Energy storage element

Abstract

To provide a power storage element that can improve energy density.SOLUTION: A power storage element includes a container and an electrode body 700 housed in the container, a current collector 500 disposed between the electrode body 700 and the lid body of the container in the Z-axis direction, and an electrode terminal fixed to the lid body, and the current collector 500 includes a terminal connection unit 510 connected to an electrode terminal, and an electrode connection unit 520 connected to the electrode body 700. The terminal connection unit 510 and the electrode connection unit 520 are arranged side by side in the X-axis direction intersecting the Z-axis direction, and the thickness D2 of the electrode connection unit 520 is smaller than the thickness D1 of the terminal connection unit 510.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an energy storage device including a container and an electrode assembly housed in the container. [Background technology]

[0002] Patent Document 1 discloses an electricity storage device including a case and an electrode assembly housed in the case. In this electricity storage device, a group of tabs of the electrode assembly is connected to a conductive member fixed to a cover member of the case. The conductive member includes a fixing piece fixed to the inner surface of the cover member and a connecting piece that intersects the fixing piece and protrudes toward the electrode assembly. The group of tabs is connected to the connecting piece by welding, and then the connecting piece is folded. In other words, the tabs and the connecting piece are folded, and in this state the electrode assembly is housed in the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 152372 Summary of the Invention [Problem to be solved by the invention]

[0004] In an energy storage element including a container and an electrode assembly housed in the container, when a current collector fixed to the wall of the container is connected to the electrode assembly by welding or the like, a space is required between the electrode assembly and the wall to accommodate the connection between the current collector and the electrode assembly. This causes pressure on the space inside the container for housing the electrode assembly. As a result, it becomes difficult to improve the energy density of the energy storage element. This problem is particularly pronounced when, as in the above-mentioned conventional energy storage device, the portion of the current collector (the conductive member in Patent Document 1) connected to the electrode assembly is folded and arranged inside the container.

[0005] In consideration of the above problems, an object of the present invention is to provide an energy storage element capable of improving energy density. [Means for solving the problem]

[0006] An energy storage element according to one embodiment of the present invention is an energy storage element comprising a container and an electrode body housed in the container, and comprising a current collector arranged between the electrode body and a wall of the container in a first direction, and an electrode terminal fixed to the wall, the current collector having a terminal connection portion connected to the electrode terminal and an electrode connection portion connected to the electrode body, the terminal connection portion and the electrode connection portion being arranged side by side in a second direction intersecting the first direction, and the thickness of the electrode connection portion being smaller than the thickness of the terminal connection portion. [Effects of the Invention]

[0007] According to the energy storage device of the present invention, the energy density can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing the appearance of an energy storage device according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the components of the energy storage device according to the embodiment. [Figure 3] FIG. 3 is a perspective view showing the appearance of the current collector according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the current collector taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing a VV cross section of the current collector in FIG. [Figure 6] FIG. 6 is a cross-sectional view showing the current collector taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a partially enlarged view showing an intermediate portion of a current collector according to an embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing a cross section taken along line VIII-VIII of the middle part in FIG. [Figure 9] FIG. 9 is a cross-sectional view showing a cross section taken along line IX-IX of the intermediate portion in FIG. [Figure 10]FIG. 10 is a perspective view showing the appearance of a current collector according to the first modification of the embodiment. [Figure 11] FIG. 11 is a perspective view showing the appearance of a current collector according to the second modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An energy storage element according to one embodiment of the present invention is an energy storage element comprising a container and an electrode body housed in the container, and comprising a current collector arranged between the electrode body and a wall of the container in a first direction, and an electrode terminal fixed to the wall, the current collector having a terminal connection portion connected to the electrode terminal and an electrode connection portion connected to the electrode body, the terminal connection portion and the electrode connection portion being arranged side by side in a second direction intersecting the first direction, and the thickness of the electrode connection portion being smaller than the thickness of the terminal connection portion.

[0010] According to this configuration, since the electrode connection portion is formed thinner than the terminal connection portion, for example, the tab portion of the electrode body joined to the electrode connection portion can be positioned closer to the wall of the container. In other words, in the energy storage element of this aspect, the relatively thick terminal connection portion can suppress deformation of the connection portion between the current collector and the electrode terminal. The relatively thin electrode connection portion can increase the volume occupancy of the electrode body within the container. Therefore, the energy storage element of this aspect can improve energy density.

