Energy storage devices

Abstract

To provide an energy storage device in which the electrode body is less susceptible to damage from welding spatter. [Solution] The present invention provides an energy storage device comprising an electrode body, a case body 12 having an opening 12h, a sealing plate 14 that seals the opening 12h, a welded joint 10w, and a shielding portion 25 that separates the welded joint 10w from the electrode body inside the case body 12, wherein a space S surrounded by the shielding portion 25, the case body 12, and the sealing plate 14 is secured around the periphery of the welded joint 10w.

Description

Technical Field

[0001] The present invention relates to a power storage device.

Background Art

[0002] Conventionally, a power storage device including an electrode body, a case body having an opening for accommodating the electrode body, a sealing plate for sealing the opening, and a welded joint provided at the periphery of the opening is known (for example, Japanese Patent Application Laid-Open No. 2009-026707).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When forming the welded joint, the melted metal becomes fine particles (so-called welding spatter) and enters the inside of the case body from the gap between the case body and the sealing plate, and there is a risk that the electrode body may be damaged.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power storage device in which the electrode body is less likely to be damaged by welding spatter.

Means for Solving the Problems

[0006] According to the present invention, there are provided an electrode body, a case body having an opening for accommodating the electrode body, a sealing plate for sealing the opening, a welded joint provided at the butting portion between the case body and the sealing plate, and a shielding portion inside the case body for shielding at least a part of the welded joint and the electrode body from each other. A power storage device is provided in which a space surrounded by the shielding portion, the case body, and the sealing plate is secured at least at the periphery of a part of the welded joint. <u

[0007] With the above configuration, even if welding spatter is scattered inside the case body during welding, the space described above can contain the spatter and isolate it from the electrode body. Therefore, damage to the electrode body due to welding spatter can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view showing an energy storage device according to one embodiment. [Figure 2] Figure 2 is a schematic longitudinal cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 3 is an enlarged cross-sectional view of the main part of Figure 2. [Figure 4] Figure 4 is a schematic plan view of the sealing plate shown in Figure 1. [Figure 5] Figure 5 is a diagram corresponding to Figure 3, relating to the first modified example. [Figure 6] Figure 6 is a diagram corresponding to Figure 3, relating to the second modified example. [Figure 7] Figure 7 is a diagram corresponding to Figure 4, relating to the third modified example. [Modes for carrying out the invention]

[0009] Hereinafter, preferred embodiments of the energy storage module disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned herein but necessary for carrying out the disclosed technology (for example, the general configuration and manufacturing process of energy storage devices that do not characterize the disclosed technology) can be understood as design matters of those skilled in the art based on the prior art. The disclosed technology can be carried out based on the contents disclosed herein and common technical knowledge in the art. In addition, in the following drawings, the same reference numerals are used to denote members and parts that perform the same function.

[0010] In this specification, "energy storage device" refers to any device capable of repeated charging and discharging through the movement of a charge carrier between a positive electrode and a negative electrode via an electrolyte. Energy storage devices are a concept that encompasses secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors such as lithium-ion capacitors and electric double-layer capacitors. Furthermore, in this specification, the notation "A~B" indicating a range shall encompass not only the meaning of "greater than A and less than or equal to B," but also the meanings of "greater than A" and "less than B."

[0011] Figure 1 is a perspective view of an energy storage device 100 according to one embodiment. Figure 2 is a schematic longitudinal cross-sectional view of the energy storage device 100 in Figure 1 along line II-II, showing the internal structure of the energy storage device 100. Figure 3 is an enlarged cross-sectional view of the main part of Figure 2. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, back, up, and down, respectively, and the symbols X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up and down direction perpendicular to the short side direction and the long side direction, respectively. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the energy storage device 100 in any way.

[0012] As shown in Figure 1, the energy storage device 100 has a hexahedron shape (more specifically, a rectangular parallelepiped shape). As shown in Figure 2, the energy storage device 100 comprises a battery case 10, an electrode body 20, and a shielding portion 25. The energy storage device 100 further comprises a non-aqueous electrolyte (not shown), a positive electrode terminal 30, and a negative electrode terminal 40. The energy storage device 100 is a non-aqueous electrolyte secondary battery (more specifically, a non-aqueous electrolyte secondary battery). Preferably, the energy storage device 100 is a lithium-ion secondary battery.

