Battery module

Abstract

This invention provides a technology for suppressing thermal runaway of the electrode stack in a battery module in which multiple bipolar electrode sheets are stacked. [Solution] The battery module comprises an electrode stack and a pouch-type module case that houses the electrode stack. The electrode stack includes a plurality of stacked bipolar electrode sheets, a resin outer frame provided on the outer periphery of the plurality of electrode sheets and integrally holding the plurality of electrode sheets, and an electrolyte sealed between the plurality of electrode sheets by the outer frame. Each of the plurality of electrode sheets has at least one through hole formed on its outer periphery.

Description

Technical Field

[0001] The technology disclosed in the present specification relates to a battery module.

Background Art

[0002] Patent Document 1 describes a battery module. This battery module includes an electrode laminate and a module case that accommodates the electrode laminate. The electrode laminate has a plurality of stacked electrode sheets. A plurality of through holes are formed in each of the plurality of electrode sheets.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In a battery module having an electrode laminate in which a plurality of bipolar electrode sheets are stacked, the plurality of electrode sheets are arranged in close contact with each other. Therefore, for example, when an internal short circuit occurs between some of the electrode sheets and abnormal heat generation occurs in those electrode sheets, the heat easily transfers to the adjacent electrode sheets, and as a result, the abnormal heat generation may spread to the entire electrode laminate. In the present specification, such a phenomenon is referred to as thermal runaway of the electrode laminate.

[0005] In view of the above, the present specification provides a technique for suppressing thermal runaway of an electrode laminate in a battery module in which a plurality of bipolar electrode sheets are stacked.

Means for Solving the Problems

[0006] The technology disclosed herein is embodied in a battery module. This battery module comprises an electrode stack and a pouch-type module case that houses the electrode stack. The electrode stack has a plurality of stacked bipolar electrode sheets, a resin outer frame provided on the outer periphery of the plurality of electrode sheets and holding the plurality of electrode sheets together, and an electrolyte sealed between the plurality of electrode sheets by the outer frame. Each of the plurality of electrode sheets has at least one through-hole formed on its outer periphery.

[0007] In the battery module described above, if, for example, an internal short circuit occurs between some electrode sheets, and abnormal heat generation occurs in those electrode sheets, the electrolyte filled between those electrode sheets is rapidly heated. A portion of the heated electrolyte evaporates, becoming high-temperature, high-pressure vapor that melts the outer frame and is ejected to the outside of the electrode stack. At this time, since through holes are formed in the outer circumference of the electrode sheets, the high-temperature, high-pressure vapor that melted the outer frame flows through these through holes into the spaces between adjacent electrode sheets. As a result, the spacing between adjacent electrode sheets increases, suppressing heat transfer from the area where abnormal heat generation occurred. This prevents thermal runaway of the electrode stack. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing the configuration of the battery module 2 in the embodiment. [Figure 2] This is a cross-sectional view of the battery module 2 in plane II-II in Figure 1. [Figure 3] This is a cross-sectional view showing the internal state of the battery module 2 when an internal short circuit occurs between some of the electrode sheets of the battery module 2 in the embodiment, causing abnormal heat generation in those electrode sheets. [Modes for carrying out the invention]

[0009] An embodiment of the battery module 2 will be described with reference to the drawings. The battery module 2 in this embodiment is a lithium-ion battery, although it is not particularly limited. The battery module 2 may be used in a battery pack mounted on a vehicle. In that case, the battery pack is a power source that supplies power to the vehicle's motor and may comprise one or more battery modules 2. The vehicle on which the battery pack is mounted may be an electric vehicle in which the wheels are driven by a motor. Examples of electric vehicles in this context include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and so on.

[0010] As shown in Figure 1, the battery module 2 comprises an electrode stack 4 and a module case 42 that houses the electrode stack 4. The module case 42 is a pouch-type case. The electrode stack 4 is composed of a plurality of lithium-ion battery cells 10 (hereinafter simply referred to as cells 10) stacked along the z-direction. Each of the 10 cells is sealed with an electrolyte. The electrolyte mainly consists of lithium salts, organic solvents, and additives. The specific composition of the electrolyte is not particularly limited.

[0011] Multiple cells 10 have a substantially flat shape extending in the x and y directions and are stacked in the z direction. As shown in Figure 1, each cell 10 has a first electrode foil 12, a positive electrode layer 14, a separator 16, a negative electrode layer 18, and a second electrode foil 20. These are stacked from top to bottom in the order of the first electrode foil 12, positive electrode layer 14, separator 16, negative electrode layer 18, and second electrode foil 20.

[0012] The first electrode foil 12 is made of a conductive material. An example of the conductive material constituting the first electrode foil 12 is aluminum.