[0011] The width of the electrode connection portion in a third direction intersecting the first direction and the second direction may be larger than the width of the terminal connection portion in the third direction.

[0012] According to this configuration, in the conductive path formed in the current collector along the second direction, the cross-sectional area of ​​the electrode connection portion is prevented from being smaller than the cross-sectional area of ​​the terminal connection portion, thereby reducing the possibility that the electrode connection portion will interfere with conduction during charging and discharging of the energy storage element, even if the electrode connection portion is formed relatively thin in order to improve energy density, for example.

[0013] The area of ​​a cross section of the electrode connection portion perpendicular to the second direction may be equal to or larger than the area of ​​a cross section of the terminal connection portion perpendicular to the second direction.

[0014] According to this configuration, the resistance value of the electrode connection portion in the conductive path inside the energy storage element 10 is equal to or less than the resistance value of the terminal connection portion. The melting resistance of the electrode connection portion is equal to or greater than the melting resistance of the terminal connection portion. This can improve the reliability of the energy storage element, for example, by improving the energy density.

[0015] The current collector may further have an intermediate portion connecting the terminal connection portion and the electrode connection portion, and the intermediate portion may be formed so that its thickness decreases and its width in the third direction increases as it approaches the electrode connection portion from the terminal connection portion.

[0016] According to this configuration, a portion where the cross-sectional shape changes so that the cross-sectional area is approximately constant is provided at the portion where the terminal connection portion and the electrode connection portion are connected. As a result, a portion where the cross-sectional area suddenly decreases is not formed at the boundary between the terminal connection portion and the electrode connection portion. Therefore, problems such as a decrease in charge / discharge efficiency are less likely to occur. This contributes to improving the reliability of the energy storage element, for example, by improving the energy density.

[0017] An end portion of the electrode connection portion in a third direction intersecting the first direction and the second direction may be bent toward the electrode body.

[0018] According to this configuration, the electrode connection portion has a folded end, which prevents a reduction in cross-sectional area due to its relatively thinness, and allows the width in the third direction to be approximately the same as that of the terminal connection portion. Therefore, for example, it is possible to reuse an existing gasket as the gasket disposed between the current collector and the wall portion. This, for example, reduces the manufacturing cost of an energy storage element with improved energy density.

[0019] The surface of the current collector facing the wall portion may be flat, and the surface of the current collector facing the electrode body may have a step formed thereon due to the difference in thickness between the terminal connection portion and the electrode connection portion.

[0020] With this configuration, almost all of the space obtained by thinning the electrode connection part can be used as space to accommodate the electrode assembly, which means that the effect of improving energy density by thinning the electrode connection part is maximized.

[0021] The present invention can be realized not only as such an electricity storage element, but also as a current collector included in the electricity storage element.

[0022] Hereinafter, with reference to the drawings, an energy storage device according to an embodiment (and its modified examples) of the present invention will be described. The embodiments described below all show comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are merely examples and are not intended to limit the present invention. Dimensions, etc. are not strictly illustrated in the drawings.

[0023] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (positive and negative) of an energy storage element are aligned, the direction in which a pair of current collectors are aligned, the direction in which a pair of tabs of an electrode assembly are aligned, the direction in which a pair of spacers are aligned, or the direction in which the short side surfaces of a container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of a container face each other, the lateral direction of the short side surfaces of a container, or the thickness direction of a container. The Z-axis direction is defined as the direction in which the electrode terminals, current collectors, and electrode assembly are aligned, the direction in which the container body and lid of an energy storage element are aligned, the longitudinal direction of the short side surfaces of a container, the winding axis direction of the electrode assembly, the extension direction of the spacers, or the up-down direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Depending on the mode of use, the Z-axis direction may not be the up-down direction; however, for convenience of explanation, the Z-axis direction will be described below as the up-down direction. In the following description, for example, the positive X-axis direction indicates the direction of the arrow on the X-axis, and the negative X-axis direction indicates the direction opposite to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions.

[0024] (Embodiment) [1. General explanation of energy storage elements] First, an energy storage device 10 according to the present embodiment will be generally described with reference to Figures 1 and 2. Figure 1 is a perspective view showing the appearance of the energy storage device 10 according to the embodiment. Figure 2 is an exploded perspective view showing the components of the energy storage device 10 according to the embodiment.

