Secondary battery and manufacturing method of the secondary battery

Abstract

To provide a secondary battery in which a length of an electrode body in a winding axis direction can be increased and a battery capacity can be increased.SOLUTION: In a secondary battery 1 including a housing 11, a lid 13, an electrode body 40, and battery terminals PS and NS, the electrode body 40 has an arc part 50a at an upper part of at least one end in a winding axis direction, tab groups 51 and 56 in which tabs of a positive electrode material or a negative electrode material are laminated extend from an arc part 50a, and is housed inside the housing 11 so that the winding axis is horizontal. Battery terminals PS and NS have current collecting terminals 27 and 28 having bonding surfaces Ma and Mb to be bonded to the tab groups 51 and 56 of the electrode body 40 at a tip part thereof. The tab groups 51 and 56 and the current collecting terminals 27 and 28 are located in a space between the lid 13 and the electrode body 40 in a state where the tab groups 51 and 56 are bonded to bonding surfaces Ma and Mb.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary battery and a method for manufacturing the secondary battery. [Background technology]

[0002] Conventionally, secondary batteries used in electric vehicles, such as electric automobiles, that are driven by a motor, include an electrode assembly, a case that houses the electrode assembly, and battery terminals that are attached to the case and electrically connected to the electrode assembly. In this type of secondary battery, one method for electrically connecting the battery terminals to the electrode assembly is to form a group of tabs on the electrode assembly and then join the battery terminals to the group of tabs. For example, the secondary battery disclosed in Patent Document 1 has been proposed as a secondary battery in which the electrode assembly and battery terminals are electrically connected in this manner.

[0003] The secondary battery described in Patent Document 1 includes a flat electrode body formed by winding electrode body materials (positive and negative electrode materials) in a stacked state around a winding axis, and battery terminals electrically connected to the electrode body. The electrode body has tab groups extending from both end faces in the winding axis direction, and the battery terminals have plate-shaped current collectors joined to the tab groups of the electrode body. In this secondary battery, the current collectors of the battery terminals are arranged so as to face both end faces in the winding axis direction of the electrode body, and the current collectors are joined to the tab groups. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Chinese Utility Model No. 205385061 Summary of the Invention [Problem to be solved by the invention]

[0005] In the secondary battery described in Patent Document 1, in order to join the current collectors of the battery terminals to the tabs of the electrode body, a space is required between the battery case and both longitudinal end faces of the electrode body to arrange the current collectors. Therefore, the length of the electrode body in the winding axis direction must be shortened by the amount of this space, which inevitably reduces the battery capacity.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a secondary battery in which the length of the electrode body in the winding axis direction can be increased and the battery capacity can be increased, and a method for manufacturing such a secondary battery. [Means for solving the problem]

[0007] The secondary battery according to the present invention, which achieves the above object, has the following characteristic configuration: A secondary battery comprising: a housing having an opening at an upper portion; a lid attached to the opening of the housing; a flat electrode body in which a positive electrode material and a negative electrode material are stacked with a separator interposed therebetween and wound around a winding axis; and a battery terminal attached to the lid, The electrode body is an arc portion is provided at an upper portion of at least one end in the winding axis direction, and a tab group formed by stacking tabs of the positive electrode material or the negative electrode material extends from the arc portion; The winding shaft is housed inside the housing so as to be horizontal, The battery terminals are a current collecting terminal having a joining surface at a tip end thereof to be joined to the tab group of the electrode body; The tab group and the current collecting terminal are located in the space between the cover body and the electrode body with the tab group joined to the joining surface.

[0008] According to the above-described characteristic configuration, no space is required for disposing a current collecting terminal between the end of the electrode body in the winding axis direction and the housing, and therefore, according to the secondary battery of the present invention, the length of the electrode body in the winding axis direction can be increased, and the battery capacity can be increased.

[0009] Further characteristic configurations of the secondary battery according to the present invention are as follows: the electrode body has the arc portions at both ends in the winding axis direction, a positive electrode tab group formed by stacking tabs of the positive electrode material extends from the arc portion on one side in the winding axis direction, and a negative electrode tab group formed by stacking tabs of the negative electrode material extends from the arc portion on the other side, The battery terminals include a positive battery terminal and a negative battery terminal.