[0013] As shown in Figure 1, the battery case 10 has a flattened, bottomed rectangular parallelepiped (square) shape. As shown in Figure 2, the battery case 10 comprises a case body 12 having an opening 12h and housing the electrode body 20 and the non-aqueous electrolyte, and a sealing plate 14 that seals the opening 12h. More specifically, the battery case 10 comprises a case body 12 having openings 12h at both ends in the long side direction Y, and two sealing plates 14 that close the pair of openings 12h of the case body 12, respectively.

[0014] The case body 12 is a hollow rectangular tube. As shown in Figure 1, the case body 12 has a substantially rectangular bottom surface 12a having a pair of long sides and a pair of short sides, a pair of long sides 12b extending upward from the pair of long sides (edges) of the bottom surface 12a and facing each other, and an upper surface 12c facing the bottom surface 12a. The long sides 12b have a larger area than the bottom surface 12a and the upper surface 12c. The upper surface 12c is substantially rectangular, similar to the bottom surface 12a. The upper surface 12c connects the upper ends of the pair of long sides 12b.

[0015] In this specification, "approximately rectangular" is a term that includes not only a perfect rectangle, but also shapes such as those where the corners connecting the long and short sides of a rectangle are rounded (R-shaped), or shapes with notches at the corners.

[0016] The case body 12 is formed, for example, by bending a single metal plate into a cylindrical shape and joining the joints (e.g., by welding). Therefore, the bottom surface 12a, the pair of long sides 12b, and the top surface 12c are all flat and have a substantially uniform plate thickness T2 (see Figure 3). A welded joint 12d is provided on the top surface 12c of the case body 12. In the case body 12, the boundary portion (edge) between the long side 12b and the bottom surface 12a, and the boundary portion (edge) between the long side 12b and the top surface 12c are bent portions. As a result, even if gas is generated inside the battery case 10 and the internal pressure rises, for example, the battery case 10 is less likely to be damaged. Thus, safety is enhanced.

[0017] The thickness T2 (thickness of the metal plate) of the case body 12 may vary depending on the material and the like. From the viewpoint of improving mechanical strength, rigidity, durability, etc., it is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. Also, from the viewpoint of improving the energy density of the power storage device 100, the thickness T2 of the case body 12 is preferably 2 mm or less, more preferably 1 mm or less, even more preferably 0.7 mm or less, and particularly preferably 0.5 mm or less.

[0018] As shown in FIG. 2, a gas discharge valve 13 is provided on the lower surface 12a of the case body 12. The gas discharge valve 13 is configured to break when the pressure in the battery case 10 becomes a predetermined value or more and discharge the gas in the battery case 10 to the outside. In the present embodiment, the number of the gas discharge valves 13 is one, but in other embodiments, it may be two or more. Also, the position, area, shape, etc. of the gas discharge valve 13 can be changed as appropriate.

[0019] The sealing plate 14 is a substantially rectangular plate-like member. The area of the sealing plate 14 is smaller than the long side surface 12b here. The sealing plate 14 is flat and has a substantially uniform plate thickness T4 (see FIG. 3). The plate thickness T4 of the sealing plate 14 may vary depending on the material and the like. From the viewpoint of improving mechanical strength, rigidity, durability, etc., it is preferably 0.1 mm or more, more preferably ......

[0020] As will be described in detail later, in some embodiments, a shielding portion 25 is provided on either the case body 12 or the sealing plate 14, and it is preferable that the thickness of the member provided with the shielding portion 25 is relatively thicker than the thickness of the member not provided with the shielding portion 25. As shown in FIG. 3, in this embodiment, the shielding portion 25 is provided on the sealing plate 14. In this case, it is preferable that the plate thickness T4 of the sealing plate 14 is thicker than the plate thickness T2 of the case body 12 (T2 < T4). The plate thickness T4 of the sealing plate 14 is preferably 1.5 times or more the plate thickness T2 of the case body 12, more preferably 2 times or more, and even more preferably, for example, 2 to 3 times.

