case 3 has a case body 31 and a lid 32. The case body 31 is a housing with an opening at the top. The lid 32 is joined to the case body 31 so as to close the opening of the case body 31. The case body 31 and the lid 32 are joined by welding. The inside of Case 3 is sealed. Inside Case 3, the electrode bodies 2, a heat insulating material 4, a thermal expansion material 5, and an electrolyte are housed.

[0014] The thermal insulation material 4 is installed inside the case 3 and suppresses heat transfer between the electrode bodies 2. The thermal insulation material 4 is an insulating material. The thermal insulation material 4 is made of a material that does not deform when it receives heat from the electrode bodies 2. In the secondary battery 1, the thermal insulation material 4 is placed between the multiple electrode bodies 2 in order to selectively expand the thermal expansion material 5 on the side of the electrode body 2 that has overheated abnormally.

[0015] The thermal insulation material 4 is a flat plate-shaped member placed between adjacent electrode bodies 2. The thermal insulation material 4 is provided between the first electrode body 11 and the second electrode body 12, which are adjacent in the X direction. The first electrode body 11 and the second electrode body 12 are in contact with the thermal insulation material 4. One side of the first electrode body 11 in the X direction is in overall surface contact with the thermal insulation material 4. The other side of the second electrode body 12 in the X direction is in overall surface contact with the thermal insulation material 4. The thermal insulation material 4 extends upward from the bottom 33 of the case body 31. As shown in Figure 1, in the Z direction, the thermal insulation material 4 extends to the same height as the top surface 2a of the electrode body 2. The thermal insulation material 4 is attached to the case body 31. The thermal insulation material 4 is attached to the side walls 34 and the bottom 33 of the case body 31. Inside the case 3, the thermal insulation material 4 divides the case into a first housing chamber where the first electrode body 11 is housed and a second housing chamber where the second electrode body 12 is housed. Figure 1 shows the normal state when electrode body 2 is not overheating.

[0016] The thermal expansion material 5 is positioned between the electrode body 2 and the case 3 and is formed to expand and contract. The thermal expansion material 5 can expand in response to the heat generated by the electrode body 2. The thermal expansion material 5 is an insulating material and is made of, for example, resin. The mounting position of the thermal expansion material 5 is the bottom 33 of the case body 31.

[0017] The thermal expansion material 5 is provided between the lower surface 2b of the electrode body 2 and the inner surface 33a of the bottom 33 of the case body 31. As shown in Figure 1, under normal conditions, the thermal expansion material 5 is in contact with the lower surface 2b of the electrode body 2 and also in contact with the inner surface 33a of the bottom 33. The thermal expansion material 5 is sandwiched between the inner surface 33a and the lower surface 2b. An insulating film is provided between the inner surface of the side wall 34 of the case body 31 and the side surface of the electrode body 2.

[0018] The two thermal expansion materials 5 are composed of a first thermal expansion material 21 and a second thermal expansion material 22. The first thermal expansion material 21 and the second thermal expansion material 22 are constructed to have the same structure. The first thermal expansion material 21 and the second thermal expansion material 22 are separated by an insulating material 4. The first thermal expansion material 21 is a flat plate-shaped member placed in the first housing chamber and in contact with the lower surface 2b of the first electrode body 11. In the X and Y directions, the first thermal expansion material 21 is in overall contact with the lower surface 2b of the first electrode body 11. The second thermal expansion material 22 is a flat plate-shaped member placed in the second housing chamber and in contact with the lower surface 2b of the second electrode body 12. In the X and Y directions, the second thermal expansion material 22 is in overall contact with the lower surface 2b of the second electrode body 12.

[0019] When the first electrode body 11 overheats abnormally from the state shown in Figure 1, the state transitions to the state shown in Figure 2. As shown in Figure 2, when any of the electrode bodies 2 overheats abnormally, the thermal expansion material 5 on the side with the abnormal heat expands and displaces the position of the electrode body 2 in the abnormal heat state. This reduces the thermal contact area between the multiple electrode bodies 2, and also reduces the change in the external shape of the case 3.