[0025] The energy storage device 10 is a secondary battery that can charge and discharge electricity, specifically a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage device 10 is used as a battery for driving or starting the engine of a mobile object such as an automobile, such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), a motorcycle, a watercraft, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway, such as a train, a monorail, or a linear motor car.

[0026] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may not be a secondary battery, but may be a primary battery that allows stored electricity to be used without the user having to charge it. The energy storage element 10 may be a laminated energy storage element. In the present embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped (cornered) shape, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a polygonal prism shape, a cylindrical shape, an elongated cylindrical shape, or the like other than a rectangular parallelepiped shape.

[0027] As shown in FIG. 1, the energy storage device 10 includes a container 100, a pair of electrode terminals 200 (positive and negative), and a pair of upper gaskets 300 (positive and negative). As shown in FIG. 2, the container 100 contains a pair of lower gaskets 400 (positive and negative), a pair of current collectors 500 (positive and negative), and an electrode assembly 700. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but is not shown. The type of electrolyte is not particularly limited as long as it does not impair the performance of the energy storage device 10, and various types can be selected. In addition to the above components, a spacer disposed above or to the side of the electrode assembly 700, or an insulating film enveloping the electrode assembly 700, etc. may also be disposed.

[0028] The container 100 is a rectangular parallelepiped (box-shaped) case having a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. With this configuration, the container 100 has a structure in which the interior can be sealed by, for example, welding the container body 110 and the lid 120 together after the electrode assembly 700 and the like are housed inside the container body 110. The materials of the container body 110 and the lid 120 are not particularly limited, but are preferably weldable metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheet.

[0029] The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100, and has an opening formed on the positive side of the Z axis. The lid body 120 is a rectangular plate-like member that is long in the X axis direction and constitutes the lid of the container 100, and is positioned to close the opening of the container body 110. The lid body 120 is provided with a gas exhaust valve 122 that exhausts gas inside the container 100 when the internal pressure of the container 100 rises excessively.

[0030] The electrode body 700 is an electricity storage element (power generation element) that includes a positive electrode plate, a negative electrode plate, and a separator and can store electricity. Specifically, the electrode body 700 is formed by winding layers of positive and negative electrode plates with a separator sandwiched between them. As a result, multiple tabs of the positive electrode plates are stacked to form a positive electrode side tab portion 720, and multiple tabs of the negative electrode plates are stacked to form a negative electrode side tab portion 730. In other words, the electrode body 700 has an electrode body main body portion 710 and tab portions 720 and 730 that protrude from a portion of the electrode body main body portion 710 in the positive direction of the Z axis and extend in the positive direction of the Y axis. In this embodiment, the electrode body 700 has an oval cross-sectional shape, but the cross-sectional shape of the electrode body 700 may be an ellipse or the like.

[0031] The electrode terminal 200 is electrically connected to the electrode body 700 via the current collector 500. The electrode terminal 200 is connected to the current collector 500 and attached to the lid 120 by crimping or the like. Specifically, the electrode terminal 200 has a shaft portion 201 (rivet portion) extending downward (in the negative Z-axis direction). The shaft portion 201 is inserted into the through-hole 301 of the upper gasket 300, the through-hole 123 of the lid 120, the through-hole 401 of the lower gasket 400, and the through-hole 501 of the current collector 500, and is crimped. As a result, the electrode terminal 200, together with the upper gasket 300, the lower gasket 400, and the current collector 500, is fixed to the lid 120. The electrode terminal 200 is formed of a conductive material such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy.

[0032] The current collector 500 is a rectangular, flat member that electrically connects the electrode assembly 700 and the electrode terminal 200. Specifically, the positive electrode side current collector 500 has a terminal connection part 510 joined to the positive electrode terminal 200 by crimping or the like, and an electrode connection part 520 connected (joined) to a tab part 730 on the positive electrode side of the electrode assembly 700 by welding or the like. The negative electrode side current collector 500 is similar, having a terminal connection part 510 joined to the negative electrode terminal 200 by crimping or the like, and an electrode connection part 520 connected (joined) to a tab part 730 on the negative electrode side of the electrode assembly 700 by welding or the like. The current collector 500 is formed of a metal such as aluminum, an aluminum alloy, copper, or a copper alloy. The method for connecting (joining) the current collector 500 and the electrode terminal 200 is not limited to crimping, and welding such as ultrasonic welding, laser welding, or resistance welding, or mechanical joining other than crimping such as screw fastening may be used. The method for connecting (joining) the current collector 500 and the tab portion 720 or 730 may be any welding such as ultrasonic welding, laser welding, or resistance welding, or mechanical joining such as crimping or screw fastening. Details of the current collector 500 will be described later using FIGS. 3 to 8.