[0021] As shown in FIG. 2, a liquid injection hole 15 is provided in one of the sealing plates 14. The liquid injection hole 15 is for injecting a non-aqueous electrolyte into the battery case 10 after assembling the pair of sealing plates 14 to the case body 12. The liquid injection hole 15 is sealed with a sealing member 16 after injecting the non-aqueous electrolyte. As the sealing member 16, a conventionally known member can be used without particular limitation. As an example of the sealing member 16, a blind rivet can be mentioned. In this embodiment, the liquid injection hole 15 is provided in the sealing plate 14, but in other embodiments, the liquid injection hole 15 may be provided in the case body 12.

[0022] The materials of the case body 12 and the sealing plate 14 may be the same as those conventionally used, and there is no particular limitation. The case body 12 and the sealing plate 14 are preferably made of a metal such as stainless steel, aluminum, aluminum alloy, iron, iron alloy, etc., and more preferably made of stainless steel. Stainless steel has a higher melting point and higher mechanical strength than, for example, aluminum or aluminum alloy. Therefore, stainless steel is less likely to be damaged even if gas is generated in the battery case 10 and the pressure in the battery case 10 rises, and has excellent safety. Also, as will be described in detail later, according to the technology disclosed herein, even when such a metal with a high melting point is used, it is easy to preferably form a welded joint 10w with a deep melting depth at the boundary between the case body 12 and the sealing plate 14.

[0023] As shown in Figures 2 and 3, the case body 12 and the sealing plate 14 are butted together at the periphery of the pair of openings 12h of the case body 12. The wall surface extends vertically through the openings 12h of the case body 12. There is no step on the periphery of the openings 12h of the case body 12 on which the sealing plate 14 is placed. A welded joint 10w is provided at the butt joint between the case body 12 and the sealing plate 14. In some embodiments, the welded joint 10w is preferably a laser-welded joint formed by laser welding. The welded joint 10w is provided in an annular shape along the periphery of the pair of openings 12h of the case body 12 (along the outer edge of the sealing plate 14). The battery case 10 is integrated by welding the sealing plate 14 to the periphery of the pair of openings 12h of the case body 12. As a result, the openings 12h of the case body 12 are airtightly sealed.

[0024] The shielding portion 25 is a member that shields at least a portion of the welded joint 10w from the electrode body 20 inside the case body 12. The shielding portion 25 is a part that partitions a portion of the space S described later, and has the function of protecting the electrode body 20 from welding spatter that may be scattered inside the case body 12 when forming the welded joint 10w. In some embodiments, it is preferable that the shielding portion 25 is provided on one of the case body 12 and the sealing plate 14, and is in contact with or close to the other of the case body 12 and the sealing plate 14. This makes it easier to stably exhibit the effects of the technology disclosed herein. It also improves the assembleability and productivity of the energy storage device 100. In this specification, "in contact with or close to" means that it may also include embodiments in which the shielding portion exists at a predetermined distance from the target member, to the extent that the effects of the technology disclosed herein can be obtained.

[0025] As shown in Figure 3, the shielding portion 25 is provided on the sealing plate 14. More specifically, the shielding portion 25 is joined (e.g., welded) to the inner wall surface of the sealing plate 14. A joint portion 25w is provided at the boundary between the inner wall surface of the sealing plate 14 and the shielding portion 25. The shielding portion 25 is integrated with the sealing plate 14. The shielding portion 25 is not joined to the case body 12. The shielding portion 25 is in contact with or close to (preferably in contact with) the case body 12. By providing the shielding portion 25 on the sealing plate 14, the technology disclosed herein can be implemented more easily. In addition, the case body 12 can be made thinner, and the energy density can be improved. However, as will be described in the second modified example later, the shielding portion 25 may be provided on a member other than the sealing plate 14, for example, on an insulating member such as the case body 12 or a spacer.

[0026] The material of the shielding portion 25 may be the same as or different from that of the case body 12 and / or sealing plate 14. The shielding portion 25 is preferably made of a metal such as stainless steel, aluminum, aluminum alloy, iron, or iron alloy, and more preferably stainless steel. In some embodiments, the material of the shielding portion 25 preferably has a melting point that is the same as or higher than that of the case body 12 and / or sealing plate 14. This makes it easier to achieve a high level of effectiveness of the technology disclosed herein.

