JP7611876B2 - Secondary battery and electrode terminal - Google Patents

Description

The present invention relates to a secondary battery and an electrode terminal.

Secondary batteries such as lithium-ion secondary batteries are suitable for use as portable power sources for personal computers, mobile terminals, and the like, and as power sources for driving vehicles such as electric vehicles (BEVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). Such secondary batteries, for example, have an electrode body having a positive electrode and a negative electrode, a battery case having an opening and housing the electrode body, a sealing plate having a terminal mounting hole and sealing the opening, an electrode terminal having one end connected to the electrode body inside the battery case and the other end inserted into the terminal mounting hole and drawn out to the outside of the sealing plate, and a resin insulating member that insulates the outer surface of the sealing plate from the electrode terminal. Patent Document 1 is an example of such a technology.

JP 2022-41144 A

In general, insulating members made of resin have lower heat resistance than electrode terminals made of metal. Therefore, when the temperature of the electrode terminal rises due to the passage of electricity, there is a risk that the sealing and insulating properties will decrease due to deformation of the insulating member, etc. In addition, in recent years, there is a demand for secondary batteries with high output characteristics, even if the battery body is relatively small in size. In such secondary batteries with a relatively small battery body size, various components tend to be small in proportion to the size. For this reason, when a large current flows for the purpose of high output, the temperature of the electrode terminals is likely to rise, and there is a risk that it will exceed the heat resistance temperature of the insulating member, for example. Therefore, in secondary batteries with a relatively small battery size, there is a demand for electrode terminals with a heat capacity (which can also be called "thermal mass") that allows the passage of a large current.

The present invention was made in consideration of the above circumstances, and its main objective is to provide a secondary battery with improved safety for a secondary battery with a relatively small battery size. Another objective is to provide an electrode terminal that optimally improves the safety of the battery.

The secondary battery disclosed herein includes an electrode assembly having a positive electrode and a negative electrode, a battery case having an opening and housing the electrode assembly, a sealing plate having a terminal mounting hole and sealing the opening, an electrode terminal having a first flange portion disposed outside the battery case, a second flange portion disposed inside the battery case, and a shaft portion positioned between the first flange portion and the second flange portion and inserted into the terminal mounting hole, and an external insulating member made of resin that insulates the outer surface of the sealing plate from the first flange portion. The secondary battery has a battery capacity of 10 Ah or less and a battery volume including the battery case of 200 ^cm3 or less. Here, in the secondary battery, a height H1 from the outer surface of the sealing plate to the top of the electrode terminal is at least twice as high as a height H2 from the outer surface of the sealing plate to the top of the external insulating member.

With this configuration, the heat capacity of the electrode terminals can be increased even for secondary batteries that are relatively small in size and designed for high output. This prevents the electrode terminals from generating heat due to current flow and prevents the temperature from exceeding the heat resistance temperature of the external insulating member, which is a resin member. This makes it easier to ensure the sealing properties of the external insulating member, and more optimally improves the safety of the secondary battery.

FIG. 1 is a partial cross-sectional view that illustrates a battery according to one embodiment. FIG. 2 is a cross-sectional view that illustrates a schematic view of the vicinity of a positive electrode terminal according to one embodiment. FIG. 3A is a diagram illustrating the vicinity of a conventional positive electrode terminal and a bus bar. FIG. 3B is a diagram illustrating the vicinity of the positive electrode terminal and the bus bar according to one embodiment. FIG. 4A is a diagram showing a schematic view of the lower end portion of a conventional positive electrode terminal. FIG. 4B is a diagram illustrating a schematic view of a lower end portion of a positive electrode terminal according to one embodiment. FIG. 5A is a diagram illustrating a conventional positive electrode conductive member. FIG. 5B is a diagram illustrating a positive electrode conductive member according to one embodiment.

Below, an embodiment of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of a battery that do not characterize the technology disclosed herein) can be understood as design matters for a person skilled in the art based on the conventional technology in the field. The technology disclosed here can be implemented based on the contents disclosed in this specification and the technical common sense in the field. In the following, the same reference numerals are used for members and parts that perform the same function, and duplicated descriptions can be omitted or simplified. Note that in this specification, the notation "A to B" indicating a range includes the meaning of "A or more and B or less", as well as "greater than A" and "less than B".

In this specification, the term "battery" refers to any power storage device capable of extracting electrical energy, and is a concept that includes primary batteries and secondary batteries. In addition, in this specification, the term "secondary battery" refers to any power storage device that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes via an electrolyte, and is a concept that includes so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as electric double-layer capacitors.