[0010] According to the above characteristic configuration, the distance between the positive battery terminal and the negative battery terminal is increased, thereby increasing the safety of the secondary battery.

[0011] Further characteristic configurations of the secondary battery according to the present invention are as follows: the current collecting terminal has, in order from a tip side, at least a plate-shaped first portion having the joint surface and a plate-shaped second portion continuous with the first portion, the second portion is located in a space between the cover body and the electrode body, The first portion is located between the second portion and the housing in the winding axis direction, and is bent toward the second portion so that the joint surface faces the housing.

[0012] According to the above characteristic configuration, for example, the tab group and the current collecting terminal can be joined by arranging the first part horizontally so that the joining surface faces downward, and then ultrasonically joining the tab group and the current collecting terminal from above and below using a horn and anvil. Then, by simply performing the relatively simple task of bending the first part toward the second part, a configuration can be realized in which the tab group and the current collecting terminal are positioned in the space between the cover body and the electrode body.

[0013] Further characteristic configurations of the secondary battery according to the present invention are as follows: the tab group has a main body portion to which the current collecting terminal is joined and a connection portion connected to an end of the electrode body, The main body portion has a length longer than the connection portion in the winding direction of the electrode body.

[0014] According to the above-described characteristic configuration, the portion of the main body that is not connected to the end of the electrode body can move freely relative to the end of the electrode body, making it easier to secure a flat surface of sufficient size for joining to the current collecting terminal.

[0015] Further characteristic configurations of the secondary battery according to the present invention are as follows: A plurality of the electrode bodies is provided, The tab group of the plurality of electrode bodies is joined to the same joining surface of the current collecting terminal.

[0016] According to the above characteristic configuration, the number of electrode bodies that can be joined to the current collecting terminal can be increased simply by increasing the joining surface of the current collecting terminal without increasing the number of parts, making it easier to increase the battery capacity.

[0017] The method for producing a secondary battery according to the present invention for achieving the above object comprises the steps of: The battery comprises a housing having an opening at an upper portion, a lid that closes the opening of the housing, a flat electrode body in which strip-shaped positive electrode material and negative electrode material are stacked with a separator interposed therebetween and wound around a winding axis, and a battery terminal attached to the lid, the electrode body has an arc portion at an upper portion of at least one end in the winding axis direction, and a tab group formed by stacking tabs of the positive electrode material or the negative electrode material extends from the arc portion; The battery terminal has a current collecting terminal having a tip end with a joining surface to be joined to the tab group of the electrode body, a joining process in which the tab group of the electrode body and the joining surface of the current collecting terminal of the battery terminal are arranged so as to face each other in the vertical direction, and the tab group and the current collecting terminal are joined together; a bending step of bending the tab group and the current collecting terminal after the joining step so that their joint portions are positioned in a space between the lid body and the electrode body; After the bending step, the electrode body integrated with the lid body via the battery terminal is housed inside the housing so that the winding axis is horizontal, and the opening edge of the housing and the peripheral edge of the lid body are welded together.

[0018] According to the above characteristic configuration, there is no need for space to place a collector terminal between the end of the electrode body in the winding axis direction and the housing, and a secondary battery with increased battery capacity can be manufactured by increasing the length of the electrode body in the winding axis direction. [Effects of the Invention]