[0033] The upper gasket 300 is a flat, insulating sealing member disposed between the lid 120 of the container 100 and the electrode terminal 200. The lower gasket 400 is a flat, insulating sealing member disposed between the lid 120 and the current collector 500. The upper gasket 300 and the lower gasket 400 are formed from an insulating material such as a resin such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide resin (PPS), polyethylene terephthalate (PET), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), or polyethersulfone (PES), or a composite material containing these resins.

[0034] [2. Current Collector Structure] Next, the configuration of the current collector 500 will be described in detail with reference to Fig. 3 to Fig. 8. First, the basic configuration of the current collector 500 will be described with reference to Fig. 3 to Fig. 6. In this embodiment, the current collectors 500 on the positive electrode side and the negative electrode side have the same configuration, and therefore, the following description will focus on the current collector 500 on the positive electrode side.

[0035] FIG. 3 is a perspective view showing the appearance of a current collector 500 according to an embodiment. Specifically, FIG. 3 is a perspective view of the positive electrode side current collector 500 when viewed obliquely from below (the electrode assembly 700 side). FIG. 4 is a cross-sectional view showing the IV-IV cross section of the current collector 500 in FIG. 3. FIG. 5 is a cross-sectional view showing the VV cross section of the current collector 500 in FIG. 3. FIG. 6 is a cross-sectional view showing the VI-VI cross section of the current collector 500 in FIG. 3. In FIG. 4, in order to show the general positional relationship between the electrode assembly 700 and the current collector 500, in addition to the cross section of the current collector 500, a side view of a portion of the electrode assembly 700 is also shown schematically.

[0036] 3 to 6, a current collector 500 according to the present embodiment has a terminal connection portion 510 and an electrode connection portion 520. A through-hole 501 is formed in the terminal connection portion 510, through which the shaft portion 201 of the electrode terminal 200 passes. As described above, the shaft portion 201 of the electrode terminal 200 is inserted into the through-hole 501, and the tip portion of the shaft portion 201 exposed from the through-hole 501 is crimped. This mechanically and electrically connects the electrode terminal 200 and the current collector 500.

[0037] The electrode connection part 520 is the part to which the electrode body 700 is connected, and the electrode connection part 520 of the positive electrode side current collector 500 is connected to the positive electrode side tab part 720 of the electrode body 700, as shown in Fig. 4. For this connection, a predetermined method such as ultrasonic bonding is used, as described above.

[0038] The current collector 500 having such a configuration is disposed between the electrode assembly 700 and the lid 120 (see FIG. 2) in the Z-axis direction. The terminal connection portion 510 and the electrode connection portion 520 are disposed side by side in the X-axis direction. The Z-axis direction is an example of a first direction, the X-axis direction is an example of a second direction intersecting the first direction, and the lid 120 is an example of a wall portion of the container. Furthermore, as shown in FIGS. 5 and 6, the electrode connection portion 520 is formed thinner than the terminal connection portion 510.

[0039] That is, the energy storage element 10 according to this embodiment includes a container 100, an electrode assembly 700 housed in the container 100, a current collector 500 arranged between the electrode assembly 700 and a lid 120 of the container 100 in the Z-axis direction, and an electrode terminal 200 fixed to the lid 120. The current collector 500 has a terminal connection portion 510 connected to the electrode terminal 200, and an electrode connection portion 520 connected to the electrode assembly 700. The terminal connection portion 510 and the electrode connection portion 520 are arranged side by side in the X-axis direction intersecting the Z-axis direction, and a thickness D2 of the electrode connection portion 520 is smaller than a thickness D1 of the terminal connection portion 510.

[0040] That is, when the positive direction of the Z axis is taken as the upward direction, in the current collector 500 located above the electrode body 700, the portion connected to the electrode terminal 200 (terminal connection portion 510) and the portion connected to the electrode body 700 (electrode connection portion 520) are aligned in the horizontal direction (left-right direction). Therefore, for example, even if the crimping portion formed on the lower surface of the electrode connection portion 520 protrudes relatively significantly from the lower surface, the crimping portion can be accommodated in the space to the side of the tab portion 720 without interfering with the electrode body main body portion 710.