[0013] The positive electrode layer 14 is in contact with the lower surface of the first electrode foil 12. The positive electrode layer 14 is a layer containing a positive electrode active material. Examples of positive electrode active materials include lithium-containing materials such as Li, LiCoO2, and LiNiO2. The positive electrode active material may be composed of one type of material or multiple types of materials. The positive electrode layer 14 is also immersed in an electrolyte solution.

[0014] The separator 16 is in contact with the lower surface of the positive electrode layer 14. The separator 16 is made of a material that allows the charge carrier (in this case, lithium ions) to pass through. Examples of materials that make up the separator 16 include polypropylene and polyethylene. The electrolyte permeates the separator 16.

[0015] The negative electrode layer 18 is in contact with the lower surface of the separator 16. The negative electrode layer 18 is a layer containing a negative electrode active material. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon. The negative electrode active material may be composed of one type of material or multiple types of materials. The negative electrode layer 18 is also immersed in an electrolyte solution.

[0016] The second electrode foil 20 is in contact with the lower surface of the negative electrode layer 18. The second electrode foil 20 is in contact with the upper surface of the first electrode foil 12 of the adjacent cell 10. The second electrode foil 20 is made of a conductive material. Copper is an example of the conductive material that makes up the second electrode foil 20.

[0017] The second electrode foil 20 is bonded to the first electrode foil 12 of an adjacent cell 10. That is, the first electrode foil 12 and the second electrode foil 20 are composed of a single integrated electrode foil material 11. This electrode foil material 11 has the positive electrode layer 14 and negative electrode layer 18 described above on its front and back sides, and functions as a bipolar electrode sheet (hereinafter referred to as electrode sheet 11).

[0018] As shown in Figures 1 and 2, multiple through holes 11b are formed in the outer peripheral portion 11a of the electrode sheet 11. The multiple through holes 11b penetrate the first electrode foil 12 and the second electrode foil 20 in the z direction. The number, size, and arrangement of the multiple through holes 11b are not particularly limited. For example, in this embodiment, the electrode sheet 11 has three through holes 11b formed in each of a pair of short sides of the outer peripheral portion 11a that are opposite in the y direction. Also, three through holes 11b are formed in each of a pair of long sides of the outer peripheral portion 11a that are opposite in the x direction. Note that the electrode sheet 11 placed at the top and the electrode sheet 11 placed at the bottom of the electrode stack 4 do not have through holes 11b formed in them. However, as a modification, one or more through holes 11b may be formed in the electrode sheet 11 placed at the top or bottom of the electrode stack 4.

[0019] In the following, when viewing the battery module 2 in a plan view along the z-direction, the side closer to the outer edge 42a of the module case 42 (i.e., the side moving from the center of the battery module 2 toward the outer edge 42a) is referred to as the outer edge side.

[0020] In the x and y directions, the negative electrode layer 18 is larger than the positive electrode layer 14, the separator 16 is larger than the negative electrode layer 18, and the electrode sheet 11 (first electrode foil 12 and second electrode foil 20) is larger than the separator 16. Therefore, in the x and y directions, the outer edge 11c of the electrode sheet 11 is located further outward than the outer edge 16a of the separator 16. Also, in the x and y directions, the outer edge 11c of the electrode sheet 11 is located further outward than the outer edge 18a of the negative electrode layer 18. Furthermore, in the x and y directions, the outer edge 18a of the negative electrode layer 18 is located further outward than the outer edge 14a of the positive electrode layer 14.

[0021] The cell 10 has a spacer 26. The spacer 26 has a frame shape and extends along the outer peripheral portion 11a of the electrode sheet 11. The spacer 26 is made of a resin material. The spacer 26 is disposed between the first electrode foil 12 and the separator 16. The spacer 26 is in contact with the upper surface of the separator 16. In the x-direction and the y-direction, the spacer 26 is disposed on the outer peripheral side of the outer peripheral edge 14a of the positive electrode layer 14. A gap is provided between the spacer 26 and the positive electrode layer 14. The gap is filled with an electrolytic solution. In the y-direction, the outer peripheral edge 26a of the spacer 26 is disposed on the outer peripheral side of the outer peripheral edge 16a of the separator 16. That is, when viewed along the z-direction, the outer peripheral edge 26a of the spacer 26 extends from a position overlapping the negative electrode layer 18 to the outer peripheral side beyond the outer peripheral edge 16a of the separator 16. At the position overlapping the negative electrode layer 18, the spacer 26 is sandwiched between the lower surface of the first electrode foil 12 and the upper surface of the separator 16. The spacer 26 and the separator 16 are displaced downward on the outer peripheral side of the negative electrode layer 18. For this reason, at the outer peripheral portion of the spacer 26, a gap is provided between the upper surface of the spacer 26 and the lower surface of the first electrode foil 12. This gap is also filled with the electrolytic solution.