[0019] As described above, the secondary battery and the method for manufacturing the secondary battery according to the present invention can realize a secondary battery with a large battery capacity by increasing the length of the electrode body in the winding axis direction. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an exploded perspective view of a secondary battery according to an embodiment; [Figure 2] FIG. 1 is a cross-sectional view showing a schematic configuration of a secondary battery. [Figure 3] FIG. 2 is a perspective view showing a partially developed electrode assembly. [Figure 4] FIG. 2 is a perspective view showing the internal structure of the negative electrode side of the secondary battery. [Figure 5] 1 is a diagram showing a flow of a method for manufacturing a secondary battery according to an embodiment; [Figure 6] FIG. 10 is a front view illustrating the joining step. [Figure 7] FIG. 7 is an enlarged perspective view showing part A in FIG. 6. [Figure 8] FIG. 10 is a front view illustrating the bending process. [Figure 9] FIG. 10 is a side view showing the internal structure of a secondary battery according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] A secondary battery and a manufacturing method thereof according to an embodiment of the present invention will be described below with reference to the drawings. Note that the following description will be given taking as an example an embodiment in which the secondary battery is a lithium-ion secondary battery. In addition, the following description and drawings will be simplified as appropriate for clarity of explanation.

[0022] [Overview of Secondary Battery 1] An overview of a secondary battery 1 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is an exploded perspective view of the secondary battery 1. Figure 2 is a cross-sectional view showing a schematic configuration of the secondary battery 1. In the following description, the direction parallel to the height direction of the secondary battery 1 is referred to as the Z-axis direction, the direction parallel to the winding axis direction of the electrode body 40 is referred to as the X-axis direction, and the direction parallel to the thickness direction of the electrode body 20 is referred to as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0023] 1 and 2, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 13, battery terminals PS and NS consisting of external terminals 25, 26 and current collecting terminals 27, 28 attached to the sealing plate 13, and an electrode body 40 electrically connected to the current collecting terminals 27, 28. The secondary battery 1 is a sealed secondary battery in which the electrode body 40, the current collecting terminals 27, 28, etc. are housed inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 13, and an electrolyte is injected into the inside of the case body 11.

[0024] [Configuration of battery case 10] As shown in FIGS. 1 and 2, a battery case 10 of this embodiment is composed of a case body 11 that is roughly rectangular and has an open top, and a sealing plate 13 that seals the opening of the case body 11. In the battery case 10 of this embodiment, the case body 11 and the sealing plate 13 are both made of aluminum, but this is not limited to this. Various metals and alloys can be used as materials for the case body 11 and the sealing plate 13. In this embodiment, the case body 11 corresponds to the "casing," and the sealing plate 13 corresponds to the "lid."

[0025] In this embodiment, the sealing plate 13 has a shape corresponding to the shape of the opening of the case body 11 and is configured to be able to seal the opening of the case body 11. Specifically, the sealing plate 13 in this embodiment is made of a flat plate member that is generally rectangular when viewed in the Z-axis direction. The sealing plate 13 has a positive battery terminal PS disposed at one end in the longitudinal direction (X-axis direction) and a negative battery terminal NS disposed at the other end in the longitudinal direction.

[0026] In this embodiment, the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11 are laser welded together, and the opening of the case body 11 is closed by the sealing plate 13, as will be described in detail later.

[0027] [Configuration of electrode body 40] Fig. 3 is a perspective view showing a partially developed electrode assembly 40. As shown in Fig. 3, the electrode assembly 40 is composed of a wound body obtained by stacking long strip-shaped positive electrode material 41 and negative electrode material 46 with a similarly strip-shaped separator 49 interposed therebetween, winding the stack, and then compressing the stack into a flat shape. In this embodiment, the positive electrode material 41 is aluminum foil, and the negative electrode material 46 is copper foil.

[0028] The cathode material 41 has a cathode coated portion 41a in which a cathode active material is applied to both sides, and a cathode uncoated portion 41b at one end in the X-axis direction where the cathode active material is not applied. The cathode material 41 also has a plurality of cathode tabs 42 extending outward at intervals from the end at one end in the X-axis direction. The intervals between the plurality of cathode tabs 42 are set so that, after winding, a cathode tab group 51 is formed in an upper arc portion 50a (described later).

[0029] The negative electrode material 46 has a negative electrode coated portion 46a in which a negative electrode active material is coated on both sides, and a negative electrode uncoated portion 46b in which the negative electrode active material is not coated at the other end in the X axis direction. The negative electrode material 46 also has a plurality of negative electrode tabs 47 extending outward at intervals from the other end in the X axis direction. The intervals between the plurality of negative electrode tabs 47 are set so that, after winding, a negative electrode tab group 56 is formed in an upper arc portion 50a, which will be described later.