[0041] Furthermore, in this embodiment, since the electrode connection portion 520 is formed thinner than the terminal connection portion 510, for example, the tab portion 720 of the electrode assembly 700 joined to the electrode connection portion 520 can be positioned closer to the lid 120. Because the electrode connection portion 520 is relatively thick, as described above, when the shaft portion 201 of the electrode terminal 200 is crimped, deformation due to crimping force is suppressed. That is, in the energy storage element 10 according to this embodiment, the relatively thick terminal connection portion 510 suppresses deformation of the connection portion of the current collector 500 with the electrode terminal 200, and the relatively thin electrode connection portion 520 can increase the volume occupancy of the electrode assembly 700 within the container 100. Therefore, the energy storage element 10 according to this embodiment can improve energy density.

[0042] The thickness D1 of the terminal connection portion 510 of the current collector 500 is, for example, about 1 mm, and the thickness D2 of the electrode connection portion 520 is, for example, about 0.5 mm. These numerical values ​​are merely examples, and the thicknesses D1 and D2 of the terminal connection portion 510 and the electrode connection portion 520 may be determined appropriately depending on the material of the current collector 500, the electricity storage capacity of the electrode assembly 700, the size of the container 100, or the like, as long as they satisfy the relationship D1>D2.

[0043] For example, as shown in FIGS. 3, 5 and 6, the width L2 of the electrode connection portion 520 in the Y-axis direction intersecting the Z-axis direction and the X-axis direction is larger than the width L1 of the terminal connection portion 510 in the Y-axis direction.

[0044] This configuration prevents the cross-sectional area of ​​the electrode connection portion 520 from becoming smaller than the cross-sectional area of ​​the terminal connection portion 510 in the conductive path along the X-axis direction formed in the current collector 500. Simply put, the reduction in the cross-sectional area caused by thinning the electrode connection portion 520 can be compensated for by increasing the width of the electrode connection portion 520. This reduces the possibility that the electrode connection portion 520 will interfere with conduction during charging and discharging of the energy storage element 10, even if the electrode connection portion 520 is formed relatively thin in order to improve energy density, for example.

[0045] Focusing on the relationship between the cross-sectional area of ​​electrode connection portion 520 and the cross-sectional area of ​​terminal connection portion 510, it can also be said that area S2 of the cross section of electrode connection portion 520 perpendicular to the X-axis direction is equal to or greater than area S1 of the cross section of terminal connection portion 510 perpendicular to the X-axis direction.

[0046] According to this configuration, the resistance value of electrode connection portion 520 in the conductive path inside energy storage element 10 is equal to or less than the resistance value of terminal connection portion 510. The fusing resistance of electrode connection portion 520 is equal to or greater than the fusing resistance of terminal connection portion 510. This makes it possible to improve the reliability of energy storage element 10, for example, which has an improved energy density.

[0047] Current collector 500 according to the present embodiment has intermediate portion 530 that smoothly connects terminal connection portion 510 and electrode connection portion 520, which have different thicknesses and widths. Features of intermediate portion 530 will be described with reference to FIGS. 7 and 8. FIG. 7 is a partially enlarged view showing intermediate portion 530 of current collector 500 according to the embodiment. In FIG. 7, the approximate area of ​​intermediate portion 530 in current collector 500 is represented by a dotted area. FIG. 8 is a cross-sectional view showing the VIII-VIII cross section of intermediate portion 530 in FIG. 7. FIG. 9 is a cross-sectional view showing the IX-IX cross section of intermediate portion 530 in FIG. 7.

[0048] 7 to 9, current collector 500 according to the present embodiment further includes intermediate portion 530 connecting terminal connection portion 510 and electrode connection portion 520. Intermediate portion 530 is formed so that its thickness decreases and its width in the Y-axis direction increases from terminal connection portion 510 toward electrode connection portion 520.

[0049] That is, in the intermediate portion 530, the thickness is T1 and the width in the Y-axis direction is W1 in the VIII-VIII cross section at a position close to the terminal connection portion 510. In the IX-IX cross section at a position far from the terminal connection portion 510 (a position close to the electrode connection portion 520), the thickness is T2 and the width in the Y-axis direction is W2. In this case, T2<T1であり、かつ、W2> Therefore, for example, the cross-sectional area of ​​the VIII-VIII cross section (T1×W1) and the cross-sectional area of ​​the IX-IX cross section (T2×W2) can be made substantially the same. Furthermore, T1×W1 and T2×W2 can be made substantially the same as the cross-sectional area S1 of the terminal connecting portion 510 and the cross-sectional area S2 of the electrode connecting portion 520.

