POWER STORAGE DEVICE

A power storage device includes: a plurality of power storage cells; and a case having an inner space in which the plurality of power storage cells are accommodated, and an outer surface that defines the inner space. The outer surface of the case includes a pleated portion that is capable of becoming elongated in response to an increase in pressure of the inner space. The pleated portion is formed on substantially an entire periphery of the case along a peripheral direction of the case.

This nonprovisional application is based on Japanese Patent Application No. 2021-156474 filed on Sep. 27, 2021, with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present technology relates to a power storage device.

Description of the Background Art

Japanese Patent Laying-Open No. 2009-146812 illustrates that a pleated portion is provided on a side surface of a battery case on the side on which a safety valve is provided and the pleated portion becomes elongated to allow gas to flow to the safety valve side when an internal pressure of the battery case is increased, thereby improving gas discharging efficiency.

When a temperature in the case of the power storage device is increased, it may be required to increase an amount of heat radiation from a surface of the case in order to suppress further temperature increase. In view of the above, the conventional power storage device does not necessarily have a sufficient configuration.

SUMMARY OF THE INVENTION

An object of the present technology is to provide a power storage device to suppress an increase in temperature in a case of the power storage device.

An power storage device according to the present technology includes: a plurality of power storage cells; and a case having an inner space in which the plurality of power storage cells are accommodated, and an outer surface that defines the inner space. The outer surface of the case includes a pleated portion that is capable of becoming elongated in response to an increase in pressure of the inner space. The pleated portion is formed on substantially an entire periphery of the case along a peripheral direction of the case.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present technology will be described. It should be noted that the same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly.

It should be noted that in the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment.

It should be noted that in the present specification, the terms “comprise”, “include”, and “have” are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included.

Also, in the present specification, when geometric terms and terms representing positional/directional relations are used, for example, when terms such as “parallel”, “orthogonal”, “obliquely at 45°”, “coaxial”, and “along” are used, these terms permit manufacturing errors or slight fluctuations. In the present specification, when terms representing relative positional relations such as “upper side” and “lower side” are used, each of these terms is used to indicate a relative positional relation in one state, and the relative positional relation may be reversed or turned at any angle in accordance with an installation direction of each mechanism (for example, the entire mechanism is reversed upside down).

In the present specification, the term “battery” is not limited to a lithium ion battery, and may include another battery such as a nickel-metal hydride battery.

In the present specification, when the terms “power storage cell” or “power storage module” are used, the “power storage cell” or the “power storage module” is not limited to a battery cell or a battery module, and may include a capacitor cell or a capacitor module.

FIG.1is a perspective view showing an external appearance of a battery pack1(power storage device). As shown inFIG.1, battery pack1has a case100. Case100has: a main body member110(first member) including a first flange111; and a cover member120(second member) including a second flange121joined to first flange111. A plurality of battery cells are accommodated in a space formed inside main body member110and cover member120. The plurality of battery cells may be stacked in a direction of arrow DR1or in a direction of arrow DR2.

FIG.2is a diagram showing a battery cell200accommodated in case100. As shown inFIG.2, battery cell200is formed to have a substantially rectangular parallelepiped shape with a flat surface. It should be noted that the battery cell of the present technology is not limited to such a battery cell having a prismatic shape and includes a different type of battery cell such as a battery cell having a substantially cylindrical shape.

Battery cell200includes an electrode terminal210and a battery case220. Electrode terminal210includes a positive electrode terminal211and a negative electrode terminal212. Positive electrode terminal211and negative electrode terminal212are arranged side by side in an X axis direction. Electrode terminal210is provided on the upper surface of battery case220. Each of the upper surface and bottom surface of battery case220has a substantially rectangular shape in which the X axis direction corresponds to a long side direction and a Y axis direction corresponds to a short side direction. An electrode assembly and an electrolyte solution are accommodated in battery case220. Battery cells200are stacked in the Y axis direction.

FIG.3is a diagram schematically showing a portion corresponding to an A-A cross section of case100shown inFIG.1.FIG.4is a diagram schematically showing a state in which case100is expanded from the state shown inFIG.3.

As shown inFIG.3, case100has an inner space10in which the plurality of battery cells200are accommodated, and an outer surface20that defines inner space10.