[0030] In this embodiment, each positive electrode tab 42 and each negative electrode tab 47 has a main body portion 42a, 47a and a connection portion 42b, 47b. Each main body portion 42a, 47a is a portion to which a current collector terminal 27, 28 of each battery terminal PS, NS (described later) is joined. Meanwhile, each connection portion 42b, 47b is a portion connected to an end of the positive electrode material 41 and the negative electrode material 46.

[0031] Specifically, in this embodiment, each positive electrode tab 42 and each negative electrode tab 47 has a rectangular shape with its longitudinal direction parallel to the X-axis direction when the electrode body 40 is unfolded. Furthermore, slits 42c, 47c are formed on both sides in the short side direction at the base portion of each positive electrode tab 42 and each negative electrode tab 47. That is, in this embodiment, each connection portion 42b, 47b is a portion sandwiched between the slits 42c, 47c on both sides in the short side direction, and the length of each tab 42, 47 in the direction parallel to the short side direction is shorter than that of each main body portion 42a, 47a.

[0032] The separator 49 is disposed so as to insulate the positive electrode coated portion 41a of the positive electrode material 41 from the negative electrode coated portion 46a of the negative electrode material 46. The separator 49 can be made of an insulating material (such as a porous insulating resin material) that is permeable to ions.

[0033] The electrode body 40 has a main body 60 having an upper arc portion 50a and a lower arc portion 50b at both ends in the X-axis direction, with a positive electrode tab group 51 extending from the upper arc portion 50a at one end in the X-axis direction and a negative electrode tab group 56 extending from the upper arc portion 50a at the other end.

[0034] The positive electrode tab group 51 and the negative electrode tab group 56 are formed by stacking the positive electrode tabs 42 and the negative electrode tabs 47 in layers when the positive electrode material 41 and the negative electrode material 46, on which a plurality of positive electrode tabs 42 and a plurality of negative electrode tabs 47 are formed, are wound. The positive electrode tab group 51 has a main body portion 52 formed by stacking the main body portions 42a of the positive electrode tabs 42 and a connection portion 53 formed by stacking the connection portions 42b. The negative electrode tab group 56 has a main body portion 57 formed by stacking the main body portions 47a of the negative electrode tabs 47 and a connection portion 58 formed by stacking the connection portions 47b of the negative electrode tabs 47. The main body portions 52 and 57 of each tab group 51 and 56 are longer in the winding direction of the electrode body 40 (arrow R in FIG. 3 ) than the connection portions 53 and 58. Therefore, the portions of the main bodies 52 and 57 that are not connected to the ends of the electrode body 40 can move freely relative to the ends of the electrode body 40. This makes it easy to ensure a flat surface of the size required for joining with the current collecting terminals 27 and 28, which will be described later.

[0035] [Configuration of the positive electrode side and negative electrode side] In this embodiment, the secondary battery 1 includes, as its positive electrode side configuration, a positive battery terminal PS consisting of a positive electrode external terminal 25 and a positive electrode current collector terminal 27, a positive electrode insulating member 29, and a positive electrode gasket 31. The secondary battery 1 also includes, as its negative electrode side configuration, a negative electrode battery terminal NS consisting of a negative electrode external terminal 26 and a negative electrode current collector terminal 28, a negative electrode insulating member 30, and a negative electrode gasket 32.

[0036] Although detailed description will be omitted, in the secondary battery 1 of this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27, and the negative electrode external terminal 26 and the negative electrode current collector terminal 28 are integrated by crimping to form the respective battery terminals PS and NS. In this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27 that constitute the positive electrode battery terminal PS are both made of aluminum. On the other hand, with regard to the negative electrode battery terminal NS, the negative electrode external terminal 26 is made of aluminum, and the negative electrode current collector terminal 28 is made of copper.