[0050] Thus, in current collector 500 according to the present embodiment, intermediate portion 530 is provided in the portion where terminal connection portion 510 and electrode connection portion 520 are connected, changing the cross-sectional shape so that the cross-sectional area is approximately constant. This prevents the formation of a location where the cross-sectional area suddenly decreases at the boundary between terminal connection portion 510 and electrode connection portion 520.

[0051] In other words, if a terminal connection portion 510 having the cross-sectional shape shown in FIG. 5 and an electrode connection portion 520 having the cross-sectional shape shown in FIG. 6 are directly connected, a small cross-sectional area portion having a cross-sectional area represented by "L1 x D2" is formed at the boundary between the terminal connection portion 510 and the electrode connection portion 520. This small cross-sectional area portion has a higher resistance than other portions in the conductive path formed in the current collector 500, and is a factor in reducing the charge / discharge efficiency of the energy storage element 10. Problems such as melting may also occur in the small cross-sectional area portion. Therefore, in the current collector 500 according to the present embodiment, an intermediate portion 530 having a shape that suppresses changes in the cross-sectional area perpendicular to the X-axis direction is provided between the terminal connection portion 510 and the electrode connection portion 520, which are aligned in the X-axis direction. As a result, a decrease in the charge / discharge efficiency of the energy storage element 10 or occurrence of melting or the like in the current collector 500 is suppressed. This contributes to improving the reliability of the energy storage element 10, for example, by improving the energy density.

[0052] Intermediate portion 530 is a portion between terminal connection portion 510 and electrode connection portion 520, which have different thicknesses, and therefore forms step 535 (see FIG. 4) in side view. Step 535 faces the electrode body 700 side.

[0053] In other words, in this embodiment, the surface of the current collector 500 facing the lid body 120 is flat, and a step 535 is formed on the surface of the current collector 500 facing the electrode body 700 due to the difference in thickness between the terminal connection portion 510 and the electrode connection portion 520.

[0054] According to this configuration, for example, almost all of the space obtained by thinning the electrode connecting section 520 can be used as a space for accommodating the electrode body 700. In other words, the effect of improving energy density by thinning the electrode connecting section 520 is maximized.

[0055] The energy storage element 10 according to the embodiment has been described above, but the energy storage element 10 may include a current collector that connects the electrode body 700 and the electrode terminal 200 and has a shape different from the shapes shown in Figures 2 to 8. Therefore, below, modified examples of the current collector included in the energy storage element 10 will be described with reference to Figure 10, focusing on the differences from the above embodiment.

[0056] (Variation 1) Fig. 10 is a perspective view showing the appearance of a current collector 500a according to Modification 1 of the embodiment. Specifically, Fig. 10 is a perspective view of the positive electrode side current collector 500a as viewed obliquely from below (the electrode body 700 side). The current collector 500a shown in Fig. 10 is a current collector that can be provided in the energy storage element 10 in place of the current collector 500 according to the above embodiment.

[0057] 10 has a terminal connection portion 510 connected to the electrode terminal 200, and an electrode connection portion 525 connected to the electrode body 700. The terminal connection portion 510 and the electrode connection portion 525 are arranged side by side in the X-axis direction, and the thickness of the electrode connection portion 525 is smaller than the thickness of the terminal connection portion 510. These features are common to the current collector 500 according to the above embodiment.

[0058] In the current collector 500a according to this modification, the end 525a of the electrode connection portion 525 in the third direction (Y-axis direction) is bent toward the electrode body 700. In other words, the electrode connection portion 525 has the end 525a bent toward the electrode body 700.

[0059] According to this configuration, the electrode connection portion 525 has the bent end portion 525a, which prevents a reduction in cross-sectional area due to its relatively thinness, and allows the width in the Y-axis direction to be approximately the same as that of the terminal connection portion 510. Therefore, for example, an existing gasket can be used as the lower gasket disposed between the current collector 500a and the lid 120. This reduces the manufacturing cost of the energy storage element 10 with improved energy density, for example.