Figure 1 is a partial cross-sectional view of the secondary battery 100. Figure 2 is a partially enlarged cross-sectional view showing the vicinity of the positive terminal 40. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. The symbol Y represents the "long side direction of the battery," and the symbol Z represents the "height direction of the battery." However, these directions are merely used for the convenience of description, and do not limit the installation form of the secondary battery 100 in any way.

<Secondary battery>
As shown in Fig. 1, the secondary battery 100 includes a battery case 10, an electrode body 20, a negative electrode terminal 30, a positive electrode terminal 40, a gasket 50, and an insulator 60. The negative electrode terminal 30 and/or the positive electrode terminal 40 are an example of an electrode terminal. The gasket 50 is an example of an external insulating member. Although not shown, the secondary battery 100 further includes an electrolyte. The secondary battery 100 is preferably a secondary battery, and more preferably a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

The secondary battery 100 disclosed herein may be a battery with a relatively small battery size and an aim to increase output. Therefore, the secondary battery 100 disclosed herein has a battery capacity of 10 Ah or less and a battery volume of 200 cm ³ or less. The battery capacity of the secondary battery 100 may be, for example, 9 Ah or less, 8 Ah or less, or 7 Ah or less. The lower limit of the battery capacity is not particularly limited, but may be, for example, about 3 Ah or more. The battery volume of the secondary battery 100 may be, for example, 180 cm ³ or less, or 150 cm ³ or less. The lower limit of the battery volume is also not particularly limited, but may be, for example, about 90 cm ³ or more.
In this specification, the term "battery capacity" refers to the capacity of 1 C constant current discharge (voltage 3 V to 4.1 V) in an atmosphere of 20±5° C. In addition, in this specification, the term "battery volume" refers to the external volume of the battery case. Here, the external volume of the battery case refers to the external volume defined by the outer circumferential surface that defines the external shape of the battery case, excluding the positive electrode terminal, the negative electrode terminal, etc.

As shown in FIG. 1, the battery case 10 includes an exterior body 12 and a sealing plate 14. The exterior body 12 and the sealing plate 14 are an example of case members that constitute the battery case 10. Here, the battery case 10 has a flattened rectangular parallelepiped (square) outer shape. The battery case 10 is integrated, for example, by joining (e.g., welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The exterior body 12 and the sealing plate 14 are formed, for example, from aluminum or an aluminum alloy.

The exterior body 12 is a housing that contains the electrode body 20 and the electrolyte. The exterior body 12 is a bottomed, square-shaped container with an opening 12h on the top surface. The opening 12h is approximately rectangular. The exterior body 12 has a bottom wall, a pair of long side walls that extend from the bottom wall and face each other, and a pair of short side walls that extend from the bottom wall and face each other. The bottom wall is approximately rectangular. The bottom wall faces the opening 12h.

The sealing plate 14 is a plate-shaped member that seals the opening 12h of the exterior body 12. The sealing plate 14 is substantially rectangular in plan view. The sealing plate 14 faces the bottom wall of the exterior body 12. The sealing plate 14 is provided with a gas exhaust valve 15 and an injection hole (not shown) for injecting an electrolyte. The gas exhaust valve 15 is a thin-walled portion that is configured to break when the pressure inside the battery case 10 reaches a predetermined value or more, and to discharge the gas inside the battery case 10 to the outside. As shown in FIG. 2, the sealing plate 14 has an outer surface 14A that faces the outside and is on the outside of the battery case 10 when the opening 12h is sealed, and an inner surface 14B that faces the inside of the secondary battery 100 and faces the electrode body 20.

As shown in FIG. 1, the sealing plate 14 has terminal mounting holes 18, 19 penetrating the outer surface 14A and the inner surface 14B. The terminal mounting holes 18, 19 are provided at both ends of the sealing plate 14 in the long side direction Y. Here, the terminal mounting hole 18 is for the negative electrode terminal 30, and the terminal mounting hole 19 is for the positive electrode terminal 40. The terminal mounting holes 18, 19 are annular (e.g., circular) in plan view. The terminal mounting hole 19 has an inner diameter large enough to insert the shaft portion 43 of the positive electrode terminal 40 before crimping, which will be described later. In addition, the terminal mounting hole 19 has an inner diameter smaller than that of the first flange portion 41 of the positive electrode terminal 40, which will be described later.

The battery case 10 may accommodate an electrolyte together with the electrode body 20 as described above. As the electrolyte, any electrolyte used in conventionally known batteries may be used without any particular limitation. As an example, a non-aqueous electrolyte solution in which a supporting salt is dissolved in a non-aqueous solvent may be used. As an example of the non-aqueous solvent, a carbonate-based solvent such as ethylene carbonate, dimethyl carbonate, or ethyl methyl carbonate may be used. As an example of the supporting salt, a fluorine-containing lithium salt such as LiPF ₆ may be used. However, the electrolyte may be in a solid state (solid electrolyte) and may be integrated with the electrode body 20.