[0037] In this embodiment, the positive electrode external terminal 25 and the negative electrode external terminal 26 are insulated from the sealing plate 13 by a positive electrode gasket 31 and a negative electrode gasket 32. The positive electrode current collector terminal 27 and the negative electrode current collector terminal 28 are insulated from the sealing plate 13 by a positive electrode insulating member 29 and a negative electrode insulating member 30. Airtightness is maintained between each battery terminal PS, NS and the sealing plate 13 by each insulating member 29, 30 and each gasket 31, 32. In this embodiment, the insulating members 29, 30 and the gaskets 31, 32 are made of PFA resin, but the material is not limited to PFA resin. The insulating members 29, 30 and the gaskets 31, 32 may be made of any insulating material.

[0038] In this embodiment, each current collecting terminal 27, 28 is formed by bending a plate-like member, and has base portions 27a, 28a that are crimped to the respective external terminals 25, 26, intermediate portions 27b, 28b that are continuous with the base portions 27a, 28a, and tip portions 27c, 28c that are continuous with the intermediate portions 27b, 28b and have bonding surfaces Ma, Mb on one surface to which each tab group 51, 56 of the electrode body 40 is bonded (see also FIG. 7). In this embodiment, the intermediate portions 27b, 28b correspond to the "second portion," and the tip portions 27c, 28c correspond to the "first portion."

[0039] In this embodiment, the base portions 27a, 28a of the current collecting terminals 27, 28 are arranged on the lower surface of the sealing plate 13 so as to extend horizontally. The middle portions 27b, 28b of the current collecting terminals 27, 28 extend downward in the Z-axis direction from the ends of the base portions 27a, 28a and are located in the space between the sealing plate 13 and the electrode assembly 40. The tip portions 27c, 28c are folded back from the ends of the middle portions 27b, 28b and extend upward in the Z-axis direction. Furthermore, the tip portions 27c, 28c are located between the middle portions 27b, 28b and the end side surface of the case body 11 in the X-axis direction, and the bonding surfaces Ma, Mb to which the tab groups 51, 56 of the electrode assembly 40 are bonded face the end side surface of the case body 11. As will be described in detail later, after the main body portions 52, 57 of the tab groups 51, 56 are joined to the joining surfaces Ma, Mb of the current collecting terminals 27, 28, the tip portions 27c, 28c are bent toward the intermediate portions 27b, 28b.

[0040] 4 is a perspective view showing the internal structure of the negative electrode side. As shown in FIGS. 1, 2, and 4, in the secondary battery 1 of this embodiment, the base portions 27a, 28a, middle portions 27b, 28b, and tip portions 27c, 28c of each current collecting terminal 27, 28 are all located in the space between the lower surface of the sealing plate 13 and the top of the main body portion 60 of the electrode assembly 40. Similarly, the tab groups 51, 56 joined to the joining surfaces Ma, Mb of the tip portions 27c, 28c are also located in the space between the lower surface of the sealing plate 13 and the top of the main body portion 60 of the electrode assembly 40. In other words, in the secondary battery 1, the current collecting terminals 27, 28 and the tab groups 51, 56 are located in the space between the sealing plate 13 and the electrode assembly 40 with the tab groups 51, 56 joined to the joining surfaces Ma, Mb. Therefore, no space is required for arranging the current collecting terminals 27, 28 between the end of the electrode body 40 in the winding axis direction (X-axis direction) and the end side surface of the case body 11.

[0041] That is, in the secondary battery 1 of this embodiment, the length of the electrode body 40 in the X-axis direction can be increased and the volume of the electrode body 40 in the battery case 10 can be increased compared to when space is required to arrange the current collecting terminals 27, 28. Therefore, the battery capacity can be increased without changing the size of the battery case 10.

[0042] Furthermore, in the secondary battery 1 of this embodiment, a positive electrode tab group 51 is formed at one end in the X-axis direction of the electrode body 40, and a negative electrode tab group 56 is formed at the other end, with battery terminals PS and NS joined to these tab groups 51 and 56. In other words, in the secondary battery 1 of this embodiment, the positive electrode battery terminal PS and the negative electrode battery terminal NS are sufficiently far apart, making it safer than when the battery terminals PS and NS are close to each other.