[0027] As shown in Figure 3, the shielding portion 25 has an L-shaped cross-section in a cross-sectional view along the long side surface 12b of the case body 12 (a cross-sectional view in the thickness direction of the case body 12 and the sealing plate 14). The shielding portion 25 has a first portion P1 that extends along the inner wall surface of the case body 12 and a second portion P2 that extends along the inner wall surface of the sealing plate 14. This makes it easier to adjust the volume of the space S and makes it easier to secure a wide space S stably. However, as will be described in the first modified example below, the shielding portion 25 may have a shape other than an L-shape in cross-section, such as an I-shape or a wavy cross-section.

[0028] The first part P1 is the part connected to the sealing plate 14 here. The above-described joint 25w is provided at the boundary between the inner wall surface of the sealing plate 14 and the first part P1. The first part P1 extends horizontally along the long side direction Y from the inner wall surface of the sealing plate 14 here. In some embodiments, in the cross-sectional view of FIG. 3, it is preferable that the length L1 of the first part P1 (the average length in the long side direction Y of FIG. 3, which is the length protruding from the inner wall surface of the sealing plate 14 here) is longer than the plate thickness T4 of the sealing plate 14 (T4 < L1). Thereby, it becomes easier to stably secure a wide space S. Also, it becomes easier to exhibit the effects of the technology disclosed here at a higher level.

[0029] The second part P2 is the part that extends vertically (along the vertical direction Z) from the first part P1 toward the case body 12 side here and abuts or is close to (preferably abuts) the inner wall surface of the case body 12. It is more preferable that the second part P2 abuts the inner wall surface of the case body 12. The second part P2 extends along the side surface in the long side direction Y of the electrode body 20. In some embodiments, in the cross-sectional view of FIG. 3, it is preferable that the length L2 of the second part P2 (the average length in the vertical direction Z of FIG. 3, which is the length extending from the first part P1 here) is longer than the plate thickness T2 of the case body 12 (T2 < L2). Thereby, it becomes easier to stably secure a wide space S. Also, it becomes easier to stably exhibit the effects of the technology disclosed here. The length L2 of the second part P2 is shorter than the length L1 of the first part P1 here (L2 < L1). Thereby, it becomes difficult for the shielding part 25 to interfere with the case body 12, and the assembling property and workability can be improved.

[0030] Figure 4 is a schematic plan view of the sealing plate 14. Figure 4 shows the inner wall surface of the sealing plate 14 (the surface facing the electrode body 20). As shown in Figure 4, in this embodiment, the shielding portion 25 is provided in an annular shape along the outer edge of the sealing plate 14. As a result, in the energy storage device 100, the shielding portion 25 is provided in an annular shape (continuously) along the welded joint 10w. The shielding portion 25 shields the annular welded joint 10w and the electrode body 20 around its entire circumference. However, as will be described in the third modified example later, the shielding portion 25 does not necessarily have to be provided in an annular shape (continuously) along the outer edge of the sealing plate 14.

[0031] As shown in Figure 3, a space S is secured around the periphery of at least a portion of the welded joint 10w, surrounded by the shielding portion 25, the case body 12, and the sealing plate 14. In the cross-sectional view of Figure 3, space S is a roughly rectangular (more specifically, roughly rectangular) space surrounded by the first portion P1 and the second portion P2 of the shielding portion 25, the inner wall surface of the case body 12, and the inner wall surface of the sealing plate 14. As can be seen from Figures 3 and 4, space S is provided in an annular shape along the outer edge of the sealing plate 14 (along the annular welded joint 10w).

[0032] By securing a space S inside the battery case 10 (more specifically inside the case body 12) in this way, even if welding spatter is scattered inside the case body 12 when forming the welded joint 10w, the welding spatter can be contained in the space S and isolated from the electrode body 20. Therefore, the electrode body 20 is less likely to be damaged by welding spatter. Furthermore, even if the battery case 10 (case body 12 and / or sealing plate 14) is made thinner than conventional models from the viewpoint of improving the energy density of the energy storage device 100, a welded joint 10w with a deep weld depth (penetration) can be formed without worrying about welding spatter. Therefore, even if the battery case 10 is made thinner than conventional models, the sealing performance of the welded joint 10w can be stably ensured.