As shown in FIG. 1, the electrode body 20 is housed inside the exterior body 12. The electrode body 20 is housed inside the exterior body 12, for example, covered with an insulating film such as an electrode body holder 29. The electrode body 20 may be, for example, a wound electrode body in which a strip-shaped positive electrode sheet and a strip-shaped negative electrode sheet are stacked in a state insulated via two strip-shaped separator sheets and wound in the long side direction around the winding axis. Alternatively, the electrode body may be a laminated electrode body in which rectangular positive electrode sheets and rectangular negative electrode sheets are alternately stacked via rectangular separator sheets. The electrode body may also be a zigzag-shaped laminated electrode body formed by sandwiching multiple positive electrode sheets and multiple negative electrode sheets between separator sheets folded in a zigzag shape.

The positive electrode sheet has a strip-shaped positive electrode collector 22c and a positive electrode active material layer 22a fixed on at least one surface of the positive electrode collector 22c. For each member constituting the positive electrode sheet, a conventionally known material that can be used in a general battery (e.g., a lithium ion secondary battery) can be used without any particular restrictions. For example, the positive electrode collector 22c is preferably made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal complex oxide such as a lithium nickel cobalt manganese complex oxide) that can reversibly absorb and release charge carriers. The positive electrode active material layer 22a may contain any component other than the positive electrode active material, such as a conductive material, a binder, or various additive components.

The negative electrode sheet has a strip-shaped negative electrode collector 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode collector 24c. For each member constituting the negative electrode sheet, a conventionally known material that can be used in a general battery (e.g., a lithium ion secondary battery) can be used without any particular restrictions. For example, the negative electrode collector 24c is preferably composed of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly absorb and release charge carriers. The negative electrode active material layer 24a may contain any component other than the negative electrode active material, such as a conductive material, a binder, a dispersant, or various additive components.

The separator sheet is an insulating sheet in which a plurality of fine through-holes through which charge carriers can pass are formed. The separator sheet is, for example, made of a porous resin substrate. Examples of the resin substrate include sheets (films) made of resins such as polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters, polyamides, and cellulose. The separator sheet may have a single-layer structure, or may have a structure in which two or more types of porous resin sheets with different properties and characteristics (such as thickness and porosity) are laminated (for example, a three-layer structure in which a PP layer is laminated on both sides of a PE layer). The separator sheet may also have a heat-resistant layer (Heat Resistant Layer: HRL layer) made of ceramic particles or the like on its surface.

In the center of the long side direction Y of the electrode body 20, a laminated portion is formed in which the positive electrode active material layer 22a and the negative electrode active material layer 24a are laminated in an insulated state. Also, as shown in FIG. 1, at the upper end of the electrode body 20 in the vertical direction Z, there is a portion where the positive electrode active material layer 22a is not fixed and a part of the positive electrode collector 22c is exposed (hereinafter also referred to as the "positive electrode collector exposed portion"). Similarly, at the upper end of the electrode body 20 in the vertical direction Z, there is a portion where the negative electrode active material layer 24a is not fixed and a part of the negative electrode collector 24c is exposed (hereinafter also referred to as the "negative electrode collector exposed portion"). A positive electrode collector member 44 is attached to the positive electrode collector exposed portion. The positive electrode collector member 44 may be made of the same metal material as the positive electrode collector 22c, for example, a conductive metal such as aluminum or an aluminum alloy. Also, a negative electrode collector member 34 is attached to the negative electrode collector exposed portion. The negative electrode current collector 34 can be made of the same metal material as the negative electrode current collector 24c, such as a conductive metal such as copper or a copper alloy.

The negative electrode terminal 30 is attached to the other end of the sealing plate 14 in the long side direction Y (the right end in FIG. 1). The negative electrode terminal 30 is electrically connected to the electrode body 20 through the negative electrode current collector 34 inside the battery case 10. The positive electrode terminal 40 is attached to one end of the sealing plate 14 in the long side direction Y (the left end in FIG. 1). The positive electrode terminal 40 is electrically connected to the electrode body 20 through the positive electrode current collector 44 inside the battery case 10. That is, one end of the negative electrode terminal 30 and the positive electrode terminal 40 is electrically connected to the electrode body 20 inside the battery case 10, and the other end is inserted into the terminal mounting holes 18, 19 and exposed to the outside of the sealing plate 14. The negative electrode terminal 30 is preferably formed of a metal having excellent electrical conductivity, such as copper or a copper alloy. In addition, the positive electrode terminal 40 is preferably formed of a metal having excellent electrical conductivity, such as aluminum or an aluminum alloy. Furthermore, the negative electrode terminal 30 and the positive electrode terminal 40 are insulated from the sealing plate 14 by a gasket 50 and an insulator 60, respectively.
In this specification, the structure of the positive electrode terminal 40 side will be described in detail as an example, but the structure of the negative electrode terminal 30 side may be similar. In that case, in the following description, the word "positive electrode" may be appropriately read as "negative electrode".