[0043] Next, a method for manufacturing the secondary battery 1 will be described. The method for manufacturing the secondary battery 1 includes a joining step, a bending step, and a sealing step. Each step will be described below with reference to Figs. 5 to 8. Fig. 5 is a diagram showing the flow of the method for manufacturing a secondary battery. Fig. 6 is a front view for explaining the joining step, and Fig. 7 is an enlarged perspective view of part A in Fig. 6. Furthermore, Fig. 8 is a front view for explaining the bending step.

[0044] [Joining process] The bonding process is a process of electrically connecting the prefabricated electrode body 40 and the battery terminals PS, NS attached to the sealing plate 13. The electrode body 40 can be fabricated and the battery terminals PS, NS can be attached to the sealing plate 13 using any known method. In the bonding process, the tab groups 51, 56 of the electrode body 40 and the bonding surfaces Ma, Mb of the current collector terminals 27, 28 of the battery terminals PS, NS are arranged to face each other in the vertical direction (Z-axis direction), and the tab groups 51, 56 are bonded to the current collector terminals 27, 28.

[0045] Specifically, in this embodiment, as shown in FIGS. 6 and 7 , the main body portions 52, 57 of the tab groups 51, 56 of the electrode assembly 40 and the tip portions 27c, 28c of the current collecting terminals 27, 28 are arranged horizontally and facing each other in the vertical direction, and the upper surfaces of the main body portions 52, 57 are brought into contact with the lower surfaces (joining surfaces Ma, Mb) of the tip portions 27c, 28c. Next, an anvil (not shown) is pressed against the upper surfaces of the tip portions 27c, 28c, and a horn (not shown) is pressed against the lower surfaces of the main body portions 52, 57 in the vertical direction (X-axis direction) to apply pressure. Thereafter, ultrasonic vibrations are applied horizontally by the horn. This joins the tip portions 27c, 28c of the current collecting terminals 27, 28 to the main body portions 52, 57 of the tab groups 51, 56.

[0046] In this embodiment, as described above, the portions of the main body portions 52, 57 of each tab group 51, 56 that are not connected to the main body portion 60 of the electrode body 40 can move freely relative to the main body portion 60 of the electrode body 40. This ensures a sufficiently large flat surface required for ultrasonic bonding, making bonding failure less likely to occur.

[0047] The upper surfaces of the tip portions 27c, 28c of the current collecting terminals 27, 28 must have an area equal to or larger than the area required for ultrasonic bonding. Furthermore, as described below, when the tip portions 27c, 28c are bent, the tip portions 27c, 28c and the intermediate portions 27b, 28b must fit into the space between the lower surface of the sealing plate 13 and the top of the main body portion 60 of the electrode assembly 40. That is, the length Lz of the intermediate portions 27b, 28b of the current collecting terminals 27, 28 along the Z-axis direction and the length Lx of the tip portions 27c, 28c along the X-axis direction must be equal to or smaller than the distance Ra (see FIG. 8 ) from the lower surface of the sealing plate 13 to the top of the main body portion 60 of the electrode assembly 40. Therefore, in the current collecting terminals 27, 28 before bending in this embodiment, the upper surfaces of the tip portions 27c, 28c are equal to or larger than the area required for ultrasonic bonding, and the length Lx is shorter than the distance Ra.

[0048] [Bending process] The bending step is a step performed after the joining step. In the bending step, the tab groups 51, 56 and the current collecting terminals 27, 28 are bent so that their joints are positioned in the space between the sealing plate 13 and the electrode body 40.

[0049] 8, in the present embodiment, with the tip portions 27c, 28c of the current collecting terminals 27, 28 and the main body portions 52, 57 of the tab groups 51, 56 joined together, the tip portions 27c, 28c and the tab groups 51, 56 are bent so that the upper surfaces of the tip portions 27c, 28c abut against the side surfaces of the intermediate portions 27b, 28b. As a result, with the joining surfaces Ma, Mb of the current collecting terminals 27, 28 facing outward in the X-axis direction, the tip portions 27c, 28c of the current collecting terminals 27, 28 and the tab groups 51, 56 fit into the space between the lower surface of the sealing plate 13 and the uppermost part of the main body portion 60 of the electrode body 40.