When a battery cell200in case100exhibits thermal runaway, the temperature and pressure of inner space10are increased. In battery pack1according to the present embodiment, outer surface20of case100includes a pleated portion21that can become elongated in response to an increase in pressure of inner space10. Pleated portion21is formed on substantially an entire periphery of case100along a peripheral direction of case100(the direction of arrow DR1and the direction of arrow DR2). The expression “substantially the entire periphery” herein is not necessarily limited to the case where pleated portion21is continuously formed on the entire periphery in the peripheral direction, and may include a case where pleated portion21is discontinuously formed on the entire periphery in the peripheral direction, and a case where pleated portion21is formed on almost the entire periphery in the peripheral direction but is not formed partially thereon.

When the pressure of inner space10is increased to become more than or equal to a predetermined value, pleated portion21becomes elongated in a direction (direction of arrow DR3) intersecting the peripheral direction of case100as shown inFIG.4. Thus, the volume of inner space10and the surface area of outer surface20are increased. With the increased volume of inner space10, an increase in internal pressure is reduced. Further, the increased surface area of outer surface20leads to improved efficiency of heat radiation from case100. As a result, damage of battery pack1is suppressed.

As an example, a ratio of increase of inner space10due to the elongation of pleated portion21is about more than or equal to 0.1% and less than or equal to 100%, but the scope of the present technology is not limited thereto.

As an example, the ratio of increase of the surface area of case100due to the elongation of pleated portion21is about more than or equal to 0.1% and less than or equal to 100%, but the scope of the present technology is not limited thereto.FIG.5is a diagram schematically showing pleated portion21provided in case100.FIG.6is a diagram showing a state in which pleated portion21is elongated from the state shown inFIG.5.

In the example ofFIGS.5and6, pleated portion21is formed in cover member120facing electrode terminals210. Pleated portion21is formed to extend in a direction (direction of arrow DR3) intersecting the extending direction of each of first flange111and second flange121when pleated portion21is in an non-elongated state. In the example ofFIGS.5and6, pleated portion21is formed at a position adjacent to second flange121, but the scope of the present technology is not limited thereto.

Case100includes a safety valve30that brings inner space10into communication with outside of case100when the pressure of inner space10becomes more than or equal to a predetermined operation pressure (first pressure: about 0.2 MPa, for example). Pleated portion21is formed to become elongated when the pressure of inner space10becomes more than or equal to a predetermined operation pressure (second pressure: 0.18 MPa, for example) smaller than the operation pressure (first pressure) of safety valve30. When pleated portion21is operated by an increased pressure of inner space10due to thermal runaway of a battery cell200, upper surface122of cover member120is moved (raised) in a direction of separating away from battery cell200along the direction of arrow DR3as shown inFIG.6. Inner space10is increased according to an amount of elongation of pleated portion21. The surface area of outer surface20is also increased according to the amount of elongation of pleated portion21.

By setting the operation pressure (second pressure) of pleated portion21to be smaller than the operation pressure (first pressure) of safety valve30, pleated portion21can be operated to increase the volume of inner space10and the surface area of outer surface20before safety valve30is operated to discharge the gas inside case100to the outside of case100, thereby suppressing an increase in temperature of battery pack1. When the pressure of inner space10continues to be increased even after the operation of pleated portion21and reaches the operation pressure of safety valve30, safety valve30is opened to discharge the gas inside inner space10to the outside of case100.

FIG.7is a cross sectional view showing a detail of pleated portion21. As shown inFIG.7, pleated portion21is formed to have certain pitch (P), depth (D), and thickness (T), but these can be changed as appropriate. The pitch (P) of pleated portion21is, for example, about ¼ of the thickness of cover member120. The depth of pleated portion21is, for example, about ½ of the protruding width of each of first flange111and second flange121. The thickness (T) of pleated portion21is, for example, substantially the same as the thickness of cover member120. The length of pleated portion21(size in the upward/downward direction inFIG.7) can also be changed as appropriate.

FIG.8is a diagram schematically showing a modification of pleated portion21. In the example ofFIG.8, as with the example ofFIGS.5and6, pleated portion21is formed in cover member120facing electrode terminals210. On the other hand, in the example shown inFIG.8, unlike the example shown inFIGS.5and6, pleated portion21is formed to extend in a direction (the direction of arrow DR1and the direction of arrow DR2) along the extending direction of each of first flange111and second flange121when pleated portion21is in a non-elongated state.

In the above-described examples, it has been illustratively described that pleated portion21is formed in cover member120; however, the scope of the present technology is not limited thereto, and pleated portion21may be formed in main body member110.

Although the embodiments of the present invention have been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.