The secondary battery 100 disclosed herein has a battery capacity of 10 Ah or less, a battery volume including the battery case of 200 cm ³ or less, and a height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive electrode terminal 40 is higher than a height H2 from the outer surface 14A of the sealing plate 14 to the top 50t of the gasket 50 (see FIG. 2). Preferably, the height H1 of the positive electrode terminal 40 is at least twice as high as the height H2 of the gasket 50. This improves the heat capacity (also called "thermal mass") of the electrode terminal, and can suppress a temperature rise due to current flow even in the electrode terminal of a battery that has a relatively small battery size and is intended to increase output. By suppressing the temperature rise of the electrode terminal, the heat resistance temperature of the external insulating member in contact with the electrode terminal is prevented from being exceeded. Therefore, the external insulating member and the electrode terminal are kept in a suitably sealed state, and the safety of the secondary battery 100 is suitably improved.

Conventionally, in a secondary battery having a battery capacity of 10 Ah or less and a battery volume including the battery case of 200 cm ³ or less, the thermal mass of the electrode terminal was generally about 1.9 J/K. However, in recent years, even secondary batteries having a relatively small battery size are required to have high output, and electrode terminals having a thermal mass capable of withstanding the passage of a large current are required. Therefore, in the secondary battery 100 disclosed herein, the height H1 of the positive electrode terminal 40 is made twice or more higher than the height H2 of the gasket 50. According to this configuration, the thermal mass of the positive electrode terminal 40 can be made larger than the conventional 1.9 J/K, which is advantageous in the passage of a large current. Also, FIG. 3A is a diagram showing a schematic diagram of a connection between a conventional positive electrode terminal 140 and a bus bar 310. FIG. 3B is a diagram showing a schematic diagram of a connection between the positive electrode terminal 40 and a bus bar 210 of the secondary battery 100 disclosed herein. In the secondary battery 100 disclosed herein, the first flange portion 41 of the positive electrode terminal 40 is exposed from the gasket 50. Therefore, as shown in FIG. 3B , even when the first flange portion 41 and the bus bar 210 are connected, a clearance can be provided between the gasket 50 and the bus bar 210. This makes it easier for the positive electrode terminal 40 to be cooled, and more preferably prevents the temperature of the positive electrode terminal 40 from exceeding the heat resistance temperature of the gasket 50. Therefore, by making the height H1 of the positive electrode terminal 40 twice or more higher than the height H2 of the gasket 50, a secondary battery 100 with high safety can be realized.

The height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive electrode terminal 40 may be at least twice as high as the height H2 from the outer surface 14A of the sealing plate 14 to the top 50t of the gasket 50, and is preferably at least 2.5 times higher, may be at least 3 times higher, or may be at least 3.5 times higher. On the other hand, if the length of the electrode terminal becomes too long, it is not preferable from the viewpoint of volume efficiency when mounted on a vehicle. Therefore, the height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive electrode terminal 40 is preferably at most 5 times the height H2 from the outer surface 14A of the sealing plate 14 to the top 50t of the gasket 50, and may be at most 4.5 times higher. In this specification, the "height H1 from the outer surface of the sealing plate to the top of the positive electrode terminal" is the longest in the vertical direction Z of the positive electrode terminal exposed outside the sealing plate. In addition, in this specification, "height H2 from the outer surface of the sealing plate to the top of the gasket" refers to the maximum length of the gasket exposed to the outside of the sealing plate in the vertical direction Z.

In the secondary battery 100 disclosed herein, the height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive electrode terminal 40 is preferably longer than the diameter of the terminal mounting hole 19 of the sealing plate 14. By making the height H1 of the positive electrode terminal 40 thus long, the effect of improving the thermal mass can be more effectively achieved.