[0060] In this modification, the end 525a of the electrode connection portion 525 in the positive Y-axis direction is bent toward the electrode body 700. In other words, the cross section perpendicular to the conduction direction (X-axis direction) is L-shaped. Therefore, when the electrode connection portion 525 is joined to the tab portion 720, as can be seen from FIG. 2, for example, the end 525a is located on the positive Y-axis side of the tip of the tab portion 720. In other words, the end 525a is positioned so as not to press down on the tab portion 720 from above. Therefore, since the electrode connection portion 525 is relatively thin, it is possible to obtain an improved energy density effect, and by making the cross section L-shaped, it is possible to ensure that the electrode connection portion 525 has a cross-sectional area approximately the same as that of the terminal connection portion 510. The L-shaped cross section of the electrode connection portion 525 improves the structural strength of the electrode connection portion 525.

[0061] (Variation 2) Fig. 11 is a perspective view showing the appearance of a current collector 500b according to Modification 2 of the embodiment. Specifically, Fig. 11 is a perspective view of the positive electrode side current collector 500b as viewed obliquely from below (the electrode body 700 side). The current collector 500b shown in Fig. 11 is a current collector that can be provided in the energy storage element 10 in place of the current collector 500 according to the above embodiment.

[0062] The current collector 500b shown in FIG. 11 has a terminal connection portion 510 connected to the electrode terminal 200 and an electrode connection portion 526 connected to the electrode assembly 700. The terminal connection portion 510 and the electrode connection portion 526 are arranged side by side in the X-axis direction, and the thickness of the electrode connection portion 526 is smaller than the thickness of the terminal connection portion 510. These features are common to the current collector 500 according to the above-described embodiment. In the current collector 500b according to this modification, the width of the terminal connection portion 510 in the Y-axis direction and the width of the electrode connection portion 526 in the Y-axis direction are substantially the same. In other words, the electrode connection portion 526 according to the embodiment of this modification is not formed in a shape that is clearly wider than the terminal connection portion 510, unlike the electrode connection portion 520 of the current collector 500.

[0063] That is, the current collector 500b is formed in a substantially rectangular shape when viewed from the first direction (Z-axis direction). This makes it less likely that problems due to the size of the electrode connection portion 526 will occur, such as the current collector 500b not being able to be accommodated within the range of the lower gasket 400 due to the wide width of the electrode connection portion 526 in the Y-axis direction, or the electrode connection portion 526 being too close to the inner surface of the container 100. In the current collector 500b, the cross-sectional area of ​​the electrode connection portion 526 is smaller than the cross-sectional area of ​​the terminal connection portion 510 in the conductive path along the X-axis direction. However, as long as the cross-sectional area of ​​the electrode connection portion 526 has a value that does not substantially impede conduction during charging and discharging of the energy storage device 10, the cross-sectional area of ​​the terminal connection portion 510 is equal to or greater than that value. Therefore, even if the energy storage device 10 includes the current collector 500b, the current collector 500b will not degrade the performance or reliability of the energy storage device 10. In this modification, the thickness of electrode connection portion 526 is also smaller than the thickness of terminal connection portion 510, thereby improving the energy density of energy storage element 10. In this way, the width of the electrode connection portion may be equal to or smaller than the width of the terminal connection portion, provided that the conditions that the terminal connection portion and the electrode connection portion are aligned in the second direction and the thickness of the electrode connection portion is smaller than the thickness of the terminal connection portion are satisfied.

[0064] (Other embodiments) Although the energy storage element according to the embodiment and its modifications of the present invention has been described above, the present invention is not limited to the above-described embodiment and its modifications. In other words, the embodiment and its modifications disclosed herein are examples in all respects, and the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

[0065] For example, in the energy storage element 10 according to the embodiment, both the positive electrode side and the negative electrode side are provided with current collectors 500 having electrode connection portions 520 thinner than the terminal connection portions 510. However, the current collectors 500 may be disposed on at least one of the positive electrode side and the negative electrode side. For example, if one of the current collectors on the positive electrode side or the negative electrode side can be formed thin due to reasons such as high rigidity of the material of the current collector, a current collector having uniform thicknesses of the terminal connection portion and electrode connection portion may be used as the one current collector, and the current collector 500 may be used as the other current collector. For example, if the container 100 is electrically connected to one of the positive electrode and negative electrode of the electrode assembly 700, the current collector 500 may be used as a member connecting the other of the positive electrode and negative electrode of the electrode assembly 700 to the electrode terminal 200.