[0033] In addition, according to the inventors' findings, when forming the welded joint 10w, "heat buildup" can be created in the space S. This makes it easier to melt even metals with high melting points (e.g., stainless steel), and makes it easier to stably form welded joints 10w with deep welding depths. Therefore, even when using metals with high melting points (e.g., stainless steel) for the battery case 10 (case body 12 and / or sealing plate 14), the sealing performance of the welded joint 10w can be improved.

[0034] In some embodiments, it is preferable that the volume of the space S is greater than the volume of the welded joint 10w provided at the butt joint between the case body 12 and the sealing plate 14. In some embodiments, it is preferable that the depth of the space S (average length in the vertical direction Z in Figure 3) is greater than the plate thickness T2 of the case body 12. This allows the space S to suitably contain the molten metal even if it melts and drips into the case body 12 during welding. Thus, the effects of the technology disclosed herein can be more easily realized at a higher level. The relative size of the volume of the space S and the volume of the welded joint 10w can be determined, for example, by comparing the areas of both in a cross-sectional view of the sealing plate 14 in the thickness direction, as shown in Figure 3.

[0035] As shown in Figure 2, the electrode body 20 is housed inside the battery case 10. Although not shown in the illustration, the electrode body 20 has a positive electrode and a negative electrode. The configuration of the electrode body 20 can be the same as conventional designs and is not particularly limited. The positive electrode typically has a positive electrode current collector and a positive electrode active material layer fixed to the positive electrode current collector. The negative electrode typically has a negative electrode current collector and a negative electrode active material layer fixed to the negative electrode current collector. The electrode body 20 may be housed inside the battery case 10 covered with a resin insulating sheet (electrode body holder). The electrode body 20 may be housed inside the battery case 10 integrated with a resin insulating member (e.g., a spacer).

[0036] The number of electrode bodies 20 housed inside the battery case 10 is not particularly limited; there may be one or two or more. In this embodiment, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked with a strip-shaped separator in between, and wound in the longitudinal direction around a winding axis. In this embodiment, the electrode body 20 is arranged inside the battery case 10 in an orientation in which the winding axis is substantially parallel to the long side direction Y. However, in other embodiments, the electrode body 20 may be a laminated electrode body in which a plurality of rectangular positive electrodes and a plurality of rectangular negative electrodes are stacked in the short side direction X, for example, with insulation via a separator. Furthermore, each component constituting the electrode body 20 (positive electrode, negative electrode, separator, etc.) may be the same as those in a general energy storage device, and there are no particular restrictions.

[0037] As shown in Figure 2, the positive electrode of the electrode body 20 is provided with a positive electrode tab 23. The positive electrode tab 23 is part of the positive electrode current collector. The positive electrode tab 23 is convex and protrudes from the electrode body 20 toward the first sealing plate 14 (to the right in the long side direction Y of Figure 2). The positive electrode tab 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 32. On the other hand, the negative electrode of the electrode body 20 is provided with a negative electrode tab 24. The negative electrode tab 24 is part of the negative electrode current collector. The negative electrode tab 24 is convex and protrudes from the electrode body 20 toward the second sealing plate 14 (to the left in the long side direction Y of Figure 2). The negative electrode tab 24 is electrically connected to the negative electrode terminal 40 via the negative electrode current collector 42.

[0038] The non-aqueous electrolyte is housed inside the battery case 10 together with the electrode body 20. The non-aqueous electrolyte may be the same as conventional ones and is not particularly limited. The non-aqueous electrolyte is a non-aqueous liquid electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, for example, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The supporting salt (electrolyte salt) is, for example, a fluorine-containing lithium salt such as LiPF6 or a fluorine-containing sodium salt such as NaPF6. However, in other embodiments, instead of the non-aqueous electrolyte, there may be a solid electrolyte (solid electrolyte) integrated with the electrode body 20.