[0050] Here, the tabs 42, 47 of the electrode materials 41, 46 are stacked with misalignment during fabrication of the electrode body 40, resulting in misalignment of the tabs in the tab groups 51, 56. However, in this embodiment, the connection portions 53, 58 that bend when bending the tab groups 51, 56 are shorter in length in the winding direction of the electrode body 40 than the main body portions 52, 57, improving the ease of bending.

[0051] 7, each of the current collecting terminals 27, 28 before bending has a recess K formed at the boundary between the side surface of the intermediate portion 27b, 28b and the upper surface of the tip portion 27c, 28c. This improves the ease of bending the tip portion 27c, 28c toward the intermediate portion 27b, 28b.

[0052] [Sealing process] The sealing process is a process performed after the folding process. In the sealing process, the electrode body 40, which is integrated with the sealing plate 13 via the battery terminals PS and NS, is housed inside the case body 11 so that the winding axis P (see FIG. 1) is horizontal, and the opening edge 11a of the case body 11 and the peripheral edge 13a of the sealing plate 13 are welded together.

[0053] Specifically, in this embodiment, the structure in which the sealing plate 13, the battery terminals PS, NS, and the electrode assembly 40 are integrated is placed with the electrode assembly 40 on the upper side, and then the case body 11 is placed over it. Thereafter, a laser beam of a predetermined output is irradiated onto the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13, and the case body 11 and the sealing plate 13 are welded together to close the opening of the case body 11.

[0054] As described above, according to the method for manufacturing the secondary battery 1 of this embodiment, the tab groups 51, 56 and the current collecting terminals 27, 28 can be joined by ultrasonic bonding using a horn and anvil, and then, by simply performing the relatively simple task of bending the tip portions 27c, 28c toward the middle portions 27b, 28b, it is possible to manufacture a secondary battery 1 in which the current collecting terminals 27, 28 and the tab groups 51, 56 are positioned in the space between the sealing plate 13 and the electrode body 40 with the tab groups 51, 56 joined to the joining surfaces Ma, Mb. In other words, according to this manufacturing method, compared to a case in which space is required to arrange the current collecting terminals 27, 28, the length of the electrode body 40 in the X-axis direction is longer, and the volume of the electrode body 40 in the battery case 10 is increased, making it possible to manufacture a high-capacity secondary battery 1.

[0055] [Another embodiment] [1] In the above embodiment, the secondary battery 1 includes one electrode body 40, but the present invention is not limited to this. As shown in FIG. 9, the secondary battery may include multiple electrode bodies 40. When the secondary battery includes multiple electrode bodies 40, it is preferable to enlarge the bonding surfaces Ma and Mb of the current collecting terminals 27 and 28 and bond the tab groups 51 and 56 of the multiple electrode bodies 40 to the same bonding surfaces Ma and Mb. In this way, the number of electrode bodies that can be bonded to the current collecting terminals can be increased simply by enlarging the bonding surfaces without increasing the number of components, which makes it easier to increase the battery capacity.

[0056] [2] In the above embodiment, the collector terminals 27, 28 and the tab groups 51, 56 are joined to the joining surfaces Ma, Mb on both the positive and negative electrode sides and are positioned in the space between the sealing plate 13 and the electrode assembly 40. However, the present invention is not limited to this. Any configuration may be used as long as the collector terminals and the tab groups are positioned in the space between the sealing plate and the electrode assembly on at least one of the positive and negative electrode sides.

[0057] [3] In the above embodiment, the current collecting terminals 27, 28 are each made of a member having a base portion 27 a, 28 a, an intermediate portion 27 b, 28 b, and a tip portion 27 c, 28 c. However, the current collecting terminals are not limited to this. The current collecting terminals may have a shape that has a bonding surface at the tip and that allows them to be positioned in the space between the sealing plate and the electrode body together with the tab group bonded to the bonding surface when the secondary battery is assembled.