In addition, in the secondary battery 100 disclosed herein, the height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive electrode terminal 40 is preferably at least 1 mm higher than the height H2 from the outer surface 14A of the sealing plate 14 to the top 50t of the gasket 50. The height H1 of the positive electrode terminal 40 is more preferably 1.5 mm or more higher than the height H2 of the gasket 50, may be 2 mm or more higher, more preferably 3 mm or more higher, and particularly preferably 4 mm or more higher. This allows the thermal mass of the positive electrode terminal 40 to be increased, and the temperature of the positive electrode terminal 40 is prevented from exceeding the heat resistance temperature of the gasket 50. In addition, since the length of the portion exposed from the gasket 50 is increased, a cooling effect can be expected, and the temperature rise of the positive electrode terminal 40 can be further suppressed.

As shown in FIG. 2, the positive electrode terminal 40 has a first flange portion 41, a second flange portion 42, and a shaft portion 43. The positive electrode terminal 40 is crimped to the peripheral portion surrounding the terminal mounting hole 19 of the sealing plate 14 while being insulated from the sealing plate 14 by crimping. The positive electrode terminal 40 is fixed to the sealing plate 14 by crimping and is electrically connected to the positive electrode current collecting member 44.

2, the first flange portion 41 has a larger outer diameter than the shaft portion 43. The first flange portion 41 also has a larger outer diameter than the terminal mounting hole 19 of the sealing plate 14. The first flange portion 41 is a portion that protrudes from the terminal mounting hole 19 of the sealing plate 14 to the outside of the battery case 10. The outer shape of the first flange portion 41 here is approximately cylindrical. As shown in FIG. 2, the first flange portion 41 has a lower surface 41d and a side surface (outer peripheral surface) 41a that extends upward in the vertical direction Z from the lower surface 41d.

In the secondary battery 100 disclosed herein, the height H1 of the positive electrode terminal 40 can be adjusted to be higher than the height H2 of the gasket 50 by increasing the length of the side surface 41a of the first flange portion 41 in the vertical direction Z. As described above, the first flange portion 41 has a larger outer diameter and a larger volume than the shaft portion 43, so by increasing the length of the first flange portion 41 in the vertical direction Z, the thermal mass of the positive electrode terminal 40 can be efficiently improved.

As shown in FIG. 2, the shaft portion 43 extends downward from the lower end of the first flange portion 41. The shaft portion 43 is cylindrical here. The axis of the shaft portion 43 coincides with the axis of the first flange portion 41. Before the crimping process, the lower end side of the shaft portion 43, i.e., the side opposite to the side where the first flange portion 41 is located in the vertical direction Z, may be hollow. The shaft portion 43 is a portion that is inserted into the terminal mounting hole 19 of the sealing plate 14 when the positive electrode terminal 40 is attached to the sealing plate 14. The lower end side of the shaft portion 43 is expanded by the crimping process when the positive electrode terminal 40 is attached to the sealing plate 14, and is a portion that constitutes the second flange portion 42. The shaft portion 43 is electrically connected to the positive electrode current collecting member 44 inside the battery case 10 by the crimping process.

As shown in FIG. 2, in the secondary battery 100 disclosed herein, the lower end 43d of the shaft portion 43 after the crimping process is preferably flat. FIG. 4A is a diagram showing the lower end 143d of the shaft portion 143 of the conventional positive terminal 140. FIG. 4B is a diagram showing the lower end 43d of the shaft portion 43 of the positive terminal 40 of the secondary battery 100 disclosed herein. As will be described in detail later, in the conventional positive terminal 140, as shown in FIG. 4A, a convex punch tool 320 having a convex portion 321 on the upper part was used during the crimping process. In order to avoid interference with the punch tool 320, in the conventional positive terminal 140, the lower end 143d of the shaft portion 143 had a concave portion 143c. However, in the secondary battery 100 disclosed herein, as shown in FIG. 4B, the crimping process is performed using a punch tool 220 with a flat upper part, so that a concave portion is not necessary and the lower end 43d of the shaft portion 43 is flat. This allows the volume of the shaft 43 to be increased compared to conventional models, further improving the thermal mass.

As shown in FIG. 2, the second flange portion 42 has a larger outer diameter than the shaft portion 43. The first flange portion 41 has a larger outer diameter than the terminal mounting hole 19 of the sealing plate 14. The second flange portion 42 extends from the lower end side of the shaft portion 43 and is crimped to the positive electrode current collecting member 44.

The positive electrode current collector 44 is attached to the exposed portion of the positive electrode current collector 22c, and constitutes a conductive path that electrically connects the positive electrode and the positive electrode terminal 40. As shown in FIG. 2, the positive electrode current collector 44 has a flat portion 44f that spreads horizontally along the inner surface 14B side of the sealing plate 14. The flat portion 44f has a through hole 44h at a position corresponding to the terminal mounting hole 19. The through hole 44h has an inner diameter that allows the shaft portion 43 of the positive electrode terminal 40 before crimping, which will be described later, to be inserted therethrough. The positive electrode current collector 44 is fixed to the sealing plate 14 by crimping in a state insulated via the insulator 60.