[0039] The positive terminal 30 and the negative terminal 40 are, here, fixed to opposing surfaces of the battery case 10 (specifically, a pair of sealing plates 14). More specifically, the positive terminal 30 is attached to the first sealing plate 14 (the sealing plate 14 on the right side in the long side direction Y in Figures 1 and 2). The positive terminal 30 is preferably made of metal, and more preferably of aluminum or an aluminum alloy. As shown in Figure 2, the positive terminal 30 is electrically connected to the positive tab 23 inside the battery case 10 via the positive current collector 32.

[0040] The negative terminal 40 is attached to the second sealing plate 14 (the sealing plate 14 on the left side in the long side direction Y in Figures 1 and 2). The negative terminal 40 is preferably made of metal, and more preferably of copper or a copper alloy. As shown in Figure 2, the negative terminal 40 is electrically connected to the negative tab 24 inside the battery case 10 via the negative current collector 42. In this embodiment, the positive terminal 30 and the negative terminal 40 are provided on a pair of sealing plates 14, respectively, but in other embodiments, the positive terminal 30 and the negative terminal 40 may be provided on the same sealing plate 14, or they may be provided on the case body 12.

[0041] The energy storage device 100 described above can be manufactured by a manufacturing method that typically includes, for example, a battery case preparation step, an electrode housing step, a welding and joining step, and a liquid injection step, in this order. In the battery case preparation step, a case body 12 and two sealing plates 14 are prepared. The case body 12 can be prepared, for example, by bending a single metal plate to form a cylindrical shape and joining the joint (for example, by welding). The sealing plates 14 can be prepared, for example, by joining (for example, by welding) a shielding portion 25 to a rectangular metal plate sized to fit the opening 12h of the case body 12. This results in a sealing plate assembly in which the shielding portion 25 is integrated with the sealing plate 14. A positive electrode terminal 30 is attached to the first sealing plate 14, and a negative electrode terminal 40 is attached to the second sealing plate 14.

[0042] In the electrode housing process, the separately prepared electrode body 20 is housed in the case body 12. In one example, after housing the electrode body 20 in the case body 12, the positive electrode tab 23 of the electrode body 20 is joined to the positive electrode current collector 32 and electrically connected to the positive electrode terminal 30 provided on the first sealing plate 14. The negative electrode tab 24 of the electrode body 20 is joined to the negative electrode current collector 42 and electrically connected to the negative electrode terminal 40 provided on the second sealing plate 14.

[0043] In the welding process, the opening 12h of the case body 12 is sealed with a sealing plate 14 (sealing plate assembly). In one example, when the sealing plate 14 is butted against the opening 12h of the case body 12, a space S is secured inside the case body 12, surrounded by the shielding portion 25, the case body 12, and the sealing plate 14, around the periphery of the opening 12h. In this state, the butt joint between the case body 12 and the sealing plate 14 is welded together. The welding method is not particularly limited, but examples include laser welding, electron beam welding, ultrasonic welding, and resistance welding. Laser welding is preferred among these. This forms a welded joint 10w, sealing the opening 12h of the case body 12.

[0044] As described above, the space S is secured around the periphery of the opening 12h, so even if welding spatter is scattered inside the case body 12 when forming the welded joint 10w, the space S can catch the welding spatter and isolate it from the electrode body 20. Therefore, according to the technology disclosed herein, the electrode body 20 is less likely to be damaged in this process. In addition, since a welded joint 10w with a deep welding depth (penetration) can be formed without worrying about welding spatter, the sealing performance of the welded joint 10w can be stably ensured. Furthermore, when forming the welded joint 10w, "heat buildup" can occur in the space S. This makes it easier to melt even metals with high melting points (e.g., stainless steel), making it easier to stably form a welded joint 10w with a deep welding depth. Therefore, metals with high melting points (e.g., stainless steel) can also be suitably used.

[0045] In the electrolyte injection process, a non-aqueous electrolyte is injected into the battery case 10. In this embodiment, the non-aqueous electrolyte is poured into the battery case 10 through the injection hole 15. After the non-aqueous electrolyte is injected, the injection hole 15 is sealed with a sealing member 16. In this manner, the energy storage device 100 can be manufactured.