[0022] The electrode laminate 4 includes an outer frame 23. The outer frame 23 is made of a resin material. The outer frame 23 constitutes the outer peripheral edge of the electrode laminate 4 (that is, the plurality of cells 10). The outer frame 23 is provided on the outer peripheral portions 11a of the plurality of electrode sheets 11, and holds the plurality of electrode sheets 11 integrally. The aforementioned electrolytic solution is sealed between the plurality of electrode sheets 11 by the outer frame 23. The outer frame 23 has a first portion 21 that seals the space between the first electrode foil 12 and the spacer 26, and a second portion 22 that seals the space between the spacer 26 and the second electrode foil 20.

[0023] The first portion 21 is sandwiched between the lower surface of the first electrode foil 12 and the upper surface of the spacer 26. In the x-direction and the y-direction, the first portion 21 is disposed on the outer peripheral side relative to the outer peripheral edge 14a of the positive electrode layer 14 and the outer peripheral edge 18a of the negative electrode layer 18. When viewed along the z-direction, the spacer 26 extends from a position overlapping the negative electrode layer 18 to a position overlapping the first portion 21. At the position overlapping the first portion 21, the spacer 26 is sandwiched between the lower surface of the first portion 21, the upper surface of the separator 16, and the upper surface of the second portion 22.

[0024] The second portion 22 is sandwiched between the upper surface of the second electrode foil 20, the lower surface of the separator 16, and the lower surface of the spacer 26. In the x-direction and the y-direction, the second portion 22 is disposed on the outer peripheral side of the cell 10 relative to the outer peripheral edge 18a of the negative electrode layer 18. A gap is provided between the second portion 22 and the negative electrode layer 18. The gap is also filled with an electrolytic solution.

[0025] The module case 42 has a first film 44 and a second film 46. A part of the outer peripheral edge 44a of the first film 44 and a part of the outer peripheral edge 46a of the second film 46 are welded.

[0026] The first film 44 has a current collector plate 48 and a first film material 50. The current collector plate 48 is made of a conductive material. Examples of the conductive material of the current collector plate 48 include aluminum, copper, and the like. The current collector plate 48 is electrically connected to the first electrode foil 12 of the cell 10 located at the uppermost part of the electrode laminate 4 via the second electrode foil 20. The first film material 50 is composed of a film (here, an aluminum laminate film). The first film material 50 is insulated from the current collector plate 48.

[0027] The second film 46 has a current collector plate 52 and a second film material 54. The current collector plate 52 is made of a conductive material. Examples of conductive materials for the current collector plate 52 include aluminum and copper. The current collector plate 52 is electrically connected to the second electrode foil 20 of the cell 10 located at the bottom of the electrode laminate 4 via the first electrode foil 12. The second film material 54 is made of a film (in this case, an aluminum laminate film). The second film material 54 is insulated from the current collector plate 52.

[0028] In the battery module 2, if an internal short circuit occurs between some electrode sheets 11, abnormal heat generation occurs in those electrode sheets 11. Subsequently, the electrolyte filled between the electrode sheets 11 is rapidly heated. As shown in Figure 3, a portion of the heated electrolyte evaporates, becoming high-temperature, high-pressure vapor that melts the outer frame 23 and is ejected to the outside of the electrode stack 4. The electrolyte ejected from the electrode stack 4 destroys weak points in the module case 42 (for example, the welded portion between the first film 44 and the second film 46) and is ejected to the outside of the module case 42. At this time, since multiple through holes 11b are formed in the outer peripheral portion 11a of the electrode sheet 11, the high-temperature, high-pressure vapor that melted the outer frame 23 also flows through the multiple through holes 11b into the spaces between adjacent electrode sheets 11. As a result, the distance between adjacent electrode sheets 11 increases, suppressing heat transfer from the area where abnormal heat generation occurred. This suppresses thermal runaway of the electrode stack 4. [Explanation of Symbols]

[0029] 2: Battery module, 4: Electrode stack, 10: Cell, 11: Electrode sheet, 11a: Outer periphery, 11b: Through hole, 12: First electrode foil, 14: Positive electrode layer, 16: Separator, 18: Negative electrode layer, 20: Second electrode foil, 21: First part, 22: Second part, 23: Sealing member, 26: Spacer, 42: Module case, 44: First film, 46: Second film, 48: Current collector plate, 50: First film material, 52: Current collector plate, 54: Second film material

Claims

[Claim 1] It is a battery module, Electrode stack and, A pouch-type module case for housing the electrode stack, Equipped with, The electrode stack is Multiple stacked bipolar electrode sheets, A resin outer frame is provided on the outer periphery of the plurality of electrode sheets and integrally holds the plurality of electrode sheets, The system comprises an electrolyte sealed between the plurality of electrode sheets by the outer frame, Each of the plurality of electrode sheets has at least one through hole formed in its outer peripheral portion. Battery module.

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