Figure 5A is a diagram showing a conventional positive terminal 140. Figure 5B is a diagram showing a conventional positive terminal 40 of the secondary battery 100 disclosed herein. As shown in Figure 5A, the conventional positive current collecting member 144 is provided with a recess 144a and a countersunk hole 144b. The length of the recess 144a in the vertical direction Z is shorter than that of the flat plate portion 144f of the positive current collecting member 144. The length of the countersunk hole 144b in the vertical direction Z is shorter than that of the recess 144a. In other words, the conventional positive current collecting member 144 has the recess 144a as a first thin portion having a thickness smaller than that of the flat plate portion 144f, and the countersunk hole 144b as a second thin portion having a thickness even smaller than that of the first thin portion. According to the results of the study by the inventors, it was found that the positive electrode current collecting member 144 has a recess 144a and a countersunk hole 144b, which slightly shortens the length L1 in the vertical direction Z of the shaft portion 143 of the positive electrode terminal 140, which is not preferable from the viewpoint of improving the thermal mass of the positive electrode terminal. In contrast, the positive electrode current collecting member 44 of the secondary battery 100 disclosed herein does not have a recess or a countersunk hole, as shown in FIG. 5B. Therefore, the length L2 in the vertical direction Z of the shaft portion 43 of the positive electrode terminal 40 can be further extended downward. This can further improve the thermal mass, suppress excessive heat generation of the positive electrode terminal 40, and provide a secondary battery 100 with high safety.

2, the gasket 50 is a resin insulating member arranged between the outer surface 14A side of the sealing plate 14 and the positive electrode terminal 40. The gasket 50 is an example of an external insulating member. Here, the gasket 50 has a function of insulating the sealing plate 14 from the positive electrode terminal 40 and closing the terminal mounting hole 19. The gasket 50 can be made of a resin material that has electrical insulation and can be elastically deformed, such as a fluorinated resin such as perfluoroalkoxy fluororesin (PFA) or polytetrafluoroethylene (PTFE), polyphenylene sulfide resin (PPS), polypropylene (PP), etc. Among them, perfluoroalkoxy fluororesin is preferable. In addition to the above-mentioned resin material such as PFA, an inorganic filler may be added to the gasket 50.

The gasket 50 has a tube portion 51, a base portion 52, and a side wall portion 53. The tube portion 51 is a portion that prevents the sealing plate 14 and the shaft portion 43 of the positive electrode terminal 40 from coming into direct contact with each other. The tube portion 51 has a hollow cylindrical shape. The tube portion 51 has a through hole 51h that penetrates in the vertical direction Z. The through hole 51h is configured so that the shaft portion 43 of the positive electrode terminal 40 before the crimping process can be inserted therethrough. The tube portion 51 is inserted into the terminal mounting hole 19 of the sealing plate 14. The base portion 52 is a portion that prevents the sealing plate 14 and the lower surface 41d of the first flange portion 41 of the positive electrode terminal 40 described later from coming into direct contact with each other. The base portion 52 is configured, for example, in a ring shape so as to surround the terminal mounting hole 19 of the sealing plate 14. The base portion 52 extends along the outer surface 14A of the sealing plate 14. The base 52 is sandwiched between the lower surface 41d of the first flange portion 41 of the positive terminal 40 and the outer surface 14A of the sealing plate 14, and is compressed in the vertical direction Z by, for example, crimping. The side wall portion 53 is a portion that extends upward from the periphery of the base 52. The side wall portion 53 surrounds a portion of the periphery of the side surface 41a of the first flange portion 41.

The insulator 60 is an insulating member disposed between the inner surface 14B side of the sealing plate 14 and the positive electrode current collecting member 44. The insulator 60 has a function of insulating the sealing plate 14 and the positive electrode current collecting member 44. As shown in FIG. 2, the insulator 60 has a flat portion that spreads horizontally along the inner surface 14B of the sealing plate 14. The flat portion has a through hole 60h at a position corresponding to the terminal mounting hole 19. The through hole 60h has an inner diameter large enough to insert the shaft portion 43 of the positive electrode terminal 40. The insulator 60 has resistance to the electrolyte used and electrical insulation properties, and can be made of a resin material that can be elastically deformed, such as a fluorinated resin such as perfluoroalkoxy fluorine resin (PFA) or polyphenylene sulfide resin (PPS). The flat portion of the insulator 60 is sandwiched between the inner surface 14B of the sealing plate 14 and the upper surface of the positive electrode current collecting member 44, and is compressed in the vertical direction Z, for example by crimping.