[0046] The energy storage device 100 can be used for various applications, but it is particularly suitable as a power source (driving power supply) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0047] The embodiments of the technology disclosed herein have been described above. However, the above description is illustrative and does not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. In the following descriptions of modifications, explanations of matters common to the embodiments will be omitted or simplified.

[0048] <First Modified Example> In the embodiment described above, the shielding portion 25 had an L-shaped cross-section and consisted of a first portion P1 and a second portion. However, it is not limited to this. Figure 5 is a diagram corresponding to Figure 3 relating to the first modified example. The shielding portion 125 shown in Figure 5 has an I-shaped cross-section and has a straight portion Ps extending from the inner wall surface of the sealing plate 114 toward the inner wall surface of the case body 112. The straight portion Ps has a substantially uniform thickness. The straight portion Ps is connected to the sealing plate 114. A joint portion 125w is provided at the boundary between the inner wall surface of the sealing plate 114 and the first portion P1. In this modified example, the space S1 is a substantially triangular space enclosed by the straight portion Ps of the shielding portion 125, the inner wall surface of the case body 112, and the inner wall surface of the sealing plate 114 in the cross-sectional view of Figure 5. Even in energy storage devices having such shielding portion 125 and space S1, the effects of the technology disclosed herein can be suitably demonstrated.

[0049] <Second Modification> In the above-described embodiment and the first modification, shielding portions 25 and 125 were provided on the sealing plates 14 and 114, and joint portions 25w and 125w were provided at the boundary between the sealing plates 14 and 114 and the shielding portions 25 and 125. However, the member on which the shielding portion is provided is not limited to the sealing plate. The shielding portion can also be provided on the case body, or on a third member (for example, a spacer or a resin insulating member placed inside the case body 12).

[0050] Figure 6 is a diagram corresponding to Figure 3 relating to a second modified example. The shielding portion 225 shown in Figure 6 is provided on the case body 212. The shielding portion 225 has a first portion P3 connected to the case body 212 and extending along the inner wall surface of the sealing plate 214, and a second portion P4 extending from one end of the first portion P3 along the inner wall surface of the case body 212 and in contact with or close to (preferably in contact with) the inner wall surface of the sealing plate 214. A joint portion 225w is provided at the boundary between the inner wall surface of the case body 212 and the first portion P3. The shielding portion 225 is not joined to the sealing plate 214. In this modified example, contrary to the embodiment described above, it is preferable that the plate thickness T2 of the case body 12 on which the shielding portion 225 is provided is thicker than the plate thickness T4 of the sealing plate 14 (T2 > T4).

[0051] In this modified example, space S2 is a roughly rectangular (more specifically, roughly rectangular) space enclosed by the first part P3 and the second part P4 of the shielding portion 225, the inner wall surface of the case body 212, and the inner wall surface of the sealing plate 214, as seen in the cross-sectional view in Figure 6. The effects of the technology disclosed herein can be suitably demonstrated even in an energy storage device having such a shielding portion 225 and space S2.

[0052] <Third Modification> Figure 7 is a diagram corresponding to Figure 4 in the third modification. The sealing plate 314 shown in Figure 7 is provided with four shielding portions 325. The shielding portions 325 are provided at each corner of the substantially rectangular sealing plate 314. More specifically, in this modification, the corners of the sealing plate 314 are rounded in an R shape, and a substantially C-shaped shielding portion 325 is provided at each of the four R-shaped corners in a plan view. No shielding portions 325 are provided in the straight parts of the sealing plate 314 (parts along the short side direction X or the vertical direction Z). As a result, in the energy storage device of this modification, a shielding portion 325 is provided at each of the four corners (4 corners) of the substantially rectangular welded joint in a plan view.

[0053] According to the inventors' research, during welding, the long side surface 12b of the case body 12 is pressed and fixed with a pair of block-shaped clamps (jigs), and in this state, the sealing plate 14 is welded to the periphery of the opening 12h of the case body 12. In such cases, relatively large gaps tend to occur at the roughly rectangular corners. In contrast, large gaps are less likely to occur in the straight portion of the sealing plate 314 because it is held in place by the jig. Therefore, by providing shielding portions 325 at least at the roughly rectangular corners, the effects of the technology disclosed herein can be suitably demonstrated.