[0058] [4] In the above embodiment, the tab groups 51, 56 have the main body portions 52, 57 and the connecting portions 53, 58. However, the present invention is not limited to this. The tab groups 51, 56 may not have the connecting portions 53, 58, in other words, no slits may be formed between the main body portion 60 of the electrode body 40 and the main body portions 52, 57 of the tab groups 51, 56.

[0059] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0060] 1: Secondary battery 11: Case body (housing) 13: Sealing plate (lid body) 40: Electrode body 41: Cathode material 42: Positive electrode tab 46: Anode material 47: Negative electrode tab 49: Separator 50a: Upper arc section (arc section) 51: Positive electrode tab group 56: Negative electrode tab group 52, 57: Main body 53,58: Connection part PS: Positive battery terminal (battery terminal) NS: Negative battery terminal (battery terminal) 27,28: collector terminals 27a, 28a: base 27b, 28b: Middle part (Part 2) 27c, 28c: Tip (Part 1) Ma,Mb:Joint surface P: Rewinding axis R: Rewind direction

Claims

1. A secondary battery comprising: a housing having an opening at an upper portion; a lid attached to the opening of the housing; a flat electrode body in which a positive electrode material and a negative electrode material are stacked with a separator interposed therebetween and wound around a winding axis; and a battery terminal attached to the lid, The electrode body is an arc portion is provided at an upper portion of at least one end in the winding axis direction, and a tab group formed by stacking tabs of the positive electrode material or the negative electrode material extends from the arc portion; The winding shaft is housed inside the housing so as to be horizontal, The battery terminals are a current collecting terminal having a joining surface at a tip end thereof to be joined to the tab group of the electrode body; The tab group and the current collecting terminal are positioned in the space between the lid body and the electrode body with the tab group joined to the joining surface.

2. the electrode body has the arc portions at both ends in the winding axis direction, a positive electrode tab group formed by stacking tabs of the positive electrode material extends from the arc portion on one side in the winding axis direction, and a negative electrode tab group formed by stacking tabs of the negative electrode material extends from the arc portion on the other side, The secondary battery according to claim 1 , wherein the battery terminals include a positive battery terminal and a negative battery terminal.

3. the current collecting terminal has, in order from a tip side, at least a plate-shaped first portion having the joining surface and a plate-shaped second portion continuous with the first portion, the second portion is located in a space between the cover body and the electrode body, 2. The secondary battery according to claim 1, wherein the first portion is located between the second portion and the housing in the winding axis direction, and is bent toward the second portion so that the joint surface faces the housing.

4. the tab group has a main body portion to which the current collecting terminal is joined and a connection portion connected to an end of the electrode body, The secondary battery according to claim 1 , wherein the main body portion is longer than the connecting portion in the winding direction of the electrode body.

5. A plurality of the electrode bodies is provided, 5. The secondary battery according to claim 1, wherein the tab group of the plurality of electrode assemblies is joined to the same joining surface of the current collecting terminal.

6. The battery comprises a housing having an opening at an upper portion, a lid that closes the opening of the housing, a flat electrode body in which strip-shaped positive electrode material and negative electrode material are stacked with a separator interposed therebetween and wound around a winding axis, and a battery terminal attached to the lid, the electrode body has an arc portion at an upper portion of at least one end in the winding axis direction, and a tab group formed by stacking tabs of the positive electrode material or the negative electrode material extends from the arc portion; The battery terminal has a current collecting terminal having a tip end with a joining surface to be joined to the tab group of the electrode body, a joining process in which the tab group of the electrode body and the joining surface of the current collecting terminal of the battery terminal are arranged so as to face each other in the vertical direction, and the tab group and the current collecting terminal are joined together; a bending step of bending the tab group and the current collecting terminal after the joining step so that their joint portions are positioned in a space between the lid body and the electrode body; a sealing step of, after the bending step, accommodating the electrode body integrated with the lid body via the battery terminal inside the housing so that the winding axis is horizontal, and welding an opening edge portion of the housing and a peripheral edge portion of the lid body.

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