<Secondary Battery Manufacturing Method>
Next, a description will be given of an example of a method for manufacturing the secondary battery 100. The manufacturing method disclosed herein includes, for example, a preparing step, an attaching step, and a sealing step.

In the preparation process, at least the exterior body 12, the sealing plate 14, the negative electrode terminal 30, the positive electrode terminal 40, and the electrode body 20 are prepared. Here, the negative electrode terminal 30 and the positive electrode terminal 40 are prepared so that their length in the vertical direction Z is long enough that they are at least twice as high as the height H2 from the outer surface 14A of the sealing plate 14 to the top of the external insulating part when attached to the sealing plate 14.

In the mounting process, the negative terminal 30, the negative current collector 34, the positive terminal 40, and the positive current collector 44 are mounted on the sealing plate 14. The positive terminal 40 and the positive current collector 44 are fixed to the sealing plate 14 by crimping (riveting), for example, as shown in FIG. 2. The crimping process is performed by sandwiching a gasket 50 between the positive terminal 40 and the sealing plate 14, and further sandwiching an insulator 60 between the sealing plate 14 and the positive current collector 44. More specifically, the shaft portion 43 of the positive terminal 40 before crimping is passed through the cylindrical portion 51 of the gasket 50, the terminal mounting hole 19 of the sealing plate 14, the through hole 60h of the insulator 60, and the through hole 44h of the positive current collector 44 in that order from above the sealing plate 14, and protrudes downward from the sealing plate 14. Then, as shown in FIG. 4B, a punch tool 220 with a flat top is used to crimp the shaft portion 43 protruding downward from the sealing plate 14 so that a compressive force is applied in the vertical direction Z. This forms a second flange portion 42 at the tip of the shaft portion 43 of the positive electrode terminal 40.

In the conventional crimping process, a convex punch tool 320 as shown in FIG. 4A was used. Specifically, the shaft portion 143 of the positive terminal 140 before crimping is passed through the tube portion 51 of the gasket 50, the terminal mounting hole 19 of the sealing plate 14, the through hole 60h of the insulator 60, and the through hole 144h of the positive current collecting member 144 in order from above the sealing plate 14, and protrudes downward from the sealing plate 14. Then, the shaft portion 143 protruding downward from the sealing plate 14 was crimped using a convex punch tool 320 having a convex portion 321 at the top so that a compressive force is applied in the vertical direction Z. For this reason, the lower end portion 143d of the shaft portion 143 has a concave portion 143c in order to avoid interference with the punch tool 320. However, as a result of the study by the inventors from the viewpoint of improving the thermal mass, it was found that crimping can be performed suitably even if the upper portion of the punch tool is flat as shown in FIG. 4B. Therefore, the crimping process for the secondary battery 100 disclosed herein uses a punch tool 220 with a flat top.

By the above-mentioned crimping process, the base 52 of the gasket 50 and the flat portion of the insulator 60 are compressed, the positive terminal 40, the gasket 50, the insulator 60, and the positive current collector 44 are fixed integrally to the sealing plate 14, and the terminal mounting hole 19 is sealed. The method of attaching the negative terminal 30 and the negative current collector 34 may be the same as the above-mentioned method of attaching the positive terminal 40 and the positive current collector 44. The positive current collector 44 is welded to the positive current collector exposed portion of the positive current collector 22c, and the positive electrode of the electrode body 20 and the positive terminal 40 are electrically connected. Similarly, the negative current collector 34 is welded to the negative current collector exposed portion of the negative current collector 24c, and the negative electrode of the electrode body 20 and the negative terminal 30 are electrically connected. This integrates the sealing plate 14, the negative electrode terminal 30, the positive electrode terminal 40, and the electrode body 20.

In the sealing process, the electrode body 20 integrated with the sealing plate 14 as described above and the electrolyte are contained in the exterior body 12 and sealed. Specifically, the electrode body 20 is inserted through the opening 12h of the exterior body 12, and the periphery of the sealing plate 14 and the opening 12h of the exterior body 12 are joined by laser welding or the like. Then, an electrolyte (e.g., a nonaqueous electrolyte) is injected through the injection hole, and the injection hole is closed with a sealing member to hermetically seal the secondary battery 100. In this manner, the secondary battery 100 can be manufactured.