[0054] <Fourth Modification> In the above-described embodiment, the case body 12 was rectangular and had openings 12h at both ends in the long side direction Y. Also, there were two sealing plates 14. However, it is not limited to this. In the modified battery case, the case body 12 may be a bottomed rectangular (box-shaped) with an opening at only one end. In this case, there may be one sealing plate.

[0055] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: An energy storage device comprising: an electrode body; a case body having an opening and housing the electrode body; a sealing plate that closes the opening; a welded joint provided at the abutting portion between the case body and the sealing plate; and a shielding portion inside the case body that separates at least a part of the welded joint from the electrode body, wherein a space surrounded by the shielding portion, the case body, and the sealing plate is secured around the periphery of at least a part of the welded joint. Item 2: The energy storage device according to Item 1, wherein the shielding portion is provided on one of the case body and the sealing plate, and is in contact with or close to the other of the case body and the sealing plate. Item 3: The energy storage device according to item 1 or 2, wherein the shielding portion is provided on the sealing plate. Item 4: The energy storage device described in Item 3, wherein the thickness of the sealing plate is greater than the thickness of the case body. Item 5: The energy storage device according to any one of items 1 to 4, wherein the shielding portion is provided in an annular shape along the welded joint. Item 6: The energy storage device according to any one of items 1 to 4, wherein the welded joint is substantially rectangular in plan view, and the shielding portion is provided at least at the four corners of the substantially rectangular shape. Item 7: The energy storage device according to any one of items 1 to 6, wherein the volume of the space is greater than the volume of the welded joint provided at the butt joint. Item 8: The energy storage device according to any one of items 1 to 7, wherein the shielding portion has an L-shaped cross-section and comprises a first portion extending along the inner wall surface of the case body and a second portion extending along the inner wall surface of the sealing plate. Item 9: The energy storage device according to Item 8, wherein the length of the first part extending along the case body is longer than the thickness of the sealing plate. Item 10: The energy storage device according to item 8 or 9, wherein the length of the second part extending along the sealing plate is longer than the thickness of the case body. Item 11: The energy storage device according to any one of items 1 to 10, wherein the case body and the sealing plate are made of stainless steel. [Explanation of Symbols]

[0056] 10 Battery Case 10w welded joint 12, 112, 212 Case body 14, 114, 214, 314 Sealing plate 20 Electrode body 25, 125, 225, 325 Shielding part 100 Energy Storage Devices S, S1, S2 space

Claims

1. Electrode body and A case body having an opening and housing the electrode body, A sealing plate that seals the opening, A welded joint is provided at the butt joint between the case body and the sealing plate, Inside the case body, a shielding portion is provided to separate at least a part of the welded joint from the electrode body. Equipped with, An energy storage device in which a space enclosed by the shielding portion, the case body, and the sealing plate is secured around the periphery of at least a part of the welded joint.

2. The shielding portion is provided on one of the case body and the sealing plate, and is in contact with or close to the other of the case body and the sealing plate. The energy storage device according to claim 1.

3. The shielding portion is provided on the sealing plate, The energy storage device according to claim 1.

4. The thickness of the sealing plate is greater than the thickness of the case body. The energy storage device according to claim 3.

5. The shielding portion is provided in an annular shape along the welded joint. An energy storage device according to any one of claims 1 to 4.

6. Third variation The welded joint is substantially rectangular in plan view, and the shielding portion is provided at least at the four corners of the substantially rectangular shape. An energy storage device according to any one of claims 1 to 4.

7. The volume of the aforementioned space is greater than the volume of the welded joint provided at the butt joint. The energy storage device according to any one of claims 2 to 4.

8. The shielding portion has an L-shaped cross-section and comprises a first portion extending along the inner wall surface of the case body and a second portion extending along the inner wall surface of the sealing plate. An energy storage device according to any one of claims 1 to 4.

9. The length of the first portion extending along the case body is longer than the thickness of the sealing plate. The energy storage device according to claim 8.

10. The length of the second portion extending along the sealing plate is longer than the thickness of the case body. The energy storage device according to claim 8.

11. The case body and the sealing plate are made of stainless steel. An energy storage device according to any one of claims 1 to 4.

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