[0020] As shown in FIG. 2, when the first electrode body 11 generates abnormal heat, the first thermal expansion material 21 expands, and the first thermal expansion material 21 pushes out the first electrode body 11 upward. The first electrode body 11 pushed upward is displaced relatively upward with respect to the heat insulating material 4 and the second electrode body 12. The amount of upward displacement can be absorbed by the positive electrode tab and the negative electrode tab connected to the first electrode body 11. Then, the upper surface 2a of the first electrode body 11 is displaced upward from the heat insulating material 4, and the contact area with the heat insulating material 4 decreases. That is, the thermally contacting area between the abnormally heating first electrode body 11 and the adjacent second electrode body 12 decreases. Thereby, in the second electrode body 12 in a normal state, the heat reception from the abnormally heating first electrode body 11 decreases.

[0021] As described above, according to the embodiment, in the secondary battery 1 having a plurality of electrode bodies 2, when any one of the electrode bodies 2 generates abnormal heat, the thermal expansion material 5 on the side of the abnormally heating electrode body 2 expands, whereby the thermally contacting area between the electrode bodies 2 can be decreased. Thereby, in the electrode body 2 in a normal state, the heat reception from the abnormally heating electrode body 2 decreases.

[0022] Note that the number of the plurality of electrode bodies 2 is not limited to two. The plurality of electrode bodies 2 may be two or more.

[0023] Further, the insulating film provided between the inner surface of the side wall portion 34 of the case body 31 and the side surface of the electrode body 2 may be formed so as to entirely cover the inner surface of the side wall portion 34, or may be formed so as to entirely cover the side surface of the electrode body 2. For example, it may have a first insulating film that entirely covers the side surface of the first electrode body 11 and a second insulating film that entirely covers the side surface of the second electrode body 12.

[0024] Further, the plurality of electrode bodies 2 are not limited to a configuration in which each is connected to a positive electrode tab and a negative electrode tab. The plurality of electrode bodies 2 may be electrically connected in series, or may be electrically connected in parallel.

[0025] Furthermore, the electrode body 2 is not limited to an electrode body composed of a wound body. The electrode body 2 may be a laminate that is not wound. For example, the electrode body 2 may be a laminate with a substantially rectangular parallelepiped shape in which a positive electrode sheet, a negative electrode sheet, and a separator are stacked in the X direction. Alternatively, the electrode body 2 may be a laminate with a substantially rectangular parallelepiped shape in which a positive electrode sheet, a negative electrode sheet, and a separator are stacked in the Y direction. Alternatively, the electrode body 2 may be a laminate with a substantially rectangular parallelepiped shape in which a positive electrode sheet, a negative electrode sheet, and a separator are stacked in the Z direction.

[0026] Furthermore, the structure of the electrode body 2 is not limited to a roughly rectangular parallelepiped shape. For example, as shown in Figure 3, the secondary battery 1 may have multiple L-shaped electrode bodies 2. In the modified secondary battery 1, the electrode body 2 is formed in an L-shape. This modified example does not include the insulating material 4. Inside the case 3, the L-shaped first electrode body 11 and the L-shaped second electrode body 12 are arranged alternately. When the secondary battery 1 is viewed from the Y direction, the first electrode body 11 has an L-shape that is inverted vertically, and the second electrode body 12 has an L-shape that is inverted horizontally. The first electrode body 11 is entirely covered with the first insulating film. The second electrode body 12 is entirely covered with the second insulating film. The mounting position of the thermal expansion material 5 is the central part of the L-shaped electrode body 2.

[0027] When any of the electrode bodies 2 overheats abnormally from the state shown in Figure 3, the system transitions to the state shown in Figure 4. As shown in Figure 4, when any of the electrode bodies 2 overheats abnormally, the thermal expansion material 5 located in the central part expands, displacing the position of the first electrode body 11 upwards, thereby reducing the contact area between the multiple electrode bodies 2. In this modified example, although the change in the external shape of the case 3 is larger compared to the embodiment, the responsiveness is improved compared to the embodiment. [Explanation of Symbols]

[0028] 1 Secondary battery 2 Electrode body 3 cases 4. Insulation 5 Thermal expansion material 11 First electrode body 12 Second electrode body 21 1st thermal expansion material 22 Second thermal expansion material 31 Case body 32 Lid 33 Bottom 33a Inner surface 34 Side wall section

Claims

1. Multiple electrode bodies, A case for housing the multiple electrode bodies, A secondary battery equipped with, An insulating material is provided between the plurality of electrode bodies inside the case, A thermal expansion material is provided between the lower surface of the electrode body and the bottom of the case. A secondary battery characterized by having the following features.

2. The thermal expansion material, when it expands due to heat, pushes the lower surface of the electrode body upward, thereby displacing the position of the electrode body upward. The secondary battery according to claim 1.

Images