<Uses of secondary batteries>
The secondary battery 100 can be used for various purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, but examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

The secondary battery 100 can also be suitably used as an assembled battery in which a plurality of secondary batteries 100 are electrically connected to each other via, for example, a bus bar 210. In this case, the electrical connection between the plurality of secondary batteries 100 can be made by, for example, bridging the flat bus bar 210 across the first flange portion of the positive terminal and the negative terminal. The bus bar 210 can be made of, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The bus bar 210 and the first flange portion can also be electrically connected by welding, for example, laser welding. As described above, the height H1 from the outer surface 14A of the sealing plate 14 to the top 40t of the positive terminal 40 is twice or more higher than the height H2 from the outer surface 14A of the sealing plate 14 to the top 50t of the gasket 50, so that a clearance can be provided between the bus bar 210 and the gasket 50 when the assembled battery is constructed. This allows the positive terminal 40 to be cooled more easily, preventing it from exceeding the heat resistance temperature of the gasket 50, and ensuring more appropriate sealing and insulation. Therefore, the secondary battery 100 disclosed herein can provide a battery pack with improved safety.

Although several embodiments of the present invention have been described above, the above embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and changes to the above-exemplified embodiments. For example, it is possible to replace part of the above-mentioned embodiments with other modified forms, and it is also possible to add other modified forms to the above-mentioned embodiments. Furthermore, if a technical feature is not described as essential, it can also be deleted as appropriate.

As described above, specific aspects of the technology disclosed herein include those described in the following sections.
Item 1: A secondary battery comprising: an electrode body having a positive electrode and a negative electrode; a battery case having an opening and accommodating the electrode body; a sealing plate having a terminal mounting hole and sealing the opening; an electrode terminal having a first flange portion disposed on the outside of the battery case, a second flange portion disposed on the inside of the battery case, and a shaft portion positioned between the first flange portion and the second flange portion and inserted into the terminal mounting hole; and an external insulating member made of resin that insulates an outer surface of the sealing plate from the first flange portion, wherein the battery capacity is 10 Ah or less and the battery volume including the battery case is 200 ^cm3 or less, and wherein a height H1 from the outer surface of the sealing plate to a top of the electrode terminal is at least twice as high as a height H2 from the outer surface of the sealing plate to a top of the insulating member.
Item 2: The secondary battery according to item 1, wherein a lower end side of the shaft portion is flat.
Item 3: The secondary battery according to item 1 or 2, wherein the height H1 of the electrode terminal is longer than the diameter of the terminal mounting hole.
Item 4: The secondary battery according to any one of items 1 to 3, wherein the height H1 of the electrode terminal is at least 1 mm higher than the height H2 of the external insulating member.
Item 5: An electrode terminal which is either a positive electrode terminal or a negative electrode terminal of a secondary battery, the electrode terminal being provided in the secondary battery according to any one of Items 1 to 4.

REFERENCE SIGNS LIST 10 Battery case 12 Exterior body 12h Opening 14 Sealing plate 18, 19 Terminal mounting hole 20 Electrode body 30 Negative electrode terminal 40 Positive electrode terminal 40t Top portion 41 First flange portion 42 Second flange portion 43 Shaft portion 50 Gasket 50t Top portion 51 Cylindrical portion 52 Base portion 53 Side wall portion 60 Insulator 100 Secondary battery 210 Bus bar 220 Punching tool

Claims (5)

An electrode assembly having a positive electrode and a negative electrode;
a battery case having an opening and housing the electrode assembly;
a sealing plate having a terminal mounting hole and sealing the opening;
an electrode terminal including a first flange portion disposed outside the battery case, a second flange portion disposed inside the battery case, and a shaft portion positioned between the first flange portion and the second flange portion and inserted into the terminal mounting hole;
an external insulating member made of resin that insulates an outer surface of the sealing plate from the first flange portion;
The battery capacity is 10 Ah or less, and the battery volume including the battery case is 200 ^cm3 or less,
wherein the lower end side of the shaft portion is flat, and a height H1 from the outer surface of the sealing plate to the top of the electrode terminal is adjusted to be at least twice a height H2 from the outer surface of the sealing plate to the top of the external insulating member , and the secondary battery is configured so that the heat capacity of the electrode terminal is greater than 1.9 J/K . 2 . The secondary battery according to claim 1 , wherein a height H1 of the electrode terminal is adjusted to be 3 to 5 times a height H2 of the external insulating member . The secondary battery according to claim 1, wherein the height H1 of the electrode terminal is longer than the diameter of the terminal mounting hole. The secondary battery according to claim 1, wherein the height H1 of the electrode terminal is at least 1 mm higher than the height H2 of the external insulating member. An electrode terminal, either a positive electrode terminal or a negative electrode terminal, of a secondary battery, provided in the secondary battery according to any one of claims 1 to 4.

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