[0066] Although the current collector 500 according to the embodiment is disposed on the energy storage element 10 in a position where the terminal connection portion 510 is located on the outer side in the first direction (X-axis direction), it may also be disposed on the energy storage element 10 in a position where the terminal connection portion 510 is located on the inner side in the X-axis direction (toward the center of the lid 120 in the X-axis direction). For example, when the positive and negative electrode terminals 200 are disposed closer to the center of the lid 120 in the longitudinal direction (X-axis direction), both of the two current collectors 500 in FIG. 2 may be disposed in a position rotated 180° around the Z-axis.

[0067] In the current collector 500, the electrode connection portion 520 has a portion that protrudes beyond the terminal connection portion 510 on both sides in the Y-axis direction, but the electrode connection portion 520 may have a portion that protrudes beyond the terminal connection portion 510 on only one of the two sides. That is, the position of the electrode connection portion 520 in the third direction (Y-axis direction) relative to the terminal connection portion 510 in the current collector 500 may be determined appropriately depending on, for example, the positional relationship between the electrode terminal 200 and the tab portion 720 or 730 connected to the electrode connection portion 520.

[0068] The type of electrode body provided in energy storage element 10 is not limited to the wound type. For example, energy storage element 10 may be provided with a laminated electrode body in which flat electrode plates are stacked, or an electrode body having a structure in which long strip-shaped electrode plates are stacked in a bellows shape by repeatedly folding in peaks and valleys.

[0069] The various supplementary points regarding the current collector 500 according to the embodiment described above may also be applied to the current collector 500a according to the modified examples. Configurations constructed by arbitrarily combining the embodiments and modified examples are also included within the scope of the present invention.

[0070] The present invention can be realized not only as such an electricity storage element, but also as a current collector included in the electricity storage element. [Industrial Applicability]

[0071] The present invention can be applied to an electric storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0072] 10. Energy storage element 100 containers 200 electrode terminal 500, 500a current collector 510 Terminal connection part 520, 525 Electrode connection part 525a end 530 Middle section 535 steps 700 Electrode body

Claims

1. An energy storage element including a container and an electrode assembly housed in the container, The electrode body includes an electrode body main body portion and a tab portion, The storage element is a current collector disposed between the electrode body main body and the wall of the container in a first direction; an electrode terminal fixed to the wall portion; The current collector is a terminal connection portion connected to the electrode terminal; an electrode connection portion connected to the tab portion, the terminal connection portion and the electrode connection portion are arranged side by side in a second direction intersecting the first direction, In the first direction, a position of one surface of the electrode connection portion in the first direction is between a position of the one surface of the terminal connection portion in the first direction and a position of the other surface of the terminal connection portion in the first direction, the thickness of the electrode connection portion is smaller than the thickness of the terminal connection portion; the tab portion is connected to the one surface of the electrode connection portion in the first direction and overlaps the terminal connection portion when viewed from the second direction; an area of ​​the tab portion overlapping the current collector when viewed from the first direction is equal to or less than an area of ​​the one surface of the electrode connection portion in the first direction; Energy storage element.

2. An energy storage element including a container and an electrode assembly housed in the container, The electrode body includes an electrode body main body portion and a tab portion, The storage element is a current collector disposed between the electrode body main body and the wall of the container in a first direction; an electrode terminal fixed to the wall portion; The current collector is a terminal connection portion connected to the electrode terminal; an electrode connection portion connected to the tab portion, the terminal connection portion and the electrode connection portion are arranged side by side in a second direction intersecting the first direction, In the first direction, a position of one surface of the electrode connection portion in the first direction is between a position of the one surface of the terminal connection portion in the first direction and a position of the other surface of the terminal connection portion in the first direction, the tab portion is connected to the one surface of the electrode connection portion in the first direction and overlaps the terminal connection portion when viewed from the second direction; the other surface of the electrode connection portion in the first direction and the other surface of the terminal connection portion in the first direction are formed on the same plane. Energy storage element.

3. The one surface of the electrode connection portion in the first direction is a surface facing the electrode body main body portion. The energy storage element according to claim 1 or 2.

4. the current collector further has an intermediate portion connecting the terminal connection portion and the electrode connection portion, the intermediate portion is formed so that the thickness thereof decreases from the terminal connection portion toward the electrode connection portion. The energy storage element according to any one of claims 1 to 3.

5. The surface of the current collector facing the wall portion is flat. The energy storage element according to any one of claims 1 to 4.

Images